how do you cure a stumble off idle, the car run great after the stumble, i know a lean condition causes a stumble. heres what i have ,87 gn i installed a new iac , new tps , new maf , new 340 walboro pump, set fuel pressure 42 lbs, here are my scanmaster readings, o2- 680 af 04 lv8 32 int 128 bl 132 rpm 800 tps 42, iac 17 cc 25 to 255 , motor . te 44 turbo, terry houston down pipe, 50 # inj ericks chip, 206/206 comp cam. stumble causes bad 60 ft ,,,. 2.44, 60 12.24 et 113.88 mph i need help? jedeley
stumble off idle. stumbles even when power brakeing
- Thread starter jedley
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- Joined
- May 26, 2001
- Messages
- 9,208
The first thing I would do is up the base fuel pressure 5#'s or so.
Does your pump gas have 10 or 15% alcohol?
The gas blend is different all over the country, and summer blend gas can really suck in some places like here, and many GN's run like crap because it it.
My street car likes 55 psi base fuel pressure or it will bog like crazy.
Does your pump gas have 10 or 15% alcohol?
The gas blend is different all over the country, and summer blend gas can really suck in some places like here, and many GN's run like crap because it it.
My street car likes 55 psi base fuel pressure or it will bog like crazy.
i raised the fuel pressure to 50 # and no diff, we have 92 oct with no alky.
- Joined
- May 28, 2001
- Messages
- 16,518
Data log it, and capture the incident....
wideband will allow you to see the afr so you don't have to wonder.logging it would be even better which has been suggested. you changed a lot of things several sensors and fuel pump was there a problem with the car prior to the parts swap?does the car get knock?
this can make you or break you
- Joined
- Feb 18, 2006
- Messages
- 10,083
Was there any work done to the car prior to this condition?
Couple things come to mind.
Check fuel pressure regulator. Make sure fuel pressure is rising with vacuum drop.
Look for vacuum leaks and pre turbo maf pipe leaks.
If those check out you can try slightly moving the cam sensor.
Couple things come to mind.
Check fuel pressure regulator. Make sure fuel pressure is rising with vacuum drop.
Look for vacuum leaks and pre turbo maf pipe leaks.
If those check out you can try slightly moving the cam sensor.
i have a stock maf , and i replaced it with a new delco maf and it made no difference
i have a scanmaster, the problem was the car was stumbleing so i started changeing parts trying to fix the problem. the car does not show any knock. as i run race gas when i run it hard, also i have smc alky injection witch is an older unit so i turned it off thinking that was the problem . i have a out side fuel pressure gauge which showed that i had 65# lbs at full throttle in high gear .i have a accufab pressure regulator. the fuel pump was a walboro 255 which was 8 years old so i up dated it to walboro 340. one thing i found when changing the pump i pulled the screen filter off the pump and to my suprise the inlet in the pump was packed full of stuff that looked like lint , no metal no rust just packed full of lint that got past the screen filter . i still have the stumble.
