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MG MGB Technical - V8 EFI help needed
| I apologise for posting a V8 question here but the V8 board seems pretty moribund and I know a number of correspondents here also run V8s.
Briefly, my MGB GT is fitted with a pretty standard 1991 Range Rover 3.9 litre engine, complete with the hot-wire injection. The ECU is a normal 14CUX but with an Optimax chip. The engine was completely reconditioned 30K miles ago. All has been well for several years and 30K miles, but this year it has started to misfire at low revs, and shakes itself about when idling. I naturally considered the ignition system to be the cause of this errant behaviour and over the last few months have completely renewed it with new NGK plugs, new HT leads, new 123-tune distributor supplied with its own new coil. I have programmed the dissy with a generic type of Range Rover curve and it starts and runs well except for the misfire and also it smells rich. Having said that, the plugs are not black, but the correct pale colour. So my thoughts turn to the fuel injection. Could there be a duff injector? They are Lucas injectors, now 27 years old. In the Haynes RR manual they describe how to test the various components of the system with a multimeter and I have been through it this afternoon. Every single item I could test gives readings in the acceptable range. I don't have the facilities to test the individual injectors. I don't know how to proceed. I could throw loads of money at it and buy a set of shiny new Bosch injectors for £600, but what if that doesn't fix it? Any thoughts, kind people? |
| Mike Howlett |
| Mike,
I know this won't be a palatable suggestion, and I've no idea of the practicalities, but can you easily uninstall the chip to see if the chip is causing or making the misfire worse. And/or - do you have a good quality, reasonably priced, diagnostic and/or rolling road tuner anywhere near you as sometimes theses problems need the correct equipment and knowledge of how to interpret findings. Obviously you need someone that knows what they're doing and won't spend hours at your expense trying to work it out. Or contact the chip supplier for some info perhaps. Only coincidence, my neighbour has just had four new injectors on his bog standard J reg four pot petrol Merc 200E. |
| Nigel Atkins |
| Hi Nigel. I can't uninstall the chip because I have nothing with which to replace it, and without some sort of chip it ain't going to work. The original chip was soldered directly to the circuit board and a socket had to be installed to plug in the Optimax chip, so an original chip could no longer be fitted. Many hundreds (if not thousands) of Optimax chips have been used in the 14CUX and in my car it has worked well until recently, so I consider the chip to be the most unlikely culprit.
I don't know of any dyno-equipped tuner in Ayrshire (where I live) or even in the Glasgow area. If there are any would they know about the Rover engine which is now getting pretty old. The majority of workshops will deal with modern injection systems. The Rover efi is a very crude design comparatively. The chip supplier (Mark Adams of Tornado Systems) is the best bet and I have been in touch with him. He has given me some things to try but they weren't the answer. He is very willing to have the car in the workshop and to sort it out and I know he has extensive knowledge of the Rover V8. Trouble is he is in Shrewsbury, some 300 miles from here. I could drive the car there but would have to arrange to stay over somewhere which makes the whole enterprise a pretty expensive affair. Its a tricky problem. Thanks for your input. |
| Mike Howlett |
| Mike Are there no Land Rover/Range Rover people up your way? |
| Dave O'Neill 2 |
| Mike
Couple of things 1-It could be a camshaft on the way out but normally that happens really gradually and you would have noticed it creeping in over a longer period and also with that you would hear a definate hammering sound through the inlet up in the revs under load 2-My money is on a clogged injector-- You have two choices-- Pull them all out and have them cleaned When they clean them ,they are flow tested and if there is a faulty one they can try recleaning it or if that fails get another Or If you want to track it down yourself-- If it's a definate missfire at idle you need to find which cylinder is causing the problem by either pulling one plug lead off at a time to determine which cyl. isn't working- ---USE PLASTIC PLIERS-- for this as the high voltages in modern coils are killers If you don't want to go pulling plug leads with it going ,me either, you can disconnect one injector at a time to track the missfire down--When you have found the faulty cyl. swap the injector into another cyl. and then retest to see if the missfire follows the injector (faulty injector) or if the miss stays on the original cyl -then it's not the injector causing it and could be something like a sucked in manifold gasket or a cracked booster hose but determining which cylinder it is is the priority and work from there The reason for it smelling rich at idle is caused by the missfire--A missfire sends a false lean (unburnt fuel)signal to the oxygen sensor and the ECU reacts by richening the mixture to get the correct reading at the sensor People stress out about fuel injection but it's simple really and doesn't really cause much bother If you had someone in your area with a scope in their workshop they should be able to diagnose it for you in two seconds flat Let us know how you get on willy ps I have never had an injector die electrically internally but there is always the chance of a wiring issue or a missfitting connector- pulling the connectors from the injectors one at a time running as above will help prove that out |
| William Revit |
| Thanks Willy. That's helpful. My car doesn't have catalysts so there is no oxygen sensor and I have the tune resistor for "No Cats" installed.
I checked the hose trunking from the AFM to the plenum as a split there threw a spanner in the works on my BMW Z3. But the MG trunk is sound. I suspect an injector and must try disconnecting them one by one as you suggest. Might be a while before I can do that as the lady indoors seems to want to go away for a few days. No sense of what's important! I expect there is a workshop locally who could help, but how to find one that knows what they are doing? That's the question. |
| Mike Howlett |
| Mike,
Dave has improved on what I was thinking, perhaps a Landie/Range Rover independent, or a sports/kit car specialist. Even those that deal with moderns may include staff old enough to have dealt with older cars or those a bit younger may have learnt such stuff. Doesn't have to be a rolling road but they often have the kit and sometimes knowledge, I was thinking of stuff like the old Sun(?) analysers or slightly more updated. I always like the idea of cleaning and the idea of swapping round to help narrow down the possibilities. I remember the name of Mark Adams (IIRC) from years ago, can't remember if he was the chap that used to custom program a chip to individual cars in the days of (or before?) laptops being for the few and not the many. As you can tell I've no real idea of chips (other than with chip shop curry sauce) and wondered if yours might have been a plug-in or piggy back type of thing. Probably the injectors will sort your problem as they did for my neighbours who are now up Mallaig sort of area enjoying relief from the intense heat down here. I'm very lucky as my wife is taking the day off to accompany me to Peter Burgess for a rolling road tune up, her friends are all jealous. We might include a country pub for a swift half of real ale and Peter and Keith makes us very welcome so she enjoys the day. The next two days we enjoy quality time apart as she goes to a wedding using wedding cars tonbridge with a friend. Perhaps you could mention the concept of quality time together and apart. :) |
| Nigel Atkins |
| Poor idling (shaking about???) can be caused by a faulty stepper motor. I know it causes problems on RV8's. |
| Allan Reeling |
| Nigel, how lucky you are to be close (ish) to Peter Burgess. Allan, yes I thought about the stepper motor and have had it out to clean. I didn't try to dismantle it, just squirted carb cleaner liberally in it. I don't know how to check that it works satisfactorily. |
| Mike Howlett |
| Mike,
I do have to go up the M1, never a pleasant drive, Peter is rather selfish living so far from me! My experience with stepper motors is that they intermittently stick, no fun when you can't drop the revs and you're approaching a tight bend with the torque of a V8. Cleaning was tried but I was told the problem would return, and it did. I tried a new stepper motor and was told it'd be OK for a while but later it'd need cleaning at some stage, IIRC it did. The cleaning did stop the problem for a while, I can't remember the details but I can't remember there being much to disassembly. A careful dismantle, clean and reassembly should do more good than harm I'd have thought. |
| Nigel Atkins |
| Nigel When are you visiting Alfreton? I'm only six miles up the road, now. Having said that, I'm in MK tomorrow and Wednesday :o( Apologies for thread drift! |
| Dave O'Neill 2 |
| Blimey Dave you really do get on well with Peter then. Sod's Law we're up with Peter and Keith on Wednesday, perhaps another time. And Sod's Law things are falling apart at the moment on the car, when I've got other stuff to do and the incessant heat is restricting my options and opportunities, will we ever survive - er, yes, whatever don't get done will have to wait or go without. |
| Nigel Atkins |
| Mike
Nothing to do with the missfire, but You mentioned your car has no cats and a no cats tune resistor fitted- i take it that it was a later motor with cats originally-- If so ,depending on the model it would/could have originally had 4 oxygen sensors 2 Front/upstream -controlling mixture 2 Rear/downstream of the cats-monitoring cat operation It's normal practice(naughty according to mr.plod) when doing a cat delete to trick the rear oxygen sensors into thinking everything is normal which has been done on your car with the 'nocats'resistor- there are also other methods of doing this, but that's not an issue Where I'm going with this is that your car would still have front O2 sensors controlling mixture and still stand by my statement that the sensors are reading lean caused by the missfire and richening the idle mixture to compensate making it smelly at idle willy |
| William Revit |
| Willy, there are no oxygen sensors on my car. Of that I am certain. Looking at the drawing of the Range Rover exhaust system in the Haynes manual, cars with cats in the early nineties only had two oxygen sensors, one on each bank, pre-cat. My system is entirely different from the cylinder heads down.
The tune resistor is not a bodge but is what the maker did. Apparently at that time not all the cars had cats and so that the ECU knew what it was dealing with a resistor was wired in between pins 5 and 27. For a non-cat car this is between 446 and 494 ohms, but on a cat equipped car it was between 3700 and 4100 ohms. Mine has a 490 ohm resistor. |
| Mike Howlett |
| Mike
Interesting Not saying it was a bodge at all Just getting my head around how it's set up So it's got no feedback at all then--I'm happy to accept that if that's how it is Dumb Me has just read your initial post again and see that it's a 91 3.9 Seeing as it has no O2 sensors the mixture will be set by the program in the ECU with inputs from Throttle sensor Temperature(coolant) sensor Air temp/flow meter Getting a bit off the missfire track here but if it is actually rich at idle it could be caused by one of these sensors The ECU won't change so I doubt that's a cause IF it were to be the throttle sensor, you usually have idle cutting out problems or throttle spots where it flatspots You could check it with a mutimeter, most run from .5vapprox. through to full throotle at 4.5v approx A nice linear sweep of voltage is what you need Coolant sensor- usually when they get a film of contaminant on them they simply take longer to get the heat into them so just run a tiddle rich during warm up so not an issue but you could pull it out and clean the bulb if you wanted to Now the airflow meter Being a hotwire type, basically how it works is--It has power through the exposed wire which runs almost red hot and has a high electrical resistance, and as the throttle is opened the airflow accross the wire is increased and the air cools it which in turn reduces the electrical resistance of the wire and increases the signal to the ECU If the wire is real dirty it doesn't heat up properly and also doesn't cool off properly with airflow ,causing richer than normal idle and possible lean mid to higher mid range If you take the airflow meter off and give it a real good squirt/flush with carby cleaner or contact cleaner from both ends specially up in the middle venturi if it's got one it should clean it up fine If you hold it up to the light and look through it you will see the fine wire in there that needs the clean All maintenance stuff and probably nothing to do with your missfire but if you like fiddling it's all good stuff to fiddle with willy |
| William Revit |
| Hi Willy. The Haynes Range Rover manual gives a load of checks you can do on the various components of the system using a multimeter. I went through it all a couple of days ago and everything was in spec.
The air flow meter is a possibility and worth looking at. The other thing I may have messed up is the base idle. I twiddled with the screw on the AFM without much effect. Probably should have left it alone! There are a number of jobs that need doing on the BGT so I will probably take it off the road for the winter and see if I can't sort everything at once. Thanks for your input. I always think your posts are worth reading. |
| Mike Howlett |
| Mike
The adjuster on the airflow meter would be for mixture not base idle speed, this could be where your rich smell is coming from Basse idle speed would be set by disconnecting the stepper motor and setting the speed via an allen key adjuster on the throttle body--usually hidden under a bung then reconnect the stepper and let it idle for a minuite or so to let it settle The adjuster on the airflow meter needs to be set using an exhaust gas analiser or your book might have a resistance to set it to-it's only a trimpot so don't get too heavy handed screwing it around whereas the actual speed screw on the throttle body is a mechanical screw Not sure of the idle specs but it's usually a good idea to give the throttle body bore and butterfly a good cleanout first to allow an acurate adjustment Not sure on Rovers but usually on this sort of thing you would set base idle(stepper disconnected) to about 600-650 rpm and when the stepper is reconnected it should be high to start and settle back to around 700-750 When I'm doing idle mixture adjustments I usually have the stepper disconnected so the ECU doesn't ramp the revs up and down and you can play with base idle speed and mixture at the same time to get it spot on and then replug the stepper, but you need an exhaust gas analiser for that I'll be interested to hear what you find with the missfire part of it Hope it's not a camshaft for you to deal with Willy |
| William Revit |
| Mike Rover made a small meter for the American market to check the 14CUX system. The error codes are available on the web. The meters are around and come up on ebay from time to time. The stepper motor has always been the weak link. I have had several. In the end all the components are suspect and dont forget the fuel pump and the return valve on the end of the fuel line. Roger |
| Roger Walker |
| Thanks Roger. I had a look on ebay and there was a Sun PDL900, which looked as though it would reach over £100. I would rather not pay that for a used tool.
How do I tell if the stepper motor is faulty? The car's idle speed is fine, it just shakes like it is misfiring. I'm not sure what you mean by the fuel return valve. I have two fuel pumps. A low pressure pump feeds a swirl pot, and then a high pressure pump feeds the engine, returning to the swirl pot which overflows back to the tank. I squirted carb cleaner through the Air Flow Meter yesterday and measured the output from it and adjusted it to 1.42 volts, as specified for a non-cat engine. I haven't had the opportunity to try the car since doing that. |
| Mike Howlett |
| Mike
I have been where you now are - even Landrover were non-plussed. I reasoned that anything that gave me a quick readout on the fuel injection system was an essential addition to the workshop - even if it cost £100. To save time and all the worry, you need a "Range Rover On Board Diagnostic display" PRC 17M. The diagnostic display will show when the stepper motor is sick - the motor can be so unreliable that it won't work one day but be OK the next - so you might want to keep it after replacement. The valve on the end of the fuel line is the "Fuel Pressure Regulator". They are mechanical so generally work but if fuel pressure is low, you may need to think about it. I ran with a swirl pot and two pumps for a while but have gone back to the RV8 single pump quite low beside the tank. I reasoned that there had been an air pressure build up inside the swirl pot which interfered with the suction pump action and ended up starving the HP pump and system of fuel. All un-proved but it didn't work properly. The diagnostic meter will not show all the potential probs with the 14CUX system - for example air leaks around the plenum chamber (faulty brake servo ?) or stale fuel - best take the fuel quality issue seriously -the anecdotal evidence weighs heavily against environmental agencies' political pontifications - there are a number of system cleaners - I use TEC 2000. Roger |
| Roger Walker |
| Ah the fuel pressure regulator. I no longer have the standard item but have an adjustable regulator with pressure gauge, so I know the pressure is within spec.
I've had no problems with a swirl pot and two pumps. I can't imagine how you could get an air pressure build up in my pot. The return feed to the tank is right at the highest point, so any air that was in the pot would quickly be passed back to the tank with the returning fuel. Googling PRC 17M brings up no hits of any relevance. Thanks again for your comments. |
| Mike Howlett |
| Google PRC17EM |
| R G Everitt |
| Mike Have you had any luck tracking down which cylinder is misfiring yet If it's shaking it's most likely a missfire -----not idle or fuel pressure or general running issues You have to find which cyl. is causing the shake first willy |
| William Revit |
| Short each plug lead in the cap in turn to earth. If one (or more) makes no difference they are not firing. Firing cylinders will make it worse. |
| paulh4 |
| Short each plug lead in the cap in turn to earth. If one (or more) makes no difference they are not firing. Firing cylinders will make it worse. |
| paulh4 |
| Sorry Paul. I understand the theory of shorting each plug, but how? Both ends of the HT leads are fully shrouded. I could just pull off the leads one by one, but for one thing they aren't easy to get at on a hot engine, and then there's the voltages involved which scare me a bit. |
| Mike Howlett |
| Mike
You can get the same results by pulling the connector off one injector at a time---or ---You are quite right to be wary of the voltage in the plug leads --safety first--- There's 40-50,000 volts there waiting to kill you or do you some serious damage If you are going to pull plug leads, get yourself a set of plastic pliers, not insulated steel, propper full plastic pliers You can pull the leads from the dist. cap instead of the plugs if they are tucked away and hard to get at If the leads are a tight fit in the cap you can (without the motor going)pull them all up a bit and have them so that they are easier to pull individually to test for a missfire If you have a local fishing shop, they have nice big flat jaw plastic pliers-cheap- they are called lipgrip pliers -for holding fish while removing hooks-I think I paid about $2 for mine willy |
| William Revit |
| The shrouds on mine at the distributor end can be slid back along the cable, then you can get a probe down beside the cable to the connector, that has a wire going back securely connected to an earth point. The distributor is also very easy to get at.
As far as voltage goes that's why I say to earth them, rather than simply pulling the lead out of the cap or off the plug. That way you get very high voltages that can break down the cap and rotor, as well as give you a helluva belt. But if you can easily disconnect the injectors in turn then that will tell you the same thing, it's just that on the ones I have dealt with their connectors are on pretty tight. |
| paulh4 |
| Mike, do you have a timing light with a clip on inductive pick-up? Connect it to each lead in turn to check for a regular pulse. Any plug that's mis-firing should be identifiable. Let me know if you would like to borrow one. Best of.... MGmike |
| M McAndrew |
| That's a brilliant idea Mike. I have exactly the right tool. Why didn't I think of that? I won't be doing that until tomorrow, but I will report back. |
| Mike Howlett |
| Mike
Checking with a timing light is ok but will only tell you if you have spark at the lead or not, It won't identify a misfiring plug or other things like vac. leaks,faulty injectors or camshafts etc On a scope differences in cylinders can be identified but sadly not with a single timing light BUT worth a try if you have one just in case it happens to be a missing spark going somewhere else other than where it's supposed to be going---although, you have replaced all the ignition system already and still have the issue making me think that's not the problem Paul's idea of something like paper clips poked down each post on the cap so each can be shorted has merit--If you're going to do that though use something with a well insulated handle to short them out- at least you will be able to identify which cyl. isn't working properly using this method and can then progress on towards finding the cause- -------Please be over wary/carefull around them sparks------ |
| William Revit |
| Using the securely earthed wire I mentioned prevents any chance of receiving a shock from the HT.
Once you have identified which cylinder isn't functioning (if that is indeed the cause of the rocking) then as William says a timing light on a lead can be used to see if you have an HT pulse from the cap. By comparing that with being clipped onto the coil lead you can identify if the rotor or cap is breaking down - pulse on the coil lead but not on the plug lead, or if there is some strange problem with the trigger - missing pulse on the coil lead as well. But if you have a non-firing cylinder this should be very evident from the exhaust. |
| paulh4 |
| Mike PRC 17M - Trawl through http://www.britishv8.org/articles/rover-14cux-efi.htm You will see the number from the photo.Two were sold on ebay within 10 minutes of my last post |
| Roger Walker |
| One thing which was deemed an issue by LR and MG was the possibility of cross firing between cylinders 5 and 7. They both made the specific point to keep the leads well separated to avoid an induced voltage in lead 7 when 5 was firing. 7 follows 5 in the firing sequence and they are adjacent cylinders, the leads therefore follow more or less the same path. As 5 is firing 7 is on it's way up to TDC. A premature spark to 7, even a reduced one, would cause a shake similar to that experienced when "running on" occurs. |
| Allan Reeling |
Indeed, for the factory V8 (at least) they say to swap over 3 and 5 in the comb to prevent this.
 |
| paulh4 |
| Lovely drawing Paul! Yes, I knew about HT leads 5 and 7 and mine are as separated as they can be. I've been trying Mike McAndrew's test using the timing gun, but all plug leads show a regular spark. Not surprising since the entire ignition system is new. Perhaps I should test the compressions. Big job with eight cylinders! |
| Mike Howlett |
| I recently helped a friend with an issue on a 4 cyl B not firing properly on a couple of cylinders, in this case we knew which ones were the issue but I thought I’d try a thermal image camera on the plugs, it was immediately obvious which ones were cooler. I also use a couple of Colortunes to get an idea how things are running, a bit of a pain on a V8 but it may be worth a try if all else fails |
| R.A Davis |
| Mike - try shorting each plug lead in the cap to earth and see if you get a more or less equal drop on all cylinders. That will highlight ignition, fuelling, valve, compression problems and anything else on a particular cylinder.
Never done it on the V8 mind you. On the roadster there is a difference between cylinders - not surprising with the crude mechanics and tolerances of the B series, but they do all cause an idle drop and an uneven beat. Some say you can find one cylinder that doesn't make a difference when nothing is wrong, but I can't really see that. |
| paulh4 |
| If you do discover a "lazy" cylinder, it might be worth checking the cam and tappet operation.
A simple indicator is to remove a rocker cover, clean the exposed bit of the push rod and dab it with Tipex (other markers are available). Then start the engine. Healthy tappets on a healthy cam lobe will rotate, taking the push rod with them, any push rods which don't need investigating. You will also be able to see the valves working and roughly assess the degree of opening. Low lift could be down to a bad cam lobe, but often a tappet failing to "pump up". Often low lift and non rotation go together. |
| Allan Reeling |
| Which reminds me that you can also use a 'dial-back' timing light to 'freeze' push-rod and rocker movement. You will have to experiment which plug lead the timing light pick-up needs to be on for each valve, but when selected correctly by turning the dial on the timing light you can watch the push-rod go up and down, and should clearly see the lowest point and the highest and hence travel, perhaps against a ruler, for comparison with other rockers. If valve operation is not consistent then you will get 'jitter' in the image.
Also possible to compare lift with a calibrated rod that can slide in a holder fixed to the head somehow. |
| paulh4 |
| Good ideas Paul. |
| Allan Reeling |
| If by any chance your misfire/erratic running is down to a worn cam lobe, if you remove your rocker covers and turn the engine over by hand and look at the rockers you will be able to see the difference in movement of the arm, its a fairly common fault on these V8s, we had SD1s Range rovers, and Sherpas when I was at work and we were forever putting camshafts in them |
| Andy Tilney |
| Yes, I was told ten years ago that the V8's camshaft was really only good for about 100,000 miles. I fitted a new Cyclone camshaft from Real Steel, and so far it has only done about 32,000 with 3,000 mile oil changes. The camshaft is described as
Designed for 3.9 Hot-Wire injection engines. OK for most applications, including automatic transmission. Worth an extra 26hp over a std engine. If the cylinder block and cylinder head faces have not been heavily machined, and the valve guides are fitted to the correct length, then this cam should bolt straight in. Use 3 degrees extra ignition advance, and a "cone" style free flowing air cleaner. In dyno tests, we obtained 26bhp extra at 5000rpm, with an extra 27ft lbs of torque at the same rpm. Rpm Range = Idle-5500rpm @ .050" In.206 Ex.206 Lift-1.60 RockersIn; .433" Ex; .433" Lobe Sep 108 degrees Re-reading that, I don't think I factored in the extra 3 degrees ignition advance when I programmed my new 123-Tune dissy. Must try that. |
| Mike Howlett |
| There's a fair bit of guessing what it might be going on here, jumping at stuff that may/may not be at fault 1st things 1st Need to find if there is a cylinder out at idle making it rock If you don't want to do the plug shorting thing, I'd find a tune up workshop near you there somewhere that has a scope and get it hooked up to find the cause willy |
| William Revit |
| With hydraulic tappets (if that is what it has) you can't be sure that the lift turning the engine manually will be the same as when it is running. The first time I did a hot compression test on mine, wet and dry, I was horrified by the clattering at the next start-up as the tappets pumped themselves back up again.
A scope as Willy suggests will tell you more than a timing light as it should be able to see the difference between a plug that is not firing whether it be short-circuit or open-circuit, the light can't tell you either. Still not as good as shorting each plug though. |
| paulh4 |
| I had the plugs out yesterday and all eight are the same colour, a light milky coffee brown so it looks to me as though all are firing properly. I checked all the compressions while the plugs were out and all cylinders were within 5 psi of each other.
While running the engine in my garage yesterday, the shaking didn't seem so bad, just the occasional twitch. The car is perfectly driveable, it just doesn't seem quite as smooth as it should be. I wonder if the improvement might be since I set the AFM to the recommended voltage output. I'm going to try advancing the spark by 3 degrees as the camshaft supplier suggests. I already have a K&N cone type air filter. Paul is right about the hydraulic lifters. If my car has been stood for a week or more, it sounds terrible on first starting before the lifters pump up. |
| Mike Howlett |
| If adjusting the mixture has improved it ,it 'could' be sucking air somewhere efecting the mixture
You could try checking the tightness of the inlet manifold securing bolts These engines are well known for sucking in inlet gaskets If you get a piece of hose, with one end to your ear and with the other end ,slowly work along and have a good listen for a sucking noise along the top and underneath each gasket where the manifold meets the heads or, if you have a p/pack of carby cleaner give it a squirt along the gasket area with it idling and see if the idle changes |
| William Revit |
| A problem with the manifold to head joint is often caused by head skimming and decking. If there was a significant air leak between the inlet manifold and the heads, it's likely there would also be a coolant leak, visible, hopefully, on the valley gasket. Although sealing compound should be used at each end of the manifold to seal the waterways, it happens, especially with the tinplate gaskets. Water leaks under the valley gasket finish up in the sump!!!
But to me it sounds like an ignition or injection issue. But you go through everything many times and then find a partially parted wire or similar hiding!! |
| Allan Reeling |
| Also--because of their age etc. A bottle of injector cleaner in the tank mightn't be a bad idea Wait till the tank level is right down so you get a nice strong brew, tip it in and let it idle for 10 mins or so then turn off and let it sit for 1/2 hour to soak then go for a little putter round town, this varies the load a bit and helps clean them out --then go get some fuel before you run out |
| William Revit |
This thread was discussed between 05/08/2018 and 17/08/2018
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