P0108 Map Sensor; Running Rough, Stuttering

[DoubleACL]

2001 T&C EX 3.8: 108,000 miles, started running very rough at all RPMs, nearly stalling at idle - threw a P0172, system too rich.
- Cleaned intake, checked vacuum hoses, sprayed brake cleaner looking for leaks, it seemed to accelerate slightly while spraying at the connection of the pipe from the EGR to the Manifold; repaired the gasket; resolved.
- Manual/visually check wiring.
- (O2 sensor (forward) replaced at 100,000)
- Disconnected negative battery terminal for an hour to clear PCM history.
- Now it throws a P0108, Map Sensor, and after warming up, it would not want to idle less than 1800, all while still running rough.
- In addition, at times it would run perfectly for 5-10 miles, then suddenly stutter for no apparent reason.
- Also, under full acceleration, it would hit 4500rpm & then roll back and cycle rapidly between 3500 & 4500.

Replaced the MAP sensor (I'm a DIYer, even though I know swapping parts just because for a code doesn't necessarily mean the part is bad)
- Helped the idle rpm problem, and thought everything was resolved, except everytime I clear the P0108 code with my OBDII reader, it starts running again, throws the code, and on the next re-start it would settle back down again and run pretty good. Why would clearing the code somehow make it take a step backwards?
- Now on the next 10mi jaunt just when I think everything is running well (even though the CEL is still on) it starts stuttering again at about 60mph. It won't stutter if accelerated firmly, but if accelerating slightly or decellerating slightly, it stutters badly.

- Just for "fun", thinking perhaps the IAC is fouling and "spoiling" the vacuum (hence the P0108 Map Sensor code)?, I pulled the IAC & cleaned it; cleaned throttle intake while I was at it.
- On restart, the engine died at first, but then on second attempt (with a little gas), it held idle, and continued idling smooth. Could I have solved it by cleaning the IAC? (I thought).
- Erased the P0108 code with the OBDII reader.
- BAM, right back to where I started where it will not hold idle without throttling the accelerator.

Can't seem to get anywhere with clearing the code, and stopping the inconsistent rough running and stuttering. Ideas?

[dixie d]

I'm having this same problem with my 96 ram van. Did you ever find out what it was?

[RIP]

Doubt you will hear from someone who made a single post 2 years ago.

If you are experiencing the "runs great till I clear the code issue" it could be because when the PCM doesn't see the correct MAP value it reverts to a less exact Throttle Position Sensor (TPS) value in some fail modes. So, the engine runs rough, the code appears indicating a MAP failure, the PCM reverts to the TPS signal and runs better. You clear the code putting the Map signal back in the loop and it runs rough again.

From what I've read most MAP problems are caused by vacuum leaks. Look in the intake manifold area. Wouldn't hurt to check for connection corrosion and wire continuity from the MAP sensor to the PCM. Verify the 5 volt reference voltage is at the sensor.

http://www.obd-codes.com/p0108

[dixie d]

lol, I didn't even think to look. Thanks for the response and info. I'll get to work.