First off my car ran great before christmas. My plugs got fouled when my alternator went bad and since the i have changed them 2 times just to be sure. It took me a while to finally get it to idle properly but the car was tuned at fastlane and ran great even after i had brought the car home. After the plug change the car began to have a miss/hesitation above 4k rpms in an erratic manner. The weather is now consitantly around 25-30 degrees but im trying to find out what my problem is. The miss is very slight and only felt through the pedals and steering wheel sometimes and barely noticeable on the tach. I have regapped the plugs from .032 to .028 and that seemed to help. The maf is clean and the plugs and coils continue to check out ok. Does this mean i may have too much timing above 4k. What would be the first action i should take?
Aggravating Problem! Need help
- Thread starter AluminatorSnake
- Start date
datalog it-plain and simple. report back
May not have anything to do with it but good to check. There is a fuel pressure sender or controller on the drivers side fuel rail. You can disconnect that to see if there is any fuel leaking out. Sometimes the diaghram can bust causing funky stuff. Just an idea. Probably not an answer but worth a look if you haven't already.
I went return style and remove my fuel pressure sensor.
What was the weather like when it was tuned? If it was warmer and your fuel system was close to max then with it being cooler your fuel system might be maxing out.
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Explain that to me...as temp drops the pressure decreases? Physics of temp and pressure?
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Cooler air means a denser air charge. I've seen a few guys gain a couple PSI because of the cooler air. So if the motor is ingesting more air it needs more fuel to keep up. If the fuel system is already maxed or close to it then the denser air charge can push the fuel system beyond it's limits.
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+1.
Did you pull all of the plugs and verify that no others were fouled?
Cooler air is denser. This results in greater mass for a given volume. The additional mass creates a requirement for additional fuel.
Hence, if the car was tuned in warmer weather, the air was less dense than current conditions and require less fuel.
If you were already on the edge under warm weather conditions, the cool weather could have pushed you over the edge. I have my doubts on if this could be the issue.
While this is possible, I don't think it is the issue.
What plugs are you using?
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The weather was warmer in raleigh but when i picked up the car the temps that day were sub 40 and the car ran flawlessly. The temps have been fluctuating here from 15-40 but when i drive it i try and make sure its around 35-40.
Checked my plugs and they were all clean and the ceramic posts were still good and white, they were wet or anything of that nature: EXCEPT cylinders 5 and 8 they ceramic posts had some slight residue that covered maybe 25% of the white. Put the car on an analyzer and threw codes for coils missing in cylinders 5 & 8. Changed those coils and codes went away and plugs all look the same now good and clean. But the car still has the same problem slight miss, that i can barely feel but i can hear it in the exhaust.
NGK TR6 plugs that started out gapped at .032 when i brought the car back now they are all gapped at .028 and they all maintained the correct gap, checked them yesterday
Ohh the car has lethals budget return with 2 255 pumps on 42lb injectors. Should be plenty of fuel. And the air fuel is holding steady around mid 11's. reading it from a complete digital innovate guage.
let us know what the datalog tells you (I sent PID list last night to you)
Will do as soon as the snow from last night melts encased
Where are you at in VA ?
Coils could still be bad even though they check out ok... its under load that the problems start... floor the car up to 90 or 100 and sometimes that sends a cel.. you can have the car out of drive and rev the shit out of it and the coils will still check o.k its when ur driving.. my mach did the exact same thing...
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Did that multiple times even with the old coils cause i would do either a 3rd or 4th gear pull and it never threw codes that my handheld would read. Changed all the coils for new ones after i had the codes for the 5&8 cylinders missing and that solved the code issue. Also while data logging it yesterday it didnt show any misses
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