Had the blazer 3 days now. Its had a really rough/missing idle so after doing alot of research I narrowed it down to the EGR being open at idle due to the symptoms it has (runs bad under 30mph, rough idle, running lean)

So today I've been testing the EGR step by step and the valve itself is fine, the pintle changed the voltage like it should and it has the correct amount of volts to the middle wire.

Next test was the red power wire that runs from the PCM to the EGR. It was suppose to read 10-12 volts, which I only got .5 volts from it. Double checked the connection and it was good. Going to try jumping it.

I checked continuity between the PCM pin and the valve and it was good.

So as of right now I'm thinking I need to get a new computer unless anyone has any other ideas.

Thanks

 

Well, I jumped power to the 12V and it idled way worse. The normal bad idle it has, the tach doesnt move and it doesnt want to die. It just idles like its missing a little bit (worse with a load on it, not bad in park/neutral) but when I go to take off from a stop, it chugs till about 2500 rpm then feels fine. Seems fine to while in all the other gears at high speeds.

But when I jumped it, it almost died, probably would have if I didn't shut it off (this was in park too)

My first thought was the EGR was dirty due to people listing symptoms as;

1. EGR Valve Fault Codes that light up the CHECK ENGINE LIGHT (CEL) on your Instrument Cluster.
   
   EGR Valve Fault Codes:
   P0401 EGR System Flow Insufficient.
   P0403 EGR Solenoid Circuit.
   P0404 EGR System Performance.
   P0405 EGR Pintle Position Circuit Low Voltage.
   P1404 EGR Valve Stuck Open.
   P1406 EGR Valve Pintle Position.
   
   
2. Rough Idle.
   
   
3. Really BAD gas mileage.
   
   
4. Lack of power as you accelerate the vehicle down the road.
   
   
5. Car (or Truck or Mini-van) seems to run ok above 30 mph but once you come to an idle, the engine barely stays running.
   
   
6. Vehicle runs great.. just the annoying Check Engine Light is on with one of the above Diagnostic Trouble Codes stored in the PCM's memory.

The ones that apply to mine are;

1. No CEL but I scanned it and got code P0171 or P0174 (running lean bank 1 or 2) Dont remember which bank it was
   
   
2. Has a rough idle but not as if it were going to die
   
   
3. Cant say for gas mileage as I havent driven it much
   
   
4. It accelerates fine down the road. Stomp on the gas and it chugs/misses till about 2500 then its smooth sailing from their whether I floor it or cruise
   
   
5. Again, 2500 rpm (around 30 mph) it starts to run better but when I come to a stop I wouldnt say it barely stays running, just feels like its missing/chugging/shaking a little (Does need motor mounts as well)
   
   
6. Last, still no CEL's

Going to go rent a fuel pressure gauge tomorrow and test that.

Mostly just waiting for my tax return so I can do cap/rotor/plugs/wires/filters/shocks and probably run some seafoam through it.