850 idling issues.

Chrisxb · Post by **Chrisxb** » 18 Mar 2012, 16:42

I'm having a problem with my wife's 1993 850 not idling and stalling in traffic. This has been going on since last summer and seems to be temperature sensitive. It only acts up when the ambient temp goes above the mid 60s. When it's cold out it runs fine. It was setting the dtc for intermittent rpm signal. I checked the wiring and cleaned the terminals which made no difference. I replaced the sensor which also didn't help. There were other codes which I can't remember the specifics of but pointed me in the direction of the MAF sensor. I replaced that too. I've been over the vacuum lines several times and replaced a few loose fitting connections but that hasn't helped either. I also replaced the O2 sensor. I'm wondering if the IAC valve may be the problem. When the ignition is on it hums like an old electric transformer. Is this normal? I'm thinking that it may have a mechanical malfunction when it gets too hot. The car will idle for 10-15 seconds, drops off and sputters then surges up to about 1800 rpms and repeats this until it finally dies. If you sit at a light too long blipping the throttle becomes ineffective and you can't get the revs up. At this point the light turns green, the guy behind you lays on the horn and the only way to move is to turn off the ignition and restart it. When it's acting like this it will fall on it's face when you first hit the gas then go, otherwise it pulls out smoothly. It also runs fine at highway speeds. It is not currently setting any codes but since the weather has gotten warmer it's been doing this. Any help would be appreciated.

Post by **jblackburn** » 18 Mar 2012, 18:27

Disconnect and plug off the purge valve to the EVAP system. Gasoline vapors from the canister may be choking it out at idle.

This line comes up through a series of white one-way valves by the battery, goes to a valve on the radiator shroud, and then goes to the intake manifold by the throttle body.

You can see the hose I'm talking about highlighted in this picture.

The IAC buzzing is normal.

Chrisxb · Post by **Chrisxb** » 19 Mar 2012, 15:21

Thanks for the idea. My line is routed slightly differently it comes from under the air box, goes behind the trans dipstick then to an elbow under the IAC. Anyhow I disconnected it, plugged the fitting and ran the car for about 10minutes. Nothing changed.

Chrisxb · Post by **Chrisxb** » 12 Apr 2012, 19:56

It's fixed! I checked the fuel pressure and is was 80psi. I checked the return line and vacuum line for clogs and they were ok. So I bought a new regulator. When I took the fuel rail off I found that one of the intake bolts was missing. I installed the regulator and replaced the bolt and now it idles fine. Not sure if it was the fuel pressure or an intake leak but now it's fixed.

Post by **jblackburn** » 12 Apr 2012, 22:42

Wow! 80?!?

I bet it was a combination of both. I trapped a bracket in between my intake manifold and engine and the thing wouldn't stay running at all!