topaz

I have a 1999 F-150 4X4 a couple of days ago I was driving along and was in overdrive as I started to push throttle down it started to buck, and has been doing it on and off, but when I get out of overdrive it seems to be fine, is there a overdrive sensor.

Darrell

otto457

When was the last time the plugs and COP were changed? Many times a low grade mis fire will cause a bucking at 40-50 when it shifts into OD.

sprousef150

Had the same problem at 90 k It was a coil pack no. 7 it got worse and the check engine light came on. I hooked my scan tool up to it and it told me no. 7 misfire. I have 120,000 on my truck now and have replaced no. 5,6,7 & 3. I replaced the plugs at 90k when I changed no. 7. Used MC Platnums, What came in it. it needed it. common problem on 97 -03's used accell coil packs

topaz

First thank all of you for your replies, one COP and 8 platinum plugs were changed less then a year ago, now when I first start it up in the morning t runs fine, but after it warms up it and I stop then start it again it runs rough until I get to 35 MPH then mellows out, I put my code reader on truck several times but NO codes, I took it to a local auto repair shop and they said that I should change #4 cop, but if it was bad wouldn't it show up on reader, when asked what there reader said I got no answer. Any more help would most appreciated.

otto457

As a rule of thumb COPs should be changed when the plugs are changed, because the connections within get weak. Check for vacuum leaks, and clean the throttle body (IAC and EGR ports included) as these can also add to warm misfire problems.


No. The PCM is very slow to throw a code until it is absolutely sure. Low grade misfires usually don't throw a code, but the effects can be felt. I don't know how the shop told you to replace #4 though without a code.