[Bandini]

I have seen some odd engine problems during or after track days. There seems to be a pattern where the car runs perfect during sessions, but after cooling down the gremlins appear. Last time when I started it for the third session it would only run on three cylinders. I switched the spark plugs and tried several times without luck. Now, after months of winter storage, we checked it again. Compression good, spark good, fuel injection good - engine runs perfectly.

Other times the car has run perfect all day on track, but then as I drive home in legal speed it just shuts down. It starts again normally, goes for a while and then shuts down again.

Now my mechanic has a hunch that it could be the engine software acting funny, perhaps due to overheating. What do you think? I have a ProMAX chip. If I recall correctly it's the mild ROW version. I guess the obvious thing would be to put the stock chip back in before the next track day, but A I remeber it was a hassle reaching the chip and B I quite like the higher rev limit on track. Also, there isn't always a problem, so one problem free track day wouldn't really be answer enough.

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[flash]

while typically chips don't fail, what some of them can do is cause a lean condition, which can confuse the DME, forcing it into limp mode

this is not the first time i've heard of something like this happening with that chip, but i don't think i've heard of it happening overseas

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[94SilverCab]

Doesn't sound like a chip problem. Maybe injectors?

I'm sure smarter people than me will chime in.

Jay

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[DaveN]

Ahh I harken back to the days of yesteryear when my 944 did the exact same thing. Only took me 4 months to find and fix the cold solder joint in the DME. But, I have never heard of this in a 968 - yet?
Maybe just a chip working it's way loose and heat expansion is what keeps the contact. One could try to GENTLY press on any socketed chip and make sure they are seated properly. Also, make sure the retainer is on the EPROM, it's there for this very reason.

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[Bandini]

Sounds good. I was told I probably had a failed head gasket, and believed it all winter. Now I'm hopeful it's something I can actually fix myself. I don't know what it looked like, but I remember it was rather cramped around the chip. It wouldn't really surprise me if I broke something in there. I'll try to check. Any other easy fixes I could try? Like e g replacing the fuel pump relay?

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[jfrahm]

The DME relay should be replaced if it is not the 993 part number, and maybe even if it is. These commonly fail and while some have resoldered them and had them work again it is better to get the newer part in there.

-Joel.

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[Bandini]

At last - problem solved!

Turned out it was as simple as a bad plug wire. I got a new set of 8mm wires from RS Barn, and replaced the rotor, cap, plugs and DME relay while I was at it. Total cost - a lot less than I expected a few months ago.

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[Anchorman]

Once again, a demonstration of Occam's Razor.

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[MC968CS]

Interesting....wires on my car also gave me issues at a track day earlier this year. Glad you found it.

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[Cloud9...68]

I should have chimed in on this earlier, because I also had a stumbling problem with my car that got worse as it got hotter, and it also turned out to be the plug wires. I had aftermarket wires, so I blamed it on these particular wires, but like with so many things on a 16 - 19 year-old car, time and heat will wreak havoc on rubber and plastic items.

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