misfire between cylinders 1 and 3
 

I have an 03 f250... 5.4 motor... I have random misfire between 1 and 3 when engine is in a pull... and only in the upper 2 gears.. (6 speed)... I have had at 2 diff shops and they tell me they have never had this issue... all 8 coil packs have been replaced... all plugs.. and even 2 injectors on cylinder 1 and 3... fuel system has been cleaned... compression is good on all cylinders... these are 20 year exp mechanics.. 1 works at a ford dealership.. they say they are completely stumped.. best suggestion they have is something in the motor is messed up.. wtf.. ok..lol.. I have asked them about cam or crank sensors and they say it would throw a code... I am at a total loss here.. can anyone help out please... thanks

I don't think anybody will dispute this, but even the best technicians get stumped too !
Just for the record, defective crank sensors do not always throw a code. That said, there are diagnostic steps and procedures that are utilized by techs with the right equipment that will "most times" pin down a problem.
Ford computers in the vehicle(PCM) don't always tell the truth and they will indicate a certain cyl with a misfire and it winds up being an adjacent cyl. This is of no help to a tech that is relying on it's info. As you may already know, Ford engines are particular about the oil used in them. Using the incorrect oil causes oil pressure problems which affect camshaft timing and performance and this type problem usually ends up with an engine replacement. The cost to repair approaches the cost of engine replacement.
Lets hope that isn't the case here.

I have faithfully changed my oil every 3-5k miles... and always paid more for the ford motorcraft oil... 134,000 miles..

what should my next move be????

The frequency of oil changes is important, but so also is the factory recommended grade and type.
The shops that looked for the problem , were they Ford dealership shops ? They are supposed to have the factory equipment and training in its use to diagnose just about any engine problem. A good portion of outside shops, if they don't do a lot of Ford work won't invest in that equip because it is expensive and requires some training. The dealers are required to do that. They also have access to a library of factory info.
There are many outside shops that have a good tech and the equip with access to subscribed info , they are not always easy to find.

I have had it to 1 dealership and 1 outside shop... I have used the exact grade it says on the oil cap... I know the motor has a lot of usage... 130k miles... but at 11 miles to the gallon... so twice the wear of a truck that gets 22 mpg.. I need some ideas on what other things it could be... could mice have chewed on wires somewhere... I do live in the country.. could this nightmare be a simple sensor that is going bad and not throwing a code... if I spend thousands on new motor and still have problem... I might shoot myself.. truck was running great before all of this started... it don't smoke.. I have babied it since its birth in 03...

Thanks for your time and help!!!

Dan there is a website where you can get all the suggestions you seek. It is www.IATN.
That is the International Automotive Technicians Network. Lets hope they can help you out.

could cam or crank sensor do this? 1 is $15 the other is $30... heres a couple clues... first diagnosis was random misfire over 6 cylinders .. all coils packs replaced with ford packs.. now its 1 and 3 on same side of motor.. they even put on new coils packs to replace the 2 new ones... on 1 and 3.. and tried new ford injectors on 1 and 3... why all this all of a sudden... and the truck runs strong in the first 4 gears... and will shake you to death in the top 2 gears..

One of the big three is dropping out,, fuel pressure / volume ( you never mentioned it being checked under WOT conditions) ignition, or injector fuel drop. It was really common for the 7.3 to misfire, die or go flat on a hard pull in the higher gears and steep long grades etc. since this is when fuel demand and volume required is greatest. ' Always' a good starting point to prove out available fuel values before moving on.

So,, it runs great other then on a hard throttle angle in high gears? Dragging the brake in lower gears going WOT for a few seconds will produce a misfire? In the high gears,, is the misfire 'immediate' tipping in the throttle or is there a slight delay before the misfire occurs?

in fifth gear there is a slight delay.. in od it is instant... it will do it in fourth at the end of the gear in a big pull/hill... I would assume they checked that out... just going by all the effort they put into it... I know they said they hooked some kind of machine on it as they were test driving it... I know these mechanics know their stuff... so im not knocking them at all... I ask them.. what is your best guess... 1 says possible weak valve spring.. other says something possibly in the motor... they are just completely stumped... both say they have never experienced this...

I just test drove truck.. and it was not real bad.. no shaking but not a lot of power hi end gears... next time I drive it might shake like hell... is the same pull on road... test drive conditions are the same.. I did notice.. my headlights come on when my light switch is on aux.. turned left and the inside cab light does not come on thru switch now.. but works with door open... headlights never came on when switched to the left on aux.. I noticed a 1 time clicking noise when I turned to the left... that got my attention.. maybe im trying to notice too much but this is new...

There are some questions of which the answers may shine some light on the problem.
1. Has the windshield ever been replaced in this truck?
2. The shaking you describe, does it feel kike it is coming from the engine or from the steering/suspension system?
3. Have you washed the engine compartment at any time?

There is a function when diagnosing called "Freeze Frame", did the people who checked out the truck mention anything about that information?

no windshield replacement... can feel the shaking thru stick... its the motor for sure... and no under hood washing but does not mean water has not gotten under hood... another thing both mechanics say is the problem is inter mitten ... sometimes its not there as bad... sometimes its worst

Has anything been done to the driveline, u-joints etc.?
Not being there to actually see/feel what you do , just trying to touch all the bases.

Hayapower offered some suggestions , were you able to try them? If so , what were the results?

Something else you might check, unplug each of the three plugs going to the PCM and see if there is any corrosion at the pins there.
Also , at the fuse panel behind the panel at the lower left of the steering column , there have been some unexplained electrical problems when moisture got into that area due to a leaking windshield (they leaked right from the factory). It is possible there is more than one problem we are dealing with.

u joints are solid... I ask the mechanics about fuel pressure under hi demand and they said absolutely not... its not a fuel supply problem..


the ford mechanic said he talk to other mechanics at his shop and all tend to agree that is something deeper in the motor when looking at all data and things done... (still no proof.. compression is good when in shop not driving)


I will check the electric connections tomm... thru out... I had problems with mice getting in my truck in the past... ugh.. sunflower seeds was the only damage I noticed...

Can you manage to get an oil pressure reading from a mechanical gauge ?
If so. allow engine to get thoroughly warmed up then get readings at idle and approx 2500 RPM. Not positive if your engine has VVT. Just another base to cover,
Another thing to try is to unplug the alt and test run it, let us know if there is any change.

Do you know if anyone has removed the valve cover on the bank with # 1 & 3 to check for any broken valve springs for those cyls?