Tune going weird?

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Mar 6, 2009 | 03:04 PM

fauslpss

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From: Sarasota

Tune going weird?

I have a Cam car that is SD tuned by a reputable tuner for some reason the tune degrades over time. Symptoms are when leaving aggressively from a stop it stumbles and then goes, also it does not recover from idle very well sometimes it will stay at 600 rpm for a min? Any help would be appreciated Id like to figure it out before I go see him.

P.S. I have 42#s from FICinjectors that are at 79% dc and Im only around 430hp. I have 255 lph pump with the hot wire. Tuner said he had to put in high figures to get the a/r right for the size injector.

Thanks Eric

Mar 7, 2009 | 12:20 PM

Ed Wright

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From: Tulsa, OK

The "tune' can't "degrade over time". It can not change. The PCM runs a checksum on the calibration often. If one bit changes you will get an SES light and a memory error code. The only way that could change woul be a failing flash memory chip. That would be a PCM issue, not the tuning. If the fuel trims are off some, or you have a knock (false or otherwise) detected the PCM can back the timing down. Don't blame your tuner until you know what is wrong. If you suspect it is learning something to cause a change in performance, reset the PCM to see if it runs better again. That info will also help your tuner determin what to look at when you go back. More often than not, something on the vehicle "degrades", as the tuning can not change.

Good luck, Ed

Mar 7, 2009 | 01:19 PM