As a break from bashing how about something technical? I'm trying to diagnose a problem with my '95 where it will not stay on until it warms up. I need to hold the throttle about an inch or it will idle way too low and therefore just shut off. Slowly as it warms up, less throttle is required to keep it idling at 900-1000 rpm. Finally when it reaches about the first line on the temp gauge, it's able to hold the proper idle on its own, and is fine for the rest of the drive.

While the engine is still cold / still warming up, if you rev the engine, it will most likely stall on the down-rev as it approaches idle speed.

The engine in this car was just rebuilt. I have 250 miles on SAE 30 non-detergent oil. New spark plugs (Bosch platinum 1-electrode, gap checked), cap, rotor, AOS breather hose, throttle gaskets, brake booster hose, ISV hoses. The only rubber/plastic that was not replaced on this engine is the hard vauum lines and rubber elbows. The fuel filter was replaced last year. The fuel tank was run until R and refilled with shell 91 just 3 weeks ago and even before this it would behave like this so I think the fuel is OK.

While everything was apart I "cleaned" the ISV by squirting brake clean in any/all openings and shook it vigorously. I would squirt, shake, empty, repeat. Is this right, wrong, damaging, etc? I really think this problem is related to the ISV or some other form of air intake control, because if it was a fuel or spark issue it would not depend so linearly and solely on temperature.

ANy info on the ISV that might help me? Would it be worth swapping ISVs on my two cars to try to eliminate/confirm the ISV as the culprit?

 

This sounds like the ISV is leaking. You should be able to blow in one end, cap the other end and not hear any air coming out of it.

 

Thanks Luis. Can a leaky ISV be repaired, like with silicone or glue? Maybe using brake cleaner destroyed the seals... My brother tells me the VW guys only use alcohol to clean their ISVs.

 

Any leaks from your AOS hoses?

 

can you jump the diagnostic port to disable the ISV as in a 951?

step 3 listed here
http://www.clarks-garage.com/shop-manual/fuel-08.htm

 

Well it's back to school for the week - no more troubleshooting until next weekend. I'll look into the diagnositc port jumper Todd.

I put the '95 ISV into the '93 which runs great. I thought if the ISV was the problem, it would follow over to the '93. But the '93 ran great with both ISVs so it can't be that. I tried Luis' test and it held pressure in both directions.

I did notice that the hose clamps were sort of easy to undo, so they were probably not tight enough. When I put it back together I made them tighter and the problem is much reduced! It's still not perfect but much better. Now it will hold idle on its own, at about 900, and it holds it fairly steady. But revving will result in a stall when it comes back to idle.

I want to know if there is anything stored in the computer that sets a configuration for the ISV, throttle/fueling, etc that I need to be concerned about. The battery was disconnected for about 3 months so maybe the computer lost a setting? I don't know.

I'm really confused because it only misbehaves when the engine is cold. Thanks for the help guys.

 

Okay, if it passed the leak test, then keep in mind that there's a little motor in there that wears out over time. How many miles on the little guy? The ISV in my S2 passed the leak test but had a good 150K miles on it and would go beserk every now and then. The ISV in my 80K mile 951 leaked like a sieve and killed the idle. HTH

 

Hmm good point. It has 180k on it. But it worked fine when I slapped it into the other car...?

I rechecked all the big air hoses for loose connections - the hose from AOS to throttle, the hose from intake to brake booster, the ISV hoses, and one hose from the lower left intake to somewhere by the emissions junk. Did I miss one? I think all the little vacuum tubes are connected, but I don't think a loose one of these could cause big cold-idle problems?

Could it be injector-related? The one thing I cheaped-out on during the engine rebuild was the injectors - I just put new orings on and put them back in instead of sending them out to get refurbished. They were fine before...

 

I don't remember seeing a dagnostic port on 968's like 951. I think this would have to be done thru the obd1 diagnostic port.
I would check all the vacuum connections and other fittings on the intake manifold.
Raj

 

Alright, I was ready to put the car back into DD mode regardless of this morning inconvenience. It was still running SAE 30 non-detergent oil for the break-in, so I went and bought some synthetic and changed the oil and filter. I had left off the vanity cover so I put that on, but before doing that I changed the plug wires. At the last second I took off the MAF and cleaned it with QD electrical cleaner.

Now the problem is 99% gone.
I doubt it was the plug wires - maybe?
I doubt it was the oil - maybe?
It was probably the MAF. But it was perfectly fine before the rebuild?

 

Now that you mention it, the AFM connector plug messes up the idle on my S2 every few months. Each time it happens, I disconnect it, reconnect, and the problem goes away.

This is a relatively new AFM with around 30K miles, btw.

 

Hmm, it may well have just been the plug and by dis- and reconnecting it fixed it.... ? I suppose. Well it's idling pretty well now so if it manifests again I'll try the plug trick before anything else. Thanks Luis and all.