RPMs on the bounce....

[ODDferkOUT]

Hey all...

I've had this problem probably for a month now, but never really addressed it. When I had my water pump replaced, the RPMs on my car would bounce. Not by much at first, but it would gradually increased to the point where it's irradically boucing up and down between around 900-1500 RPMs. If I turn on the A/C it's fine. With it off, it just starts up again. Any suggestions as to what this might be? Fuel pump? Clogged injection?

 

[Ben]

maybe the idle control unit (is that what its called?) but im really not sure.

 

[frolf]

could be a lot of things. i want to say fuel pump off hand. any more info would be good though. good luck

 

[junglestylz]

Idle control valve, vacuum leak, TPS, etc.

 

[Rukus]

that sounds like an open idle control air valve.

 

[ODDferkOUT]

Is it an easy fix? Seeing that I've fairly brain-dead when it comes to fixing cars...

 

[ScottMc]

I had a similar problem. nothing to do with the water pump i dont think. I fixed it by striping down the intake system and checked for leaks in the vacuum hoses. the one which connects the air flow meter to the throttle body is particularly prone to cracking. I replaced this part for about £9 at BMW and whilst i had everything in bits i clean all it all with degreaser. Problem solved. good luck!!

 

[mikev]

i know its not the same car but is the lowest idle speed 900Rpm!!!! mine sits at 650.

 

[ODDferkOUT]

i know its not the same car but is the lowest idle speed 900Rpm!!!! mine sits at 650.

Once the A/C is engaged it's around 650-700, but with it off it has the rough idle. It's odd. I can't explain it. I know it's not related to the water pump being replaced, but the problem did arise the second I started the car after I got it replaced.

 

[junglestylz]

Most likely if it was your Idle control valve it would repeatedly bounce from right around 900 to 1300 rpm.

 

[Ben]

they probably busted a hole in one of the hoses when they were replacing the water pump.

 

[mrferg]

Mine used to have a crazy idle like that, I removed the idle control valve and filled it with carb cleaner, let it sit, emptied it and reinstalled it. Works ALOT better now! It's an easy fix too...

 

[xLibelle]

mine likes to studder and for a second of good revs, then sounds like it catches its breath.

i guess its dirty and needs an overhaul.

 

[vlad]

It's easy to check for vacuum leaks. Get a can of carburetor cleaner, and gently spray a little around the vacuum hoses and the intake parts of the car. If the RPM changes, check by spraying a bit in the same place again. If the RPM changes again, you have a vacuum leak in that spot.

REMEMBER! Perform this test on a cold engine, and DO NOT get carburetor cleaner near the exhaust! This stuff is highly flammable!

 

[ODDferkOUT]

Found it...

...I guess when I replaced the air filter I failed to re-fasten one of the clamps. Gathered that it was in a hidden location, I forgot about it. I fastened it and it seems to work fine now. Heh.