Summoning the geniuses of the forum: Problem accelerating from a stop / hill, engine stumble [updated]

[Bigburb3500]

Nope, but what I did try was to test with the sensor unplugged and the hesitation occurs anyway. So for now that sensor I think may be out of the equation.

Depending how long it has been on going the computer could have “learned” to compensate. Don’t these GM computers “learn” for a long while?

The battery and cables are a great place to look as well as mentioned earlier by @davidavidd. I used to have Audi’s and if the battery voltage dropped too low the whole car freaked. Good luck with the diagnosis! I am following along and interested in the final repair.

 

[davidavidd]

Depending how long it has been on going the computer could have “learned” to compensate. Don’t these GM computers “learn” for a long while?

The battery and cables are a great place to look as well as mentioned earlier by @davidavidd. I used to have Audi’s and if the battery voltage dropped too low the whole car freaked. Good luck with the diagnosis! I am following along and interested in the final repair.

Lol, the ECU "learn" against my pocket, gas consumption has been skyrocketing. Posting update with pictures right now.

 

[Bigburb3500]

Lol, the ECU "learn" against my pocket, gas consumption has been skyrocketing. Posting update with pictures right now.

Unfortunately, the old trifecta: Power, Reliability, Efficiency. You can only have 2.

 

[davidavidd]

Ok, I started the cleaning process, this is what I found so far:

- Small coolant leak in a hose, easy to fix.
- EVAP solenoid hose very brittle (I'm going to change it)
- Partially open throttle body, with a considerable layer of sticky oil and carbon, the gasket was crushed and in very poor condition
- The intake manifold is covered in a paste of grime, carbon and oil (expected). The gasket was apparently allowing air in at several points.
- I have seen several charcoal pellets, even a small buildup near the vlom. 100% sure it is charcoal, not mice p*#p lol.

- The valves and ports look relatively clean, not carbonized, BUT I have removed these manifolds before and have never smelled gasoline as much as this time. I would venture to say that there are small puddles of gasoline on about four valves. This makes me suspect that some injectors are in direct flow without containing the pressure (maybe contaminated with carbon from the EVAP system?)

- Oil pressure sensor filter in good condition, not clogged.

- The injectors look very dirty, 1 bad o-ring.

Tomorrow I will finish washing the parts, I will also take the injectors to be cleaned and tested.

I'm waiting for the fitting so I can use my pressure gauge on the fuel rail.

The battery cables look good, I always apply dielectric grease to the terminals, they do not look brittle, corroded or rotten.

Thank you all for your responses, they have been very helpful.

Some pictures:

 

[j91z28d1]

having the injectors clean and tested is a good idea, maintance and rule them out as what's casing the issue.

not thst it would effect much of this, but a catch can is a total worth while investent on these trucks. I don't know how much it would cost down your way, but Amazon has ones most use for about 30$. mine catches a good about of oil between changes.

 

[davidavidd]

having the injectors clean and tested is a good idea, maintance and rule them out as what's casing the issue.

not thst it would effect much of this, but a catch can is a total worth while investent on these trucks. I don't know how much it would cost down your way, but Amazon has ones most use for about 30$. mine catches a good about of oil between changes.

That's the point, I already have one catch can installed , I don't know if it's not working properly, maybe I should relocate it.

 

[j91z28d1]

That's the point, I already have one catch can installed , I don't know if it's not working properly, maybe I should relocate it.

oh that's interesting. definitely something to look it into. might double check the hose routing. also what type, it seems like ones a that have metal mesh inside them work better than ones that are just a plain can.

 

[davidavidd]

Quick update: The rain delayed me a bit but I finished the cleaning process, some injectors were dirty but nothing out of the ordinary, all working, new gaskets for everything; unfortunately the problem continues.

Tomorrow I'm going to test the fuel pressure parked and driving.

 

[Carisvan]

How old are your spark plugs and wires? I did not see them being mentioned in the thread. At that mileage, you should have replaced the plugs at least twice and the wires at least once. I just did mine on a 2017 Tahoe at 91,000 miles, and the improvement is remarkable. My truck was running a bit sluggish and hesitating during acceleration. The plugs I pulled out were filthy.

 

[clubdriven]

I have had a similar issue on other vehicles and it was one of the ignition coils. It was intermittent until the coil melted due to arcing.