Help! CIS problem - car died

plain fan · 11-21-2001, 06:32 PM

If you've read my oil cooler post, this IS NOT a problem with the oil cooler. I was getting off the interstate and slowing down on the off ramp. I was braking and had just downshifted, there is a light at the end of the ramp, the Alternator light came one, the green light came own and the damn thing died on me! I was able to get the car stopped before I rolled into the car in front of me. I turned the car off, turned the switch and it started right up, I was able to get home w/o having to stop again, but the car repeated the same problem going into the drive way. Please help, the car is idling around 800 rpm, I believe this is to low but I'm not sure. I just got it back from the shop today with the oil leaking problem fixed and now I just feel like an expensive.....please help.

john walker's workshop · 11-22-2001, 07:40 AM

i would start by getting the idle up to 1000rpm. see if the top hose to the deleleration valve, to the left of the throttle housing, has been plugged. most cars are ok with it plugged, but a few die a lot. you might have the shop recheck the CO. 3.5% at idle works well.

plain fan · 11-22-2001, 09:06 AM

Thank you for replying John. When the engine was out of the car last month for a clutch job, they said that the valve was blocked, the reason for the car idling close to or over 2K after it was warmed up. I drove the car home and nothing was wrong with it, but that was during the day when it was warmer. I'll crank the idle up to 1K today and check the hose. I'll post what I find out, thanks again.

john walker's workshop · 11-22-2001, 09:28 AM

you can adjust the decel valve so the idle won't hang up so long. loosen the jamnut and turn the threaded tube that the hose goes on. can never remember which way, but you'll find out. after each turn, rev the engine and see how slow it comes back to idle. you want a short delay, but not too long.

plain fan · 11-22-2001, 11:29 AM

Thanks for replying again John, I haven't had the opportunity to get out to the garage and adjust the idle but I will and will post asap. What do you mean by "idle hanging up?" I know the car was slowly going down to the idle speed after acceleration. Sometimes after slowing for a light and coming to a complete stop the car would still be slowly idling down, are you saying this should be shorter? Thanks again.

john walker's workshop · 11-22-2001, 12:41 PM

by idle hanging up, i mean hanging at 2000RPM like your tech said it did before he plugged the decel valve hose to disable it. i don't mean gradually dropping from 1000RPM to the point where it dies. if the decel valve is adjusted properly, you can have it in the system, and it will allow the idle speed to come down to normal in just a few seconds, instead of immediately, which often fixes the dying problem. a 1000RPM idle, correct timing, and 3.5% CO helps too.

plain fan · 11-22-2001, 01:37 PM

Thank you for continuing to offer help John. I'm starting to mess with the adjustment, but it looks like the hose is still connected to the valve, not detached and plugged. I realized that when I was driving home after picking up the car I didn't get on the interstate and have the car at high rpm, therefore the problem didn't show up. The car was in the shop originally for a valve job but the oil cooler replacement got thrown in as well. In Oklahoma no one sniffs the exhaust and the car is exempt, by age, so I don't have the air pump hooked up and running, will I need to do this? Thanks again.

plain fan · 11-22-2001, 02:21 PM

John, I started the car up and let it warm up, it only reached ~500 rpm! Then for the heck of it, I gunned the engine to see what the decel valve would do, after letting off the accelerator pedal it dropped down to almost 0 and died. Well, I tried to start the car back up and it wouldn't stay running unless I gave it a little gas to get the rpm up to 1K then it would settle down and run, otherwise the car wouldn't run.
I got the car running and started to adjust the rpm to 1K like you said, I turned the screw about a quarter both ways and the rpm didn't change. Did I not turn the screw enough? The manuals say that this could be a sign of a vacuum leak somewhere so I'm heading back out to look for a hose not attached well, or possibly a bad hose. Should I start looking at other possibilities?
Thanks again.

john walker's workshop · 07:10 AM

a quarter turn won't do much. keep turning counterclockwise until it gets to 1000 RPM. hot of course. you are turning the big screw with the spring on it, on the left side of throttle housing, aren't you? you really should go back to the mechanic and have him reset the CO, and check the ignition timing again. raising the RPM that much changes the CO. check the decel hose to see if it has vacuum. a lot of people put BBs in the hose and reinstall it.

plain fan · 07:17 AM

Thank you for all your help John, last night I looked for a loose hose or something of that sort but couldn't find anything. I did find a hose coming from the airbox, located just above the silver manifolds, the workshop manuals show that this should be plugged, but my car has a hose running from it then plugged up. I checked the decel hose and nothing is plugging them up so I assume that it was working. Well it was before I took the car in to have the valves adjusted and wound up having the engine pulled to change oil coolers. I'm taking the car back on Monday, they're closed today, and having them fix the problem, I suspect that maybe a hose is not on like it should be when they reinstalled the engine. Once again thank you for your help and your advice. I guess I'm going to get a tool that will test pressure/vacuum and learn how to test the CIS system myself. Do you use the Porsche tool(as shown in the workbook) or do you use a different tool? Thanks again.

john walker's workshop · 11-23-2001, 08:04 AM

to test for vacuum, put your finger on the hose and see if it sucks. the hose must have a clean cut end to do this.

plain fan · 11-24-2001, 07:18 AM

John, is the vacuum that strong on the lines? If I don't feel a vacuum on my finger do I assume that the part that the hose is coming from is bad? I don't know the CIS system all that well, does the factory manuals cover the flow of vacuum in the system?
Thanks.

john walker's workshop · 11-24-2001, 09:14 AM

it's certainly strong enough to feel with your finger. a wet finger seals the hose better. follow the hose to where it begins, and see if that port has vacuum. BB in the hose?

plain fan · 11-25-2001, 09:07 AM

There wasn't a BBB in the hose, it was clear, but I think I have greater problem since I can't adjust the idle speed. I can't reach some of the hoses but so far I haven't been able to find any hose that is not attached.

plain fan · 11-25-2001, 03:21 PM

John, I certainly have quite a bit of vacuum on my finger, so it seems to be drawing fine. With my finger over the hose the car would still die after the rpm was raised. I took my finger off the hose, so it was sucking air, and the rpm had to be raised to 6K before the car would die. This doesn't seem right at all, with a created vacuum leak the car almost wouldn't die. But every time I started the car it would jump up to 2k then slowly idle back down to around 1K. I was performing these tests in a garage so I would think the car got warm enough that it wouldn't need to engage the cold start circuit, could this also be creating a problem, if the CIS was adjusted correctly? I plan on taking the car back into the shop tomorrow, thank you for all your help.

plain fan · 11-28-2001, 05:27 PM

John, I got the car back today and I thought I would let you know what the mechanic found. Evidently it is one of those SCs that is very picky about the CIS adjustments, he said mine was one of the pickiest SCs that he has ever worked on. All it took was some adjustments, but now I've decided to get the vacuum tester/co2 tester and learn how to do the tests myself. Thanks for your help and time.