Ok let me just get this story out in the open, Im running out of ideas and need fresh minds to help me pinpoint this problem.

I bought a 2003 f150 for $1800 with 77k on the odometer. It didnt run. Come to find out the fuel pump was bad. So we I replaced the fuel pump, fuel filter, all injectors. As the tank was loaded with rust, filter was clogged. Just rather play it safe.

Anyways the truck had new cop's all the way around.. white ones with no name, so I assume their eBay specials. I put new plugs in it, had to replace the return line since it was clogged.

Then get it running, had no power and ran like garbage. Come to find out the cats were clogged. So replaced all 4 cats, and the truck ran great for 1.5 weeks. Had 2 codes that kept coming up. The running rich ones. po172 and po175.

So I hooked up my scanner to see if the conditions were true. Sure enough I looked at the data and saw it drawing back long term fuel trim to -25 - 30. So I was starting to suspect the mass air. But drove it with my scanner hooked up and watched the data to make sure my hunch is right.

So this morning I go out start the truck and notice its running funny. Get to work and notice a very noticeable misfire. Cylinder 6. Hmm possible chinese coil went bad? So at lunch I swap out the coil with a msd coil, just to see if that cured the issue.. no dice.... After work I popped the plug out and it looked fine but changed it with a new one just because. No change.....

So i decided to go home and then the whole entire bank 2 went into misfire.....

Following codes. po356, po305, 306, 307, 308...... Pulled plugs and they look great.

Im scratching my head here.... I work on cars for a living and every once in awhile Ill run into one that challenges your knowledge... To be honest im running out of ideas... Maybe a fresh mind can shed some light on something I overlooked.

Any ideas?

 

Do a compression test

 

305, 306, 307 and 308 are cylinder specific misfire codes (entire drivers side bank) and 356 is also a coil issue (either a PCM, wire harness or coils).
With all 4 drivers side coils throwing a code, I would check the wiring harness.

 

I know it isn't the PCM thus far. Not ruling it out at the moment. Pretty sure the coils are all ok. I have msd ones which I know worked so it did not change it.

Where would be the common wire shorts on the drivers side harness? Ill just power probe the wire from pcm and follow it and do tests along the way from pcm, until I would not have a signal from the power probe.

Thanks Ill start with the harness, and do a compression check just because. With only 77k on the truck id assume compression should be pretty good.

 

You keep on running it with those misfires and you will be putting cats on again.
Many cylinders out are passing raw gas to the cats where it can burn and melt the cats if you force run the motor to long.
I would not be dismissing so many things out of hand on a truck that has been ABUSED and neglected and worked on at 77k miles.
Your working with a computer system that demands things either work or thay do not.
.
Here is what you need to know about the PCM drivers; they are switches that are triggered by the program to provide a ground to coils that already have common fused 12 volts standing on them and the injectors.
Take an ohm meter and look back at the PCM drivers from the coil connectors.
This design is done so you can see a resistance of about 10,000 ohms to ground as a way for diagnostics.
If you see a near short/low resistance or an open/ very high, the driver or harness is faulty.
As stated, with a bank suddenly going out, it suggest a harness issue or a workmanship issue. Think common issue/cause for this failure.
The 3xx codes are secondary side codes. The 35x codes are primary side codes.
BTW just because a coil is from MSD does not mean it is any better than a stock coil. The stock OEM coil has more history, quality and use right from the assembly line than any other coil on the market.
I'm not trying to ride you but get your attention to not dismiss things so easily and do diagnostics from a technical point of view and be awhere there can be multiple issues at the same time causing confusion.
Good luck.

 

Maybe they look great because there is no fuel going into those cylinders? If the return line was plugged, then there is crap from the tank and all the way back, so if you just popped in new injectors and filter, the crap post filter, will clog the injectors. I know the fuel trims don't support this, but if the plugs look great, then its not running rich.

 

Oh agreed and im not insulted by anyones post and I dont take it to heart, Ive been in this field for 25 years ( as a mechanic) and as i said Ill be the first I dont know everything and that is why I posted to this forum as i was getting frustrated in fixing someone elses mess and when you get frustrated you start over thinking things and start missing the most basic things.

@ Bluegrass your right I shouldnt be driving with the new cats only drove it to work the other day so I could utilize the lift, and the next day to do more work under the truck, But to do some more repairs to this poor truck. So I havent drivenmuch as the dang cats arent cheap, Anyways, Im gonna follow the wires from the drivers side, and see if i can locate a visible issue, as it drove perfect the one day and the next it acted up so from one day to the next something happened, and Im thinking melted wire or something along that lines.

@ Ishootstuff I should of clarified better on the plugs, Im more a verbal talk to guy so typing what i think and what i say is totally different to. But the plugs showed good color no signs of rich or lean.

Im going outside and ill post my findings if i find anything.

 

Didnt find anything visually. Gonna have to print up some wiring schematics at work from pro demand, as if I remember correctly the coil wiring routes behind the intake. And That may be where my problem is...

 

Swap #5 coil w/#1. Check DTC' s once more. Actually, MSD's COP's are cheep China coils in red. Visteon/Motorcraft ONLY for that engine.

Yes, Ignition wiring runs behind the intake. There's a dip in the harness just above the AC accumulator. Visually check for harness damage there.

I didn't catch which plugs you are using. (?)

 

BTW, - Bank 1 converters are fuel soaked by now. Just so you know, - if you do get fire on that bank, it's going to be hell on those convertors on that side. I wouldn't chance it without drying those out first. $$$...

 

Already took them off and put straight pipes in place till i find the issue.

 

are you sure the injectors are not the issue...or the fuel pressure regulator. typically they don't give problems...but. I would agree that, more so, it is either faulty COPS or the connectors to them...or spark plugs

 

I haven't located the issue on the harness yet, but Ill double check the area by the accumulator.

Motorcraft Platinum are the plugs I put in the truck.

I dont think its a fuel injector issue thus far as its running raw fuel on that side and fuel pressure is right where it should be. Their new bosch injectors ( all changed), new regulator, new return line (old one was clogged) , new fuel filter, new fuel pump.

The coils were on the truck when I got it, and according to him they were new. Their all white and no brand name on them so I am going to safely assume their Chinese eBay ones. I just find it hard to believe that all 4 coils go bad on 5,6,7,8 in one day. I mean its possible but I just cant swallow that as the cause, Im still thinking its a harness issue.

Im to the point now where Im going to run new wires for each coil wire from the computer and see if that cures it running on only 4 cylinders.

Idk just frustrating the hell out of me. lol

 

We fixed a 5.4 F250 that had harness damage on the drivers frame rail causing misfire,dead cylinder #7 IIRC just a single wire about 2" long was replaced and ready to go again.

sounds like you need to check spark, check fuel injector pulse as well.

check fuel pressure too. The clogged return line could have taken out the fuel pressure regulator. An open regulator would definitely give you rich condition. And a clogged return would put higher toll on the fuel pump (which has already died once)

 

ok ran new wire to the coils from computer, now I am firing on all cylinders. Still didnt seem like it was running right, then I peeked around and looked at tail pipe and saw black smoke... First thing I did was check fuel pressure and its back to doing its over 100psi crap again.. I cant win with this truck... New fuel pump, regulator, filter, injectors, and even replaced the return line and now its doing this crap again.... Gonna try another new regulator and if that dont work, then Im going to drop the tank and check the return line again an see if its clogged yet again..... This truck is surely challenging me ....