Intermittent Buck/Jerk While Driving

[joegr]

Jrand is on my ignore list. What ever he has said about drive cycles is BS as far as fixing your problems. A drive cycle after a reset just makes the relearn happen faster. It's only for diagnostic purposes.

Having a dealer stress test all the coils will cost more than it would for you to replace all the coils and plugs yourself.
There are a few (very very few) really good independents that would take this as a challenge and do the proper instrumentation of your car to figure this issue out.

 

[joegr]

...1. If I replace it with the same number from the same year, engine,trans, will it be necessary to have it reprogrammed?...

It depends on what you mean by "reprogrammed." No matter what, anytime a PCM is replaced, Your keys, cluster (PATS), and PCM all have to be "married" together before you can even start the car. This is a security feature to keep car thieves from stealing your car just by swapping the PCM. Some 3rd scan tools can enable you to do this, or a dealer can do it. If you don't have the tool and you can't get someone with the tool to come to you, you'll have to tow the car to them.

 

[md1twal3]

Good to know. I'd been cranking it thinking the PCM wasn't my issue. I did purchase one that is the exact number from an LKQ. Should be here early next week. I have a decent scanner, I'll read up to see if it has this capability. Otherwise, I do have tech friends at a Ford dealer that I can dolly it to if needed. I'll update when I know more...

 

[md1twal3]

ISSUE SOLVED....but it wasn't the PCM. I finally broke down and towed it to a Ford dealer. Fortunately have a friend working there. Turns out, there was "inadiquate" power to the diode side of the PCM relay. I say inadiquate because I tested it with a test light, however ohms law tells us that 12V will travel on a single strand of wire but may not carry the amperage required to trigger the circuit due to excessive resistance.

The wire to the diode side of the relay was corroded behind the RF headlight. Consequently, the car was in a mild accident about a year ago and damaged a bunch of the wires in that harness. I spend hours repairing them at the time and went over them with a fine tooth comb but clearly missed this one!

So all set, thanks LvC for the help! A big learning opportunity for me and a good reminder for all of us that a circuit "having juice" isn't necessarily good enough.