4.3L Vortec Idling issue ( missing maybe )
 

vehicle: 93 Chevy S-10 Blazer Tahoe

Engine: 4.3 L Vortec ( Vin W )
6 Cylinder

New 'Nut Kit' ( Fuel Lines inside Plenum ), a engine from the junkyard guarnteed to be good 150,000 Miles, Transmission from Junk Yard Guaranteed good 94,000 Miles on it.

New FPR ( fuel pressure Regulator ) Holds 60 Pounds of pressure,
replaced a vacuum hose That looks worn a bit as well.

Issue: Sounds Like a Miss is in The engine when idling, some what smooths out but doesnt go completely away at Higher RPM. ' Not a dead miss Though'
Must Hold gas down a bit when starting sometimes ( usually after its warmed up).

Pulled The PVC valve off and no change in idleing detected, however you stop the airflow where the pvc plugs in and it dies immediatly. I can hear the valve rattling fast as there is hard suction on it.

Does Not Throw any Check engine Light, The Oil pressure shows Low oil Pressure, ( Unsure if guage works right or not )

I know This may be a needle in a haystack But all suggestions will be appreciated and I will Check Most of These?

Question: Does EGR affect idling? Does strait pipe w/o a catalytic converter mess with idling? Does a vacuum leak near the heater cotrols inside tHe cab affect the engine? Would a Vacuum leak on the transfer case/Transmission cause idling issues?

I just purchased my 94 S10 Blazer 4.3 Blazer and it was doing the same thing. It was indeed the EGR Valve and it hadn't thrown a code until a couple days after I purchased it. I have had a lot of experience with these engines and have encountered several with bad EGR valves. If it is the EGR it will eventually throw a code (35 I think) at least mine did. It was around $165.00 new at Advanved Auto Parts. Mine runs like a top now. The EGR is very easy to change but getting the new gasket to stay in place while getting the bolt under the throtlte body in is a little tricky. I would deffinately try it.

You don't necessarily need to replace the EGR. Simply buy a screened gasket from the Dorman/HELP! section of your local autoparts place (on the hooks in the aisles where the replacement window handles, etc are), then remove your EGR and clean the pintle and seat thoroughly, then reinstall with the screened gasket. I use a little bit of the Loctite hi-tack stick (purple) to stick the gasket to the EGR while I reinstall.

You'll need a 10mm socket with at least 9" of extensions for the driver's side bolt. A 10mm ratcheting wrench does the passenger side bolt quite nicely (a 10mm box is fine but ratcheting makes it faster).

As you can see on mine, it had serious chunks of carbon holding it open. Clean them out, then use sensor-safe cleaner (I use MAF cleaner) to clean the pintle (Torx bolt) and the seat so it closes and seals.

Yeah in same cases you are absolutely right Leann but in my situation the pintle was totally collapsed and had no spring pressure at all. It was junk.....

Today You remove The hose from the PVC valve and it revvs way up, engine is rocking a bit and vibrating like a race car so to speak idles about like one too, do see some flood (black puffs ) when gas is quickly pressed, pressure is still good though w/o change.

wanted to add: I removed the tps plug and the engine died earlier today teh engine sounded teh best it has when i removed teh tps plug (throttle position sensor). This time it through The following codes:

22 Throttle Position Sensor Voltage Low
34 Manifold Absolute Pressure Sensor Signal Too Low
45 Rich Exhaust

Keep in Mind This is after Unplugging The TPS while the engine was running

Strange Part: Did this earlier and engine revved up sounding great ( roughly 1500 rpm) did it just now and engine died as it should have.
pulled hose off pvc valve it revved up just now and did it earlier and it had no effect

I am so puzzled here?