Hesitation Whilst Accelerating.

[GT3.My]

Hi, first post on this board, am hoping I'll receive some input on my problem. Thanks in advance!

Some background- I recently sent my Mk1 GT3 touring into the workshop (the local, Malaysian (KL) OPC) for a little mid life upgrade- (the ones relevant to this problem are:) had a lightweight flywheel w/RSR pressure plate, a shortened final drive and, a GruppeM intake installed, the former two purchased from Carnewal.

After I got the car back, I've noticed that the engine seems to hesitate a little around the 4k RPM mark, just a little dip in acceleration but, enough to cause a little jerk. It happens regardless if I'm on full throttle or part throttle but, does seem to be worse when I'm in either 5th or 6th full throttling from a low (around 2.5k) RPM, whereby it seems to hesitate twice on the way to the redline. If revs are kept above 5k, the engine responds without any problem.

After doing some research on the various forums, it would seem that this could be a potential cam position sensor (hall sensor?) problem and, in some cases, seems to clear itself up through some hard driving (which I have tried to do but with no avail).

Questions are: will a faulty sensor show up on diagnostics? Or could my symptoms be caused by the mods or combination thereof?

Also, the car has been sat around the workshop for the last 3 months and hence I'm quite hesitant to put it back in IF there is a chance it'll clear itself up. I miss having the car at my disposal!

Thanks!

[david thomas]

Hi, first post on this board, am hoping I'll receive some input on my problem. Thanks in advance!

Some background- I recently sent my Mk1 GT3 touring into the workshop (the local, Malaysian (KL) OPC) for a little mid life upgrade- (the ones relevant to this problem are:) had a lightweight flywheel w/RSR pressure plate, a shortened final drive and, a GruppeM intake installed, the former two purchased from Carnewal.

After I got the car back, I've noticed that the engine seems to hesitate a little around the 4k RPM mark, just a little dip in acceleration but, enough to cause a little jerk. It happens regardless if I'm on full throttle or part throttle but, does seem to be worse when I'm in either 5th or 6th full throttling from a low (around 2.5k) RPM, whereby it seems to hesitate twice on the way to the redline. If revs are kept above 5k, the engine responds without any problem.

After doing some research on the various forums, it would seem that this could be a potential cam position sensor (hall sensor?) problem and, in some cases, seems to clear itself up through some hard driving (which I have tried to do but with no avail).

Questions are: will a faulty sensor show up on diagnostics? Or could my symptoms be caused by the mods or combination thereof?

Also, the car has been sat around the workshop for the last 3 months and hence I'm quite hesitant to put it back in IF there is a chance it'll clear itself up. I miss having the car at my disposal!

Thanks!

[david thomas]

Hi, first post on this board, am hoping I'll receive some input on my problem. Thanks in advance!

Some background- I recently sent my Mk1 GT3 touring into the workshop (the local, Malaysian (KL) OPC) for a little mid life upgrade- (the ones relevant to this problem are:) had a lightweight flywheel w/RSR pressure plate, a shortened final drive and, a GruppeM intake installed, the former two purchased from Carnewal.

After I got the car back, I've noticed that the engine seems to hesitate a little around the 4k RPM mark, just a little dip in acceleration but, enough to cause a little jerk. It happens regardless if I'm on full throttle or part throttle but, does seem to be worse when I'm in either 5th or 6th full throttling from a low (around 2.5k) RPM, whereby it seems to hesitate twice on the way to the redline. If revs are kept above 5k, the engine responds without any problem.

After doing some research on the various forums, it would seem that this could be a potential cam position sensor (hall sensor?) problem and, in some cases, seems to clear itself up through some hard driving (which I have tried to do but with no avail).

Questions are: will a faulty sensor show up on diagnostics? Or could my symptoms be caused by the mods or combination thereof?

Also, the car has been sat around the workshop for the last 3 months and hence I'm quite hesitant to put it back in IF there is a chance it'll clear itself up. I miss having the car at my disposal!

Thanks!

Hi, I own a mark1 GT3. I have encountered a problem just like yours. My problem was solved when I changed the ignition coils, 2 of the coils had rusted away around the laminated metal part causing an intermittent missfire. The coils and leads on these cars are open to the elements and I beleive this is a common problem. Also it is easy to break the plugs when changing them if you do not use the correct socket.

Regards Dave

Edited October 14, 2007 by david thomas

[clord]

GT3.My..... I think that you are getting few responses to your problem, here, because it could be so many different things that might be the cause. As you know, we did not get the Mk I GT3 in the US. Do you have any ECU codes logged? My guess would be to start with the aftermarket intake system. Assure there are no vaccuum leaks after the MAF, first. Then assure the new intake resonance characteristics work with the factory resonance flap timing (run by the ECU). As mentioned above, check the intake cam timing adjuster and position/hall sensors. It would be interesting to watch the air/fuel ratios when your hesitations happen. Please let us know what you find!

[GT3.My]

Thanks all for the replies.

Took the car out again this evening and the hesitation's still there. It's quite annoying but does encourage one to keep the revs above 5k all the time!

David, the plugs were changed by the OPC as part of the major service I requested they undertake when the car was in there, hence I would be appalled if they did not notice any rusted ignition coils! Still, I will bring it up with them when I put the car in, again, on Tuesday.

Clord, I would hope that the reasonance characteristics of the GruppeM work with the factory's flap timing, as the intake was developed specifically for the MK1 and mine's completely stock ECU-wise. Still, even if it doesn't, it looks **** good in the very sparten GT3 engine bay and I would hesitate to remove it!

Alright, so the current checklist of potentional problems reads:

1. Cam sensors/Hall sensors;

2. Ignition coils, and;

3. Vacuum leak after MAF.

If anyone has had any similar experiences please feel free to add to the list.

I will keep everyone appraised of any additional information I have after Tuesday.

EDIT: Thing is, will the above faults/problems show up as faults in the Porsche diagnostics tool? Or will it be a down and dirty process of elimination? Have a tight schedule this week and would like to be prepared.

Edited October 14, 2007 by GT3.My

[1999Porsche911]

Get yourself a good scanner so you are not bllind. You sensors will most likely tell you what is going on.