Vacuum leak, rough idle - blown intake or head gasket? - Saab 900 Bulletin Board - Saabnet.com
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Vacuum leak, rough idle - blown intake or head gasket?
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Posted by LarryV 93CE (more from LarryV 93CE) on Tue, 15 Jul 2008 00:05:10 Share Post by Email
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Hey gang,
My never-given-me-any-grief 93 CE with 90K miles is giving me grief finally. It's hard to start, runs very rough at first (missing), smooths out a bit after a few seconds of 2000 rpm, and then idles roughly but runs reasonably well otherwise. As I listen around for sounds of trouble, I hear a lot of vacuum noise around the AIC valve, but more like below and to the right of it (facing the intake manifold). I've checked hoses and wrapped my hands around everything I can get at and have not made any change in the pitch of the hiss. It might be the normal sound of the AIC but I don't recall hearing it before and I'm paranoid because of the rough idle.
So there's more. The idle varies and decreases until it sounds like it might stall, then pops back up to normal. I'm hearing a lot of injector clacking too. To test whether one cylinder might be misfiring, I pulled plug wires one-at-a-time. Removing the #1 plug wire made no difference to the idle. I checked the spark plug and it seems oily. Swapped out the plug wire and that made no difference. Tomorrow I'll do a compression test. I'm concerned that I've blown a headgasket but that doesn't account for the vacuum sound. Would a leaky intake gasket account for these symptons? I'm sorry to say that the hiss is coming from the area of #4, not #1 so what the heck?
Furthermore, the EGR valve is clicking. It's amazing what you hear when you're trying to find what's wrong!
Anobody want to venture an opinion on any of this?

posted by 67.103.44...

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