89 383 "backfire" problem
Thread Starter
Instructor
Joined: Jan 2005
Posts: 197
Likes: 0
From: East Amherst New York
89 383 "backfire" problem
I recently got up and running a new 383 for my 89 a4.
The problem is when I step on the gas at part throtle it "pops"
out the intake.After a pop or two and a slight stumble it takes off
excelent.
I did a scan (at idle) and came up with the following:
TPS .52volts
Block Learn 108
Integrator 116
IAC steps 160
Spark advance 19.9
inj pulse 2.0 ms
Mass air 12 gr/sec
Any help here would be greatly appreciated.
Thanks
The problem is when I step on the gas at part throtle it "pops"
out the intake.After a pop or two and a slight stumble it takes off
excelent.
I did a scan (at idle) and came up with the following:
TPS .52volts
Block Learn 108
Integrator 116
IAC steps 160
Spark advance 19.9
inj pulse 2.0 ms
Mass air 12 gr/sec
Any help here would be greatly appreciated.
Thanks
Safety Car
Joined: Sep 2003
Posts: 3,597
Likes: 22
From: Orange County NY
St. Jude Donor '10-'11-'12-'13
TPS is good, but the BLM / INT numbers indicate a rich condition (at idle). IAC steps are high, so if your IAC motor is functioning properly, you should re-set the base idle to get numbers in the 20-50 range at idle. Spark advance at idle is also normal (low rpm, low load conditions); so is inj pulse and MAF number.
The backfiring you are experiencing is most likely a momentary lean condition when you whack the throttle. You would need to increase the "accerleration enrichment" parameters in the PROM tune. Are you using the stock chip, or did you have a custom chip done? The stock chip would certainly explain the rich condition AND the lean pop off throttle. If not stock, then there is probably further tuning to be done.
The backfiring you are experiencing is most likely a momentary lean condition when you whack the throttle. You would need to increase the "accerleration enrichment" parameters in the PROM tune. Are you using the stock chip, or did you have a custom chip done? The stock chip would certainly explain the rich condition AND the lean pop off throttle. If not stock, then there is probably further tuning to be done.
Thread Starter
Instructor
Joined: Jan 2005
Posts: 197
Likes: 0
From: East Amherst New York
Had a custom chip done by Fastchip-Ed Wright.
I was wondering if the high IAC count could cause the lean pop.
The IAC is brand new. If so how do you reset the IAC.
Thanks
I was wondering if the high IAC count could cause the lean pop.
The IAC is brand new. If so how do you reset the IAC.
Thanks
Safety Car
Joined: Sep 2003
Posts: 3,597
Likes: 22
From: Orange County NY
St. Jude Donor '10-'11-'12-'13
The stock $6E mask / arap bin (if that is what Ed used as a base) calls for 160 steps at the "idle rpm start up position" out of a total of 255, though it should drop down to mid double digit numbers after that. Though it is high, I doubt it has anything to do with the lean pop you are experiencing. I really think it is an acceleration enrichment issue. Once in closed loop, watch the O2 voltage when you hit the throttle - it probably goes very low right at that moment.
To set the base idle, ground terminals A and B in the ALDL connector below the dash. Turn the key to the "on" position, but do not start the car. Wait about 30 seconds for the IAC motor to fully close. Now disconnect the electrical connector to the IAC motor. Now remove the ground from the ALDL and start the engine. Adjust the idle using the throttle stop screw in the throttle body. For my 383, I adjusted the idle to about 850 rpm (target idle on the chip is 1200 when cold, 950 when warmed up). I typically see between 30 and 60 steps depending on idle rpm.
To set the base idle, ground terminals A and B in the ALDL connector below the dash. Turn the key to the "on" position, but do not start the car. Wait about 30 seconds for the IAC motor to fully close. Now disconnect the electrical connector to the IAC motor. Now remove the ground from the ALDL and start the engine. Adjust the idle using the throttle stop screw in the throttle body. For my 383, I adjusted the idle to about 850 rpm (target idle on the chip is 1200 when cold, 950 when warmed up). I typically see between 30 and 60 steps depending on idle rpm.
