LOOKING FOR ADVICE TO FIX MY 2005 GMC JIMMY. ENGINE MISFIRES UPHILLS OR UNDER LOAD . JUST CHANGED CAP AND ROTOR

 

You can look them up in this thread:
Posted OBDII Trouble Code Diagnosis

 

If you want to start doing your own diagnostics and repair then you should start as suggested here and start reading up on trouble codes, their causes and possible solutions.

But thats just the start. Trouble codes don't tell you what part to replace, just what part of the system is indicating a problem. Taking this sometimes vague or inconclusive information and turning that into which part needs replacing is not always so straight forward. A MAF sensor code can mean that the MAF is bad but not always, might be a vacuum leak, wiring problem, MAP sensor problem, bad ECM .... A rich code tells you that the ECM thinks the bank is rich but it may also be a bad sensor telling the PCM erroneously that the bank is rich. If it is rich, why? Injectors, fuel pressure, O2 sensor, ignition ... There are misfires, but where? Is the engine really misfiring and is it really the indicated cylinders? The misfire counter uses any momentary changes in crankshaft speed to infer a misfire, it doesn't actually look at ignition waveforms. If the misfire is real, why? Ignition, fuel delivery, compression, ...

So, the question is how far down this rabbit hole do you want to go? I for one, live for fixing strange problems with no obvious answer. I love these rabbit holes but a lot of people don't enjoy this type of thing, their brain is not wired for it. Start by reading up on your codes as suggested. Then I will pose the next set of questions that need to be answered and you can decide if this is for you:

1) Set up a misfire counter by cylinder to see if its random, one bank only or one/few cylinder(s) only.

2) Is that bank really rich? Pull a couple of spark plugs on bank 1 (drivers side) and see what they look like. Compare to the other bank.

3) What do the fuel trims look like at idle and again at 2500rpms after the engine warms up and is in closed loop fuel system operation (the O2 sensors are controlling the fuel injector pulse width). You need all 4 numbers (STFT1, LTFT1, STFT2, LTFT2) mindful of sign (+/-).

4) What does the MAF live data look like at idle and 1700 rpms? I have data at these 2 rpms for our trucks.

5) What do the O2 sensors look like on a live data graph?

6) Do the other key sensors make sense in live data - ECT, MAP, TPS?

If your interested in this type of thing then I will do my best to help you as well as other members here that can offer ideas to pursue. If not then I understand, you may not want to fill your head up with all the crazy stuff that keeps some of us up at night here. Without proper diagnosis however then you have 2 choices - a mechanic (some good some bad), or parts replacement by guessing which can get expensive and frustrating and in this case, your codes do not give you enough info for a quality educated guess. It can still be too many things.

As I type this I see an ad for chicken and waffles on the side of this web page. Time for lunch!

George