92 oldsmobile 88 stalling when cold fine when warmed up - Page 15 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 05-07-2006, 08:55 PM   #141
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also its not as noticable with the oil filler cap off now that i changed all the vaccum lines and the purge valve but you can still tell the difference and it still does the jerking and stalling
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Old 05-07-2006, 11:00 PM   #142
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Just thought of something else I should have done. I should have removed different vacuum lines to determine the effect on the manifold vacuum. Maybe tomorrow when it is light, I will do that and report.
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Old 05-07-2006, 11:02 PM   #143
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Quote:
Originally Posted by 92olds88royale
also its not as noticable with the oil filler cap off now that i changed all the vaccum lines and the purge valve but you can still tell the difference and it still does the jerking and stalling
Does it still suck against your hand, and cause the idle to improve when you cover the hole?
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Old 05-07-2006, 11:54 PM   #144
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it never sucked against my hand but with the oil filler cap off it will throw the car into a rough idle still and it still stalls and jerks after about a minute of the car being on
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Old 05-08-2006, 02:48 AM   #145
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Quote:
Originally Posted by 92olds88royale
it never sucked against my hand but with the oil filler cap off it will throw the car into a rough idle still and it still stalls and jerks after about a minute of the car being on
Forgive me if I have asked before, but when you put your hand over the oil fill hole, if you do not feel any vacuum, do you feel any pressure? What would happen if you were to strike a stick match, blow it out and while it is smoking, pass it across the open hole with the engine idling? Will the smoke be drawn in, blown out, or be unaffected?

And the stalling and jerking after a minute - does that happen with the filler cap on?
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Old 05-08-2006, 02:36 PM   #146
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I went out this morning and tested the effect on manifold vacuum of opening the intake manifold to the atmosphere, and was surprised to see that the PCM could compensate for a fairly large leak. I removed the big pipe from the power brake booster and used the tapered plastic tip (closed) from a tube of RTV silicone to create various degrees of a vacuum leak. At warm idle, the PCM could bring the vacuum back to 19 inches of mercury in a few seconds until the leak was made very large. So, testing for small vacuum leaks, using a vacuum gauge alone, may not work. The gauge will work if the leak is very large. I am guessing that the PCM uses spark advance and the idle air control to compensate for vacuum leaks, so it may be possible to infer a vacuum leak if those are way off spec with a scan tool.

Here'* the thing. The idle change/oil cap symptom indicates a leak between the crankcase and the intake manifold. This should be verifiable using the vacuum gauge as I indicated earlier, by opening the fill cap and watching the gauge. If it drops, as it almost certainly will, a leak between the intake manifold and the crankcase will be confirmed. If the gauge shows less than 18 inches of mercury when the cap is opened and the PCM is unable to compensate, it is a pretty big leak. If your valve guides and rings are OK as we might expect with your low mileage, the most likely candidate is a leaking lower intake manifold gasket.

With the mileage and age of the vehicle, deterioration of that gasket is not unlikely. Changing it out along with the upper intake manifold gasket and throttle body gasket should be do-able for under $100 in parts, and will ensure that you don't get any internal coolant leaks in the near future, either.

I would try that before injectors.
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Old 05-09-2006, 08:40 AM   #147
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Olds98, please do yourself a favor and purchase a vacuum gauge. Here'* one for $25 at AutoZone for example:

Actron Vacuum Pressure Tester Kit

Read the instructions how to use it and read this tech article for some basic vacuum testing knowledge:

http://autorepair.about.com/cs/troub.../aa112401a.htm

Then perform some vacuum tests and report the results back to us in detail.

We have spent over 8 pages suggesting that you do this and as of today, you still haven't properly tested your car for vacuum leaks, but persist to ask for advice. This is it! This is the advice! DO the vacuum testing...THEN report results. That is the only way that we can eliminate vacuum leaks as a potential problem and try to move on.
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Old 07-05-2006, 05:46 PM   #148
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Ripped the whole engine down and the lower intake gaskets were ******* done. replaced them and the car runs like brand new once again.
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Old 07-06-2006, 02:08 PM   #149
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Hooray! Good for you. Thanks for reporting back to us what the problem was. I am sure it will be a great help to others.

So, it seems deteriorated lower intake manifold gaskets were causing the vacuum leak. OK, now that you have it fixed.......what happens when you open the oil filler cap at idle? Nothing, we hope?

Oh, one more thing - could you please edit the title of this thread by adding (fixed) to the title so it will be easier for others to find in future searches of the archives?
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Old 07-15-2006, 11:50 AM   #150
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The other day I found a method of checking for intake leaks. With the engine idling turn on a propane torch ( on not lit ) & direct the propane around the intake gasket. If the idle smoothes out & or RPM picks up then you've got a leak. Anyone here ever try it?
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