2001 4 door 2wd


Hey guys, could use some input. Im about at wits end with this thing. Recently my blazers been running poorly, poor mpg, was having black smoke out the exhaust, and would stall at idle. I always have a flashing CEL for p0300 when under load. Additionally the plugs on the drivers bank are very fouled, the other bank is fine. This thing has mostly new parts. New fuel pump, fuel filter, every piece of ignition, header back exhaust, lim gaskets, etc. Only premium parts were used. It should be noted that recently i removed the trans to do a rear main and oil pan gasket about 2 ish months ago. So far i did the fuel pressure tests, it was good, did cylinder compression, all 170-180 psi. Note that cyl. 6 took a couple extra cranks to build compression. I checked #6 for bent pushrods, seemed good. Checked plug wire routing, swapped FPR and injectors(had mpfi, switched to a good scfi) after the injectors it stopped making black smoke, but still runs bad and throws a hard p0306 code. Additionally i get an 02 sensor code p0141. Ive tried unplugging various sensors, no vaccum leaks, most everything on this motor is new, cam retard is correct, Could a bad 02 sensor really make it run this bad? Im thinking its gotta be that or a computer problem, or god forbid a valve issue on #6 cylinder...

Should also be noted that the injectors i had in it and the ones i put in were used(delphi of course) and in good working order, but worth mentioning, does anyone know the average life of the MPFI injectors?

Thanks for any input

 

Update: i swapped the downstream 02 sensor behind the cat with the one that was throwing a code upstream, no difference. I unbolted the exhaust, same deal, and you can hear it misfire a little better and an occasional pop. Definetlty a bad cyl. 6 misfire though, if i unplug the wire on 6 seems to run about the same, does this sound like #6 might be dead?

 

Alexei
I was pushing my 99 up a pretty good hill and it threw a code for #4. My wires are AC and plugs are AC. Less than 1500 miles on wires and 200 miles on plugs. Removed #4 plug and it smelled gassy on the end and had not been firing. Wire checked out ok and found tracking on porcelain. Had a new plug, for I had ordered on Amazon and had two new plugs. Installed and end of problem. You would not think a new plug would fail. Mind did! Hope this helps. I also removed the wire and checked the end. I thought that perhaps the terminal had been pulled loose. I worked silicone around the boot and wire and was able to slide the boot back for an inspection.

 

Thanks for the input ebbervonfloyd, so i went to check for spark on #6 cylinder, plug was wet with gas. Hooked it up and set it down so i could see spark, as soon as i fired it up got a nice pop. Shut her down and was greeted with a nice cracked plug jacket, and turns out the electrode was broken. Plugs had about 10k miles, im guessing it had an internal breakage and my test totaled the plug completely threw in an old autolite platinum and bam seems to be fixed now. This drove me crazy. so like ebbervonfloyd said check your plugs, even if they seem ok and are new. i wish i had discovered this before tearing apart everything on my blazer but now i know better for next time

You can see the crack here, electrode broke in half with a little force. These were accel copper core performance plugs with 10k miles. Will go for delco double platinum next time, always use AC parts.

 

I am very happy that it fixed the problem for you. My plugs were AC Delco Iridium and like I said very few miles. My friend has a ecoboost pickup by Ford and they are having problems of the Porcelain breaking out the side also.

 

Make sure your not breaking the plug body with the socket during the plug install by getting off center when you crank it down.

George