misfire between cylinders 1 and 3
#1
03-28-2015, 08:01 PM
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
#2
03-29-2015, 08:04 AM
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.
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.
#3
03-29-2015, 08:14 AM
I have faithfully changed my oil every 3-5k miles... and always paid more for the ford motorcraft oil... 134,000 miles..
#5
03-29-2015, 10:19 AM
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.
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.
#6
03-29-2015, 12:06 PM
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...
#9
03-29-2015, 12:32 PM
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..
#10
03-29-2015, 01:47 PM
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?
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?