Hello guys! My Blazer has 212k miles right now, but I've made sure to take good care of it since it was given to me by my mom. It's a good truck and always has been, but for the last 6k miles or so, I've had a bad misfire problem that only seems to get worse. I hooked it up to the OBDII scanner in Auto-tech class and It came up with Cylinder 1 at 60k misfires, cylinder 5 at 45k misfires, and cylinder 6 at 44k misfires and just continuing to rise! When I power brake, or get the rpms up to 3k-4k the misfires stop and it runs smooth apart from the engine flying into the air from the worn out motor mounts. I also have a problem where it spits out a black residue from the exhaust everywhere. I can't tell what it is because it doesn't really have a smell, but it spits out A LOT. My teacher told me that both of my O2 sensors were out according to the OBDII scanner, so I have 2 coming in tomorrow.

Any suggestions on what could be causing the misfire? I changed out the cap and rotor, AND the whole distributor after that, but it still misfires, and it only seems to be getting worse everyday I also get HORRIBLE gas mileage. everyday I drive 20 miles max, and I'm putting in $20 every 2 days. I've also changed out the spark plug wires and plugs about 3,000 miles ago

 

Anybody?

 

im having a similer problem, no power when i step on the gas, idle is rough, the ODB reports multiple misfires & O2 failure. anyways, going to do a basic tuneup today... plugs, wires, air filter, oil & filter, + O2 sensors.
i recently had ignition relay problems as well (wondering if that might be part of the cause), i should check voltages on out going ign wires, to verify they get 12v (ie. to the ignition), let you know if it works...

 

I've done all of that except change out the O2 sensors and check voltages, which I will be doing today. Good luck!

 

I changed out the o2 sensors and still no luck, guess next thing to do is a valve job? I did overheat it pretty bad once

 

only 2 things really it can be. if u got 212 k on the motor its best to do a tune up. try changing the plugs,wires,cap and rotor. also *** some heavy concentrated fuel injector cleaner and maybe change ur fuel filter. if the problem consists then it will be your spyder injection system on its way out as its a faulty design.

 

correction u did the tune up. try flushing the fuel system,check ur maf sensor for cracks as well.

 

When you changed the cap and rotor did you use AC Delco branded parts? If not try changing to an AC Delco cap and rotor first. Any aftermarket caps have a very bad reputation on these trucks and usually fail very quickly because of something to do with poor insulation that causes a misfire in the cap.