rough idle

[nvious62]

i have a 94 chevy silverado that i just purchased. It is the 5.7 tbi motor it has 196,000 miles on it. The truck has a rough idle to it. Im not new to working on cars. I have changed the fuel filter, distributor cap and button, plugs and wires, the iac valve, coolant temp sensor, thermostat, rebuilt the throttle body. I have also checked the vacuum lines and intake manifolds for leaks there is none at all. The fuel pressure is right and the injectors are clean and spraying good. I also changed the 02 sensor. The truck when in park or neutral it idles nice and smooth at a 1000 rpms. When put into gear it drops down to about 6 or 7 hundred and idles rough and shakes. Im fresh out of ideas any help would be greatly appreciated. This thing has me going nuts thanks.

[J-Ri]

Possibly carbon buildup in the intake and on the valves. How bad was the throttle body when you took it off? Carbon will soak up the gas if there's enough of it. Seafoam is a very good cleaner. Just follow the directions on the can.

[nvious62]

throttle body was not to bad but the i guess enough. the egr was pretty bad but will give it a shot thanks.

[2000CAYukon]

I chased a rough idle on my 90 for a long time. Eventually found that the PCV gromet was not sealing well. I also found a small vacuum leak in the MAP sensor vacuum hose.

EGR, EGR solenoid, Pickup Coil are other sources of rough idle for TBIs.

Someone recently posted about a bad connector at the TPS as their source of a rough idle.

//2000CAYukon

[nvious62]

i have changed the grommets for the pcv valve and all the above in my previaous post still rough idle. but when sitting there in park or drive long enough the check engine light comes on but when take off and get around 20 mph it goes off. then check the code it is for the iac valve. but it only comes on when sitting there idling and goes off when take off any ideas as to what this problem is