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smoothed and filled red pearl 94
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631 Posts
Discussion Starter #1
when i rev my engine (in P or N of course) she sounds like shes gonna stall out and drops to like 500 RPM then quickly recovers and goes back to reg idle (650). is this normal or a sign of something wrong like a vac leak or something? just curious. thanks for any info.

-John
 

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Super Moderator
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11,961 Posts
if your engine is stock, it could mean that the idle air control valve might be sticking/slow/clogged

also, vacuum leaks can cause a plethora of problems, especially with a 13 yr old car because lines tend to dry rot quite easily after so much time

if you havent already, get yourself a repair manual for your car to learn where all the components of your engine are....the IAC valve should be towards the back of the engine, slighly behind/on the intake manifold.....you can take it off and spray it with carb cleaner spray until you remove all built-up gunk, and then replicate the scenario to see if the symptom continues....sometimes this helps, sometimes you need to replace it......it also wouldnt hurt to take off each vacuum line and check them, or even replace them to eliminate possibilities....start with the cheap stuff, and work your way up
 

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smoothed and filled red pearl 94
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631 Posts
Discussion Starter #3
alright

thanks maestro. my engine is tuned by BOC for 93 octane/80 mm MAF/filter/plugs/stat. i replaced the iac about a month ago. vac lines all look healthy. i guess it did not occur to me for whatever reason to consult the manuals for diagnosis...duh. thatll be next. my question still remains though: is this drop to 500 then back to normal necessarily indicative of a problem?
 

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I would guess a slight vac leak myself.Grab a can of carb cleaner and spray the lines to see if the idle change's.
 

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Refrigerator Raider Hater
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I would guess a slight vac leak myself.Grab a can of carb cleaner and spray the lines to see if the idle change's.
My bet too, but propane works and is a lot less mess.
 

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smoothed and filled red pearl 94
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631 Posts
Discussion Starter #7
what like an unlit torch?

it shouldn't take much carb cleaner for me to hear a diff in the idle, right? what is the deal with this propane method? can i just use an unlit propane torch? im think im gonna go give it a shot with the carb cleaner in a little while.
 

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Refrigerator Raider Hater
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11,719 Posts
yes, unlit. the vacuum will suck the propane into the intake, and the idle will rise. Not only aren't you spraying a corrosive chemical, but the risk of fire is reduced as well.
 

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try the evr
it has a filter that cloggs. this is the cause sometimes on 4.6's for low idle
this evr is a solenoid valve that opens and causes the egr valve to close (because it redirects the vaccum that would go to the egr and directs it to the little filter.

try it out.
 
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