Picked up a new MAP sensor at Advance Auto last night & installed, no change. ????

interesting, that stumps me as well.

There's that vacuum hose that goes down to the device underneath the alternator (air pump??) , and the vacuum hose that goes into the firewall for HVAC controls. Temporarily plug them for diagnostic purposes?

Does anyone else know if an IAC can fail and cause this?

New IAC Valve and no change.

Let me try to be a little more detailed in my explanation of the engines behavior. When the engine is cranked, the idle immediately jumps to 1,500 rpms and runs rough. As you drive down the road, you can feel the roughness of the engine through a choppy (stumbling) characteristic. After you have gotten the engine warmed up, it may (or may not) begin running smoothly, as if you had thrown a switch. Choppy and then immediately smooth, then of course, back to rough. It will fluctuate like this as long as you drive it.

When you come to a stop, the idle may be @ 1,500 rpms or 500 rpms, just no way of knowing until you stop. Check engine light flickers quite a bit, and occasionally stays on for long periods and stays off for long periods. I have not been able to get any codes though. It flashes the 12 code once, sometimes twice, and then just goes out.

Because of the way the engine behavior changes immediately and not gradually, I don't think it is a fuel related problem (I could be wrong and frequently am), it seems more like an ignition problem.

Please, any help would be appreciated. I don't want this thing to whip me and send me to a mechanic.

wait... it's screwing up giving you codes?

It's supposed to flash code 12 three times, then pause, then flash codes if any are present.

So you're saying it only flashes 12 some of the time? Or it stops flashing?

if you're completely sure that you're not making a mistake in pulling the codes, I would start looking at the ECM itself. I wouldn't say replace it right away, but maybe ask around if anyone knows how to do diagnostics on the ECM itself.

Update, finally got one code from the ecu after resetting it and waiting for the check engine light to come back on. Got code 44, lean condition. It has a new o2 sensor, is getting voltage to the sensor. I'm going to recheck for vac leaks, anything else I can try?

i have kinda similar problems to what you have described, but I think that I have begun to notice they change when I futz with the HVAC controls. though I could be wrong. As soon as I get around to it, I'm going to plug off the vacuum line going to the HVAC (it's the vacuum hose in between the A/C evaporator lines under the hood) and test for continuing problems. I hate working under the dashboard, which is what has been stopping me from actually DOING this <img src="/forums/images/graemlins/cheers.gif" alt="" /> (i guess stupid of me eh? )