2002 Chevy blazer 4.3. It doesn’t have cats on it. I’m getting codes for multiple cylinder misfire. When I accelerate it sputters bad and hard to accelerate. This is my live data while idling. Any help would be appreciated and thanks in advance. I’ve changed MAF plugs wires and cap. Cleaned throttle body. New fuel pump also.

 

 

Bump.

 

Any codes?

Does your truck stay in open loop as i see on your scanner or does it transition to closed loop when it warms up?

Can you graph O2 sensors?

Recapture those sensor readings on a cold engine with just key on and get the local pressure and temp from the weather.

George

 

That was on a cold engine, I just turned the key on and didn’t start. I’ll get more info when it’s warm. The sensors I remember were. O2 sensor codes because I don’t have a cat, MAF sensor (fixed) and cylinder 2 misfire

 

The rpm is 738 so the truck has to be running. I’m confused.

George

 

Sorry I misspoke. That was at idle. It had 2 codes . P0155 O2 Sensor heater circuit bank 2 sensor 1. Next code is P0300 Random/Multiple cylinder misfire detected. Here is the B2S1 graph while engine is warm.

 

trying to attach video.

 

So you have no cats and no rear O2 sensor but you have both precat O2 sensors and they both show voltage changes when graphed? The movie you showed is pegging high a lot but your trims look OK so something is going on.

P0155 is an O2 sensor heater circuit. We need to figure out if its the sensor or the heater wiring and get that fixed.

Does the truck eventually go into closed loop when it warms up?

Did you recheck fuel pressure after the new pump? What was the brand?

What brand of ignition components did you use?

George

 

sorry for late response. Work schedule. Ok so it does go to CL for both when warmed up. Could just a O2 sensor be causing it? I have all the O2 sensors btw or I think I do. I assume there’s 3 under it and 1 near the intake? I might try to change out the B2S1 O2 sensor,