AO

You can test them inside the cab at the IMR. See my earlier post (#33) for pinouts.

Bill Ball

No, you made yourself clear. I did not make myself clear. I knew this might be confusing, but what I am saying is loss of 4 cylinders, whether due to an ignition failure or the IMR cutting off fuel for whatever reason, is loss of 4 cylinders. So, I'm saying that when the IMR tripped in my car, I knew something was not right but I did not initially appreciate what might be happening, say, if I didn't have the IMR. Had it been an ignition failure in one coil, with no IMR, the symptoms would have been the same and by driving on I would have had a great potential for a cat fire. So, this is the problem - the first time, where it takes a while to get the picture, may be your last. You and I have experienced what 4 cylinders feels like enough to STOP if the IMR system were disabled. Mine is currently disabled and has been for 3 years. I don't recommend it, but as my car runs perfectly, I'm comfortable that it's a defect in the system that I haven't had a chance to isolate.

VehiGAZ

Perfect. Thanks Andrew! I'll check them all when its working, and then hopefully I'll be able to check these when it does into 4-cyl mode.

VehiGAZ

Ok Bill - I get what you were saying. Yes, I agree, once you experience 4-cyl mode, you will not forget it. I am assuming that all of my incidents of this were due to the IMR putting me into 4-cyl mode, not the coils.

I don't want to do another 1+ hour miserable, anemic trip like I did on the way home from LRP Saturday, so I'll order a bypass relay one way or another. I would of course like to sort out why it is tripping, though. If I could get my hands on a used ignition monitoring relay, even just for temporary testing purposes, that would be very helpful - I could isolate it from the sensors as a possible cause if I were to go 4-cyl with a different IMR.

So Stan, where do you stand with your problem? Still "up in the air" on whether it's fixed or not?

VehiGAZ

And why is it that so many GTs are having 4-cylinder mode problems all at the same time?! Sun-spots? Solar wind? Gamma rays from Planet X?!

Stan.Shaw@Excell.Net

I made my first drive since changing the O2 sensor and the car ran almost well. It is running a bit rough at idle, nothing like it was, almost like I have an old American muscle car (especially since I installed an RMB too lol )

I will review again with the MAF disconnected to see if it goes away, but will probably get through this tank of gas before putting too much effort into it.

I hadn't re-checked the vacuum system, so that may be next on the list. Make sure one of those MR elbows isn't causing this problem...

Any thoughts on whether changing the EGTs as preventative maintenance is a good idea?

VehiGAZ

They are $277.65 each from 928 Specialists. Unless you know that one of them is the cause of the problem, then no.

Good luck!

AO

THat's progress. Your plugs could have become slightly fouled from the previous BS. I would reset the LH, and then give it an italian tune-up.

Stan.Shaw@Excell.Net

Well the battery discharged, I guess I had flashing lights in my garage for a while, from the alarm, so I think the LH reset happened anyways.

I will take a few more short drives (to make me convinced it won't fail again), and then perhaps a long drive up north for exercise (the trip for the car, hiking for me).

Stan.Shaw@Excell.Net

A data point, doing many projects, decided to check cam timing, found the DS cam +5' and the PS cam +4', so out of sync by 1', and quite a bit of advance based on what I have read. Not sure whether this is likely to be part of the problems described.

H2

How's your engine temp with the cam timing off this much?

H2

Stan.Shaw@Excell.Net

Temp was relatively high, but as the radiator had a leak, was "repaired", then developed another leak in the same area, the high temp could be due to other issues.

Another data point is that during the radiator repair, quite a bit of gasket residue and gasket sealand residue was found. The radiator shop said this would have definitely caused the cooling ability of the radiator to be decreased.

So too many variables to say how much the cam timing related to high temperature issues.

worf928

If you'd written 3° on both sides I would say - no, that's not going to cause noticeable rough running problem all by itself. On the other hand, if you'd written 9°, then I'd write - yeah, that's gonna be a bit rough-ish. On an S4 I'd say 4-5° isn't going to cause rough running. On a GT.... I dunno, never had one that far out.

I'd still bet the problem is sensor related. Did you ever get something hooked up to it to get codes out of the ECUs?

Stan.Shaw@Excell.Net

No, the diganostic tool has been out and about for almost a year now, and of course like all cars I own my GT has been apart for a while now.

At least while doing the OPG &MM, I looked up and now know where the EGTs are.

Stan.Shaw@Excell.Net

So, I had some of this problem resolved last winter. A smoke test found a bad hose under the intake. Ironic that I had a refresh done, all the hoses were replaced except for one of the larger ones, a $20 hose that cost me an extra $500 in labor

But the idle and falling into some type of 4 cylinder mode still persists, more frequently recently. With the bypass relay in, it still happened and the Porsche Hammer indicting an ignition problem. (I will recheck and get the code).

So, I swapped ignition modules (ones in front of radiator) and coil wires and put the regular relay back in place. The same light comes on (green), presumably eliminating those parts as the problem. I decided to replace coils (as they are likely 20 years old), as well as dist caps and rotors.

I also still need to clean the 14 pin connector, but I am guessing a one side ignition failure would not show up there.