99 Tahoe - Trouble Accelerating / Hesitation

[Sejo]

Over the last month my 99 4WD Tahoe has been giving me problems
accelerating when I give it a heavy foot. When I hit the gas down it loses acceleration almost like it's
being starved of air or gas. When I hit the gas the engines just bogs down, begins to hesitate, and will not accelerate.

It'll drive ok if I'm light on the pedal; and the engine feels smoother than ever.

This morning I took it out on the interstate (after is sat overnight - cooled off) and ran it hard and it was MOVING - GREAT ACCELERATION. I left the truck running for an hour or so, driving around town and sitting idly in the drive way to let things warm up and I took it back out on the interstate. This time....the hesitation was back. Could my fuel pump be overheating? I changed it about 4 years ago. The symptoms only got worse after an 11 hour road trip. It got progressively worse over the last 4 hours of my trip. In the end I had to be light on the gas pedal to get it to speed; at speed it ran great, but if I had to accelerate for any reason (passing, inclines, etc.) it wouldn't GO! Just had to cruise.

Any ideas?

 

[mygreen98]

fuel pump, or fuel pressure regulator.

 

[treepete]

fuel pump

 

[Sejo]

What about if; when I slam the gas for it to go....it hesitates, the engine REVS up, but the truck doesn't move and starts to sputter?! Still the fuel pump?

 

[peterey2]

I'd say the fuel pump too. But i corrected a problem with symptoms jus like yours by simply replacing a fuel filter.

 

[Sepiroth]

Have your fuel pressure and fuel volume checked. Your pump is to be pushing 58-62psi. It does read as if your pump is starting to give up the ghost

 

[Sejo]

So I finally had to get back home.

I checked the fuel pressure. The fuel pressure at engine idle was about 55psi, and at high revs it's 60psi. I ran the truck with the gauge attached and it ran at 60psi - 55psi when coming to a stop. Whenever I encountered the problem I was having on the interstate the pressure dropped to 50psi. Fuel Pump?

I went and had the Cats checked out. The guy said they seemed ok other than a MASSIVE leak coming from their weld (replacement cats); he fixed that weld along with replacing the O2 Sensors (all 4). Thru in some complete fuel system cleaner. Also changed the fuel pump with a Bosch one from Advance Autoparts with lifetime warranty and the truck is not hesitating any more.

Could I have patched the problem temporarily, or did I fix it? The O2 sensors that were in there were the originals so I am sure they weren't helping the problem. The cats are about 2 or 3 years old. The entire exhaust system is cr@p, so I'll have to save up for a nice catback exhaust with headers.

I drove it home 11 hours 75-80MPH, stopping only to refuel, and no hesitations. I'd call it good. It was the smoothest ride I had ever had in the Tahoe.

 

[mygreen98]

probably lazy fuel pump. they stink in these vehicles !!!!!!!!!!!!!!!!!

 

[Sejo]

probably lazy fuel pump. they stink in these vehicles !!!!!!!!!!!!!!!!!

That is for sure!! This is my 2nd one already. I had to replace it in '05; I think it failed prematurely. Lifetime warranty now.

I do run the Tahoe hard on long trips and around down; bound to happen I guess.

 

[PotentialTahoe]

I too have a similar problem. My rpm and mph gauges will go out when driving and the accelerating feels very sluggish. But when the rpm and mph gauges are working, it runs as it should, very powerful good accelaration.

 

[Miss Old Motors]

I seem to have somewhat of the same problem... My truck every now and then will just seem sluggish and seem to not climb rpms as fast as it should when i mat it. Idk if it is a driveline problem in the transmission or if it is starving for fuel. it seems to be intermittent.

 

[J.P.]

i just had same problem in my 95 gmc yukon changed pump still did it, finally went to the dealer and they put it on their machine and it came up with a sensor on the transmission , changed it no more problems, dealer service guy said alot of transmission places say you have tranny problems and its just this sensor, it cost me $150.00 for sensor and half hour labor .

 

[treepete]

whats the name of that sensor, do you remember?

 

[J.P.]

The part number was GM #15547452 with is a vhicle speed sensor that goes on transmission, the price was 149.16 , if you truck is bucking and has hesitation this may be your problem, :ack:

 

[treepete]

hmmm interesting. I wonder if that is causing my odd revving when Im at 52 mph. it goes between 15 and 1600 rpm and goes back and forth in there... like its searching around.

 

[FTGF]

Very interesting indeed.

I had the same issue with the Cats first, and then a concurrent Fuel Pump Failure. Replaced everything including the O2 sensors. Did a full tune up but am still having the same RPM (hunting or searching) at low RPM's. I received a lot of feedback from forum members of things to try and check, but still haven't been able to put it to rest.

How hard was it to replace the sensor?

I have just dealt with it for a while now...

 

[PotentialTahoe]

i just had same problem in my 95 gmc yukon changed pump still did it, finally went to the dealer and they put it on their machine and it came up with a sensor on the transmission , changed it no more problems, dealer service guy said alot of transmission places say you have tranny problems and its just this sensor, it cost me $150.00 for sensor and half hour labor .

Did this problem also affect your tach and mph gauges? Mine go in and out all the time, and when they're out is when the tranny lacks power to the wheels. Also GM Parts direct has the sensor for $90, FYI. GM List is $153

 

[PotentialTahoe]

Very interesting indeed.

I had the same issue with the Cats first, and then a concurrent Fuel Pump Failure. Replaced everything including the O2 sensors. Did a full tune up but am still having the same RPM (hunting or searching) at low RPM's. I received a lot of feedback from forum members of things to try and check, but still haven't been able to put it to rest.

How hard was it to replace the sensor?

I have just dealt with it for a while now...

I located the VSS sensor, it is on the back end of the tranny right when it bolts the drive shaft. Grab an adjustible wrench and replace it. I had to special order the sensor today, $84 and it takes a week. We will see if that fixes the problem. If not, maybe dealer can put it on the machine.

 

[98 Yheti]

Although it seems very simple, it is something that is frequently overlooked. Check your air filter. If your filter is junked up, it will not give proper signal to the MAF (Mass Air Flow Sensor) and the engine can run improperly. Also check the MAF at the same time to make sure that it doesn't have a lot of crap on it. The MAF is fairly delicate so be careful, but if it is dirty, you can get cleaner from any autoparts store and can spray it on the sensors to clean them off.
Hope this helps!

 

[tahoeman21]

I agree with 98 Yheti... When i had my 99 tahoe, I had messed up MAF sensor go bad on me. A dirty K&N filter was the cause of the failure. This caused sluggish acceleration off the line and the tranny would act as if it was slipping. Once i replaced the MAF, there was no more sluggish acceleration. Now the Tahoe would take off quick as hell which i loved, and the tranny would shift nice and firm through all gears.