Hello all!

I have a 1994 full size blazer 4x4 5.7 automatic.
I'm getting voltage from the ecm to the egr solenoid when the throttle is cracked causing the eng. to stumble on take offs.
Parts replace are egr, egr solenoid, maps sensor, iac valve, tps, ecu (without prom), fuel pump, fuel filter, spark plug, cap, wires, rotor.
As i understand it the egr should only open while driving at hwy speeds and under certain conditions. Why would the ecm be sending voltage to the egr solenoid at idle.
I tested this in this manner. I hooked up a 12 marker light to the egr solenoid connector and cranked the truck and removed breather assy. to better see the egr and solenoid. as i crack the throttle the bulb lights up and you can see the egr opening as the motor starts to stumble.
Any help with this would be GREATLY APPRECIATED!

 

Anybody?

 

Do you have any engine codes? EGR should only be active during cruising speeds. Have you removed the EGR and throughly cleaned it? Checked all the wiring for a bad ground?

 

No codes. New EGR. Wiring is good.

 

Should EGR be trying to open during acceleration?

 

Yes, it may open a little under light load acceleration. But it probably shouldnt until it's up to operating temp

You might want to test your ECT sensor.
How do you know the egr is actually opening? You might try connecting the old one and watching it.
Assuming it is because it's stumbling isnt good enough.

I could be wrong but I think your EGR is a pwm device. That means voltage doesnt matter, average current does. May still be an indicator but that means what you see with the EGR coil at load is way different than not connected.

 

I can see the EGR shaft raise as I open the throttle with my hand. Hood up, breather assembly removed.

It only stumbles after warm up.

ETC sensor?

Thanks

 

anybody else?

 

I have a 4.3 TBI. It all started few months ago, but increased suddenly like few weeks ago.
When the car is cold and weather is cold, it used to run very normally, but in warmer weather, it looses some power when driven for a while, and SES lights up for a minute or less when I go up a hill. I would check codes (field check with a wire) and get codes 12 & 13.
3 months ago (summer hot weather), it started hesitating after long drives up hill; only when trying to go off (like on light stops or trying to park it).
Few weeks ago, it started hesitating all the time after driving it for only few minutes!
So today I cleaned the IAC, checked the EGR valve by plugging it directly to a vacuum line from the engine (it opens and closes completely), and changed the O2 sensor (as I was still having the SES from time to time with code 13)...
Note: 3 years ago I changed all of the above + fuel pump, fuel filter, spark plugs, wires, air filter, temperature sensor, radiator, TPS (and other things that I can't remember). I also changed the whole distributor and cap like a year ago after the magnet went in pieces as I was revving it very high. 2 months ago I changed the spark plugs, wires, air filter, and fuel filter.
One more thing: as I tested the EGR valve, I noticed that there's no vacuum from the solenoid at all, even if I rev the engine. Is that normal?!
So, after I changed the O2 sensor today, it was still driving bad. Will try to change the timing with the distributor tomorrow to see if that will make any changes, maybe I'll change the cap and the rotor with the ones I had before.
Sorry for my bad English. It's my 3rd language.