89 rough idle check engine light

[trygstad]

Truck starts fine but just after startup it idles down and up and the check engine light comes on and if you let it, it will stall out. I have changed the cap, rotor, spark plugs, wires and put on a new egr valve. Once truck gets going it runs fine but the check engine light stays on, sometimes it goes off and the truck gets more power.

Any sugestions of where to go next?

It is the 302 engine

[Rotarykai]

I think your engine is just getting cranky because it hasn't made out with a catalytic converter in so long.

-Lumberjack Jim

[boognish]

l made out with my catalytic converter last night and l'm still cranky. what kind of reply is that? but l would like to keep an eye on this post b/c l've got the same truck and its starting to act up a lil too. thinking about just beating the crap outta it and then l'd know whats wrong with it, but as of now l've got nothing to say about it b/c l'm a lil stumped as to describe quite whats going on.

[trygstad]

Yeah i wish that I could just beat my to hell, but I need it

[Rotarykai]

You should just throw a 350 crate engine in there, and carborate it. I know where you can get one from...my friend's dad has one in his Camaro and is looking to get rid of it so he can put a rotary engine in there.

[Slade901]

See if you can pull any codes.
You might have a vacuum leak. Try unplugging un-needed vacuum hoses temporarily and plug them up. Cruise control vacuum hose, brake booster hose, etc and see if the IDLE changes or makes a difference.

One way to find out if you got some vacuum leaks is to spray some carb spray around the carb, intake manifold and if you spray on leak then the IDLE would change.

[trygstad]

I bought a code reader, where does that plug in to? Is it in the engine bay or in the cab?

[97chevyman]

sounds like a bad IAC motor. Take your truck to a local shop and they will pull the codes for you. Sounds like a bad IAC or o2 sensor problem.

[trygstad]

What is an IAC?

[89F150]

Idle air control valve. it sits on the side of the throttle body. give it a clean or replace it to see if it helps.

[Rotarykai]

Try cleaning out the Samoflange bleed valve with throttle body cleaner. You should be running 11's in no time.

-I'm your son from the future!