Rough idle after start when cold. Help????

Only if you pass test #2 (can you be 100% sure that the protection relay is bad).

 

Glad to lend a hand Ron -- hopefully, we've saved a skilled F mechanic from having to replace your protection relay AND undo a bunch of needless mechanical fuel injection tweaks done by an unskilled mechanic in a fruitless quest to "fix" the problem

The "old" Stribel number for that relay is 92861512400, but I believe that it's been superceeded to 92861512402. Both AFP and RA have it at a non-crazy price, but the best price I found online was from Pelican Parts ($91) -- or you might try another Porsche source if you have one more local to you.

 

Steve, you are the best! Way to help out Ron. Great great job there.

 

I can confirm the part number is 92861512402. My car, also an 88, needed one. It should be about $90 from a Porsche supplier or $140 for the same part from a Ferrari supplier.

It made a night and day difference to how the car ran. Thanks to Brett from Gran Turismo (a.k.a. brettski here) who diagnosed it for me. He checked my car by replacing the relay with one he had from a Testarossa, which uses the same part.

 

Hey Steve,

You are great, thanks from all of us and good luck Ron, I hope car runs perfect soon.

Lino

 

Glad that you've got it sorted and working well Ron.

I'd agree with you that usually a relay (switch) problem is a yes-no kind of thing, and it either works, or it doesn't. One exception could be if the relay contacts still make a connection, but a poor connection with a fairly high resistance -- so, for example, instead of 12~14V reaching the injection ECU, maybe only 7~8V reaches the injection ECU, and it sort of works weirdly/poorly rather than being totally dead. Don't know if that's what really what happened, or even if that's what would happen, but just use it as a possible example. If things are working well, just enjoy where you are now and don't worry about where you were!

 

I am having this issue right now. I started my car last week and I noticed some slight hesitation at low RPM. I drove the car and it felt down on power but was running okay. The next day I went out to start the car and it was running very poorly. I noticed that the car no longer went through the typical warm up cycle either. It went right to a rough 1k RPM idle. It I give it gas, it stalls, or nearly stalls.

 

I'll add that prior to it running poorly it was idling high at about 1400-1600 RPM.

 

My car seems to fire easily but it is hard to keep running at first without feathering the throttle. If I give it too much throttle at first it stalls. Also, the WUR doesn't appear to be working now.

 

Steve,
I also have an 88.5 3.2 and had experienced all the similar issues described. I pulled the right rear trunk cover and pulled up plate to access the notorious relay, performed your bridge wire test, engine went back back to firing right up and no cold start coughing any longer! Yay!!!
Thanks so much for your input a couple of decades ago and thank the stars (admins) for keeping this thread alive!

 

Glad that you found it useful, and got the problem sorted Ralph. It's kind of a shame that Bosch didn't put a little red indicator LED on the injection ECU itself to confirm when it has +12V power coming from the Protection Relay. We've had way too many cases of the Protection Relay failing and an (unknowledgeable) Mechanic (wrongly) turning every adjustment screw in the CIS system trying to "fix" the problem. Every F Owner with a K-Jet with Lambda model should "calibrate" themself by touching the frequency valve when the engine is running to learn how it vibrates/buzzes when it is working correctly (so they can know when it isn't working correctly). You don't even need to be skilled Mechanic or DIYer -- and you can do it while dressed in a tuxedo and not get dirty .

 

Congratulations on getting things solved! Make sure your antenna rubber seal is good, you can get water leaking down there into the electrical items. Maybe tighten up the nut from underneath and make sure it is snug.

 

I'm going to add my thank to Steve and all those who keep this thread and forum going. My car has been running poorly for a while, but it has hardly been driven while getting a rebuilt steering rack installed. I know there are problems with the injectors as well, so...

I did decide to go check the frequency valve after looking through this thread, and found that it wasn't buzzing. I went to go see if jiggling the relay would help, and darn it, it wasn't there! A bot of fishing around found it way down in a crevice where it had fallen out. I plugged it back in, and the idle instantly smoothed out. Took it for a drive, and it didn't stall when cold. Yay!

Thanks again!