2003 Marauder will not upshift from 1st or 2nd gear when at full throtttle. It just maintains 5500rpm in 1st or 5000rpm if in 2nd gear. In order to get it to upshift I must reduce throttle position to about 1/2 throttle or a little less.
I replaced the MAF and have tested with the air cleaner on and off with no difference. I also replaced the coil packs last year, thinking it might help. It did not help.
The car and engine operate normally except at full throttle. The transmission downshifts normally. Only the full throttle upshift is abnormal. The check engine light is not illuminated.
I also had the transmission fluid changed just to see if it would fix the problem; it did not. I just checked the trans fluid level and it is a bit high at the top of the hash marked area on the dipstick.
Has anybody had this problem or have a suggestion as to where to investigate next?
Thanks