2015 Silverado 4.3L Rich condition

I do not see that you did an oil change. Need to do that an reset trims before going any further. If no change after that, can you do a VE test and report back with the results please? Also when is it rich? At idle, hot, cold, under load, all the time etc? But change oil first cause its saturated with fuel.

I did change the oil, forgot to put that in the post, changed the oil immediately after doing the high pressure fuel pump. It's rich all the time, but fuel trims seem more negative at idle than anywhere else

Attached the VE test results below, looks good to me, but let me know what you think

Did you check the alcohol %? I’ve seen rich fuel trim caused by a faulty alcohol content reading.

I had considered this, but the PID for alcohol % is at 1%

Sounds like walnut blasting is definitely in order, In cylinder pressure waveform and a first look pulse sensor on the intake will prove it if it’s an intermittent valve seating condition. First decide if it’s a real rich condition or I’d it a result of a lying input or unmetered air. If you suspect a leaking injector, crank the engine, get it to operating temperature and monitor fuel rail…

Thanks, Jeff! I will give this a shot. Unfortunately I don't have a way to measure cylinder pressure, but I will try the test for a high pressure fuel leak you mentioned. I suspected leaking injectors, but since it's both banks fuel trims going negative, I'm assuming I'd have to have at least one bad injector per bank? Or can these DI Injectors leak into the crankcase? We're a relatively small…

Those carbon deposits on the back of the valves you see are on the injector tips too so if they get to bad it can keep the pintos from closing. If you find that’s the case, I would sell injectors and a walnut blast

I got it up to operating temperature and did the test you suggested. Fuel rail pressure does indeed go up with key on engine off hot, so it would seem there aren't any leaks from the injectors. I did notice that at idle the spark advance is only about 4 degrees, and the torque management spark retard pid is showing about 21 degrees, any idea why it would be calling for torque management at idle…

Couldn’t answer that without looking at the tune file but they have been progressively pulling timing as a early protection measure for cheaper hard parts for years. how high did the pressure rise? Should have been a considerable amount over a ten minute time frame. And if that test passes an injector balance test is redundant at that point. So the fuel trims are still high negative? And is that…

So a few things on this case, what is the pulse width average and what is the engine vacuum at idle. what are the O2’s doing particularly the rear ones. It almost sounds like the cats might be getting clogged. Pay close attention to engine vacuum. some thoughts

Pulse width average is right around 1.1 ms average for both banks. Measured 18-19 inches of vacuum at idle. Both upstream o2 sensors are switching normally, and both downstream sensors are sitting right around 750mv, oscillating ever so slightly but mostly just staying between 740-750mv.

Perform an Injector Flow Test if possible. This should help verify equal amount of fuel being delivered from each injector. Reset alcohol content. Change engine oil. I’ve also seen purge solenoids not fully close, whether that would cause -30 trims or not, I doubt it, but check it.

I'd go with what Frank said, Bradley. Any chance you can do a recording and send me the data? I doubt very much that the carbon deposits have anything at all to do with the rich condition. I'm thinking you need to reset the alcohol content. I don't understand how it goes screwy, but it does sometimes.

I have seen that myself Philip but not with fuel contaminated oil, is it possible for a skewed fuel composition to cause that?

Philip You typed: "thinking you need to reset the alcohol content. I don't understand how it goes screwy, but it does sometimes" The most common "root cause" I see for alcohol content "shifting" is drivers leave the engine running or the key "ON" when fueling their GM vehicle. The PCM "calibration" looks for a "KEY OFF" condition to determine if it is necessary to recalculate "inferred" alcohol…

Great info about fuel composition strategy Mark I did not know that about filling up with engine running. But if the purge valve was stuck open wouldn’t that create a vacuum leak driving the fuel trims positive at idle? Unless of course they kept on pumping after the pump shut itself off filling the canister with liquid fuel?

Good to know. Happens all the time in cold country. I don't see it in California. Typically the purge valve will only affect it at idle until the canister is free of fuel vapor. At higher rpm usually it doesn't have enough volume to cause the problem. Freeze frame data would indeed be helpful. I'd love to have the SCM of PIDS file from a Snap On tool to examine. I'm assuming he did an oil…

I did do an oil change, I apologize, I forgot to put that in the original post. Unfortunately I don't have the original freeze frame data, the codes have since been cleared. I'm using an Autel Maxisys scan tool

I had a similar situation on a 2015 silverado but it was a 5.3L. The truck did not like aftermarket bosch 02 sensors... Ac Delco upstream sensors fixed the truck.

Looks like the factory o2 sensors are still installed

The only problem I have seen on GM engines with excess carbon buildup, is a misfire, mostly when the engine is cold. I have never seen carbon cause a rich condition. I agree with others that said you should do an injector flow test. You could have a leaking injector, but since both banks are rich I would think it would have to be more than one injector.

injector pressure drop test through my scan tool shows 45-49 psi drop across all cylinders, is this the test that you meant? Or did you mean remove the injectors and flow test them on a bench? Unfortunately I don't have the equipment to do that

That is what I was talking about and that looks good that they are all even. I believe I read above that you had fuel in the oil? I found a bulletin for a possible leaking high pressure fuel pump, which would explain the fuel in the oil. Lookup PIP5590A: DIAGNOSTIC AIDS FOR P0172 AND P0175 (JAN 22, 2019)

I did find fuel in the oil and we did put in a new high pressure fuel pump, thought for sure that would fix the problem, haha. We also changed the oil after changing the pump

I read where the ethanol reading is 1%, but I would still take a fuel sample and manually check the ethanol content, and as others have said i wouldn't rule out the purge valve or a saturated charcoal canister. Try removing the line to the purge valve from the canister and see if it makes a difference.

Did you do the Fuel Trim Reset after replacing the HP pump? Do all the O2 react instantly and fully, when adding propane, and when creating a vacuum leak? Is there a re-flash (SW Update) available?

Matt Cherry mentioned the purge valve. Have you capped it off to see if there is any change to the trims? Also can you do a VE test and post the results please?

Did a VE test, attached are the results, which look fine to me. I'll check the purge valve next.

Go into Generic scan data and graph all four 02s, the MAF and the Calculated Load Pids. At WOT, thru the 1st to 2nd trans shifts, all 02s should show rich and the Calculated Load should be near 100%

Thanks for the VE test results. Now do what Ray asked we know the engine can breathe now.

What did you figure out?

Nothing yet, the shop got really busy and this truck got put on the back burner (it's a used car for a dealership). Will update as soon as I have news, hopefully today or tomorrow!

What are they at idle and at 2500 rpms?

Were the injectors part #s cross-referenced as per #20-NA-098 to make sure the correct flow rates were installed?

Thank's for the update Brad. In your original post you talk about bad carbon. It just dawned on me that these engines eat oil past the pistons with higher miles (think 100k or above). I used to work at the GM dealer and I remember guys putting pistons in 5.3 an 4.3 GDI engines for oil consumption. Maybe this is why there is fuel smell in the oil?!

1st time poster here bare with me! ! Amazingly, a month ago ran into the exact problem, same 2015 4.3l. It got new hi pressure pump and injectors. Injectors were replaced do to a cold start misfire. Installed all injectors and part number on all 6 were same number. Now after seeing wills post wondering if I got the wrong ones from the gm parts guy. I was never asked the numbers off the old…