MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - stutter at 2k (not strickly MG related)

Hey guys, my first post on here

Firstly the car is a Lotus Elise not an MGF but it shares the engine with you guys. It's 1999 S1 111s(VVC) with Janspeed Zaust, 160T throttle body and Piper cross filter. Battery is new as are plugs (elise part platinum) and leads (standard - magnecors gave me problems), and the car is driven daily.

Now here are the strange things I am finding;

The problem is I seem to have a real engine stutter at around 2k revs. The engine feels like it dies then comes back (milliseconds we are talking here), I can drive through it but it's annoying in stop start traffic. Any ideas? (is there for example a handover process in the ECU at this point?) - it's seems to be temp dependent

And finally and this may be related to previous problem, occasionally (even when the car has been driven for some time e.g. it's up to temp), when I accelerate the rev limit seems to be at 6k not the full 7k+ now something I've noticed is that the stack temp is under registering (I've replaced the brown sender unit for the EUC, and just need to replace the blue one which is sitting in the boot), is it possible that in fact both temp senders are not so great and that this could be causing the mixture to be out (problem 2), and the rev limit to be reduced (problem 3 - I know that the Honda engines will not let you rev all the way until up to temperature). I do not know whether this would happen when the engine is not warmed up for the VVC engine as I always warm it up, I guess I could try it once to find out?

Just for the record, at Xmas I had a problem where the cam belt slipped one tooth which cause the car not to start - but this was fixed.

Any ideas to these problems would be greatly appreciated.

Thanks

Ash

Azure Blue S1 111s
Herts.
A M Molyneux

The temp sensor would give you all these problems, but you say you've replaced the brown sensor?

I would take apart and clean (use spray contact cleaner) all the contacts from the ECU to the brown sensor, then I'd start looking for ground problems (thin black wires from the ECU to the engine block)
Will Munns

Oh and BTW there is a Lotus side to this BBS, links are below.
Will Munns

Thanks Will, I've been a member of the Lotus BBS for years now (Esprit, Elan and Elise etc), I just thought that there are a few more VVC engines on this board then the Lotus one!

thanks for the advice, I'll give it a try and see what happens!

Ash
A M Molyneux

>>> the rev limit seems to be at 6k not the full 7k+ <<<
Doesn't this sound familiar? I've read somewhere, not that long ago, that the VVC unit would drop it's rev limit in a particular situation. Anyone with a better memory ;o) ?
Erik

>>the VVC unit would drop it's rev limit in a particular situation

There is a fail-safe mode that the ECU will drop into if it thinks something is wrong - like some strange sensor readings. This will limit revs.

Also, the VVC solenoids can stick. I had this once and my VVC sounded like a Elise Sports 160 - a 'heartbeat' type booming through the exhaust at idle. This was because the solenoids had stuck at a cam profile that was fine for high revs but not for low. Whether the reverse i.e. sticking at the low rev profile could cause the 6K limit problem I don't know.
Dave Livingstone

When were the ignition HT leads last changed Ash?
Rob Bell

Ash, what caused the cam belt to jump and how was it put right??
mike

Hi Rob/Mike et al.

The leads were changed in March for standard leads (which are def long enough to push snuggly on to the new platinum tipped plugs), the previous Magnecor gave me real problems with mis fires.

The Cam belt, well that was a strange one. During xmas/new year I was not using my car, and as it was so dirty I did not put the cover on so as not to sratch the body - may be unrelated but I'm not so sure.
after New year I went to start the car, and it started but ran like a dog, even after letting it run for a while it was not having any of it. I tried the next day and this time it would not start at all. after flattening the battery I finally had it towed to a Lotus specialist, who discovered the belt had slipped on tooth. The belt had been changed less than 5k ago, and looked perfect. So as a precaution I had both belts replaced, and all was fine. So it could have been ice that caused the slip or something else of course?

Ash
Ash

Its not THE most helpful thing in the world Ash, but I had this a lot when I first got my VVC.
Many visits to the garage and "non-warranty" replacment of the HT leads, Spark plugs, Ignition Coil etc..
Plus a load of garage arguing, inspections and greif never really turned up the problem.
40,000 miles came and I took the car to a Ford garage.
They replaced the Cam Belt, and being a friendly guy that you'd chat with in the pub, he said he clean and polish everything for a beer or two.

Never had the problem since.

The only real help you'll get from this is that it wasnt the sparks, HT or Coil.
And they're are all expensive on the VVC.

If I'd just gone for a good garage and service, then I'd be driving home tonight with a Mike Satur Slick Shift!

Neil H

That whole 'cam slip' thing sounds very odd Ash. As Mike will tell you, there have been problems with the bolts retaining the VVC cam pulley in position. I think that you need to seek some expert advice here.

In view of Neil's experience and the history of cam timing problems, the cam timing could very well be suspect - it doesn't need to be far off to seriously harm performance/running. A rolling road will quickly identify the problem - but I wouldn't recommend it here until an engineer can inspect your engine.
Rob Bell

thanks Guys.

I'll dig out the manual tonight and see what could be suspect. I am going to be having it serviced soon, so I'll make sure it goes to a garage with the correct engine management test gear as well so they can interogate to see if there are any clues there. I have heard about others snapping the VVC mech bolts before so it's worth a look as well.

With regard to timing, and I admit I am being lazy now (will check the manual later for this as well), how much manual intervention can one make?

cheers

Ash
A Molyneux

Ash try changing the oil temp sensor on the VVC hydraulic controller AND make sure all the engine sensor connections are secure.
Belt slip is not usual unless the tension was way off or you have tried 'bump starting' the car causing the belt to jump.
Try having it put on 'test book' diagnostics. You are not close to Yorkshire;-) so try B&G in Baldock.
Mike.
mike

Thanks for the advice Mike, I'll give the temp sensor a try. As for bump starting, I can say that this was not the case! but it's worth bearing in mind for future reference (Can't bump start the car at the moment as the cat is back on anyway!)

excuse my ignorance but who is B&G?

thanks

Ash
A Molyneux

Ash , B&G = Brown & Gammons, see advertisers.
Mike (Mersea Office)

This thread was discussed between 21/10/2004 and 25/10/2004

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.