Hello, I've been having this problem with my truck lacking power and feeling like it is missfiring intermittently even without load and have still after a year never had a CEL on in the truck. New plugs and boots, new fuel pump and filters, cleaned MAF.

The problem I have experienced this weekend is I just bought a 30ft travel trailer that is 5100pds. Towed it back from Golden B.C to Kamloops B.C through the Rocky Mountains. The truck was guttless and at times had to shift down to 3rd to get up some of the hills. Power felt like it was random and inconsistent. The valves would float in 3rd gear pulling a hill at 4500-4700 rpm and still only able to pull 60-70km/hr before shifting into 4th and fall flat on it's face but, at least it would hold around 70-80km/hr sometimes.

My truck 99 F350 V10 5spd 200,000kms with 4:38gears stock tire size should in my opinion have way more power than this, that is why I have a V10 right. I've driven a F150 with a stock 302ci AOD auto that felt like it had about the same amount of power pulling roughly the same wieght up the exact same hill.

PLEASE HELP, I'm getting discouraged with the V10 and don't want to have to buy a Diesel. Thanks for any and all help.

 

You've got some other issue-valve float is not an issue on a stock modular-even with 300K+ miles. What's the maintenance history on the truck? When were the spark plugs changed last? Fuel filter? MAF cleaned? Possibly the cat converters clogged...there are so many things that could be wrong,but valve float would be the last thing I'd consider looking at.
JL

 

If you have valve float that engine needs to come out NOW and be rebuilt. The valves in a modular won't float until you're well over 6000 RPM. I wonder how you determined you have valve float....I don't believe you do.

I think you have a misfire issue. You have one or more coil, boot, or spark plug that isn't right.

 

The plugs were changed (with Ford plugs) about 5000kms ago by myself along with filters fuel pump.

The engine was making a horrible rattling sound, My friend who works for Ford says that Ford has a TSB out on lifters being a problem and this would be a cause of valve float. He also suggested that the timing chains might be streched causeing the timing to be out of wack. Therefore floating valves.

The truck had been worked before I got it always packing around 1500-2000 pds in the box daily. Maintainence is unknown but, it was a crew truck.

 

I'd find another source for info-your friend is mistaken on the chains and the cause of valve float.
Sounds to me like you've got a fuel delivery issue,and the engine is pinging due to having a lean air/fuel mixture.
JL

 

Having the cams out of time will not cause valve float.

 

I am leaning more towards your idea of lean fuel. Could a MAF sensor be bad and not trigger a code or CEL?

 

Didn't the earlier production V10s have an issue with the cam followers? Not sure what they are, but I'd read when they were not functioning properly noise and loss of power was obvious. Educate me please! Someone... anyone...

Thanks,

RustyFuryIII

 

Never heard of cam followers being an issue, nor valve float in a modular Ford.

Unless it was overheated so bad the valve springs lost their strength, but even then, I think it'd be puking coolant out every orifice.

Check the fuel pressure under load - and clean the MAF if it hasn't already been done.

OH! And another thing - check the catalytic converter. I've heard of a few '99's that clogged a cat...

Report back and we'll definitely work on this!

 

What shape are the O2 sensors in. Its recommended to change O2 sensors every 70k miles. Bad O2s could make a cat go bad also. If local emissions allow it I would ditch the stock converter for a high performance unit anyway. An OE replacement cat will cost an arm and a leg.

 

The cat convertor is ditched all together for a resonator. No rules in Kamloops for Air-Care. Unsure on the shape of the O2 sensors. I did clean the MAF but, it hasn't changed anything.

I have ordered a MAF brand new and cam/crank sensors also, but I won't have these parts till Tuesday. Also going to replace the muffler with a high performance one just cause I want a new one anyway.

I will be checking the fuel pressure probably tommorrow on my way to the lake. I have to pull a pretty big hill on the way. Without the trailer though. If I remember right it's about 40psi fuel pressure????

The truck has never been overheated either. It does ping unloaded just driving around intermittently. I have a hunch it is a sensor problem that the stupid computer isn't picking up because of the inconsistency of the problem. If it was a hard part problem it would be all the time right?? That being said the truck won't go faster than 100-110km/hr up a hill unless I have a good run at it but then it will peter out somewere along the way and start missing and pinging.

 

Pressure should be 28-30 at idle, 38-40 key-on-engine-off, and 38-40 under load.

Really starting to sound fuel delivery related...

 

I am going tgo do a feul pressure test on it today. I now have a MAF sensor(new) in hand and cam and crank sensors. Also going to put a serp belt on it because mine is done for. Keep you all posted.

Since the temp in the morning is getting colder I have noticed a noticable increase in power even at operating temp??? Could it be air flow related, Hmmm... At this point I'm just gonna keep throwing money in it till it's fixed.

 

Fuel pressure test done:

Idle: 29psi
Key on Engine off: 35/36psi
Neutral @ 3000rpm: 27/28psi
Loaded 5th gear @1,500rpm uphill: 36/37psi
3rd gear floored on flat/uphill: max 37psi

Will a MAF sensor cause the fuel pressure to be off?

Will the 2-3psi loss cause poor running under load?

 

New MAF sensor installed -- NO CHANGE. AARG

I put a new fuel pump in about 8mnths ago and I think if I remember correctly that I had the same fuel pressures that I have now. Could I have a fuel regulator problem or a defective pump??? Definatly feels like a fuel starvation problem the more I think about it and drive the truck.