MAP sensor accuracy, Chrysler

[A_Pmech]

Hi guys,

I'm working on a 2000 Jeep Wrangler today, troubleshooting a slightly rough idle and minor off-idle hesitation problem. I can barely notice it, but the neighbor swears it's getting worse. I checked all the usual suspects including timing, plugs, wires, cap, rotor, coolant sensor, etc. All good and all new consumables as it was due anyway.

That helped a little, but upon checking the live sensor data I noticed that the MAP sensor reads low. With the engine off my scan tool shows 29.2" Hg, yet the local atmospheric pressure here is currently 30.02" Hg per calibrated instrumentation. An error of about 3%

Is this error within the tolerance window of the sensor, or is it time for a new one?

 

[Tarheelgarage]

Hi guys,

I'm working on a 2000 Jeep Wrangler today, troubleshooting a slightly rough idle and minor off-idle hesitation problem. I can barely notice it, but the neighbor swears it's getting worse. I checked all the usual suspects including timing, plugs, wires, cap, rotor, coolant sensor, etc. All good and all new consumables as it was due anyway.

That helped a little, but upon checking the live sensor data I noticed that the MAP sensor reads low. With the engine off my scan tool shows 29.2" Hg, yet the local atmospheric pressure here is currently 30.02" Hg per calibrated instrumentation. An error of about 3%

Is this error within the tolerance window of the sensor, or is it time for a new one?

You're acutually looking at the Baro side of the MAP and the results are fine. MAP sensors tend to be very reliable.
Have you given the T body a good cleaning and wipe down of the throttle plate on both sides?

 

[Tarheelgarage]

How did STFT and LTFT look at idle?

 

[A_Pmech]

Hi Tarheel,

Throttle body was spotless, as was the throttle plate.

Closed loop, temp in the green arc, at idle:
Short term fuel trim: Fluctuating -.2 to +2.0
Long term fuel trim: Same fluctuation and range

Closed loop, temp in the green arc, steady state 2000 RPM:
Short term fuel trim: -3.8
Long term fuel trim: -3.8



Another thing: I notice that at idle the #1 O2 sensor shows .060V to .8V fluctuating. Normal?

I wish the haynes manuals gave a little more info. It would make things SO much easier! Can't look at the dealer manual until Monday. Blah.

 

[Chris Adams]

Got a library card?
You can access Mitchels at most libraries free, print what you need.
I have the DVD's but don't pay to get them updated so new stuff I just stop by the library.

 

[A_Pmech]

Got a library card?
You can access Mitchels at most libraries free, print what you need.
I have the DVD's but don't pay to get them updated so new stuff I just stop by the library.

Good idea.

 

[Tarheelgarage]

If you had access to a GMM, would be nice to see the TPS sweep to rule out any glitch/dropouts.
However, most of the wear on the TPS wiper happens in the area where the throttle is usually positioned during driving (35-45mph.)

Come down here and I'll check it out for ya....

 

[A_Pmech]

If you had access to a GMM, would be nice to see the TPS sweep to rule out any glitch/dropouts.
However, most of the wear on the TPS wiper happens in the area where the throttle is usually positioned during driving (35-45mph.)

Come down here and I'll check it out for ya....

Lol, a little too far to drive!

I checked the TPS yesterday and it swept fine with no drops.

I had one go out on my SV a few months ago though. Nothing like opening up the throttle and getting nothing, then laying down a 50' trail of rubber unexpectedly! I dunno who had the bigger saucer eyes. Me, or the guy behind me in the school zone.

I wonder if I'm chasing a ghost. I told the neighbor if he continues to feel there is a problem, bring it back. It drives like every 2.5 I've ever driven though. Time will tell...

Thanks for the thoughts/ideas.

 

[bop_pa]

You might also check for any vacumn leak especially at, around, or under the manifold.

 

[bgott]

Do an injector cleaning. It sounds like you have carbon build up on the backs of the valves and dirty injectors. The injector cleaner will flush the vavles after it passes through the injectors. If that doesn't work you might want to get the injectors benched. We did a Lincoln a few weeks ago, the shop charged $30 an injector. The shop we sent the injectors to said they were over half plugged, I know that the Lincoln ran like a new car after we re- installed the injectors.

 

[Tarheelgarage]

Lol, a little too far to drive!

I checked the TPS yesterday and it swept fine with no drops.

I had one go out on my SV a few months ago though. Nothing like opening up the throttle and getting nothing, then laying down a 50' trail of rubber unexpectedly! I dunno who had the bigger saucer eyes. Me, or the guy behind me in the school zone.

I wonder if I'm chasing a ghost. I told the neighbor if he continues to feel there is a problem, bring it back. It drives like every 2.5 I've ever driven though. Time will tell...

Thanks for the thoughts/ideas.

Maybe their problem is resting inbetween their upper shoulder are...