jollygreengiant
New member
Last year I bought a 2001 Suburban with 171,000 miles on it. It runs well at lower speeds and on the interstate at 70 mph but gets poor fuel economy (10 to 15 mpg) and experiences slow and uneven acceleration between 35 and 60 mph. Driving west of Denver on I-70 with my family of six, it had to shift all the way down to second gear to make it over the steep, high pass. I’ve replaced the spark plugs, plug wires, fuel pump (it failed suddenly), the fuel filter, and used Seafoam in the gas tank and intake with little improvement. The mechanic at the Chevy dealer checked the codes and found no apparent problem and blamed the high mileage. Mechanics have suggested it may be a faulty MAP sensor, MAF sensor, fuel pressure regulator, or oxygen sensors. I checked the fuel pressure regulator and it seems to be fine. The sensors are expensive enough that I don’t want to just start changing them without some indication that they are actually faulty. Another mechanic said that the factory exhaust pipes from the catalytic converter on each side of the engine came together into one exhaust pipe with a connector flange but the previous owner had cut the “y” pipe and flange off and installed two separate exhaust pipes going back through glass packs. After I bought the suburban, I had Midas replace the rusted out glass packs with two pipes into a Flowmaster muffler and two pipes coming out. He said the problem is that the engine now does not have enough back pressure at low RPMs and the computer keeps trying to compensate resulting in poor economy, poor acceleration, and poor low end torque. Could that be correct? 
If I were confident in that diagnosis, I could probably have Midas reinstall the factory spec “y” pipe and flange in front of the new muffler for not too much.
I have another issue that I don’t think is related but who knows! When I first start up the engine, there are no warning lights lit up and the anti-lock brakes pulse when I start to skid. However, after driving a couple of miles, the ABS and Brakes warning lights come on and the anti-lock brakes no longer pulse when I start to skid. I haven’t worried too much because the brakes continued to work smoothly like it would if it didn’t have the ABS system. However, I’ve read on this forum that the ABS system is linked somehow to the traction control system and it could cause poor acceleration. Also, I also almost skidded through an intersection during a recent snow storm and would have appreciated having the ABS function.
Other than these two issues, I love my new (to me) suburban.
I would greatly appreciate any help so I can get it fixed and love it even more.
If I were confident in that diagnosis, I could probably have Midas reinstall the factory spec “y” pipe and flange in front of the new muffler for not too much.I have another issue that I don’t think is related but who knows! When I first start up the engine, there are no warning lights lit up and the anti-lock brakes pulse when I start to skid. However, after driving a couple of miles, the ABS and Brakes warning lights come on and the anti-lock brakes no longer pulse when I start to skid. I haven’t worried too much because the brakes continued to work smoothly like it would if it didn’t have the ABS system. However, I’ve read on this forum that the ABS system is linked somehow to the traction control system and it could cause poor acceleration. Also, I also almost skidded through an intersection during a recent snow storm and would have appreciated having the ABS function.
Other than these two issues, I love my new (to me) suburban.
I would greatly appreciate any help so I can get it fixed and love it even more.
