2002 GMC Envoy SLT 4.2 6 cylinder from North America
I would buy another if available new
Intermittent problem. The vehicle will start losing power while driving. The engine does "not" stall, but the mpg's drop from 18-19 to 6-9. It's almost like driving with one foot on the gas and one foot on the brake. If I take my foot off the gas, the vehicle starts slowing like I was braking. From a stop, it struggles to increase speed, sometimes knocks a little, strains, but does eventually shift gears, though not to OD. Again, like driving with a foot on the brake.
Tranny checked okay, plugs changed, throttle body cleaned and fuel filter changed. Mechanic said trial and error, since there are no service engine lights or codes on the computer. Trial and error suggesting a new throttle body or fuel pump. However, shifting into neutral, the engine accelerates smooth, doesn't cut out, so neither really fits, and both are very expensive.
Other than having to fix a warped exhaust manifold and gasket at 155K, in addition to normal wear items like cooling fan, front brakes, and a few things here and there, no problems.
Very dependable, but can't seem to find anyone with a similar problem?
Would you buy another car from this manufacturer? Yes
Review Date: 20th May, 2011
20th May 2011, 19:40
Check the spark plug wires - the insulation breaks down eventually, and the high voltage arcs to the engine block before it reaches the plugs.
21st May 2011, 11:50
We had the same problem with our TB. One day it just quit while I was idling in a parking lot. It took a full 30 seconds of cranking and then slowly sputtered to life. After that it ran fine again. We had the same things fixed on ours, and it never seemed to fully rectify the problem. I have heard that reflashing the computer can solve this as well. We never tried that though. My wife also had it stall at intersections once in awhile, which is very dangerous. She said she'd be waiting at a light, and then go to take off when it turned green, and it would quit. Amazing she didn't get rear-ended. Also, you lose power steering and brakes immediately, so it is very hard to coast it off the side of the road. She had the same result... cranking it for a ridiculously long time, and then it eventually starts up and runs fine again. Really weird issue.
We had to quit buying these trucks just because even the GM technicians couldn't actually fix the problem. It is a very common issue if you research it. That was how I knew what to ask them about fixing when it first happened (at least some theoretical fixes!). I am not quite sure why GM continued to sell these for so many years without solving that issue, as it was potentially so dangerous. It is just a machine, after all, so something had to be causing it!