Long story short I have a 2002 F-450 with the 2V 6.8l. lockers front and rear, 11' aluminum flatdeck with Bw hitch. Bought with 96,000 kms now 98,000km's.






Back in 2014 it developed a miss in lower rpms while hauling 16,000lbs behind it. Made it 2hrs back to town and started diagnosing it. Removed cat, Ran compression test on the cylinders. Started at cylinder 1 and worked through to cylinder 6 where I had little compression. Parked the truck till I had time and money to work on it.


April of 2017 - Pulled truck into shop and removed heads, sent them to machine shop and received them back. Did 3 angle valve grind, new seals and guides. Had 3 bent valves - no piston contact shown and cylinders still have cross hatching.


Finally last week had time to reinstall parts.
Installed the heads, new stainless studs on exhaust manifolds, New motocraft plugs gaped at .052, new COP's, remanned bosh injectors, new timing set. Figgured lets put in new parts and not touch it again for a while since I was in it already.


Fired it up 2 days ago after turning it over without plugs installed or injectors connected to flow oil. Missing at idle. Can feel it in the exhaust and through the rpm range but smoothes out some in the higher rmp's


Ran codes as check engine light came on. Had a small list. Turned out to be a blown fuse. replaced fuse and no codes shown. Changed both O2 sensors and pigtail to drivers side as it was probably what took the fuse out as someone previously attempted to put a weatherpack connector in and pins were hanging out the back.


Still missing bad. Pulled connectors off of the COP's while running All made a difference except for cyl #3. Put in old coil. Same issue. Tried new coil and old plug on top of engine grounding plug with wire to intake. New coil and old plug worked. Ran back to ford, bought 1 new plug, gapped and installed with new COP. Same miss.


Checked vacuume lines for leaks especially around elbows, seen none. PCV Valve appears to be good, Pulled IAC and cleaned. Ohmd to around 10. Ohm'd injector for #3 and came to 14.6


Put on Fuel pressure gauge, getting 35 PSI at idle
Put on Vacuume gauge, Getting 14 HG at idle. Give it some throttle and it drops instantaiously near 0 and goes up to around 18 and to 22 when you let off, then back to 14.


Realy starting to pull my hair out on this truck as I am working in another province so I have limited time and was hoping to have it ready for hunting season as I have early draws this year (middle of sept.)


Was hoping for other ideas. Vacuume seems a little low but I cannot find any other leaks. All gaskets were new.


Only other thought was as it has 1/4 tank of fuel and sat that way for 3 years, was if the fuel would be causing any issue.. but that realy dosent explain why cyl 3 seems to not be contributing much or if any.


Autoenginewity seems to be of little help on this vehicle even with the enhanced for powertrain package. Seems to not have much for live access other than codes for the CEL and misfire count.


Throw me a bone....


Thanks in advance

 

Definitely replace that 3 year old fuel.
Put it some fresh fuel and go drive it 150 miles, city and highway. Check codes, even if the CEL isn't on. Report back.

 

That's what my plan was for today. Try to get as much fuel out as possible. Going to pull the fuel filter and pump the tank out. Put in 10 gallons of fresh. Unfortunatly I cannot drive the truck for a while as I have the coolant lines spliced together from the oil/antifreeze cooler and they would pinch the way they are spliced. I am adding a Dual remote filler and am building a frame rail mounted oil to antifreeze cooler out of aluminum. I had to remove the factory cooler to make room for the adapter so the diff wouldn't hit.


I want to fix the miss before I finish up the oil cooler setup as I would have to pull the filter and measure my hydraulic lines for the oil setup and wait for them. I can play the waiting game for them while I'm back working my last shift out of province.


Obviously I will be unable to completely empty the tank so am thinking on putting in some wood alcohol? Good? Bad? I guess I will see what pumps out first.


Also going to change the fuel filter as well. I'm sure it was done when I bought it as I usually do that to new to me vehicles.


Will update as I go


Dose anyone have a proper vacuum reading at idle and can confirm 14 is low?


Would poor fuel make it run rough enough to cause poor vacuum?

 

From your description I would carefully inspect that #3 COP electrical plug and the wires in it. When you had it firing on top of the engine with the new coil and old plug with the spark plug grounded that COP electrical connector was in a different position and could have been making contact. But when clipped onto a mounted COP it could have an open circuit. There have been a few folks here that have reported a broken wire and or connector at the COP that has given them a hard to diagnose miss.

 

... same with the injector connector, could be a loose connection or bad wire.

 

So Here we go.


I pumped out 10 gallons of 3yr old fuel.


Then put in 10 gallons and a can of water treatment.


Figgured while I had the fuel pump disconnected I would run a compression test on cylinder 3, Didn't move the gauge. Tried cylinder 1 for a reference but forgot to open the throttle plates and pulled off a 165.


So I went to TDC for cyl #3 and ran a leakdown, results were 95% and out the intake. Pulled follower off the lash adjuster and leakdown came back with 10% leakdown.


So I guess where I'm at....atleast hopefully is a bad lash adjuster. Otherwise the valve stem is too long. And I realy cant see that happening from my machinist. Although I guess everyone screws up once in a while.


I have a new lash adjuster arriving tomorrow. So hopefully I will know more by this time tomorrow.


I guess my new questions would be
1 - Would having a somewhat open intake valve drop the vacuum?
2 - Is there anything other than valve stem length or a bad adjuster that would cause the valve not to seal?
3 - Is there any visual way to tell if the lash adjuster is bad?

 

Wow, this is a difficult one.

Hopeful case is your timing chain/chains are off by a tooth or so.

If your cam lobe was bad than valve would not completely open.....not your issue so lobes don't seem to be problem.

A bad lash adjuster probably will not cause your issue. I say probably because I guess if it froze in full up position than I guess it could hold valve open a tad I'm not sure. They are cheap so I would do what your doing and replacing it.

Worst case is when you reinstalled the lash adjusters they were all pumped up to max and you bent a valve upon 1st start, or when you torqued the head down. Getting a decent leak down after the lash adjuster is pulled is a good thing though.

The low vacuum is not low if your above 5000 ft of elevation??? If not I suspect timing chain. Than again a open intake valve can cause vacuum issues. I get 12 in hg at 8000 ft on a worn motor, 14 in hg on a good motor.

If lash adjuster don't work I would then put #3 at TDC and remove valve keepers and spring. Try to rotate valve by hand. If you cannot it's probably bent. Check spring for damage too.

Than if you don't see an issue look to timing chain, 1 tooth off could hold the valve open and when you removed lash adjuster it freed up spring to close valve.

 

So I tried a new lash adjuster yesterday. Same issue

This afternoon I am hoping to tear the intake back off, coils plugs etc. and compression test all 10 cylinders incase I have this issue with more than 1 cylinder and am only picking up #3 because it is the worst. Then pull the adjusters out and bleed them all down and check for clearance.

I found a writeup on a 4.6? I believe and they were looking for .018 to .033 between the roller and cam.

Would that be the same specs for 4.6 , 5.4, 6.8 ?

Sounds like I will end up pulling the head or both heads depending on measurements and dropping them back off at the machine shop.

Would be great if I could get it into them before closing.

I will double check timing on the teardown ... that would be great if that was the issue as that would save tossing the headgaskets and bolts with 0k on them.

Pretty much a P*** off as I am leaving for work again at 5:00am on Tuesday and Monday is a holiday.

Looks like I wont have this back together for hunting





Problem is the 2nd valve up from the bottom. See how the follower is pushing the adjuster lower than the rest

 

Compression test results


Cyl
1 - 163
2 - 173
3 - 0
4 - 166
5 - 169
6 - 167
7 - 166
8 - 169
9 - 166
10 - 165


All tested with engine cold, throttle plate open and no oil added


Are these numbers other than cyl 3 about right

 

I would say those numbers are good....except #3.

If leak down is blowing back thru intake than the intake valve is not seating. If thru oil fill hole rings are subject, if thru exhaust that valve would be suspect.

It could also be a broken intake valve spring, check that.

I suggest compressing valve lashers SLOWLY, prior to installing them. Than crank motor to start and let oil pump pump them up.

 

At 0 psi on cylinder 3 is a good indication of at least one valve bent or not sitting all the way, maybe a piece of something got lodge in there getting the stuck on the valve not allowing it to close fully. If you do remove the head you can test it yourself and even do the valve seating yourself.

 

I really think it is an issue with the valve stem length. I am trying to find a way around this without pulling the head( atleast enough to get a hunting season out of it) It seals up nice without the follower put on....so that would be no pressure from the cam lobe. Atleast to me that means the valve has a good grind and is not leaking at the seat with straight valvespring pressure. I Was thinking about chucking the old lash adjuster in the lathe and taking off .010 - .015 off the bottom as that should help and then run a leakdown again with the follower on. Should hopefully leak less or seal up..

Or wishfull thinking.... But I really have nothing to loose as I have the extra lash adjuster now.

I ran the compression test today just to see if any other cylinders had any other valve issues as I thought it would be odd to only have an issue with one.

 

Oh by the way I did isolate it to the intake valve. Valvespring dose not appear to be broken. I would hope the machineshop would not install a broken spring on a valve job (also would of hoped the valvestem length got shortened to spec) When I talked to him yesterday he didn't seem to impressed but neither did I. lol

I just don't want to spend all the time and waste gaskets and headbolts if I can fix it rather simply.

Also elevation here is right about 3200 feet

 

Shaved .020 of lash adjuster and no noticeable difference on compression or leakdown. So I'm done being cheap....


The head is coming off and I am delaying leaving for work till the machine shop is open.


My mind finally clicked last evening and I figured I could of had the head back off and on in the time Ive spent p***ing around.


Will post another update when the head is off. I'm going to pull it loaded again so I can see the clearance issues hopefully. Feeler guage it. Seems like he will only have to do 1 valve so hopefully he will do it on the spot and It will be sitting for me to throw on when I get back. Atleast its wishfull thinking. lol