Hard Starting/Loss of power under accleration.
 

Ok, 1998 F-150 4.2L 5spd 2wd.

Engine hydrolocked on me 8,000 miles ago, replaced with a completely remaned engine. Drove away from dealership, no problems. Then about 500 miles ago, on cold starts, the engine cranks and cranks for 5 plus seconds, fires off and on, then after disengaging the starter, the engine will attempt to start, but instead shakes rather violently, coffs and sputters....dies. If you keep the engine turning with the starter you can sometimes coax it to go. Sometimes it takes 5 attempts to start it.

Once the engine is warm, its starts much better, not like it used to though.

Also, the engine has no power. It struggles to get up to 50 mph. Under full throttle with rpms above 3000 rpm , it "stumbles" however will very slowly speed up depending on the gear. Under about 2000 rpm, you can punch it and it loses speed!!! You have to feather the throttle ever so slighty to get any speed what so ever.

Engine seems to idle fine, maybe a bit rough.

And last, I swear my gas gauge moves downward twice as fast. I don't think it even gets 10 mpg.


So far I have replaced plugs, with appropriatley gapped NGK's, and wires, NAPA's standard. Made absolutley no difference. My next thought is coil pack. And from there on, MAF sensor (clean/replace), fuel filter, vaccum lines, etc. What scares me the most is if there is any grief with the fuel system, ie. bad injector(s). The thought of putting a whole bunch more money into a new engine inside a $3000 truck is frightening!!! :-banghead

Anybody have any ideas?

Sounds like the MAF sensor is bad or the coil pack is cracked.

Ok, so it sounds like I am on the right track.

I am trying to sell this truck, I have it consigned, but the hard starting issue seems to be detering any buyers......and I don't blame them. Hopefully, later this week I will get some time to swap some parts into it. Thanks!

MAF sounds like a good guess.
I think you can unplug the MAF and try starting it. I have heard, but never tried, that with no MAF plugged in, the ECU goes to a generic default mode and the engine should run.
Worth trying.

Also, never overlook the possibility of a vacuum line off or leaking.
Check all around the intake plenum. You might be getting air into the intake air stream after the MAF and that has things out-to-lunch.

Keep us posted. Interesting problem.

Have the catalytic converters checked and make sure they're not stopped up as well.

Sounds like they put a Chebby motor in...

SmokinLuv,

Did you ever find out what was causing your problem? My F150 with a 4.2 is doing exactly the same thing. Everything you describe is identical in every respect.