My 1995 F-150 4.9l 2wd has a idle surge. Starts ok but will hesitate or die when letting out clutch. Have to keep the rpm up at stoplight or it will die unexpectedly. Also surges at 65-70 mph. The only error code is 542 and 556. Fuel system primary and secondary power. Changed PCM, TPS, IAC, MAP sensor, checked all vacuum, EGR feedback solenoid, plugs wires and gas canister solenoid. Must be electrical but after ringing out engine fuse panel and cabin fuse panel nothing obvious. Power interuption to fuel pump relay via the PCM relay seems likely but what is drawing the power without short. Just checked ignition switch but no opens between circuits. Any EEs out there with ideas. J Cusack

 

Sounds like a bad Crankshaft position sensor or TPS (throttle position sensor). My Mom's Durango did the same thing. Took it to the dealer, and they hooked it up to a diagnostics code scanner and found the bad part. Which was a crankshaft position sensor. You can get Autozone to scan your truck for free. Or let the dealer do it, if your gonna let them fix it anyway. Good luck!

 

Ok here is part of the problem. There are no plug wires per say. The 2000+ 4.6 ans all 5.4s have COP ignitions. The Boots do wear out. So when you do a plug change change the boot too. The boots should come with a new spring, aka wire.

JMC

 

Thanks Plugs are on the way for rockauto(29 bucks) Ford wanted 55. HAH. I'm gonna inspect all boots and COP's when installing. Wish me luck