2002 Blazer 2WD 4.3

Was stuttering at lower RPMS, Had it to "a" shop. So far they replaced:

Distributor
Fuel Filter
Plugs
Wires
Air Filter

They also did a fuel pressure test, and it was good. They also SeaFoamed it.

Got it back and still ran bad, then got worse.

I replaced the CPI with MPFI. Delphi unit.

Yesterday after spider replacement still ran rough, although not as bad. Getting P0301 cylinder 1 misfire. Spark tested cylinder one wire, very good spark. Also getting 2 cases of P0200.

Changed the oil, due to fuel in oil.

This morning started and idled awesome! Drove down the road and it DIED!

Started cranking it to restart, and the motor shakes wildly, will not start, but has a VERY STRONG rotten egg, sulfur smell!

So, this is where I am at, CAT? Could the cat cause the misfire in 1?

Any help is appreciated!

Catalytic converter is now gone.

Started back up. Still shaking and missing like hell. Cylinder 1 misfire.

Compression tested and all are right in the 135 psi range.

LOST!!!!!

Also....

took it all back apart to make sure everything was right on the spider changeout. All good.

Your Cat was a good guess to start with. That’s the firs thing I would’ve thought.

Now you should erase any/all codes it might have stored thus resetting the ECM to recognize your new parts. You can do that by disconnecting the battery for about an hour, then reconnect it,,, turn on the ignition for 5 seconds (DO NOT START) turn it back off for 10-15 seconds then start it up.
It will run like crap for a little bit and clear up once it resets its values to the new parts you installed.

One more thing to keep in mind would be your EGR Valve,,, Take it off and check it out real good, make sure it is not stuck open. That would give similar symptoms as a bad Cat.

Clean the EGR Valve really good and make sure it isn’t stuck open. If it is stuck open it could cause your vehicle to run like chit or not run at all.


Good Luck,

Keep us posted with your results and solution.

O2 sensors. Clean or replace MAF sensor. Check for exhaust leak pre upstream o2 sensors. Check/replace PCV valve. Check for vacuum leaks. Check for leak at lower intake manifold gasket.

He has a 2002 model and it may not have an EGR valve. It definitely won't if it was made late in the model year.

Yep, was just searching. No EGR.

I did change out plug 1 on a whim, and it seems to have made a slight improvement after unplugging the battery, and resetting.

Now it seems to idle, but when put in drive, or under any load, it sputters like crazy.