Koer Code 45

[bkimball]

I have a 1988 5.0L GT convertible, 5 speed, that is essentially stock except I recently replaced the stock air cleaner with a K&N unit.

I've noticed recently that the idle doesn't "stay put" and when I'm on the road WOT and let off of the gas the RPMs might drop to around 1500 and then eventually down to 800-1000 or so. It makes shifting a bit tricky and gets worse as the engine heats up. At idle when the A/C kicks in the RPMs go wild (down to 200, up to 1000, down, etc). The engine itself is running smoothly, not knocking or anything like that.

The last week or so I think the exhaust has gotten very rich as I have had trouble with backfiring when I goose the throttle. It seems to me that just changing the air cleaner can't do all of this, so I ran the KOEO and KOER tests to be sure.

KOEO came back code 11 (OK so far), but the KOER test came back code 45, indicating a thermactor/diverter/cable problem.

I'll be honest that I'm just a novice with just enough knowledge to be dangerous, but I know how to use a torque wrench and change the oil. I've read several of the threads in this forum to understand that the thermactor is really an exhaust/smog issue, not an air cleaner one.

The Mitchell manuals indicated that one possible problem (aside from the diverter) is the cable harness assembly next to the EGR valve going bad, but I really don't know how to tell for sure. I'll probably end up taking the 'stang in to the pros, but I would love to know what's really going on.

I do have some equipment, like a meter and a vacuum gage for another car, but I don't know where to connect the gage. I ran the cylinder test, came back code "9".

Thanks,

Brad