Idle Problem

[Speed350]

Hello all. Alright, I just pulled the ol' truck back out and decided to mess with it again. I posted about the problem before and I tried everything as far as the answers I recieved and nothing fixed it. The truck idles high and then starts to surge. It gets worse when I put on the brakes. I have changed the valve cover gasket, pcv valve, got good compression, checked the timing chain, ran seafoam through it, checked the idle screw, sprayed intake cleaner in the intake and scrubbed what I could get to, checked spark plugs, put on new wires, and gone over the vaccum system to no avail. Either something I have missed or haven't hit on yet. I was hoping to get this thing running good again. If anyone has had this problem and found a solution I would appreciate the help or if anyone has ANY ideas I am all ears.

[KimMG]

While the truck is running, spray carb cleaner around the intake manifold, the bushings for the butterfly valve, and vacuum hoses. If there is a difference in the idle you have a vacuum leak.

[Speed350]

Thank you for the reply KimMG. I sprayed about half a can of ether around the entire engine bay and did not hear a change in the rpms at all. Checked all the vaccum lines individually with the ether and still nothing. I am pretty much stumped.

[fourwd1]

Originally Posted by Speed350

... The truck idles high and then starts to surge. It gets worse when I put on the brakes.

OK, I'm guessing it's a 22RE. Assuming there really are no vacum leaks, set your idle back down to spec and the problem should go away. The ECU has logic that says if you hit the brakes and the engine is turning over 1000-1100 RPM, it’ll cut the fuel to the injectors to help you stop faster. The engine doesn't need gas when you are braking. So when the idle rises, fuel is cut, idle falls, fuel is restored, idle rises, etc. Set the idle back to 850-900 RPM where it’s supposed to be and it should get back to normal.

[mattjam]

Hey man, don't mean to revive an old thread, but if you havn't solved your problem, screw the idle screw out and replace the o-ring.

I had the same problem and checked everything: tps,pcv,timing, ect.It got to the point where I would set the idle @ 850-900, 10-15 minutes later, it would drop to the point where, when I came to a stop, it would cutoff.So, one day I stuck a piece of tape over the screw, went uptown, ran fine.

So replace the o-ring and see if it helps.

Just my $0.02

Matt

[corning_d3]

How about pulling the vacuum hose off the brake booster and plugging it off. There could be a bad valve in the booster..

EDIT: Just realized this is an old thread...

[Speed350]

Actually, thank you for reviving the thread. I still haven't been able to fix it. I will try the idle screw gasket and plugging the booster hose. Thanks for the help. Will update.

[Speed350]

Ok, I tried the idle screw gasket with no change. I went throughout the vaccum system and found 2 leaks. I fixed both of those and it still didn't fix it. I bypassed the brake booster by capping it off at the intake and that didn't fix it either. Still idles high. I am going to do the valve cover gasket tomorrow. Could it be the EGR valve? I pulled a vaccum on it while it was running and it idled down but it was running rough. Honestly I can't remember what the deal is with EGR as it has been awhile since I have messed with EFI.