Really need some help. Recently installed a new 5.7 in a 1995 K1500 4x4. When I first started it up all was good, but after about 200 miles I have noticed a rough idle. It runs good going down the road. It idles at about 500 rpm after warm up and stumbles(for lack of a better word) a little. There are no codes showing up. The oil pressure and tach will bounce. I replaced the EGR and TPS when I installed the engine. I was thinking that the IAC valve could be bad but again, there are no codes. Truck idles just under 1000 on initial start up. Any suggestions? Hopefully I've given enough information. Thanks' in advance.

 

timing?

 

Chris: I've double checked the timing and it is dead on. I should mention too that I replaced the distributor, cap, rotor, wire's, and plug's when I replaced the engine.

 

Check for vacuum leaks. Use spray bottle with water. If you find one you'll know cause it will want to die, spray all hoses and anywhere they might be vacuum like intake, egr, brake booster etc. good luck

 

Spent the better part of yesterday checking for a vacuum leak. If it's a vacuum leak I didn't find it.