New to the site so here is my first question. I have an 88 Silverado 4x4 with a 5.7 liter. I just replaced the engine with a factory crate engine from the dealership. New distributor, coil, wires, plugs, EGR, Water pump, and numerous sensors as well. When starting th truck first thing in the morning it doesn't run smooth. It acts like an old manual choke that hasn't been choked to run. Once it runs for a little while the engine smooths out some but still not correct. I have had it in the shop several times but noone can seem to find the right problem. Any ideas?

 

idle air control valve not functioning right. either open to far, or not far enough.

 

I'd have to agree. Can you smell gas or is it rich exhaust? Either way it is either too rich, or too lean, my opinion based on your post.

 

I did smell gas the other day when driving. I didn't think much of it cause I always carry a jug of gas in the back JIC!! It stumbles at stop lights, and while waiting in the drive thru, but as long as I keep my foot on the gas just a little it idles OK. Thanks for the info. I will check it out ASAP. I do have the Haynes book so I should be good from here. Should I worry about holming it out or should I just replace it?

 

You can thank madmaxmann04 I just concur I also believe it's the idle air valve.

 

replace it. costs 30-40 bucks.

 

Did you already replace the coolant temp sensor?

 

Yes the water temp sensor has been replaced.

 

Thanks guys I will get to this this weekend hopefully. I work 10 hour shifts and get a company vehicle to drive to work so not a necessity till Monday!! Looks like an easy swap according to the Haynes book I have.

 

very simple. shouldn't take more than 5, maybe ten minutes. unplug connector, loosen old iac, remove, replace, replug. done. the new idle air valve should come with a flat oring gasket. USE IT!! i've seen people lose their minds trying to figure out vacuum leaks only to find out that one little gasket would have prevented problems.