Stumbles on acceleration

[colaz71]

I have a 2000 Z71 Tahoe 5.7l 350. It idles smooth, and revs up in park perfectly fine. Driving around in low rpm's everything is fine. Upon pressing on the gas pedal it starts to stumble. The further I press on it, the worse it gets.

I have replaced the plugs and wires. Fuel filter. The fuel pump was replaced about 30k miles ago by the previous owner at a chevrolet dealership. I replaced the TPS also.

Please Help!!!

 

[JennaBear]

Definitely sounds like a fuel delivery problem but could also be plugged cat converters.

 

[95ThAHOE]

yeah i would definitly check that the cats arent clogged, i have had the same problem before

 

[colaz71]

Okay I will look into those things. When I take off and am taching no higher than 2500 rpm's. The truck runs fine. Yet when I give it at least half throttle or more. It doesn't want to pull past 3500 rpm's. It will but extremely slow. Even at a steady speed of 55mph. Stomping on the gas pedal only causes it to stumble. Not quite as bad as it does at a lower rpm though.

 

[GMCYukalade]

Just unplug the wiring going to the front two O2 sensors, and then take them both out (22mm wrench) - than drive it *note the SES light should/will come on - if it runs better than then you know its the cats (because the exhuast is escaping out of the holes for the o2 sensors) - put your O2s back in - *the SES may or may not go off on its own (if it doesn't take it to autozone, tell them you need to borrow the GM scanner for the SES light, and turn it off yourself, or have someone come out and scan the codes, he will tell you what it is, tell him what you did and he should turn the code off - if not, ask him if you can see the scanner and turn it off yourself (i have done this before))

 

[colaz71]

GMCYukalade- Just got done trying that. Still runs horrible. Just from take off and stomping on the gas it fell on its face. It didn't kick any SES lights though. If that means anything at all.

Also the mileage on my truck is around 130k. It has had the intake gaskets replaced around 80k by the previous owner at a dealer. I was reading up on something about the spiders cracking on these?

 

[tahoeman21]

the stumbling....

wassup colaz71?????? i had a similar problem with my 99 tahoe.....its a 4dr 2wd and the 5.7 vortec of course... mine stumbled as well, whenever i press the gas, hard... it would hesitate pretty bad in the low rpms and then it would take off.... one night i was pulling from a stop and it stumbled again until i floored the pedal all the way.... and baam!,,, the ses came on!!!

I took it to my mechanic to scan the code and the scanner popped several codes.... all of these codes were related to the MAF!!!! it took a while for the ses to come on too when i had this problem.....

So after my mechanic installed the MAF, the stumbling was gone!!!! my shift are smoother and got the power it supposed to have...

BTW... when i had this issue, when i the accelerator was floored, the engine would rev but got very little speed....with the MAF replaced..... it goes.

So my suggestion is..... check out the MAF.... its better to replaced these sensors instead of cleaning them.... if your problem does turn out to be the MAF, i recommend getting a remanufactured one. Ill save you a few bucks.... hehe. You can go new too, but its up to you.... good luck.

 

[colaz71]

tahoeman21- After your suggestion. I grabbed a spare MAF sensor from a '96 Beretta. Even though it was a smaller mm MAF. I tried it anyways. My Tahoe ran better than it ever has since I bought it!!!! I cleaned the other one to get me by until I get a new unit and it seems to run just as good as the spare one now. Dang K&N air filter!

Thanks again!!!!!

 

[Tieedekolwe]

Thank you for the*informative*posts.
матрешки

 

[MO Viet Vet]

tahoeman21- After your suggestion. I grabbed a spare MAF sensor from a '96 Beretta. Even though it was a smaller mm MAF. I tried it anyways. My Tahoe ran better than it ever has since I bought it!!!! I cleaned the other one to get me by until I get a new unit and it seems to run just as good as the spare one now. Dang K&N air filter!

Thanks again!!!!!

No need to replace the MAF if is ok after cleaning. Save the money for now.

 

[lesterl]

'bout 6.5years ago man.... But yeah, those K&N are bad at fouling up the MAF....

 

[MO Viet Vet]

The K&N make an oily mess of the MAF.