miss at idle
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Pro
Joined: May 2008
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miss at idle
I have been trying to track down a miss at idle up to 1000rpm. It is intermittent. I checked my vacuum with a gauge and it is reading around 18 - 19Hg that seems low to me, am I right, if so what should it be normally? I removed ALL the vacuum lines from the intake and plugged them, the vacuum was unchanged, this makes me think I might have a burned, slightly warped valve, am I on the right track?
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Joined: Aug 2000
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I think 18-21 inches is good.Does the vac reading hold steady or bounce around?Can you hear any vac leaks?
A vacuum leak can be detected with brake kleener or some other spray to see if the idle changes as you spray around the intake.Also,see if the egr may be sticking a bit.
A miss can also be caused by a bad wire,plug or opti,or possibly a bad injector.
If you have a timing light,you can hook the light up to each wire,one at a time and watch the flashes as you rev the engine at the TB.If its missing,the flashes will pause during the miss and you can narrow it down to which cylinder/wire it is coming from.
Its possible a bad or burnt valve can cause some problems,but you would need to pull each plug and look at them,then do a compression and then leak down test to further see what might be the problem if none of the above works.
A vacuum leak can be detected with brake kleener or some other spray to see if the idle changes as you spray around the intake.Also,see if the egr may be sticking a bit.
A miss can also be caused by a bad wire,plug or opti,or possibly a bad injector.
If you have a timing light,you can hook the light up to each wire,one at a time and watch the flashes as you rev the engine at the TB.If its missing,the flashes will pause during the miss and you can narrow it down to which cylinder/wire it is coming from.
Its possible a bad or burnt valve can cause some problems,but you would need to pull each plug and look at them,then do a compression and then leak down test to further see what might be the problem if none of the above works.
Thread Starter
Pro
Joined: May 2008
Posts: 670
Likes: 55
It holds steady. I can't hear any vacuum leaks. I removed the EGR and cleaned it, it was very dirty and I was getting a code for that but now it is gone and has not come back since the cleaning. I also put new plug wires on a year ago (Summit brand), and I did the timing light thing, all the cylinders were firing good with no obvious misses. Also replaced the injectors this last fall, car really ran good for a while after that but now I have this new miss? I think the next thing is a compression test, leak down test.
My vacuum gauge shows 18Hg to be in the "late timing" range and not normal, it is very close to normal though which would be around 20+Hg.
My vacuum gauge shows 18Hg to be in the "late timing" range and not normal, it is very close to normal though which would be around 20+Hg.
