Hesitation and stumbling under load... Help!
Thread Starter
Instructor
Joined: Aug 2008
Posts: 173
Likes: 0
From: Altus AFB Oklahoma
Hesitation and stumbling under load... Help!
While driving to work this morning I got onto the freeway, while speeding up on the on ramp my car started stumbling basically bucking starting right about 2k in third gear. I shifted to fourth fifth and sixth same thing with no codes to speak of. Wondering if it could be a fuel or spark issue and it being dark I pull over shut down and unplug my MAF fire the car back up and now it runs fine through all the gears. It actually seems to pull much harder. I am at a loss for what could be causing this issue. I cleaned the MAF when i got home that didn't seem to fix the problem. Any gurus in here have any idea what my issue could be?
Burning Brakes
Joined: Oct 2013
Posts: 859
Likes: 1
While driving to work this morning I got onto the freeway, while speeding up on the on ramp my car started stumbling basically bucking starting right about 2k in third gear. I shifted to fourth fifth and sixth same thing with no codes to speak of. Wondering if it could be a fuel or spark issue and it being dark I pull over shut down and unplug my MAF fire the car back up and now it runs fine through all the gears. It actually seems to pull much harder. I am at a loss for what could be causing this issue. I cleaned the MAF when i got home that didn't seem to fix the problem. Any gurus in here have any idea what my issue could be?
Drifting
Joined: Sep 2009
Posts: 1,719
Likes: 4
From: cinnaminson n.j.
St. Jude Donor '14
Pull your codes and post. If no codes try this.
If you have access to a scanner, you want to pull up the misfire monitor. It should show you what cylinders were misfiring in history. If not driver the car under similar conditions and have someone watch the scanner(current misfires). If it's one or two cylinders, you can load test the ignition with an st125 spark checker. Start the car, it should fire repeatedly not erratically. If doesn't fire consistently, swap the wire 1st and retest, then the coil. It's quick and easy. If it does fire consistently swap plugs. If the misfire changes cylinders, you found your problem. You can do the same with injectors.
If nothing shows in the misfire monitor, check your st and lt fuel trims. If the total for each bank is +or- 10% replace the MAF. Drive the car and see if the fuel trims go back toward 0. They are almost never perfect. +or- 5 is good.
Light throttle higher gear misfires are usually ignition. Let us know how it goes.
If you have access to a scanner, you want to pull up the misfire monitor. It should show you what cylinders were misfiring in history. If not driver the car under similar conditions and have someone watch the scanner(current misfires). If it's one or two cylinders, you can load test the ignition with an st125 spark checker. Start the car, it should fire repeatedly not erratically. If doesn't fire consistently, swap the wire 1st and retest, then the coil. It's quick and easy. If it does fire consistently swap plugs. If the misfire changes cylinders, you found your problem. You can do the same with injectors.
If nothing shows in the misfire monitor, check your st and lt fuel trims. If the total for each bank is +or- 10% replace the MAF. Drive the car and see if the fuel trims go back toward 0. They are almost never perfect. +or- 5 is good.
Light throttle higher gear misfires are usually ignition. Let us know how it goes.
Thread Starter
Instructor
Joined: Aug 2008
Posts: 173
Likes: 0
From: Altus AFB Oklahoma
I do not have access to a scanner unfortunately. Could it still be a spark issue even though it runs amazingly with the maf unplugged and the computer in speed density mode? Do mafs just go bad? And I have no codes.
