TQ: Loss of Power

[PaulHere]

Can anyone help Derek with power loss problem.

Car loses power between gear changes when car is warmed up, there is a smell of unburnt fuel car and will not rev.
Do you think it might be the exhaust warm up regulator?

I will recommend to Derek to check the earth lead, fuel tank breathing hose, and to remove and replace ignition module and corroded fusebox.

 

[924nutter]

I have to say Paul I have not heard of this one re losing power between gear changes. It is a bit ambiguous. Is the inabitly to rev only apparent during the change or does it refuse to rev generally?
An air leak would cause this as contrary to what you might think. It may be that when the engine rocks during the torque reversal a small leak may make the mixture go too lean to ignite, and because there will not be the correct airflow though the metering unit to lift the plate and meter the correct amount of fuel it will pass through the system unburnt.

I did of course have a similar problem with mine in that it would sruggle to start and when it did it would not rev, and this turned out to be a faulty igniton module. Very difficult to check and you have to use the sherlock holmes method, which as we all know is when you have illiminated the impossible, what ever remains is the truth however improbable. The module will even be seen to be generating a spark so you assume all is well and look somewhere else, but the module can lose its "timebase" for want of a better phrase and generate the spark at the wrong time. I had two ocurrances over the course of 247,000 miles and both times it was the module.

You can always get him to post exact details on the forum or he can email me directly at r19@porscheclubgb.com
I will be happy to give as much help and advice as I can

 

[924nutter]

Having though about it some more and then some, it could be that the cam belt has jumped a tooth. The normally aspirated 924 engine is a so called safe engine because with the flat head configuration; combustion chamber and cut outs in the pistion, the valves wont strike the piston and I know from experimentation in trying to get my skimmed and otherwise modified head exactly right (lower deck height means shorter run of belt to the pulleys) there is aconsiderable amount of lattitude within which the engine will continue to run. The could be especially significant if the power loss occured during a gear change after the engine was taken up to maximum rpm. BTW the car will accelerate much better if the change is at about 5900 IIRC as the unmodified engine struggles to rev beyond 6k especially in fourth.

 

[PaulHere]

Thanks John, I have passed on your comments to Derek in Gibraltar.

 

[PaulHere]

Derek has just called me to say that he has found the cause of the problem.
It was a build up of oil in three of the spark plug recesses. They have been cleaned up and the car runs fine now.

Derek told me that he thinks that the oil seeped through the threads of the plugs, I thought that was a little unlikely as there would have to be a lot of oil in the combustion chambers, more likely the oil was coming from outside somewhere and running down to the plugs.

 

[924nutter]

Well that's a new one on me Paul for sure. I am sure we are all pleased that Derek has got to the bottom of it. I think though that his assumptiion of oil seepage up (UP?) the plug threads might be erroneous, and your theory is more likely. Leaks from the cam cover gasket, distributor shaft or oily residue drips into the plug recesses from the inlet ducting being possible areas to investigate.