1990 Sierra rough, cold idle

[wallhope]

I'm having a problem with my 1990, 1500. I don't notice the problem when the engines warm but on cold start-up it idles rough and appears to be flooding it's self. Pressing the accelerator doesn't change the idle problem. Any help would be appreciated. By the way, I'm new to the forum so if I make a mistake, let me know.

[snatchmasterflex]

I found that my 88 had the same problem so I replaced my O2 sensor and BANG! problem solved. When you truck is warm does the idle rev higher then usual then drop then rise higher again then drop etc. etc. If that is the case then I suggest changing the O2, if that doesn't fix it check on the EGR sensor and see if it is still working.

[wallhope]

Thanks for the reply. I've come to the conclusion that it may be the EGR but will check the 02 as well. With that said, where exactly are those two located. Thanks again.

[dsgen]

It's likely the egr valve is dirty, or the solenoid needs replacing. If the service engine soon light isn't on it's likely the solenoid.

[fast6]

EGR valve - just had a similar problem and put in a new EGR valve and the truck runs like new.