Another p0300 mystery...

[Fless]

Just a number. I read somewhere this should be around 128. I will check the autoxray to see what it was exactly. Also forgot to mention that I did check FP engine on and off. Ignition on: 55-60, engine started, pretty much the same, engine shut off it would drop to 0 within 45 minutes.

Monitor the fuel pressure while driving, under load.

Also, I don't think the pressure should leak down that fast; I'd suspect a leaky injector or a defective valve in the fuel pump. Others might have a different perspective.

 

[rockola1971]

Symptoms fit a bad fuel pump. Like Fless says I would check fuel pressure under load. Your leak down is awfully fast. Do you have to double crank when you get in the vehicle and do a cold start? Stop leaving sensors unplugged! Did you clear the codes that, that trainwreck created?

 

[swathdiver]

2002 Yukon XL, 5.3 flex fuel, trouble code p0300, sometimes another p03xx.

Please post all the trouble codes, especially those other misfire codes (P03XX).

 

[Doubeleive]

I agree it could be fuel related but it doesn't explain the immediate misfires from simply plugging in the maf, you can connect a fuel pressure tester and place it so you can close the hood then monitor the fuel pressure thru the window as you drive

 

[swathdiver]

I agree it could be fuel related but it doesn't explain the immediate misfires from simply plugging in the maf, you can connect a fuel pressure tester and place it so you can close the hood then monitor the fuel pressure thru the window as you drive

With the MAF disconnected the engine was in closed loop and once connected, switched to open loop and freaked out. Check all O2 sensor wiring, something is not right. Need those codes.

 

[George B]

Did you check the fuel pressure regulator vacuum line for a fuel leak?

 

[xwt572]

Sorry for all of you who took the time to come up with tips about the problem, for not responding. I have been working all week and came home yesterday. I have been talking to my sons boss and he is going to take over the car. He needs the engine for some sort of project (I think an old 50-60’s chevy).
Thanks for all the tips in all this, but I think we can just close this thread.

 

[rockola1971]

Plays Taps...Another K chassis goes to the gods.