Sputtering 1999 GMC Suburban

gmc
suburban

#1

Friends,

As I mentioned in the title, I have a 1999 GMC Suburban with about 150000 miles. I love the car, but lately it has been acting peculiar immediately after starting it. Whether hot or cold weather, the car will sputter, pop, backfire, buck and generally not get up and go for the first 3-5 minutes the engine is running. I can put the gas to the floor and the car continues to sputter along at about 20 mph - bugging the heck out of drivers behind me. If I do lay on the accelerator however, the car will rev high RPMs as if it wants to go though the gears behave like its in neutral.

After about 3 minutes of sputtering, the car will again start accelerating as if nothing is wrong. This happens every time I start it.

Does anyone have thoughts on what might be going on?


#2

Engine revs + no acceleration while in drive = transmission problem. Have you checked the transmission fluid level?


#3

Haven’t looked at the transmission fluid level. I will do that.


#4

There may be two problems. One with the transmission and one with a weak fuel pump.

When the engine is started/operated when cold, it means the computer is in the open loop mode. This means the computer injects more fuel into the engine while it’s cold. When the coolant reaches about 150 degrees, the computer then goes into the closed loop mode. The computer then injects fuel into the engine based on the information it receives from the O2 sensor(s).

So the fuel pump may not be able to deliver the proper pressure/volume of fuel while the engine is cold, which causes the engine to lack power, but once the engine gets hot enough there’s enough pressure/volume so the engine runs normally.

Tester


#5

It does sound like there is a transmission related problem. Not uncommon for tis to first manifest when cold first thing in the morning. Probably best to address this first. If further problems remain after transmission is repaired, post again.