My truck is running rough, real rough. Ive pulled KOEO and KOER codes with really nothing pointing to the problem. When running I can pull plug wire 4,5,6 (individually) with no change in how its running. If I pull 1,2,3(individually) it almost dies. I have spark to all wires, checked with a spark gap tool while running that wires are in good shape. Plugs are brand new as is cap/rotor just for extra. check compression on cyl 1 and 4 and they are healthy. Im leaning towards injectors and im getting ready to pull them. I have cleaned them once several years ago but my question is this:

injections 1-3 and 4-6 are not on separate fuel rails or harnesses right? from last time I pulled them im pretty sure they arent but im not 100%.

thanks

 

Injs. 1,3,5 are on Bank 1 Wire Color - RED/Tan-Org
Injs. 2,4,6 are on Bank 2.Wire Color - RED/Tan-Red.

Should be on the same fuel rail. If you get one connector off of a suspected bad inj, check the ohms of the inj. It should be between 11-18.

Also have you checked fuel pressure? I would think that if you cleaned them a few years ago, they would still be ok, usually I've heard of them failing from staying open and not pulsing, just dumping fuel.

 

Thanks for the reply. I guess the staggered wiring for the injectors means that its not a wiring issue. Its such a pain to get to them without separating the manifold so i didnt do much in the way of tracing wires. I think i can get to #4 before i split the manifold to ohm it out.

Fuel pressure is next on my list. This truck has done this running issue a few times in the past 6 years. Either its fixed itself or something I did fixed it because Ive never been able to find the issue. I started from the easy side checking ignition and compression and all the emissions stuff. Ive blocked the egr off for the time being and checked everything else i could for vac leaks or other known issues. Even if some of the emissions stuff wasnt working right it still wouldnt run this rough. It seems to rev up fine but i can tell its not firing on all cylinders and the exhaust note is indicative of a miss.

In the past 20k miles or so on this truck i have cleaned and re-oring the injectors, cleaned the TB, replaced the tps and iac, new smog pump, new exhaust, new coil, cap/rotor/plugs/wires. Im afraid that in the past couple years the 10% ethanol gas has caused issues with something in the fueling system somewhere and ill track it down soon! I havent made any changes in the past few months other than a new set of tires. Just drove it home from work a week ago wednesday and thursday morning it started acting up.

Thanks again for the response and ill be sure to post my findings. I wasnt able to work on it today unfortunately.

 

Just a fleeting thought...If you have a chance on any downtime, you may want to pull the PCM, and check the pcb. If it's giving you problems, you will see tell-tale signs with bulging caps and hot spots on the board itself around resistors.

I'm gonna check my '92 302 when it gets warmer weather and get the ID code from it.

Do Post back with any Updates!

 

Good thought there. Ill check that as well. If things get too bad the carb manifold may come off my 85 and go on this thing

 

Timber, all the injectors meet spec. 5 of them are at 18ohms and one is at 16ohms. But since i was that far in(could only get to #6 without pulling the mani) i just pulled them all and found what may be my problem. The ends of all the injectors have a bit of build up on them. It almost seems like the intake manifold gasket might be allowing a bit of blow by or something. Ill snap some pics of the injectors before I clean them tomorrow. My pressure gauge didnt have the schrader valve fitting on it for the fuel rail and of course the auto parts stores in the area dont have one. I tested the pump(dual tank but just running the rear) with no issues. The FPR diaphragm held a vac when i tested it but im going to pull it and make sure there isnt any build up in there as well. Ill probably just replace it since im in there now as well as the intake/exhaust manifold gasket.

Now i just have to figure out how these things got soooo dirty in such a short amount of time and hope that was it.

 

My old injectors were the same. The pintle caps had cracks all around them and just plain cruddy. I ended up replacing all of them with new Design 3 injectors. Another thought of the build-up is to perhaps see if the gasket isn't sealing well or maybe there is enough blow-by from the crankcase that it's building up inside when the PCV is performing correctly. It's just a thought.

Mine was doing the same on my 302, so I relocated the line. I could literally see where the junk was building up inside the back side of the manifold from the valve location.

Pictures are a Great idea! Will have to look when you get them posted.

 

After a run to the part store they had only 1 or the 3 things i wanted. yay. I got the gaskets but im going to have to re-use the injector orings and caps. They arent cracked and the orings are in good shape so thats not a problem. Just new is better

 

Its been a rough day! Whatever ford engineer decided the accessory bracket would also cover the exhaust manifold and have a million bolts holding it on should be shot

Well new exhaust/intake mani gaskets. cleaned all the buildup from inside the ports and from the manifold(took awhile). Cleaned the injectors again. Of course when i was putting everything back together the plastic vac lines for some of the emissions stuff broke!! For the time being they are capped off at the vac canister.

drum roll.....

no change! Still running rough at idle/low rpm. You can hear the miss. Pulling the plug wires off 4-6 again dont change the idle at all but there is a healthy spark there. Im going to see if we have a pressure gauge with the right fitting at work tomorrow or go buy one to check the pressure.

Oh and i absolutely hate cheap manuals! For pulling the intake/exhaust manifold it says "loosen the bolts holding the manifolds on and remove". I couldnt have taken a wild guess at that one Pulling the manifolds off an efi truck is even more of a pain than the carbed ones. Hopefully i never have to pull this one again.

 

Well last night I was able to test the fuel pressure. Its fine. 55psi key on. 50psi while idle and it fluctuates normally with a change in vac.

My next thought is that the harness that goes behind the engine either got damaged or some field mouse played with it and wrecked the 12v to those 3 injectors. Nothing else makes sense since 4,5,6 are not on the same "batch". Either that or im having some collapsed lifter issues or something.

I will keep updating this until I find the problem!

 

Tonight i pulled the upper intake manifold again and pulled the injector harness off the truck and out of its wire loom. I couldnt find any breaks in the wires. 1,3,5 all had continuity as did 2,4,6. Since the power is common at the connector and doesnt split til inside this harness I can't see any way the injectors could be the issue. They all open normally and ohm out just fine.

Next is pulling the VC to make sure im not having lifter issues with those 3 cylinders. While i have it back down this far im going to pull the injectors again just to be on the safe side im going to move them around. i will put 4,5,6 where 1,2,3 are now and vise versa. Unfortunately I will be out of town all next week so it might be awhile before i get back to it

 

Well I got back from my trip and this weekend messed with the truck a little more. I plugged all the injectors into the harness off the truck and powered them up. All are working fine and do mass some carb spray through them. I put new seals and caps on them and put them back in the truck in different places. 4-6 are now on cylinders 1-3 and vise versa. With the truck back together it still runs rough and has the same problem. Cylinders 4-6 do not affect the idle when the plug is disconnected! I know having it apart that all the lifters are moving and everything is in spec in terms of clearance. I know there are no obstructions in the intake or exhaust runners. The injectors and their wiring are fine.

Next step i guess is some more extensive leak down and compression testing. The only two things i can think now are messed up rings or int/exh valves hanging slightly open. Im wishing for a mystery fix honestly!!!