P0108 Map Sensor; Running Rough, Stuttering

41153 Views 23 Replies 9 Participants Last post by oldstuff, Nov 5, 2014

DoubleACL

Discussion Starter · Nov 22, 2009

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, it starts running again, throw the code, and on the next re-start it would settle back down again and run prettry 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.

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

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RIP

· #2 · Nov 22, 2009 (Edited)

"Why would clearing the code make it take a step backwards?" A theory. The Powertrain Control Module (PCM), the engine's brain, is an adaptive contraption. It adapts engine operation to many and varied situations using sensor inputs, all in an effort to maintain an air to fuel ratio of 14 to 1 and the expected power. If a sensor or function gets a little out of wack, the PCM does it's best to compensate to a limit. This compensation will make the engine appear to be running along happy as a lark even though a code has been set. Then, horror of horrors, someone comes along and disconnects the battery dumping all those adaptive computations making it start from scratch at default settings.

A P0108 is a high map sensor output. Vacuum leaks will cause a low output. I'll have to do a little research and see what's up with that. The 15 minute time out monster will surely gobble me up so I'll be back.

DoubleACL

Discussion Starter · #3 · Nov 22, 2009

Good theory on backwards step after clearing the code if I was disconnecting the battery everytime to clear the code. But I'm clearing it through a code reader and only disconnected the battery once as a possible remedy to have the PCM start over collecting data. After 5 days of driving with a new MAP sensor, I'm still getting the intermittent-but-not-ignorable condition, and can't clear the code. I'll be looking for more vacuum leaks per your recommendation in the meantime. Thanks!

DoubleACL

Discussion Starter · #4 · Nov 23, 2009

Additional Info:
- Pulled a vacuum hose, causing the engine to die. With the key still on and engine off, heard a high pitched whine which I pinpointed to the IAC.
- The IAC does not whine if the car is stopped with the key, or if the key is in the KeyOnEngineOff position; it only whines when the engine if forced to die.
- If I've forced the engine to die (or it dies on it's own), the IAC whines until the connection is pulled (or the key is turned off).

Could this be related, or perhaps even the source?

DoubleACL

Discussion Starter · #5 · Nov 24, 2009

Update:
- 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.

Pretty frustrated to say the least...

bksun40

· #6 · Dec 9, 2009

2001 caravan p0108

I've got the same problem with my 2001 caravan, did you get an answer yet?

I get p0108 , when I clear it it comes right back .

DoubleACL

Discussion Starter · #7 · Dec 10, 2009

Nope. Still fighting it. Replaced the MAP Sensor with the genuine MOPAR article. Had a shop diagnose that the MAP Sensor not getting the proper voltage, and they believed the PCM was bad. I cleaned up the connectors, harness & wires leading into the PCM and believed I might have solved it but after about 5miles it started acting up again.
I know that clearing the PCM by pulling the neg. battery cable for an hour wipes out the data that the PCM is "learning" about where it needs to make adjustments based in sensor inputs & driving behaviors. But it seems that it runs better each time I clear the PCM and runs worse over time AND whenever I reset the P0108 code. Obviously I'm trying to avoid the cost of replacing the PCM. I don't have a problem replacing the PCM if the truly is the problem, but I can't afford a repeat story like with the MAP sensor where the shop said, "by golly, it wasn't the MAP sensor after all; must be something else".

bksun40

· #8 · Dec 11, 2009

Pcm

I tried replacing the pcm with one that I got from the junk yard , it came out of a van that was running when it was junked, no change! It could have been bad but my symptoms where exactly the same. I did replace the map sensor and found a wire from the map to the pcm that had no continuity , so I replaced it, no change , at first I got p0107, now I get p0108,p0106,p0107.
next thing I'm going to do is look under the van at the wiring harness were
it goes close to the exhaust to see if it is chafed , but I live is Mass.
and we got 4" of snow, so it might be on the week end.....

DoubleACL

Discussion Starter · #9 · Dec 12, 2009

I think I figured out the "area" of my problem. There's a wiring harness behind the power steering resoivor (sp) & distributor which is where the MAP sensor, Engine Coolant Temperature (ECT) Sensor, and I presume, the Knock sensor all connect. The harness runs near the backside valve cover and show signs of heat (it's wrapped in what appears to be thermal insulation, no wires are exposed, it just looks like it's been hot). With the engine running, when I press on an area with a bend in it, the engine stumbles, and when I let go, it recovers. If I keep pressing on it, the engine will die.
So my guess I've got an issue in the harness, or, I'm getting a short at one the other sensor leads using the same harness (and just so happens to share the same ground as the MAP), that is causing the issue.
Waiting for the engine to cool down so I don't burn my hands on the manifold (again).

DoubleACL

Discussion Starter · #10 · Dec 12, 2009

Here is the source (attached). And now to go find if the dealer can sell me the 1 foot long piece leading to the MAP, ECT, and Knock Sensors.

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atoman

· #11 · Dec 12, 2009

glad you found it.. if the dealer does not have the wiring or wants an arm and a leg.. check a local salvage yard
(01-03 wiring & connectors should be same for both 3.3 & 3.8 but double check the pinouts, just to make sure)

PS: if / when you splice the wiring in, it's best to use a soldering iron and heat shrink tubing then wrap the splice location with cloth type electrical tape..

bksun40

· #12 · Dec 13, 2009

Same

I checked mine today it's just like yours I pulled all the wires apart and their
all melted together. I will be going to the junk yard for a new harness also.

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RIP

· #13 · Dec 14, 2009

DoubleACL said:
Here is the source (attached). And now to go find if the dealer can sell me the 1 foot long piece leading to the MAP, ECT, and Knock Sensors.

Good lord. Is that bare copper wire we're looking at? Can you tell if heat melted the wire insulation away or was it something corrosive that leaked into the bundle? That just shouldn't happen - period! Especially on a 5 year old van. I can see insulation discintegrating/melting if it came in direct contact with an exhaust manifold or something extremely hot but, not if it's wrapped in protective insulation sitting on a valve cover. Chrysler must of gotten a sweet deal on wire from some dump somewhere.

bksun40

· #14 · Dec 14, 2009

Yup The chip that holds the harness to a bracket near the valve cover
was broken off, so I think the harness has been laying on the exhaust
manifold .We had some tranny work done about a year ago maybe it got
broken then .

bksun40

· #15 · Dec 14, 2009

bksun40 said:
Yup The chip that holds the harness to a bracket near the valve cover
was broken off, so I think the harness has been laying on the exhaust
manifold .We had some tranny work done about a year ago maybe it got
broken then .

I meant clip not chip.

RIP

· #16 · Dec 15, 2009

Ya that would do it. Even those $.10 parts can cause major headaches. My apologies to Chrysler. Then again why not use stronger clips.

bksun40

· #17 · Dec 15, 2009

I went to the junk yard today to get a harness, but I didn't realize that the fuel injectors are on the same harness, so I cut the harness out minus the fuel injector wirer's, I'm going to try to make one out of the two. I've had a lot of experience with wire soldering, and I didn't bring enough tools with me! I would have had to remove the intake manifold to get it all....

DoubleACL

Discussion Starter · #18 · Dec 16, 2009

I wish I had posted earlier; after waiting for the C102 connector harness to come into the Chrysler dealer, I picked it up last night only to find that for $45, all they give you is a new main connector and wires to splice the connector in. A very nice mechanic informed me that what I really need was a fuel injector wiring harness if I wanted it all made up, and that I'd need to remove the plenum, or, the top half of the intake manifold, not the entire manifold. That's not too bad of a job to do. However, the injector harness is $250, so I'll be splicing. I'm going to replace that foul power steering reservoir while I'm at it, thanks to the many posts regarding that on this forum.

bksun40

· #19 · Dec 18, 2009

It worked!!! I spiced in the new harness with solder and shrink wrap tubing, and it runs like a top! , I noticed that you can't rev it past 4,000 rpms sitting still, but if you go for a drive and put it in low you can rev past 4000; must be a safety thing so you can't blow it up. Thanks for all your help let me know if you have any problems.

tcwagner1

· #20 · Dec 18, 2009

Wonder if there is a TSB on this, if not there should be. Tell Chrysler.

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