1998 4.6, manual, K&A air filter, new fuel filter 200 miles ago.

I have read some great insights and knowledge from this forum.
I would appreciate any thoughts on my problem.

When I start my truck from completely cold, it accelerates normally until at operating temp.
After the truck warms up it will bogg and act like its fuel starved, missing or detonation as the engine is rough under normal and heavy accleration.
It idles fine, and will seem to accelerate somewhat normally with an extremely light pedal.
It has not thrown any codes... I have scanned for them.
I have cleaned the throttle body, EGR ports, AIC, MAF.
No Joy.

Any ideas?

Thanks for you time and expertise.

 

you might have dropped a cylinder spark plug and the computer is reading faulty plug and attempting to compinsate... do you have coil packs or cop(coil over plug)

 

coil packs and the filter change mileage is 2000 not 200... Doh!

The thing is that it runs great cold so a coil pack or plug doesn't seem likely.

Thats what is so perplexing.

 

if you have a leaking intake or head gasket at normal operating temp you will get you're lost in compresion and if you are getting coolant leak it is possible to blow plugs very quick.. I have 98 250 and that sound somewhat fermilier to some of the problems i was having... I've been going through several plugs ever few days...now I am changing the intake and head gasket...if you have one bad plug or bad wire it cannot handle the exrta pressure under load therefore the attempt to compansate...

 

But it runs great cold... a gasket leak would create a lean condition and then the computer would throw a code if there were misfires.

Didn't your truck throw codes?

 

yes I got codes but it only came on once the truck was at operating temp.... but after that my truck never ran good again cold or not till I changed those plugs and reset the computer... are you getting a hard code or soft code.

 

Resolution:

It seems that the plugs were shorting out...

How you may ask?
How about 1/4 to a 1/2 inch of oil/water in bank 1 plug wells 2, 3, and 4. The plugs had dark discoloration around the bottom of the porcelain and were oily upon removal. Even the socket was oily around the bottom of it. Unfortunatly, that oil funk went down into the cylinder when the plugs were pulled... c'est la vie, not much I could do about it.
On the other bank, there were also dark rings at the bottom of the porcelain on 2 of the plugs, but no oil.
Theory: water from someone pressure cleaning the engine forced into all the plug wells, the oil in bank 1... from the previous owner filling without a funnel and letting it run all down the heads into the wells.

The plugs that were in there were autolite double platinums, I put in motorcraft single plats.
From what I have read the double plats are needed because of how the different banks fire... one bank fires from the electrode to the ground and the other bank fires from the ground to the electrode. The single plats will wear out on one bank in about 20,000 miles or so because of the arc target isn't platinum. Thats allright... in about 6 months, (after the physical trauma subsides from the hand size reduction surgery I am considering) I'm going to try side gapping with some different plugs that I read about on this site.

Summary:
Truck running like a champ! and all the throttlebody, EGR, DPFE, (and whatever else I cleaned) was Mr. Myagi wax on, wax off for me, while good for the trucks general maintainence

Will let you know about gas mileage soon...
that is, if I can keep my foot out of it...

Thanks to all who took the time to post suggestions.

 

Thanks for the update.

 

Ok, MPG went from (on average) 12.9 to 15.9 on Texaco 87 octane.
Thats a 23% improvement!

Its almost a wash financially with gas prices increases though, not counting the cost of the plugs.

 

Thank you loudist for the info, my 2002 F250 is doing exactly what you described, and I was looking for troubleshooting info. Usually hang out in the superduty forum but tried here, and your post was right there! Thanks again, and will let you know how I make out