87 16v rough idle

[Juice87]

So about 2 months ago I changed the head gasket on my car and slightly altered the idle. I brought it in and had it fixed/tuned and it ran great(possibly better than before). However, I've read that the optimal idle rpm is 950 and its been at about 800 since I got it back. I didn't think 150 rpms would be a big deal. Anyway, it is jumping up and down now in idle and last night it stalled after I drove it. I didn't know if the low idle had anything to do with it or if its a separate problem. I also wanted to see if I could just rotate the distributor to raise the idle or if that was more trouble than its worth. Thanks

[rocco_habit8587]

I wouldn't mess with the distributor unless your planning on timing it correctly. Get a timing light and you should also take a look at your air/fuel ratio when you do the timing. This also could be an issue with the idle setting on your throttle body. In the Bentley (if you dont have one get one) there is a section that discusses checking the idle setting using a dwell meter.

I think a good starting point would be to remove the ISV and clean it up a little and see how it runs.

Do you have a timing light?

Are you familiar with where all the timing marks need to be on a 16V?

Do you have a harness that you can put onto the DPR (differential pressure regulator) on the firewall side of the fuel distributor?

Do you have a multimeter?

[Ghunt521]

Kinda got the same problem with my 16v. Starts and idles fine but when i got to pull out or go past like 5k rpm the wants to bog down and stall. Need help as well

[rocco_habit8587]

Kinda got the same problem with my 16v. Starts and idles fine but when i got to pull out or go past like 5k rpm the wants to bog down and stall. Need help as well

What do you have your timing set to? I had a similar problem with mine. Turned out that I had the timing too far advanced and I think the knock sensor was picking up pinging and that caused it to somewhat cut out around 5k. I bumped the timing back to about 7 Degrees and solved the problem.

[Juice87]

I cleaned the HELL out of the ISV and it stopped jumping but now it idles real high, like 17-1800rpm. Any words of wisdom or is it just time for a new one?

[Teighlor O']

I cleaned the HELL out of the ISV and it stopped jumping but now it idles real high, like 17-1800rpm. Any words of wisdom or is it just time for a new one?

Did you adjust the air screw on the back of the throttle body? Turn that while its idling and see if it makes a difference. The O ring on it migh be flat and not sealing it, as well.

ISV's are expensive.

[Juice87]

Did you adjust the air screw on the back of the throttle body? Turn that while its idling and see if it makes a difference. The O ring on it migh be flat and not sealing it, as well.

ISV's are expensive.

The screw on the back is all the way in so no dice there. If I gotz to buy a new ISV, expensive as they are, so be it. I'm just afraid to spend $200+ and not fix the problem. Are there any other "idle adjustment methods" with these engines?

[Juice87]

Switched out the ISV with a known working one and still idles high. What controls the controller? Stays open when should close I believe. Any thoughts?

[euroteknique]

vacuum leak?

[Juice87]

All the hoses appear solid. When I unplug the ISV it runs fine. Not great for cold starts though. Seems like its getting the wrong signals to stay open when it needs to be closed.