bad idling problem
 

I have a serious problem that I cant figure out. Its my truck, it wont idle right. Its an 89 trottle body 350 and it sounds reved up in park but when it goes into reverse or drive in revs up and down. Is there a sensor that went out and which one? Or what should I try?

Re: bad idling problem
 

idle air control valve will do that

Re: bad idling problem
 

should i take it off and clean it or what?

Re: bad idling problem
 

I never had any luck cleaning them before....try unplugging the connector and see if it smooths out at all

Re: bad idling problem
 

or a serious vaccum leak

Re: bad idling problem
 

all my vacumm lines are in and dont seem to have cracks in them. If I disconnect the vaccum from the pcv it idles a lot higher and even normal when you shift and put load on it. Once you accelerate it dies though. I did disconnect the iac this past weekend but didnt help. Im almost to the point of swapping to carb.

Re: bad idling problem
 

btt

Re: bad idling problem
 

It sound like it could be low fuel pressure to me.

Here is a thread with fuel pressure testing information and some other test information you can use.
http://67-72chevytrucks.com/vboard/s...=1#post3362772

You can do a search in the 1988-1998 forum an find many threads on this topic.

Edit:
More threads to look at.
http://67-72chevytrucks.com/vboard/s...t=surging+idle
http://67-72chevytrucks.com/vboard/s...ight=poor+idle

Re: bad idling problem
 

Well I figured I would get more help here since my truck is as square body even though its a 89 model.

Re: bad idling problem
 

you might try replacing the intake manifold gasket if they are leaking it will cause the same problem

Re: bad idling problem
 

well those are brand new. I had a head job done to it and all that is fairly new. I did take the iac off and broke it putting it back in so I now have to buy another. So new iac, pcv, and temp sensor will go in to see if it fixes the problem.

I was reading that you could take the vac line to the booster off and place your thumb on it and if it does nothing to the rpms then its not that but what do you do if I have a hydroboost?

Re: bad idling problem
 

any update? is it fixed?

Re: bad idling problem
 

since you did have the intake off to do the heads, you might check the timing first.

Re: bad idling problem
 

The throttle bodies had a bad habit of sucking the base gasket out .