Stumble
Burning Brakes
Joined: Sep 2000
Posts: 1,199
Likes: 1
From: NewCastle IN. USA
Re: Stumble (insanegt1)
depends on what kind of stumble your getting.
if it backfires into the intake or just plain falls on its face (like when you run out of gas) then its going lean.
if it blubbers, chug's, blows black smoke then its too rich.
you'll have to play with the accelleration enrichment.
timing can play a roll too.
RJ
[Modified by ol,RJ, 10:25 PM 9/11/2002]
if it backfires into the intake or just plain falls on its face (like when you run out of gas) then its going lean.
if it blubbers, chug's, blows black smoke then its too rich.
you'll have to play with the accelleration enrichment.
timing can play a roll too.
RJ
[Modified by ol,RJ, 10:25 PM 9/11/2002]
Drifting
Joined: Oct 1999
Posts: 1,722
Likes: 0
From: Gloucester Va
Re: Stumble (insanegt1)
Check your fuel pump. I had same problem. It was a bad fuel pump. There is a test you can do. First check fuel pressure. Make sure it can hold called for fuel pressure. Then check flow rate.. This is a bit messy, but just because the pump can reach the pressure does not mean it can keep it when in demand. You will have to undo the supply fuel line by the intake.
Pro
Joined: Jun 2000
Posts: 686
Likes: 0
From: Crystal Lake, IL USA
Re: Stumble (insanegt1)
I chased this problem for the better part of a year. It was spark related in my case.
Timing mark on balancer slipped 13/16" which added 13 deg to the base advance, however the module wasn't working so the car was running at 19 deg constant + something random from the module. Fixing the module led to audible knock which led to finding the balancer problem. Stumble gone.
Could easily have been fuel related. Is the regulator getting vacuum? Hook up a fuel pressure gauge and make sure the pressure increases when you give it gas. The open loop fueling tables assume 15-20% increase in fuel pressure at WOT. Adding more AE can "fix" some tip-in stumble, but you willl eventually get stuck somewhere as the underlying problem gets worse. Tape the fuel pressure gauge to the windshield and drive. Make sure pressure doesn't drop off under load - weak pump.
Could be the MAF burn-off relay. Dirty MAF wire is slow to respond, so the computer sees TPS open but the air flow not increasing so PE mode is delayed. Lean tip-in stumble.
There are more possibilities.
Timing mark on balancer slipped 13/16" which added 13 deg to the base advance, however the module wasn't working so the car was running at 19 deg constant + something random from the module. Fixing the module led to audible knock which led to finding the balancer problem. Stumble gone.
Could easily have been fuel related. Is the regulator getting vacuum? Hook up a fuel pressure gauge and make sure the pressure increases when you give it gas. The open loop fueling tables assume 15-20% increase in fuel pressure at WOT. Adding more AE can "fix" some tip-in stumble, but you willl eventually get stuck somewhere as the underlying problem gets worse. Tape the fuel pressure gauge to the windshield and drive. Make sure pressure doesn't drop off under load - weak pump.
Could be the MAF burn-off relay. Dirty MAF wire is slow to respond, so the computer sees TPS open but the air flow not increasing so PE mode is delayed. Lean tip-in stumble.
There are more possibilities.
