GC96

I have spent the last few months trying to solve a high idle/ hunting idle on my '96 C4 that is driving me nuts. I have replaced the ISV, plugs, wires, rotors and caps, and all the rubber vacuum fittings. With the advice from Steve Weiner at Rennsport Systems who was very patient and helpful to me as I tried to diagnose this problem, I also cleaned the throttle body, MAF and had a smoke test to see if there are any vacuum leaks (none found). I checked the CHT sensor and it was within spec as well. While checking the wiring harness to the DME I noticed that the case showed signs of having been opened before. So I opened the case and found that at some time the DME had been chipped using a daughterboard and an EPROM. All this points to my problem being a software issue rather than any problem with any engine component. The DME and new chip have no labels on them indicating what company did the work and I have no way of getting hold of the previous owner. It seems my only recourse will be get a new DME. Before I shell out the money I wanted to see if anyone in the Seattle area would be willing to let me borrow their DME to try and confirm that the issue is a software issue. I think I would need to borrow a '97 DME without the immobilizer for this test. If anyone is willing to do this I would really appreciate it. Thanks in advance.

GC

Stealth 993

Doubt you have a chip, since your car is a 96. The immobilizer was standard on all 96+ cars. You realize the DME is a PITA to remove the first time?

Have you checked the flywheel & FW sensor?

GC96

I have not checked the flywheel and FW sensor, can it be done without having to remove the engine or transmission? Once I opened the DME I took pictures of it and sent it to Steve Weiner and he confirmed that it had been chipped and he also concurred that I probably have a software issue.

GC

Stealth 993

Oh, if he said it was chipped, it mostly likely is the case. You might have a better chance of seeing who has a stock chip to put back in.

It's going to be very hard to find a spare DME, you might have to just buy a used one on eBay.

Steve Weiner-Rennsport Systems

The crank position and reference sensors can be accessed without removing the engine. You'll find them together installed into an alloy mounting block above the cylinder head temp sensor over the flywheel.

Their electrical connections are in the engine compartment on the left side of the engine in that vertical stack of 3 connectors.

Steve Weiner-Rennsport Systems

You cannot "put a stock chip back in" on the '96-'98 cars. The EPROM must be removed and re-programmed with a stock file.

Stealth 993

That sucks!

Can he send his ECu for you to reprogram? The stock chip is not a flash-rom(?), so you remove the stock chip solder in a flashable rom & reprogram?