Welcome to our resource for MG Car Information.



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 - Cam and crank signal not synchronised

Any ideas....

My 96 VVC is at the dealers (ex Rover MG) following a HGF. It now has a new ported head from Mike Satur fitted along with a 4-2-1 manifold and vader air filter, 52mm throttle body and fuel pump.

The head was a replacement(ported only, no valve upgrades) built up by Mike from my old one so arrived at the dealers fully tested assembled with the VVC.

The garage report that :

We have the car built up & running (after a lot of effort trying to get all the bits to connect & seal with each other). However, even though it is running, it does not seem to want to accelerate properly.
(it says its cam. signal & crank signal are not synchronised!).

They have contacted Mike and are awaiting his reply, but, if anyone else has any ideas I would gratefully pass them on.
Jon Baker

Forgot to add, PRT thermostat fiited.
Jon Baker

I guess the obvious question to ask is whether the cams are correctly timed? Has one of the cams slipped a tooth whilst the engine was being assembled?
Rob Bell

No Rob, after extensive checking & re-checking, they are sure that they have built the unit up correctly.
I have no reason to doubt their capability as they were an MGF dealer from the start and reassembled my old skimmed suceesfully head in 1999.
Jon Baker

Okay, that's fair enough - and I am sure that they will have checked, as it is the most obvious cause for the fault reported.

So assuming that the primary and secondary belts/ pulleys are correctly aligned and timed, what else can cause this problem?

This is not something that I have experience with to be honest - but I wonder whether an intermitten fault with the crank position sensor could result in a mismatched signal between the cam and crank?

It might be oscilloscope time to see what the signals from the respective sensors look like?
Rob Bell

It is quite possible that the sensors/wiring have been disturbed during the fitting of the 4-2-1 manifold and PRT (as all the hoses would have been replaced).

I know Mike had set the timing on the head before it left him, but, I don't think the head would have been tested on a running block till it got back to the dealer.

The car is 10 years old and the disturbance might be too much for some of its sensors.

It is interesting that the engine starts and idles, as I would have thought if the crank and cam sensors were out of sync the best course of action for the mems would be to stop the engine !

Its all very depressing, as I have been without my car for several months now and as you can imagine was looking forward to driving it with all the performance mods.
Jon Baker

At least on the older VVCs it is possible to fit the VVC solenoid contacts on the wrong solenoid....
Engine runs,but very lumpy and reluctant at load.

That would a convenient answer Carl !
Jon Baker

You're right Carl - I've read this being quite a common problem elsewhere - and certainly worth a go :o)
Rob Bell

Another thing,if the TB is from a Vauxhall (Opel/GM)the 3 spade connector going to the throttle-pot needs to be shifted.
Number 1 and 3 (the 2 outer ) has to change position .A needle does the trick to release them from the plastic.
But I assume you have a "standard" 52mm,and these should be a simple "bolt on".
Otherwise the symptom when driving is the same as described in prev. posting !
For more info on the GM TB see Dieters site.

Its the standard 52mm Carl.

Thanks for your help Rob and Carl, I have emailed the service manager and I'll hopefully be back with some positive news tomorrow.

Jon Baker

Jon, I have spoke to the service manager and have offered a few suggestions (electrical).

Thanks Mike, they are currently checking crank sensor etc.

Will post any news when I get it.

Jon Baker

It is prob your Crank Position Sensor right enough. I ahve some major accelerating issue just now and after clearing some codes on me ECU, the onlyone which pops up again is the crank position sensor.

As you said, it starts and runs fine and gets up to speed eventually but it has no kick at all and sometimes it just will not accelerate.

I am currently trying to find out more about the sensor (see my other post on this)
I Brown

Its worse than that Ian, starting and idling are no problem.
When you accelerate apparently you get thrown against the windscreen and the mems reports cam and crank signal not syncronised (the only error code), idle then becomes erratic until you restart the engine.
The garage have replaced both sensors (cam and crank)to no avail.
I have asked then to try disconnecting the cam sensor during the idle after restart to get the mems to lock the VVC off, which is what it does if it detects a cam sensor fault, this may result in normal acceleration if the VVC is to blame.
It seems to boil down to whether the cam and crank are really going out of sync or the mems is falsely believing they are.
Jon Baker

Burgers - so it isn't a simple case of the two sensors being plugged into the wrong connectors then Jon? :o(
Rob Bell

No Rob, I think the garage has been over everything several times. I am still waiting to hear about the cam sensor disconnect though.
Jon Baker

Well, if it aint electrical, then I guess we'll have to consider the possibility that the sensors really aren't lying, and there is a problem with the VVC cam timing?
Rob Bell

Good news at last !

Apart from a baulking if you stamp on the accelerator at 1500 rpm in a high gear my car is now runnning.
It has even passed its MOT.

Apparently changes to the stepper motor and idle air control valve settings have been effective. I will be picking it up on Friday so will find out more then.

Lesson from all this is to take it to the specialists for major tuning mods even if it has to go via a trailer.

Jon Baker

"Apparently changes to the stepper motor and idle air control valve settings have been effective"
Thats strange as they told me they had checked the syncronisation between them.
Result anyway..good luck for tommorow jon.

i dont think dealer teeling u truth the most likely cause of this problem is a stuck advance retard mech on the vvc housing a small bit of swarf will enable this to stick. this problem only ocurs with the engine running when u try to accelerate it over advances the valve timing it is easily checked using the live readings on test book. iam an ex mgf technicain and came across this problem on more than one occasion
john tech

John, the dealer was unlikely to have touched the head as it came ready to bolt on from Mike. It seems that stepper motor and IACV do need tweaking, the dealers problem was they expected to bolt the head on and that would be it. They also struggled with the 4-2-1 manifold. So, as I said before it would have been better to have gone to the trouble of getting the car down to Mike.

Anyway the car is back home now and I have to say the smile is back on my face. It drives noticeably smoother when out of the trawl through town and the power is akin to another layer of meat on your sandwich, the basic character is the same but there is more depth and flavour and noise !

The wife took it for a quick spin and she was so impressed she is stealing it to take her sister shopping to Carlisle tomorrow.

The cam crank timing fault was not a testbook logged fault but was shown on the live readings on the test book as cam sync going out of range.

Both cam and crank sensors were replaced and this had no effect, however the new crank sensor was left in as the old one looked suspect.

The cure for the failure to respond to all but the smoothest throttle was :

"setup throttle body including stepper position, closed throttle setting. Roadtest shows car runs ok but with occasional hesitation at 1500 rpm with high throttle demand"

This hesitation is something that you notice only when you slow right down to turn into junction and don't change down and then accelerate, rather than when you boot it at 1500 when working up through the gears. Me and the wife think it was there before but on a much more minor scale.

Jon Baker

Nice to hear that the car is running again.
FSE will probably solve the hesitation problem !
Or if you can get hold of an uprated fuel regulator as a cheap replacement. / Carl.

Thanks Carl, its been a long wait !

The FSE is a good idea - I do have a pre MEMS 3 mgf with the larger injectors.

I think I'll book into Mike for its next service and see what he thinks.

I don't know why the cam timing was showing as a problem on the testbook unless it was a reaction of the cams when severe hesitation occurred. In which case it was a red herring and an example of relying too much on the computer to solve the problem.
Jon Baker

Might be worth getting the car on a rolling road Jon - and perform some power runs with a broad band Lambda sensor in the tail pipe. That way if the fuelling via the FSE needs to be modified, you can do so to optimal effect.

Glad to hear that it is all now sorted - now is the time to get out and enjoy the car! :o)
Rob Bell

"This hesitation is something that you notice only when you slow right down to turn into junction and don't change down and then accelerate, rather than when you boot it at 1500 when working up through the gears." Mmmmm me thinks a slight change in driving habits might cure this jon ...rev it more;_))

I'll work on that Mike !
Jon Baker


I read your write up on your uprated fuel regulator experience.

Are you not tempted to try again now you have the DVA head ?
Jon Baker

Jon, no. I had the car on Dave Walker's rollers a couple of weeks ago. With the standard fuel rail pressure regulator, the fuelling was spot on all the way to peak power - so upping the fuel pressure probably would not have any particular benefit :o)

Carl has a broadband lambda in a secondary position in his exhaust, which means that with the aid of a stoichiometry display, can enable him to set up his FSE to suit real road driving conditions. Those with aftermarket ECUs are also similarly blessed :o) I haven't so can't - and the RR result is a best bet at real road conditions - and I have no reason to fiddle at the moment. :o)
Rob Bell

This thread was discussed between 05/06/2006 and 28/06/2006

MG MGF Technical index

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