Odd misfire on my 07 2.7 automatic

First post - 2.7 Base, Automatic with 104,450 miles

I’ve got a misfire on cylinders 1 and 3. Using the Mode-6 function on my BlueDriver, I’ve got an intermittent misfire occurring on both. It happens at exactly the same time on both cylinders, with exactly the same number of misfires per. I’ve replaced plugs (iridium) on both, no change. I’ve swapped coil 1 with coil 2, no change.

I’ve been chasing a misfire for a good while now. It started on cylinder 2. Did the standard troubleshooting, swap coils etc. I replaced all plugs, coils, and injectors. I’ve done a compression test (cold, exactly 165# per hole). I’ve tested the cooling system for hydrocarbons (none). The temp is normal. There is no water in the oil. It ran pretty well for a few weeks, with the odd misfire while sitting in gear at a light. I had run Techron in the 2 previous tanks, then went with a regular full tank. About 20 miles after filling it up, it lost its mind again and I had to limp it home. I hooked up the BlueDriver, and it said I’d lost number 4 cylinder. Swapped coil 3-4. The misfire moved to cylinder 3. Installed new Denso coil and cleaned the MAF sensor with proper CRC MAF cleaner. Test drove it again; it ran ok for 10 minutes, it lost its mind; I limped it home again. Plugged BlueDriver in, it said I had an open in the A/F sensor (the one ahead of the cat). Replaced it. Reset the ECM (I've actually reset the ECM several times during all of this). Let the engine come to temp as per ECM reset guidelines (everything off with no throttle input). Idled fine for about 10 minutes before it started the current shenanigans again. It seems to misfire every 15-20 seconds. I’ve run it up and down the street, and it’s bad enough that I don’t trust it to NOT leave me stranded.

It starts very easily and runs very smoothly when it runs. It has plenty of power - well, as much as one can expect from 159hp at the crank, turning an automatic.

What am I missing?

Thanks for your input, M

 

Does it ever misfire when cold?
Or only when warm?

 

It would now and then prior to replacing the A/F sensor. I haven’t noticed it doing it, but I’ve only started it half a dozen times since. I just went out and started it after sitting for a couple days and it ran smooth.

 

That's a gooder, for sure! The fact that the misfire followed the coil, and then showed a MAF fault makes me think wiring harness/ECM. Get yourself some good (Mitchell's, AllData, OEM, NOT Chilton's, etc) wiring diagrams and start by seeing if there are any shared connections and if there are, start there. Then, verify all powers and grounds to the coils, MAF, and ECM. If that all checks out.... buy a new truck? Seriously... work through that and report back.

 

Bump..

 

Well?????

 

I ordered a new truck 4-1/2 months ago.

 

Well that solved the problem. LOL

 

Not quite, still waiting for the new rig…