I bought a 99 f250 with the v10 in it last week. 180k on it. As soon as i got it back home i changed all of my fluids out. Oil very dark and smelled a little like gas, transfer case was as thin as hydraulic fluid etc.

I put some seafoam into the tank same night, running terrible ever since.

As soon as i get on the gas, at any range it badly hesitates and loses power. There is some vibration also when it high gears. When overdrive is on and going up a hill its real bad, truck misfiring and hesitating like crazy.

What i have done- new fuel filter from autozone, motorcraft plugs gapped .0050 (looked new from previous owner)and torqued to 14 ft/lbs, all new cop boots, seafoamed through brake booster, clean maf with carb cleaner, cleaned intake valve with carb cleaner.

when i pulled the plugs they were a little black and oily but nothing major. Previous owner had gapped at .0040. I cleaned them up and put back in.

After i finished i took for a spin and it ran like a champ! No misfires, hesitation, etc. 1st thing this morning, mot running bad. ...after putting 15 miles on... it just is running terrible again


Showing no c.e.l. and no stored codes. There is no cat on truck. Any suggestions?

Thanks.


Edit- also have white smoke out of tailpipe, has done it since i bought. I think its steam and it calms down after driving. There is a little milkiness on bottom of oil cap.

Current temps have been lower 30's and precipitation.

 

The transfer case takes ATF, so it is supposed to be thin.

 

Wont make assumptions, but milky oil or coolant usually means a head gasket. Compression tester would be the best way to determine if you have major issues, or minor issues...

Mobil 1 ATF for transfer case.

 

Oil is fine, not milky. Just the underside of cap, which from what ive read on here is condensation. Coolant is also fine.

One other issue i forgot about. When i was changing out that rear plug on passenger side (dont know cylinder numbers), i pulled the grounding strap off of frames. I happened to have a nut laying around, but i couldnt get tight enough on strap to make ir a tight connection. Could this be an issue?

I mean i took for test drive and it was fine, now not fine?

 

Oh crap... Just noticed what you posted.... "CLEANED MAF WITH CARB CLEANER".... Almost bet you fried your sensor.... Good news, its an easy fix... Bad news, its like 300 bones! ONLY USE MAF CLEANER on a MAF SENSOR!

Disconnect your MAF so the computer runs in limp mode and see if its any better. It will eventually throw a code, but that's where my money is at.

Some carb cleaners have chlorine in them and corrode the electrical elements. That's why everyone recommends against using carb cleaner.. It also is a really abrasive cleaner and leaves residue where MAF cleaner dries quickly and does not leave residue. Also every carb cleaner I have used is super pressurized, which can damage the electrodes. If you break the electrode the MAF is toast.

 

Ok i did not know about maf cleaner.

So that may be the culprit....but wouldnt it have missed off the go? Just thinking out loud here.

 

Really depends. I would unplug the MAF harness like I said and see how it drives. It took me 12 miles with the MAF sensor unplugged to throw a code... That's where I would start though.

 

I will unplug it before i drive home in the morning. I will report back tomorrow. If anyone else has suggestions feel free to chime in.

 

Now i did spray the throttle bottle with carb cleaner. It had a bit of gunk and buildup on it. Is that ok? I soaked it pretty good!

 

Ok, i disconnected the maf sensor and no change. The cel never did come on but i did get code po113 under pending codes.

I double checked all connections and they are fine. Im thinking fouled plugs maybe??

I started to check cop's but its running to rough to even hear a difference.

i also noticed that cruise control at 55mph it way much better. Its just real bad when i get on the gas anymore than a tap.

What do you think i shoukd check now?

 

Get that ground strap tightened up. Poor grounds in these computer controlled rigs can cause all kinds of problems.

 

I tightened up this morning, no change.

 

Without pulling the plugs again to see whats happening.... The only suggestions I could provide would be.

1. Have you checked your fuel pressure? Possible bad fuel pressure causing the rig to run rough... You can get a cheap fuel gauge at Napa or the like.

2. Get a water spray bottle and put water in it. Set the spray bottle so it mists, not spraying a direct spray. I would then wait until its dark out... Pop the hood, start the pickup and start misting by the coils one at a time to see if you can see any electrical sparks jumping. Electricity will always take the least resistant path to ground. So if there is a cracked boot, or a cracked coil this should show you some signs... If that doesn't work... You may have to pull the plugs again, check all your boots and COPS to make sure they aren't cracked.

 

Im going to just go ahead and buy the cheap ebay coil overs that are the 65 bucks. Ill just replace them all. 1 oem coil is as much as the set of ten.

 

I would highly suggest if your going with cheap coil on plugs.... Buy ARAPARTS coils....