Idle boost gauge indications
04-05-2005, 04:36 PM
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Idle boost gauge indications
I noticed that my 951 shows about 0.6 bar boost at idle when cold only. Once warmed up, it shows just under the 0.4 bar tick mark which I guess is normal so is the "extra" boost shown at idle cold normal?
I've also noticed that when warmed up (only, usually when it's very warm out) the car will occasionally jump idle at about 1,200 RPM or so. It will stay there unless I gun the engine and let it settle down or until I get to the next red light or stop sign (i.e. it won't drop on its own). Is this a bad ISV or something? It normally idles perfectly at 840 RPM (I set it per the manual about two months ago) but it'll do this weird "high speed" idle thing maybe once every 15 minutes when it's hot out.
I've also noticed that when warmed up (only, usually when it's very warm out) the car will occasionally jump idle at about 1,200 RPM or so. It will stay there unless I gun the engine and let it settle down or until I get to the next red light or stop sign (i.e. it won't drop on its own). Is this a bad ISV or something? It normally idles perfectly at 840 RPM (I set it per the manual about two months ago) but it'll do this weird "high speed" idle thing maybe once every 15 minutes when it's hot out.
04-05-2005, 04:40 PM
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Check your TPS (reports).
Probably sticking just enough it doesn't register as fully closed sometimes which usually makes the idles come back down slowly.
Quick and dirty first thing to look at anyway and it's probably a free fix unless the TPS is actually broken. Probalby just the adjustment via the screws has walked a little bit and so gradually it's not noticable until this sort of thing happens. Otherwise, do the usual routine and try to track down an intermittent vacuum leak somewhere as that's the next most likely culprit.
Probably sticking just enough it doesn't register as fully closed sometimes which usually makes the idles come back down slowly.
Quick and dirty first thing to look at anyway and it's probably a free fix unless the TPS is actually broken. Probalby just the adjustment via the screws has walked a little bit and so gradually it's not noticable until this sort of thing happens. Otherwise, do the usual routine and try to track down an intermittent vacuum leak somewhere as that's the next most likely culprit.
04-05-2005, 04:45 PM
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OK I'll check that. I've recently replaced all the vaccum lines back when I was diagnosing why I had no boost, but it's possible one has jiggled loose or split a little. I'll look. It's just weird since it's such an inconsistent problem. Most of the time the car runs just fine.