Very rough idle

[spaceshuttle]

So I have a 95 s50 when I start it up it revs up around 4k then goes down to 1k and just does that over and over. I have a CEL to. I checked that the hoses were tight in case it was a vacuum thing. I am thinking it could possibly be the o2 sensor because it acts the same when I unplug it.

Anyone have an idea maybe?

[blackhawkimpact]

Vacuum leak.

[Lawson509]

If you are doing a cold start, then it wont be your o2 sensor. When still cold, the DME isn't in closed loop and reading from the o2 sensor yet. It is reading off a preset fuel map. Try checking your idle valve. If the valve is sticking, it won't react quick enough and cause an varying idle.

[Reckless_Havoc]

What's the code for the CEL? Usually a good place to get started. You can do a stomp test to get the code.

[jon2681]

mine did the same thing turned out the icv was stuck sprayed brake cleaner and wd40 ,worked fine afterwards.

[ck_taft325is]

What's the code for the CEL? Usually a good place to get started. You can do a stomp test to get the code.

Besides the ICV I'd definately do a stomp test to verify.

[spaceshuttle]

Okay tried the stomp test (stomp five times in five seconds right?) and I got nothing it just stayed on. I cleaned out the ICV And now it revs up to 4k then goes down to 500 and bounces between there and 1500. And one more thing is when I tap the gas pedal it dies.

Any other suggestions?

[Vtec?lol]

buy a new icv

[greyis89]

Mine did the same as you describe and was a major vac leak from under the throttle body. A clip broke and the hose came out. Recheck all off the lines and then look into the Ivc. With that high a revs it's getting air somwhere most likely just not where it's suppose to. Hope you figure it out.

[samiam3356]

If the next thread is my 24v doesn't start. It will be because of a major vacuum leak.

Had this issue and I had to go back over the ICV lines and clamp the fuck out of them and use zip ties on the connector that goes into the back of the manifold. No more bouncy idle and the car runs perfect again.