I just replaced the intake manifold gasket on this truck last week (coolant leak). FYI-I did not remove the TBI from the manifold when I did the job. Now that the job is done, the truck runs great and the coolant leak stopped, but the truck has a rough idle. The rough idle gets worse when it is in gear, Sometimes it feels like the truck is going to die but it hasn't yet. It runs like a top when I accelerate.

When I had the intake manifold off, the ports that lead into the EGR valve were completely blocked, which I cleaned. I just replaced the EGR valve(Duralast) and the EGR Solenoid(GM-had to replace cuz I broke it). I had to adjust the timing after replacing the Intake manifold. So I know that it is timed to 0 degrees.

I read in some other forums that it is most likely a vacuum leak, so I bought a can of brake cleaner and sprayed all of the vacuum lines, brake booster lines/fittings and the gaskets around the TBI and Intake Manifold. Unfortunately, this did not result in any dramatic increase or decrease in the idle.

Since this problem just occurred after I did the I.M. gasket job, I am assuming that I did something wrong.

Any ideas are welcome!

Oh yeah...and I broke the top off of the coolant temp sensor. There are still two metal contacts sticking up so I just stuck the plug onto them. I normally wouldn't think this was a problem, but according to this post, a bad coolant temp sensor can be a problem:
https://chevroletforum.com/forum/sho...ght=rough+idle

 

My 93 had the same problem, when i switched gears it would hesitate on take off and sometimes die. I did an engine tune up and it runs great now. Rotor cap, rotor bug, spark plugs, spark plug wires, fuel filter, and air filter. If i was you pull out your plugs and see how bad they are!!!

 

Well mine doesn't hesitate at all. Here is a list of the things that I replaced and roughly how long ago:
plugs, cap and rotor-5k miles ago
wires - 20k miles ago
fuel filter- 25k miles ago
air filter-(k&n)
tps sensor 100 miles ago
egr valve & solenoid 75 miles ago

I think I am going to replace the Coolant temp sensor tonight.

 

Well just for fun, I put the old GM EGR valve back in and I replaced the coolant temp sensor. Unfortunately, the truck still has a rough idle.

I pulled the plug from cylinder 3. It was a tanish/rust color on one side and perfectly clean on the other side.

I feel like I'm running out of options...
Mike

 

I just replaced the Idle Air Controller. But it still idles rough. I also bumped the timing up to 4degrees of advance. That raised the idle speed, but it still surges up and down when idling.

 

i had that same problem with my 92.it turned out to be a bad injector that was leaking fuel.

 

Anyone know what the resolution to this issue was? I am having the same problem with a 1994 Silverado with 350 TBI, I replaced all the same stuff this guy replaced and still having issues with the idle.

 

I'm having a similar problem. When in gear it doesn't want to accelerate. I replaced the distributor cap and rotor. In addition, I replaced the TPS. that didn't work. Just now, I pushed in the air intake a bit and sprayed it with brake cleaner while running. Now it seems to have leveled out. Don't know if that helps.