[glaser67]

Hey all,

So i finally got my setup tuned last weekend enough to cause some ruckus, some 1st and 2nd gear pulls past 5500 rpm...

Later in the day I noticed my wideband was showing a little lean, figured the new heat cycles on some hard pulls on a hot day might loosen a header bolt, no big deal. Then my idle started to dip. Next drive that night it didnt want to idle at all so I parked it until today.
Now it barely idles at all (I have the ECU tuned to idle at 800 which it has been, now it barely keeps alive.

First I felt my headers and #1, 2, and 5 are cool to the touch. Pulled plugs and I think I can smell gas on at least #5. Put my stethoscope and the injectors seem to be firing. Cleaned all grounds, no affect. Fuel pressure spot on.

Engine off codes are 15 and 85 which concerns me. My grounds and terminals are rock solid, so no ECU flash to KAMF there. (Keep alive memory fueling)

If anyone has been following, its a fresh re-rebuild so I at this time I doubt mechanical issues.

I pulled a quick data log from my Quarterhorse and all sensors seem to be functioning as they should. Funny thing is, when I read the existing tune, it came up unknown instead of the tune I previously wrote to it, so I wrote the good tune to it and no change.

Right now I'm suspecting either ICM or the ECU are fried. Keep in mind the issue steadily got worse within 10 miles or so.

I'm all out of ideas where to logically go from here, any insight is greatly appreciated.

I slept on it, and after last night I'll replace with a generic MAF ECU.

Thanks,
-Glaser67

[cgrey8]

My interpretation of what you described is injectors are firing, but the plugs are not. However you seem to be jumping to the conclusion that the EEC is to blame for the cylinders not firing.

Assuming this is the same engine as listed in your signature (i.e. GUFB/A9L controlling a 5.0L in an F150), you can pull the SPOUT which eliminates the EEC from the ignition equation. If the cylinders still aren't firing, but other ones are, this is not an EEC/tune issue. It's an ignition system issue.

Since you have 5 firing cylinders, you can probably assume the coil is OK. Weak coils that are on the edge but still can run an engine, just not well, usually will run the engine at idle and very light throttle, but begin failing when the cylinder air charge increases. More air in the cylinder increases the resistance across the spark gap, which requires more voltage from the coil. If the coil can't deliver, the cylinder misfires until the cylinder air charge lowers. Often intermittently working coils will get worse or better with heat. But they are usually not prejudiced towards the cylinders that they'll fire.

And if this is a rebuild, I'd hope you also replaced the cap-n-rotor given how cheap they are. Even if you didn't, hitting the spark-tips with sand paper wouldn't hurt them.

But IMO the more likely place for problems is going to be with the wires. Plug wires can get burnt and start sparking over to the header that burned them. They can get rubbed to the point they spark to whatever is rubbing them. Or the wire's core fails to solidly connect with the connectors at each end which will cause them to work for a while, but gradually fail. Universal plug wires that you cut-n-crimp are notorious for this (or at least they have been for me). Unfortunately, I'm stuck using universals since there are no OEMs that work with my setup. But even OEM replacement wires aren't immune from this particularly if you are reusing the wires and excessive force was required to get a few of them loose from the plugs.

[glaser67]

Great information, thank you.

I'll pull the spout and see what happens.

Also, the dizzy is an OEM Motorcraft unit that I'l;l clean the points per your direction. Plugs are Ford Performance, and newer, but good info on them non the less.

I'll reply with my findings this evening.