2003 Gmc Yukon Xl 5.3

[JAMBROUS]

ENGINE MISSING HORRIBLY, CANT GO MORE THAN 25 MPH. CHANGED MAF, PLUGS AND WIRES, STILL NO CHANGE. ENGINE IDLES ROUGH, CHECK ENGINE LIGHT BLINKING. CHECKED FUEL PRESSURE, ONLY 42-46 LBS. CHANGED FUEL FILTER, STILL NO CHANGE. cHANGED FUEL PUMP, PRESSURE STILL LOW. SCANNER SHOWES THAT THE WHOLE LEFT (1-3-5-7) MISFIRES WHEN YOU PRESS THE GAS PEDAL. PCM THROWS NO CODES BUT ENGINE LIGHT STILL BLINKS WHEN YOU PRESS THE GAS PEDAL. ALSO SWAPPED COIL PACK FROM 2 AND 1 TO SEE IF MISFIRE WOULD SWAP OVER, PROBLEM STILL ON LEFT BANK OF ENGINE. TRUCK IDLES PERFECT, NO MISFIRES. LOST ON WHAT TO DO NEXT.

 

[Sepiroth]

I would start to look at fuel injectors. The fact that it is on one bank of the engine seems odd to me. Actually your whole post seems confusing to me. Right now, is it idling rough or smooth? Are there multiple misfires currently?

 

[JAMBROUS]

Not At Idle

No Misses And At Idle. I Cna Turn On And Off The Fuel Injectors With The Scanner, Although, When I Turn Off The Odd Cylinders Off, There Is Not As Noticeable A Difference As When I Turm Off An Even Cylinder.

 

[Donkey punch]

Sounds like fuel injectors, but I too am confused about your post.

 

[ballsie]

Did this just start happening, or did you do something to the truck before this started?

The first time i used Sea Foam, my truck was all jacked up for 3 days. turned out to be a gummed up throttle body. The sea foam loosened it up and it got jammed in the throttle plate.

Have you done anything?

 

[JennaBear]

The front driver's side O2 sensor sounds like the likely culprit. If it is bad or malfunctioning and the computer does not realize it (which it often does not), then it will try and compensate for a fuel condition which does not exist. This means the computer may think the engine is excessively lean or excessively rich and will compensate justly. This compensation can cause exactly this problem, especially since the issue is the entire bank and not just one cylinder (in which case, could be ignition or fuel injector problem). A good test would be to swap front O2 sensors from bank to bank. If the problem persists, it is possible that you have a plugged cat converter. Low fuel pressure is indicative of a low pressure regulator problem, given the items you have changed already.

How many miles do you have on it?

 

[JAMBROUS]

Took the truck to the muffler shop, he put a pressure gauge on the exhaust and as soon as he started it, the gauge shot up. Catalytic converter was completely stopped up. Good thing is 77,000 miles, still under warranty.

 

[JennaBear]

Glad you got it figured out!

 

[Gordo]

a thats sucks I had the same issue with an S-10 but I figured it out on the highway. that pissed alot of people off because I was only going 15 on a 65mph freeway

 

[bigzoie]

Hey so I'm having the same problem, but on passenger side bank, all plugs fouled (rich), o2 sensor black. Started after I ran through some light water, finally changed out O2 sensor bank 2 sensor 1, started working good. 2 weeks later, bad rain, ran through puddle on passenger side. Immediately bad hesitation, loss of power. Got home changed O2 sensor bank 2 sensor 1, but no improvement. I thought maybe water in wiring? Need help, what do you think?