Hey everyone, Its been a while since I been on. Knock on wood, the truck has been running fine, until recently.

Heres the problem, when I sit at a red light, the idle of the truck is good for the first min or so. Then it starts to get rough, to the point that it feels like the truck will fall apart. If I rev the gas, it stops and then it'll repeat the cycle again. Driving the truck no problem, starting isnt an issue either. First morning start-up idle is fine, its only after I driven a little bit. Any suggestions?

 

My 94 s10 blazer started doing this exact same thing about 2 weeks ago. Anyone have any ideas?

 

It could be anything ranging from but not limited to a bad (or plugged egr) or iac to a leaky spider injector assembly. I know my truck surges when idling and this I'm almost certain is due to a weak idle air control valve... but I've also seen an bad egr valve replicate this condition too. Try pullin' the codes and see where that gets ya. IIRC you can jump 2 of the pins at the diagnostic plug (make sure you know which ones to jump!!) located below the steering wheel near the kick panel. Jot down how many times the check engine light flashes and come back here and search or google "obd 1 codes". That should get you somewhere I hope.

 

check the MAP sensor, I had a similar problem.

 

My truck doesn't throw any codes and still idles like crap, Probable the EGR but there are a few things and honestly it will probably still idle bad after you replace everything. A friend suggested cleaning out carbon build up using some spray into the TB, anyone ever do something like this? I've done basically the same thing to my talon with some mopar stuff and it's way better now, burned so much carbon off the cylinders and out of the intake.

 

A google search has answered the question, swartle describes how to put seafoam through the PVC valve in this thread https://blazerforum.com/forum/engine...-build-up-755/ Thanks, exactly what I was looking for and I would recomend the OP try this as well.

 

I'd second the EGR comment. These EGR valves like to get stuck by bits of carbon that break off of the EGR passages in the lower intake manifold. The thread in the Tech Article (DIY) section should cover the basics although the CPI engine does have a more difficult path to removing the EGR valve. Definitely run the engine with the valve off & port to the intake plugged to blow any loose carbon from the EGR supply passage. Then install a new, screened gasket.

An oldie, but goodie!

 

i have same exsact problem that 94blazer pa has! and i have a 94 and live in pa too! but one thing i regularly clean and swap my egr with another one. pulling codes 43 13 a knock sensor and open oxy sensor .

 

I have idle problems too and mine is also a 94 4.3l W and I aswell live in pa lol. But mine idles rough at start up and Rev it a bit and its fine but the main problem is when idling every once in a while like 1 minute apart it will almost stall but it never actually stalls

 

ditto on the egr and also clean the tb and iac with tb or carb cleaner. let us kno how it ends up