'92 350 TBI Help

[92_Z71]

My '92 Z71 engine idles rough. It surges and sometimes it cuts off. The previous owner never changed the plugs or oil before I got it. He let it set for a couple of years without starting it. When I got it I changed the plugs, wires, and oil. But it still idles rough. The engine is stock and has 204xxx miles on it. How can I get it to idle smooth?

 

[magimerlin]

Did you change or atleast look at the cap, rotor, air filter, fuel filter...

sent from what use to be a great country...

 

[mistaake]

Did you change or atleast look at the cap, rotor, air filter, fuel filter...

sent from what use to be a great country...

That, or maybe throttle pos sensor?

 

[93stepsidez71]

My '92 Z71 engine idles rough. It surges and sometimes it cuts off. The previous owner never changed the plugs or oil before I got it. He let it set for a couple of years without starting it. When I got it I changed the plugs, wires, and oil. But it still idles rough. The engine is stock and has 204xxx miles on it. How can I get it to idle smooth?

What about a vacuum leak?

 

[magimerlin]

Pull the codes.... just cause the light ain't on doesn't mean there are non, just a fyi.... just went through this with a 91 Jimmy at work... chevy couldn't fiqure it out even had it on thier machine... piece of scrap wire later I read the codes, replaced the map, and speed sensor, and runs top notch....

sent from what use to be a great country...

 

[Justin S]

204k with improper maintenance, I sense internal tiredness

 

[sntrym]

The Idle Air Control valve can function improperly but not throw a code. I just ran into this with a 95 Yukon I'm fixing up where after a top end rebuild, it would surge at startup, then idle too high after verifying there were no vacuum leaks. The IAC has a stepper motor that should operate smoothly, but in certain cases will not but also will not throw a code. I would also check the regulator spring in the TBI as those are known to break, causing odd fuel issues also without throwing codes.

 

[Ironhead]

Another thread looking for some help. And, like so many of these threads, the original post does not give us enough information to help solve the problem. I mean, for all we know, there's a lot of water in the gas tank after it sat so long. Or maybe, after sitting so long, one or more of the rings was rusted to the cylinder wall(s), and broke when the engine was cranked to life.

I hope the OP gets his truck running nicely, without having to pay a bunch for parts and stuff, but we really, really need more information in these kinds of threads. Like, what is the compression pressure? Is it all stock? What codes does it show? etc. etc. etc.