basiccamaro

I'm posting this in the engine section hoping to find someone who can helpme, please!

I'm working on a 4.3 Vortec (multi-port injection) in a 1995 S10 Blazer (I've got an '83 Camaro too!). Anyway, it's idling very roughly, and has a very slow start unless you give it a little bit of throttle- and then it starts right up. But it basically RLS (runs like sh.. ) and misses/idles very roughly at low speeds. This is my son's car, and I'm trying to work on it and help him out while visiting from out of state for the Holidays.

Evidently the 94-95 Blazers are kind of in limbo between OBD I and OBD II. This truck has the OBD II style underdash plug.
When I put an AutoXray EZ Scan 6000 scanner on it, it would say "vehicle not responding". After three calls to AutoXray/Actron, I finally got out of them (painfully) to set the scanner vehicle configuration for a 1996 GM product.

OK, so now I can scan and observe operational data. I'm not very skilled or experienced reading the scanner, but most things seem OK, the water temp is good, it goes into closed loop, throttle position and rpm change when you hit the throtttle and etc. I don't know the correct values on some of the other readings though.

So then I selected trouble codes on the scanner. The only code I got was multiple misfires on all cylinders. No EGR codes or anything else.

My son had a new EGR valve installed a while back and it did not solve the problem. They were also supposed to have put new spark plugs in and give it a "tune up". He took it back several times but the problem was never found or the performance of the engine helped.

I'm thinking that I might pull the new EGR off again and clean it up, try to clean up the manifold passage if I can, install the screened EGR gasket and hope that helps.

So my questions are-

Is there something else I should be looking for or trying while the scanner is hooked up?

Does this seem like an EGR problem?

Why am I not showing other trouble codes during the scan?

what other codes might or should come up for this condition?

What code would show if I unplug the EGR? I've heard some people say to just unplug it, and others say that is no good. Is it really needed if you do not have to smog check?

Thanks!

ex-x-fire

I'd start w/ a good tune-up, I've had probelms w/ aftermarket cap & rotors, only use GM there.
The screened egr gaskets are a good idea, the screen keeps any carbon from getting lodged in the egr valve, making it stick open. They run really rough, sometimes they stall, or theres no power brakes (manifold vacuum is very low).
GM has had a real problem w/ the efi system on these trucks, it came from the factory w/ 2 big injectors that feed 6 poppet valves, these valves get gummed up. Also the fuel pressure regulator is inside the intake, it could be bleeding down.
A good test is a fuel pressure test, 60 psi or above. It also needs to hold pressure when the engine is off. Sometimes they wont start when the pressure is 55psi.
I've also seen uppper plenum vacuum leaks.
They do make an aftermarket (retrofit) replacement for those poppet injectors, commonly called a spider injectors. Its a big improvement over the stock ones,you should beable to get it at any parts store.