2013 Denali poor acceleration

[jetson22]

2013 Denali XL with 250k. Upon cold start there is some rough idle and missing when accelerating. It seems like it even affects the shifting. I found p0172 & P0175 as well as p0101 (mass air flow). I cleaned the MAF and the dash light went off and it seemed to run much better for about one day but now it back to the same symptoms. It's fine once you get beyond 2K rpm but struggles at anything less. Today the check light came back on with the same p0172/175 but not the MAF po101. I have ordered a new MAF and air filter. Any other ideas?

 

[blondie70]

Sounds like mine, with bad O2 sensor ?? Good Luck with it.

 

[swathdiver]

2013 Denali XL with 250k. Upon cold start there is some rough idle and missing when accelerating. It seems like it even affects the shifting. I found p0172 & P0175 as well as p0101 (mass air flow). I cleaned the MAF and the dash light went off and it seemed to run much better for about one day but now it back to the same symptoms. It's fine once you get beyond 2K rpm but struggles at anything less. Today the check light came back on with the same p0172/175 but not the MAF po101. I have ordered a new MAF and air filter. Any other ideas?

Solve the P0101 first and the others will likely take care of themselves. Don't use an aftermarket MAF, GM OE or ACDelco only if you don't want further headaches.

With that many miles, it is probably time to replace or at least tighten your intake manifold to cinch up those gaskets. You can check for that by watching the trims at idle or checking for leaks in various ways (youtube).

Take the throttle body off and clean it too with that little CRC kit from Walmart that does that and the MAF.

 

[jetson22]

Update, I changed wires and plugs. One of the wires was broke. However it never did throw a misfire code??? It seemed to run ok for a couple of days. Then it went back to previous symptoms. It runs fine as long as you are giving it throttle, like on interstate or accelerating. But when you are just taking off slowly or less than 1500 rpm then it misses, surges. At the lower speed it also seems to affect the shifting. Absolutely no codes??? One of my mechanic friends thinks maybe fuel pressure but wouldnt that affect it throughout the rpms? It is driving me crazy literally.

 

[Geotrash]

Update, I changed wires and plugs. One of the wires was broke. However it never did throw a misfire code??? It seemed to run ok for a couple of days. Then it went back to previous symptoms. It runs fine as long as you are giving it throttle, like on interstate or accelerating. But when you are just taking off slowly or less than 1500 rpm then it misses, surges. At the lower speed it also seems to affect the shifting. Absolutely no codes??? One of my mechanic friends thinks maybe fuel pressure but wouldnt that affect it throughout the rpms? It is driving me crazy literally.

+1 on the throttle body cleaning, although I replaced the one in my '07 50K miles ago when I was having some drivability problems, and that cured it for me. The Dorman replacement part is actually quite good.

To properly diagnose and avoid the parts cannon, you need a scan tool that can log the data as you drive and give you either a data file you can work with in Excel, or better yet a plot.

Something like this may be enough: https://a.co/d/3lq9Y0l

 

[jetson22]

I have a scanner by foxwell. Fuel press at the rail is in the 40's. The fuel trims are all approaching zero. I was thinking of the throttle body position sensor but wouldn't it throw a code?

 

[j91z28d1]

so it's missing and bucking while the fuel pressure hood and fuel trims are fine? huh.


does it seem to have very fuel mileage. can you read the alcohol % with your scanner? are you running gas or e85.

are you watching the live data if the miss fire while it's running badly?


I feel like you're going to need to be a really good detective to find this one. check injector pw and all date live while it's doing it and compare to good running trucks.

 

[jetson22]

Fuel mileage really has not changed. I don't think the scanner does alcohol %. Always using regular gas. I wonder why it has never thrown a misfire code? Once you get above 1500+ and stay there......no problems. When you slow down and try to accelerate gradually it happens. Almost like the gas pedal is an all or nothing thing and jerks you back in the seat?

 

[B-train]

This is a good video series (2 total). Might be worth a watch and then use your scanner to evaluate.