Hi I have a 1998 Mustang GT Manual Tranny. I have a problem with the car jerking during acceleration. It's not a problem at idle. I also notice when I'm giving it gas and let off the throttle the RPMs remain higher for a few seconds and slowly go down.
The previous owner installed a larger 78mm throttle body and cold air intake on the vehicle. Otherwise it's pretty stock.
I have code P1405 - Plugged or open upstream HI DPFE sensor hose. I found a tear on the vacuum hose and repaired it and replaced it but that changed nothing. I'm not even sure that this code has anything to do with my issue.
When you change the throttle and put a cold air intake all bets are off the cars were not made to run that way they would have to be reprogrammed by a pro to run correctly. Personally I go back to the stock everything and it wouldn't have a problem
