What else would cause shortshifting intermittently?
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What else would cause shortshifting intermittently? My car will often become less responsive to downshifts and will short shift at WOT. The TPS sensor is seeing 100% according to either my EFI live or Snapon scanners. The VSS is also reading fine and accurately (according to WOT logs the mph and rpm are right. The MAF readings are the same minus the difference due to the peak being at a different rpm. My MAP sensor is hitting the same as BARO at WOT (even with closed exhaust).
The car also feels a little sluggish during this. What else can I look for?
The car also feels a little sluggish during this. What else can I look for?
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From: Northwest AR
no ideas?
is there anything I can check or any certain values to look for? the car runs "fine" just feels down on power, shifts too early, and shifts sloppy on the 2-3 (1-2 gets firmer when its running right, but its still firm in crap mode too)
is there anything I can check or any certain values to look for? the car runs "fine" just feels down on power, shifts too early, and shifts sloppy on the 2-3 (1-2 gets firmer when its running right, but its still firm in crap mode too)
Look at the values in C3904 and C3905 under Diagnostics. You can max out the value in the TPS Test Max MAP table and lower the value in the TPS Test Min MAP table. I had the same problem a long time ago and this cured the problem.
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well i just tried changing them both without success, I'll try maxing and severely dropping them next time i guess
I do know my maf is peaking at 35-36 lbs/min when its running bad and hitting 38-41 lbs/min when its running better. But I can't tell if the readings are higher because the rpms are where they should be or because of a fault somewhere. Guess I can manually hold gear and see what it reads. I tried a different maf with no change.
I do know my maf is peaking at 35-36 lbs/min when its running bad and hitting 38-41 lbs/min when its running better. But I can't tell if the readings are higher because the rpms are where they should be or because of a fault somewhere. Guess I can manually hold gear and see what it reads. I tried a different maf with no change.
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car throws no codes other than Gen L terminal
maf is peaking right before the shift, wherever it decides to occur at that particular run (if transmission shifts at 5800, peaks at 5800...if shifts at 6100, peaks at 6100)
maf is peaking right before the shift, wherever it decides to occur at that particular run (if transmission shifts at 5800, peaks at 5800...if shifts at 6100, peaks at 6100)
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FWIW I did notice the last time it was running great and shifting properly that my idle sounded a LOT different.
The cam was loping hard, the idle was really crisp, had that nice high compression "pop" sound to it. When it's running normal (aka poorly) it sounds a lot more lifeless.
This was not something I was looking for either, I just started the car and was like "damn that sounds a lot different" then down the road realized it was running a ton better at part throttle so I got on it and it ran like a bat outta hell and my tach was hitting 6200 instead of 5800 on the 1-2 shift and a little more on the 2-3.
The cam was loping hard, the idle was really crisp, had that nice high compression "pop" sound to it. When it's running normal (aka poorly) it sounds a lot more lifeless.
This was not something I was looking for either, I just started the car and was like "damn that sounds a lot different" then down the road realized it was running a ton better at part throttle so I got on it and it ran like a bat outta hell and my tach was hitting 6200 instead of 5800 on the 1-2 shift and a little more on the 2-3.
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Look at TPS voltage, not %. If you exceed 4.75V
then you are "in violation" in the moment, though
there is something like a 10-second timeout before
a code will set. Meanwhile the PCM does its self-
protection thing, short-shifting trans, maybe also
being conservative on other things.
If you are marginal, like 4.73V on a good day and
4.76V with ignition noise, there's your intermittent.
then you are "in violation" in the moment, though
there is something like a 10-second timeout before
a code will set. Meanwhile the PCM does its self-
protection thing, short-shifting trans, maybe also
being conservative on other things.
If you are marginal, like 4.73V on a good day and
4.76V with ignition noise, there's your intermittent.
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From: Northwest AR
TPS voltage reads 4.14 and hits 100%, but if I really force the pedal I can get it as high as 4.5volts
this strikes me as odd, maybe it will help...but like I said I have replaced the tps sensor before and when logging runs I've been trying to push as hard as possible to make sure it hit 100% the whole run
this strikes me as odd, maybe it will help...but like I said I have replaced the tps sensor before and when logging runs I've been trying to push as hard as possible to make sure it hit 100% the whole run
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any other ideas? I just drove it and tried to manually downshift because the pavement was wet and sometimes my front tires lock too easy and noticed it wouldn't manually go to first gear. So I went on down to dry pavement and discovered it's not holding manual low anymore...that part might be tune related which I'm going to check since the tune is different since the last time I tried manually shifting.
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Ok so I had just changed these numbers the other day, today I maxed them out and dropped the lower one in half.
It seems to have worked, car feels a good 15-20hp stronger and will shift where I set it. So unless it decides to go to **** on me again tomorrow I think I found the problem.
So what does this mean? Why does this happen? (I really want to learn "why" not just "what" since I plan to do my own tuning in the future).
I noticed the minimum number of occurences for this before throwing a code was set to 150. I dropped it to 20. I guess this is why I never had a code come up (my battery has been off and on several times for various reasons and lately I've been pcm flashing like a drunk bitch at mardi gras)
That should fix it. Those are the upper and lower MAP limits used by the PCM for testing when it compares actual TPS to desired or predicted values in C3906 and C3907. Lowering the number in TPS Min Failure will actually cause the TPS to set sooner (i.e. 20 will cause the DTC to set after it fails the test 20 times).
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That's what I wanted in that field, so if it messes up it will give me a code quicker, correct?
Thank you very very very much. I can't tell you how happy I will be if it stays running correctly.
If I come home with a 7 second slip or break 89mph at the track tomorrow I'd like to buy you beer or 2 haha
Thank you very very very much. I can't tell you how happy I will be if it stays running correctly.
If I come home with a 7 second slip or break 89mph at the track tomorrow I'd like to buy you beer or 2 haha
That's what I wanted in that field, so if it messes up it will give me a code quicker, correct?
Thank you very very very much. I can't tell you how happy I will be if it stays running correctly.
If I come home with a 7 second slip or break 89mph at the track tomorrow I'd like to buy you beer or 2 haha
Thank you very very very much. I can't tell you how happy I will be if it stays running correctly.
If I come home with a 7 second slip or break 89mph at the track tomorrow I'd like to buy you beer or 2 haha
