1998 Chevy Tahoe Poor high load performance.

Tiny
STOPSRUS
  • MEMBER
  • 1998 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 225,000 MILES
Let me preface this by saying that this problem has existed since I got the car at 85,000 miles.

This is a 5.7, generally runs perfect. Good mileage, 18-19 highway, idles smooth, starts easy, no codes. When pushing it moderately hard like a long hill or hard acceleration on the highway, it starts dropping cylinders after 10 to 15 seconds. If I let up on the gas and slow up they cut back in over about 15 seconds, or so, and it smooths out. It feels like its running out of gas. Over the past year it has new ignition everything, fuel pump and filter, cats and exhaust, O2 sensors. Has good O2 waveforms. Shows no misfires on Matco scanner. Cannot see anything happening on the scanner when it happens. This gets dangerous going up a hill with a semi on my bumper! Any ideas?
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Wednesday, September 8th, 2010 AT 9:19 PM

3 Replies

Tiny
MERLIN2021
  • EXPERT
I do know GM has a tech bulletin about misfires due the the PCM ground strap on the rear of the cylinder head, remove it, clean both the head mounting surface and the ground strap, I use emery cloth, then attach it to the head, and cover it with RTV.
Any misfire codes? Service engine light coming on?
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Friday, September 10th, 2010 AT 3:05 PM
Tiny
STOPSRUS
  • MEMBER
No codes, no SES and nothing shows up on the diagnostic when it happens. It is always reproducible.
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Friday, September 10th, 2010 AT 5:33 PM
Tiny
MERLIN2021
  • EXPERT
Try my suggestion.
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Saturday, September 11th, 2010 AT 9:46 AM

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