Courtshark

I've been searching for about an hour now on this topic and there's about 1000 different variations on this common theme. I can't find what I consider to be a duplicate of my issue, though, so here goes:

87 S4 (see mod list below, all done by previous owner; I've had the car for all of 3 days)
Starts up, usually, no problem. Once started, engine idles fine for about 5 minutes, then dies. The shut-off is sudden, like someone cut the ignition. This is after the car just sits there; no load being put on it. Once it shuts down, it won't refire right away, but will eventually refire. Of course, this AM, it won't fire even when cold. Possible old gas, but did put in a few gallons of good new gas yesterday. Possible throttle cable problems, as when I purchased it the cable was sticking. Lubed the cable and seems to work OK, but perhaps is loose? All thoughts and advice are greatly appreciated. My brother/mechanic thinks it's a fuel pump relay, as he had a similar problem on his 83 944 from "back in the day." THANKS!

Bill Ball

Yes, it's always a good bet it's a relay until proven otherwise. You might just verify you have spark while cranking when it is hard to start (inductive timing light on one of the plug wires).

You can swap another "53" relay for the FP relay as a quick test or just jumper the panel connector pins 87 to 30. The "53" swap works for cars with LH fuel injection, like yours, but earlier cars have unique FP relays.

Loose cable wouldn't cause this problem. However, it should be snug with tiny slack in both halves of the cable. There is an adjustment at the firewall for the first half and at the quadrant for the second half. Don't make it so snug you can no longer hear the idle switch click - it's very faint, but with the motor off, moving the throttle just off the idle stop a few degrees, you should hear a click. If not, the cable may be too tight. A loose cable prevents wide open throttle. A tight cable will cause the car to idle poorly.

Yes, there can be a number of things that will cause your problem, but start with the FP relay and then get back for more if needed.

AO

Read Fabric's hard-start diagnostics writeup. It might help...
http://members.rennlist.com/fabric/i...eshooting.html

Shark_gts

There is a lead coming off the positive terminal of the battery. Check that connection is clean and secure.

Jim bailey - 928 International

Plug the LH brain from your other S-4 into this car.

fabric

I was going to say, I'm not sure where I have this on my idle/starting issue troubleshooting page, but that might be the most productive first step when you have an oddly intermittent issue like this. The LH can fail in unpredictable and previously un-encountered ways.

Bill Ball

Now, you guys are getting nasty right away. Jim, what happened with "relay, relay, relay?" He hasn't even jumped one yet!

fabric

Perhaps. But it sounds like the car runs fine at times, and it just seems like when it's truly intermittent, it ends up being the LH. I know I chased a lot of things that I didn't really need to by doing the LH last. And if he has another S4, it's easy.

Bill Ball

Yeah, OK. I just thought we should ease him into this. Also, as it is intermittent, the LH swap is not going to be a slam dunk diagnosis either.

worf928

Is the '87 and auto or a 5-speed?

Courtshark

Thanks for being gentle. It is my first time.

5 spd. 88 is an auto.

This AM: Car fired up, ran for five seconds, then died. Then refired right away and drove around with no problems, didn't stall. Just picked up tags for it yesterday, and I'll be able to try some of these diagnoses this weekend. The two cars are currently in seperate locations, but the Frankenstein swap begins bright and early tomorrow... and I am installing the headers on my car. The sound is just too sweet.

Which reminds me... can the Devek Level II headers install the same on an auto as they do on a 5 spd? They're coming off the 87 5 spd and hopefully going onto my 88 auto.

fabric

Good point. Well, hopefully my troubleshooting page is helpful, I think it covers just about everything.