Huge hesitation, mechanically inclined. Please help

[Brian Wilson]

I have a 2007 yukon denali 6.2
6 speed w/o AFM or DoD.

I have noticed a hesitation when taking off or at low speeds. It is always there and has progressively gotten worse. It's to the point I am afraid to pull out on the road with less than 1/4 mile of room. It has a great idle. It has never died on me (but I'm afraid that will happen next).

So far I have done these things
Fuel pressure check. 60 psi and 45-50psi running.
Cleaned throttle body.
Cleaned mass air sensor (is there a way to test this sensor with a multimeter) one resistor looked different than the other one.
Tested injectors. All good and clean, not sticking shut or open
Ac Delco plugs and wires changed
With factory replacements.
Compression test. All cylinders at 155-165psi
Tested ignition coils individually. All good.
Checked cats with pressure gauge. Very clear. Not a problem
Pulled valve covers to check for broken vave springs, bent valve or rod, or clasped lifter. All good
Tried taking off in trailor/tow mode, same issue but slightly better due to the higher shift rpm. Also tried to run in manual shift, same issue.

I tried running with my brother hooked to a snap on mods scan tool. No codes, no misses, fuel trim looks good, or signals are good and everything else looks great. Even when the truck is bogging down taking off.

It feels like I'm trying to take off in 4th gear honestly. The engine will not build rpm very fast at all but it doesnt drop rpm either. It doesnt try to stall or die. But I'm in 1st gear. I can feel the shifts and count them.

Does anyone have any ideas? I have tried to be as informative as I can. And I have tried everything I know.

 

[Brian Wilson]

I also changed the air filter. This is a bone stock yukon except a flowmaster 50 series that has been on it for years. This problem just started a month ago.

 

[M3kanic]

I would suggest a tune or a 6.2. That sounds exactly why I hated my wife's Tahoe. I have a 02 suburban that is tuned. When we got my wife a 10 Tahoe I was complaining about the same thing you are. I actually traded it in for a 10 Denali XL. The 6.2 is light years better and because I'm not stomping on the gas to get off the line I am getting better mpg.

 

[Brian Wilson]

I have the 6.2
It use to be a real powerhouse but something is wrong. I just can't figure out what it is. I thought engine at first. Then I thought transmission but the tray fluid looks great.

 

[#1taho]

Use the scanner to check you mass air flow tables. By your description the dark spot on the sensor it's no good. I would replace it.
But look at what the numbers on the scanner are telling you first.

 

[osiris94ej]

Cleaned your throttle body yet? Carbon buildup can cause some driveability issues. Other than that I'm not sure I know of anything else without doing some playing around with it.

Sent from my SM-N920V using Tapatalk

 

[Brian Wilson]

Going to try swapping the mass air sensor today
It just looks like 1 resistor is shiny and dark and the other is white and cloudy colored

 

[Brian Wilson]

Since they are resistors I should be able to ohm them out correct?

 

[Rocket Man]

I'd try a new MAF. My 02 Denali 6.0 had a random stalling issue that had me stumped for months and the MAF was the problem. It was so random that I doubt I could have tested it with a meter. Sounds like you don't have much to lose, they're only $70 or so. I also had no codes.

 

[Brian Wilson]

Thanks for the advice. Going to the junkyard today to get one. I hope it's the same as the 2009 escalade

 

[#1taho]

On the nbs trucks they are the same. Not sure on NNBS. But I am sure it is.

 

[Brian Wilson]

Stupid labor day. Junk yards closed.

 

[Brian Wilson]

Ok. Car is still hesitating like crazy worse than ever. Still no CEL. BUT, today the stabilitrack light came on at the same time it hesitated today. So, my question now is, does the stabilitrack system not only apply braking but also control engine throttle?

 

[Brian Wilson]

New throttle position sensor, new maf sensor, new throttle peddle assembly. Still not fixed. Took it to 2 different dealers and they say nothing is wrong. Any help with my next steps would be appreciated

 

[M3kanic]

I will say it again.

TUNE IT.

 

[Brian Wilson]

I agree. It's on my list and I have already contacted blackbear for a mail order tune. But, this is still a problem, I don't see how the original tune could have changed overnight. I need to get it back to performing correctly before I tune it. I'm afraid a tune will just mask the problem making troubleshooting it even harder. But yes, a tune is definitely in the near future.

 

[Brian Wilson]

And blackbear has informed me I have to have it fixed before they can make a tune for it anyways.

 

[M3kanic]

I have owned several full size gms and they all do what you say. It has to do with the way the ecu learns how you drive. When BlackBear did my tune for my 02 suburban I had no codes nothing telling me that there was anything wrong, but when I sent in my first data log they seen that my intake manifold gaskets were bad. So if you don't have any codes and no one can find anything. Tune it and the hesitation will be gone.

FYI my wife says that my 02 suburban is faster that here 10 yukon xl denali. (Hers is not tuned and hers even hesitates)

 

[Brian Wilson]

Thank you so much! So in my situation the car ran great and then the hesitation started badly. Then it got worse. Is there a way to check an intake gasket leak thru a scanner or maybe spraying the gasket areas with an aerosol? I'm positive Justin said I have to have it fixed before the tune. But he also mentioned if I get the auto tune or scan cable or something he might be able to help identify the problem.

 

[M3kanic]

You can do a smoke test or a carb cleaner test. When I went through Justin I bought an auto cal. But I believe that he is your best solution.