I have 99 Single cab with the 4.2 V6 in it . It has 155,000 miles on it, sat 2 years and no one drove it and I bought it for the cheap. I put new tires . 265 75 16s on it. New air filter, new fluids, cleaned MAF and throttle body. Now... The truck goes fine down the highway but has NO acceleration at all from a dead stop. I have a hard time spinning the tires on gravel almost. It seems like when you floor it, it hangs at 2000 rpms for 3-4 seconds then gradually takes off. Also has trouble in the deep snow, you can put it in 4 wheel drive and floor it in 1st and all it does is hang at 2000 rpms for 15 seconds until you get on some hard surface.

Any ideas ? Getting alot of people saying the tires are too big but they are only a 265 vs a stock 255 ?

 

I should add, there is an exhaust leak somewhere on the left header I cannot find as I can hear it tick. - I feel like if I pull the header i will snap the bolts in the block - not something I really want to tackle. No sputter or anything at take off - just slow.

 

Does it still have cats on it? Sounds classic to bad cats, or an exhaust restriction. Any codes?

Plus it is a 4.2 so it wasn't bread to be a neck snapper in the speed department!

 

It does, but it wont soon. No code. Can we just eliminate the cats or will the computer throw a fit ? I really dont care if check engine light is on aslong it runs like an ape.

 

The cats can be checked for back pressure at midas or other places very easily. Please don't take the cats off. Everybody who drives behind you in the future will thank you.

 

Its just a midwest hunting/farm truck it sees no pavement more than it does pavement.

 

What rear end gears does it have? I put some 265/75/16 tires on a 97 5.4 with 3.55 gears and it there was a difference in it's off the line performance.. I had to adjust the speedo gears to get the speedo back in sync too.

Lots of 4.2's came with 3.08's, so if that's what you got and put those taller tires on, well.... "There's your problem"...

Good luck!

Mitch

 

3.55 rear end . Put some quick steel on the cracked exhaust header last night . Changed the fuel filter - looked like stock one . Black **** came out when I dumped it . After letting it sit and dumping it again came out black as oil .

 

Drop the gas tank and flush it out.

 

Bad fuel is a very real possibility, and a rusted tank with 2 years dormant

 

I've ran a few tanks of gas through it actually ... Just still seems doggy . Maybe I'm just expecting more than it really is . Just thought it was odd I couldn't even spin the tires over 2000 rpms when I was stuck in four wheel drive in the snow .

 

202HP and 252 FTLBS at the crank. Figure between 20 and 25% drive train loss, leaves you about 150 hp to move a 4000 lb truck

 

Along with engine wear ect ... You might be right

 

fuel filter is no change. going to cats next

 

Can I weigh in on this thread and hope for some help from the friendly forum members?

I too bought a 99F150 auto 2wd that had been sitting (but only for about 6 months).
It is the ext cab, short box auto.

I too got mine running, new 265/70r16 geolanders, air filter, cleaned the throttle body, maf, iac...and oddly I have a light exhaust tick on the passengers side.

Anyway, I feel this truck is weak when accelerating. It idles perfectly smooth, runs smooth (not a misfire). Tip in and light throttle feels peppy. If I just drove light to light in my small town (speed limit is 30) - it always seems fine considering its a v6.

When I try to accelerate on the highway, I get throttle response until about 40% and then theres just nothing more. It doesn't bog down, or cough or miss, it just feels kinda like I'm not pushing the gas pedal any farther down. I can hear the engine load up with trying to accelerate, but it really doesn't accelerate any faster. It's a heavy truck with a v6, I don't expect it to really be fast but basically, it doesn't feel linear. Once it kicks down a gear, I get a better push of acceleration at the higher RPM, but between 3000 and 4500 it feels just flat.

I used to have a 2001 screw 4x4 with the 4.6 - i know the v8 is up on power but that truck was probably a lot heavier too. It didn't feel fast either, but the power came on progressively stronger as I gave it more throttle and RPM...unlike this one.

All of you who drive a 4.2 is this normal or should I be looking for something?
I don't know what my axle ratio is either, but I am turning a hair over 1700rpm at 60mph in OD.


I've done a bunch of troubleshooting but in the interest of keeping this post from going on forever, I'll save that for the case that this isn't normal.