1985-1998 [Subscribe to Daily Digest] |
I have a '93 Saab 9000 CC, i.e. the "prices from" model. The engine is a 1985 cc non-turbo (B202), with around 210 000 km behind it. The fuel injection system should be LH-Jetronic (never actually checked).
The engine has recently started to forget how to idle. This typically happens after driving some time with moderate load. When the clutch pedal is pressed, the engine rpm's fall very low and only then recover back to the specified 850 rpm. Sometimes the engine simply stalls, sometimes the rpm's go down to 200 and then recover. In any case, there is a big undershoot when coming to idling from above. When the problem is away, the revolutions drop to 1200 rather quickly, but then slow down to 850 smoothly.
When the problem occurs, it is possible to keep the engine alive by pressing the accelerator lightly for a short while. However, this is not extremely practical when decelerating to traffic lights (a third leg, please)...
The problem may occur immediately after starting the engine or after an hour of driving. Outside temperature does not seem to have much effect on this, I've witnessed the problem at -15 'C to +10 'C, but also troublefree running at the same temperature range. Sometimes there are no problems whatsoever.
When the problem manifests itself, it seems to be accompanied by low torque (or, should I say, even-lower-than-usual torque) at below 2500 rpm. At higher rpm's there don't seem to be any problems at any time.
Idling as such goes pretty well. There have been some rough idling (sounds like only three cylinders out of four or too rich mixture) with cold engine for a few minutes after a cold start, but I really am not sure if that is of the same origin.
Any ideas what could be wrong? The problem feels like a loose connector somewhere, as it has a certain on-off character. Could it be the idle air control valve and its wiring? (Even though I've got no idea how it could cause the torque loss.) A problem with some other sensor (air flow, lambda)? Leak in the manifold? (But then why would the problem be intermittent?)
The nice yellow "Check Engine" light shines its light to my day only when the engine has stalled, not otherwise. So, it seems that the LH-Jetronic is rather happy with its life. Not an ECU fault, I hope.
I'd really appreciate any ideas!
posted by 84.230.11...
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.