So....everything is running just fine, engine is warmed up, idling just fine....and then all the parameters start bouncing around. So, I shut here down, look around, restart.....sits there and idles fine for a while, and then starts the oscillations again.

I went and recorded 2 runs but all the records came out as "zeroes"....must have recorded wrong.

Anyway, since it's mostly running ok, I take it out for a run. I drive about 5 miles, stop and go, get on the freeway, stop and go some more, and they go and get back, on the freeway....we'll I get up to speed (~65 mph) steadys state...and then it starts bucking....similar to what it does at idle.

I'm beginning to suspect my O2 sensor but I don't want to just start changing parts.

I'll try to record another run next weekend. Hope I don't get all "zeroes" again.

Any ideas meanwhile?

 

Lean? What are BLMs looking like? Are you running highway mode?

 

Nope. BLMs look ok. It's the same bin I've been running for about 2 years. About 2 months ago I was driving around and it started acting like it was missing (the bucking I mention) at speed. Then I noticed that it would idling fine and then start oscillating. I believe it's related.

I think I'll unhook my 730 ECM this weekend and hook up the MEFI (I left it wired in parallel) and see how she acts. If it then idles fine and runs fine, I can then chase after the 730 ECM associated changes (IAT, O2 Sensor, VSS, or perhaps my chip.....I actually had a bad chip once).

I don't use the MEFI because I can't adjust anything on it and it REALLY stinks with it.

 

And it's all fine.
So now it looks like there is either something wrong with my 730 ECM or one of the inputs to it that the MEFI doesn't have (IAT, VSS, & O2 Sensors, or perhaps my chip is bad).

Since I have my O2 gauge hooked I can tell that it's always running rich on the MEFI though. Interesting.

It runs fine though. I think I'll stay on the MEFI for the summer then start checking on the 730 later.

Any ideas?

 

That should be easy to check. If it's a bad ECM that would be a quick and easy check....unless, of course, that other old ECM has some fault also. Oh well.....I think it's the easiest way to do a quick check.
I'm happy with the MEFI for now so it's just for fun until I have time to delve deeper.