I am in desperate need of some help. I have a 2001 Blazer with 4.3 V-6, TBI and the CEL is on. Six months ago replaced the Cat with aftermarket at muffler shop. Recently the CEL came on blinking and the truck started sputtering and had a bad miss in it. I had been overdue for tune up so I replaced plugs, wires, distributor cap and rotor. No change. I had codes read and it showed a P0300, multiple misfire. I replaced all vacuum lines and PCV valve and no change, well....not exactly. It's getting harder to start now. Just gradually, this didn't happen after any one item was changed. So today I took all three O2 sensors off and out of the exhaust. It started right up. (Also I disconnected the battery for a few minutes to clear codes before I started it.) But the CEL blinks when I drive (or try to) and when I drove it around the block it still has a major miss and sputters like crazy! It has 150,000 miles on it and it looks Great! I need to fix it to get to a new job. I've considered the EGR valve and/or the ignition control module could be bad....ANY help would be appreciated. Otherwise I need to sell it FAST!

Also, now I smell fuel strong at the front of the truck and at the rear smells like the Cat is bad again.

 

Sounds like it could be running rich. I would do a fuel pressure/leakdown test as well as test the coil. Also, what brand did you use for the tune up?

 

Unfortunately I used store brand for the tuneup. I know better from experience, but funds being as low as they are, I had to get what I could afford.

 

A blinking check engine light means the engine is misfiring. As a result, the excessively rich fuel mixture will cause the "rotten egg" smell and damage the converter. P0300 is almost always caused by a fault in secondary ignition parts: spark plugs, plug wires, distributor cap, rotor and ignition coil. Low fuel pressure and worn distributor bushings can also cause it. This is not the vehicle to experiment with aftermarket ignition parts on, you might want to see if the parts store will "upgrade" you to AC Delco, especially the plugs, cap & rotor. When you mentioned replacing the tune up parts made no difference, it's unknown if the new parts are any better than the old ones Without expensive diagnostic equipment to pinpoint the problem, you really need to start out with good quality tune up parts. The EGR valve and ignition control module will not set P0300 so save your money on those. As mentioned, checking fuel pressure, leakdown & camshaft retard are a couple of things to try.

 

Thanks Hook for the reply but unless you can front me a few bucks, then I can't do the upgrade on the tune-up parts. But I know for sure the plugs and wires HAD to be replaced. And like I said, no change afterward. I read that a "multiple misfire" code could be caused by an EGR that was stuck. Do electronic EGR valves get stuck open or shut? Just wondering...

Also when I pulled the O2 sensors, the 2 pre-Cat sensors looked light colored, like a lean spark plug. The aft sensor was colored with more reds and browns and small specks of debris on it. Does this info help?

 

If the EGR valve sticks open, it will set a DTC, (Diagnostic Trouble Code) and the symptoms are rough idle, stalling, or hesitation on accel but not a misfire. If it sticks closed it will also set a DTC but usually doesn't affect performance, other than a drop in fuel economy.

Your O2 sensors are not showing anything out of the ordinary. Watching them on a scan tool for proper switching, (cross counts) may or may not identify a problem.

 

Thank you again Captain Hook. It sounds like it might be possible that the EGR could be stuck open. It's a very hard start, rough idle, and it stalls as I stop at a red light or similar. Could it be that and another problem? I have someone coming out tomorrow to scan for codes. I don't know what kind of scanner or how experienced this person is really, but at least I'll have more information tomorrow I hope. I'll keep you informed and if you have any other ideas that would be great too. Thanks again.

 

Sounds fuel related to me. Fuel pump dying possibly.

 

Again, if there's a problem with the EGR valve, it will set a DTC in memory and turn on the SES light.