[SDHoosier]

Hi,

I have a 1999 Silverado with the 5.3L Vortec and 114k miles. It is stock except for a K&N air filter (just cleaned),dual exhaust and 285/75/16 tires. I have been noticing a problem lately that has me concerned. When I start the truck up, I always let it warm up for a minute before driving. Lately when I first take off, if I give any more than very light throttle, it bogs down, hesitates, acts like it can’t get out of it’s own way. Then after 10 seconds or so, it runs normally.

I also notice that sometimes when I am in overdrive and I slow down, then accelerate it doesn’t downshift and gets bogged down at low rpm and studders a bit, which I remedy by pushing the tow/haul button to get it to down shift. My theory is that this is caused by my 285/75/16 tires being larger than stock.

Anyone have any insight? Another thing to consider is that I had the fuel pump replaced about 30k miles ago after it went bad. Not sure if that might have anything to do with the 1st problem

Thanks for any input. I really appreciate it.

 

[454]

Sounds like it could be a fuel pump, but since you mention that you just cleaned your K&N, are you sure you didn't over oil it? There have been issues with MAF sensor fouling resulting from too much oil being applied which could cause symptoms like this.

 

[MrCritical]

I'd check that MAF as already mentioned. Plus it's time to change that fuel filter again if you haven't already.

 

[SDHoosier]

Thanks for the tips. How do I check the MAF sensor, aside from just replacing it?

 

[454]

Thanks for the tips. How do I check the MAF sensor, aside from just replacing it?

Just buy a can of MAF cleaner and spray it down.

 

[SDHoosier]

Thanks!

 

[454]

Thanks!

It also might be beneficial to go to AutoZone or somewhere similar and get your codes read. Sometimes a MAF code or misfire code doesn't necessarily trip a SES light. By getting the problem determined this way you can save some cash from buying things you might not need.

 

[SDHoosier]

I thought any codes would set of the SES light, so I didn't bother checking. Thanks for the tips.

 

[Mobile Tech]

Hi,

I have a 1999 Silverado with the 5.3L Vortec and 114k miles. It is stock except for a K&N air filter (just cleaned),dual exhaust and 285/75/16 tires. I have been noticing a problem lately that has me concerned. When I start the truck up, I always let it warm up for a minute before driving. Lately when I first take off, if I give any more than very light throttle, it bogs down, hesitates, acts like it can’t get out of it’s own way. Then after 10 seconds or so, it runs normally.

I also notice that sometimes when I am in overdrive and I slow down, then accelerate it doesn’t downshift and gets bogged down at low rpm and studders a bit, which I remedy by pushing the tow/haul button to get it to down shift. My theory is that this is caused by my 285/75/16 tires being larger than stock.

Anyone have any insight? Another thing to consider is that I had the fuel pump replaced about 30k miles ago after it went bad. Not sure if that might have anything to do with the 1st problem

Thanks for any input. I really appreciate it.

There is a TSB (Technical Service Bulletin) that will fix your concern. It involves a PCM reprogram. I have the same year model truck also with a K&N filter. I had my truck reprogramed for the same problem about 2 months ago. I only have 71,000 on my truck. Feel free to contact me for the TSB info.

Regards,
Gary

 

[greenlightning]

SDhoosier did you figure out the problem. I have the same issue with my truck.

 

[Mobile Tech]

GM Bulletin No. 01-06-04-006
Date: February, 2001

TECHNICAL

Subject:
Lean Hesitation, Sag or Stumble on light/moderate Acceleration

Models:
1999 Chevrolet and GMC C/K Pickup Models (Silverado, Sierra)
with 4.8 L, 5.3 L or 6.0 L V8 Engines (VINS V, T, U -RPOs LR4, LM7, LQ4)

Condition

Some customers may comment on the following condition:

A lean hesition, sag or stumble present during light to mederate accelerations.

Usually only present on the first one or two accelerations.

The condition occures when the coolant temp is below -6 Cel and +21 Cel (20 F and 70 F)

Fuels with a high drivability index can also be a contributor.

Cause:
CALIBRATIONS NOT OPTIMIZED FOR VARIOUS OPERATING PARAMETERS.

Correction:
Prom reprogramming

 

[Mobile Tech]

SDHoosier READ THIS !!!!!!

PCM - Lean Hesitation/Sag/Stumble on Acceleration

Bulletin No.: 01-06-04-006

Date: February, 2001

TECHNICAL

Subject:
Lean Hesitation, Sag or Stumble On Light/Moderate Acceleration
(Reprogram PCM)

Models:
1999 Chevrolet and GMC C/K Pickup Models (Silverado, Sierra)
with 4.8 L, 5.3 L or 6.0 L V8 Engine (VINS V, T, U - RPOs LR4, LM7, LQ4)

Condition

Some customers may comment on the following condition:

A lean hesitation, sag or stumble present during light to moderate accelerations.

^ Usually only present on the first one or two accelerations.

^ The condition occurs when the coolant temperature is between -6°C and +21 °C (20°F and 70°F).

^ Fuels with a high drivability index can also be a contributor.


Calibration Information




The Calibrations shown are electronic calibrations and are NOT available from GMSPO. Calibrations will be available from Techline starting November 2000, on the TIS 2000 version 19.5 TIS 00/2000 data update or later.

Cause

Calibrations not optimized for various operating parameters.

Correction

Verify that the drivability condition is not the result of an inoperative component, or a related wiring/other condition.

 

[BobDavis]

Thank You, I have been looking for a fix for this for over a year, I have changed fuel filter and cleaned the entire air intake system to no avail. I will be taking it in for a PCM reprogramming.