I have a 1987 Silverado V-10 4x4 with a 350 and th350 tranny. The problem is that when it is started for the first time the engine idle is very sparatic. It idles up then down, on and on for about 5-10 minutes. Normally, it requires me to sit in the truck and feather the throttle to keep it running until it warms up. Also, if I drive for 15-20 minutes and kill the engine long enough to run into the store then re-start it, it does not want to idle on it's own until it has benn running for 5-10 minutes. This part really confuses me because the truck has no time to cool back down. I recently had a complete diagnostics ran at the local Chevy dealer. All tests ran checked out OK. Fuel system, all sensors, compression check, throttle body, trouble codes. Nothing came back as being defective. The GM tech spent 2 days checking everything that could be tested. All tests that were ran passed. I am at a loss, if the dealer cannot find the problem, who can. One more thing, at times, after warmup, it seems a bit sluggish. Other times it runs as strong as it ever has. I have replaced spark plugs, wires, ignition coil, dist. cap, fuel pump, fuel pressure reg. all filters. Any advice would be greatly appreciated. x(
have you checked the choke. i have a 74 pickup and it seems that sometimes the choke likes to stick, it would have the same problems as to that you described...goodluck
your truck should have fuel injection. if so try replacing the idle speed motor in the trottle body, this has quit working on a couple of these old things at work.Karl ________ Trichome
I realize this is a late reply, being a new subscriber, however here's my two cents for what it's worth. After reading all the things you have tried after many diagnostics, sometimes a very simple thing can be overlooked. Try looking at your vacuum lines starting at the manifold source. I had a similar cold idle problem with my 87 fuel injected 350.....up & down.....up & down until it warmed up. Then I noticed the rubber vacuum hose collapse where it attaches to the manifold. Cutting off a half inch or replacing new hoses where needed solved the problem immediately.
