Here is the quick and dirty run down of my truck. 1998 f150 4.6 auto reg. cab, flareside 4X4. 2 Years ago the head gasket was replaced. Then again about 2 months later, and then 2 months after that Ford finally put a new head on the engine (passenger side). About 3 months after that they put a new transmission in it from the factory. Ever since then the truck will only do 140 KPH top speed! I know that the truck is not a race machine, but before the new transmission it would hit the governed speed of 160 easily. And also since the head was replaced the engine has pinged like crazy and has had poor fuel mileage, so the other day I tore the throttle body off and cleaned the EGR ports and IAC valve. The pinging did not get any better and when I went ripping down the road to "clean it out" it still only did 140 and when I got home the damn head gasket is leaking again!

Could the cat be plugged causing too much back pressure and blowing head gaskets?

It seems to have lots of power down low but it is always downshifting at highway speeds on slight inclines.

Sorry for the novel

Any Ideas would be greatly appreciated.

 

COULD be a warped block, but dont count on it. try running higher octane fuel to stop pinging

 

i agree with piperc. My truck did the same ping noise than i ran 91 octane and it quit.

 

just a thought, check the wiring loom going to the injectors and coils! Do they look like they are running to the correct cylinders in the way they exit the loom.

Like I said, just a thought. I would think that if one was wrong it would miss like crazy, but depending on the firing order and what two were wrong maybe it wouldn't be to noticible to the ear at idle.

Gene

 

Do not run higher octane gas. that is a lame old fashioned band aid. your engine was designed not to ping so something is wrong with it.

First off most pinging is caused by carbon being built up on the piston tops and then the clogged egr ports which in turn causes the the cylinders to get to hot and pre-detonate the incoming gas/air mixture. (the egr system is there to cool the cylinders)

No that you have cleaned the egr ports and hopefully checked the rest of the egr system for clogs and build up. you now need a professional carbon depletion process done. the two best are either snap on or BG.

Using a higher octane just makes the carbon build up faster. your engine will not adjust to a higher octane gas as it has no way of knowing your using it.

Also replace your 02 sensors and clean your MAF.

 

It would be interesting to know if they put a PI head on it and it caused the compression ratio to go up.. Does someone know if there was a corresponding piston change when Ford went to PI's? Or a different fuel and timing curve program used with them.

 

Ford changed the pistons to reduce the CR when they went to the PI heads. Its also entirely possible that when they installed your heads they installed them a tooth or two off.
Jes