Odd problem I believe to be MAF related
06-21-2009, 01:05 PM
#1
Odd problem I believe to be MAF related So long story short my car has never performed stellar for the mods I have. Lately the shifts have been getting sloppier and it's felt even slower.
I put on a custom cold air kit that I made from 3"pvc and some rubber elbows to get cooler air into the engine. Seemed to make no difference in performance or MAF/MAP readings. IAT came down about 10-15 degrees though.
Parked the car, the next day it was running amazing and my shifts firmed back up. Downshifts were responsive and easier to get with less throttle.
Car was now reading 40 lbs/minute air in the maf, before it was 36-37 lbs/min. Only real difference I could find on a quick inspection of the scanner.
Car sit for a week, first time I romped around yesterday it was great still. Few miles down the road shifts slopped up again, wot shifts came down a couple hundred rpm, and MAF dropped back down to 36-37 lbs/min.
I'm going to try to borrow someone else's MAF, but do you guys have any other ideas as to where I could look? On a side note another thing that occurs every so often is similar but to the extreme...the car will rush through shifts sloppily (getting to 3rd by 20mph or so) and refuse to downshift or accelerate regardless of throttle position.
I'm getting no trouble codes other than an occasional "map out of range" due to the car occasionally idling too low in neutral or park (at least I think that's the cause...the car almost dies sometimes randomly). I changed the MAP sensor and nothing changed.
I've also tried different TP sensors and IAT modules with no change in response from the car.
Any and all ideas welcome and highly appreciated. I don't want to even think about tuning until I get this lined out.
I put on a custom cold air kit that I made from 3"pvc and some rubber elbows to get cooler air into the engine. Seemed to make no difference in performance or MAF/MAP readings. IAT came down about 10-15 degrees though.
Parked the car, the next day it was running amazing and my shifts firmed back up. Downshifts were responsive and easier to get with less throttle.
Car was now reading 40 lbs/minute air in the maf, before it was 36-37 lbs/min. Only real difference I could find on a quick inspection of the scanner.
Car sit for a week, first time I romped around yesterday it was great still. Few miles down the road shifts slopped up again, wot shifts came down a couple hundred rpm, and MAF dropped back down to 36-37 lbs/min.
I'm going to try to borrow someone else's MAF, but do you guys have any other ideas as to where I could look? On a side note another thing that occurs every so often is similar but to the extreme...the car will rush through shifts sloppily (getting to 3rd by 20mph or so) and refuse to downshift or accelerate regardless of throttle position.
I'm getting no trouble codes other than an occasional "map out of range" due to the car occasionally idling too low in neutral or park (at least I think that's the cause...the car almost dies sometimes randomly). I changed the MAP sensor and nothing changed.
I've also tried different TP sensors and IAT modules with no change in response from the car.
Any and all ideas welcome and highly appreciated. I don't want to even think about tuning until I get this lined out.
06-22-2009, 08:41 AM
#2
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If you are getting intermittent sensor codes, this
could be what gives you intermittent trans firmness
behavior. Some things can put the trans to fault
mode before a code sets, scan looking for
"immature" DTCs?
The trans also will change behavior if shift-cycle-time
learning is pushing things around. The "Desired Shift
Time" keys this. I zero that table to keep adaptive
trans stuff from meddling. Trans fluid temp and other
environmentals can make one day's "learn" be not-
ideal, the next.
could be what gives you intermittent trans firmness
behavior. Some things can put the trans to fault
mode before a code sets, scan looking for
"immature" DTCs?
The trans also will change behavior if shift-cycle-time
learning is pushing things around. The "Desired Shift
Time" keys this. I zero that table to keep adaptive
trans stuff from meddling. Trans fluid temp and other
environmentals can make one day's "learn" be not-
ideal, the next.