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Car misses at 3800 rpm

 
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Old 25 May 2011, 01:50 pm
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Default Car misses at 3800 rpm

Any thoughts would help . I just replaced the timing belt on mt 2001 Crusier in the process I broke off the plug on the MAP sensor so I replaced it with a new MOPAR map sensor the car runs great until it gets to 3800 rpm in any gear then it misses and bucks .Any Ideas
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Old 25 May 2011, 02:54 pm
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Default Re: Car misses at 3800 rpm

Is the engine fault light coming on at all to give a clue as to what's happening? If not, when was the last time the plugs and wires were changed?
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Old 25 May 2011, 03:39 pm
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Default Re: Car misses at 3800 rpm

isnt that a lot liie a bad cam sensor
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Old 25 May 2011, 03:45 pm
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Default Re: Car misses at 3800 rpm

Actually cam sensor will fault at lower RPM, however the Knock sensor will fail at shift levels, which is about what he's stating he's seeing this at. Have you checked your knock sensor? Do you have anyone near you with an OBD writing tool that can monitor your knock sensor? Anyone with a DSP near you, that tool works great for this?

Now knock sensors are normally around $30, but not sure how much the Mopar one is. Anyway, it sounds to me like your knock sensor is off...
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Old 25 May 2011, 06:26 pm
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Default Re: Car misses at 3800 rpm

Thanks for the input we got a rain storm going on out there now so I'll have to check it out tomorow.
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Old 26 May 2011, 05:41 pm
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Default Re: Car misses at 3800 rpm

OK this is what I got, when the car is cold I get fault po172, after the car warms up I get po106 and po108. checked the wires coming off the MAP sensor can't see any problems.
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Old 27 May 2011, 06:40 am
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Default Re: Car misses at 3800 rpm

Here's what I found in a search.


Fault code P0172-Fuel System 1/1 Rich will require a good deal more work to pinpoint the problem. The powertrain diagnostic manual lists possible causes as: Good Trip Equal To Zero, O2 Sensor Heater Operation, O2 Sensor, EVAP Purge Solenoid Operation, O2 Signal Circuit, O2 Return Circuit, MAP Sensor Operation, ECT Sensor Operation, Engine Mechanical Problem, Fuel Filter/Pressure, Regulator and PCM. There are several pages of tests in the manual to help determine the cause of the O2 sensor reading overly rich for too long. You will need professional diagnostic tests with a scanner that can read and record the datastream to locate the cause of the fault. Please refrain from throwing parts at it in hopes of a cure.

------------------------------------

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR TROUBLE CODES

These include P0105, P0106, P0107, P0108 & P0109, and can be set if the MAP sensor output remains too high or too low (out of range), or the MAP sensor readings do not correspond to the Throttle Position Sensor (TPS) readings.

MAP sensors monitor changes in intake vacuum, which is a way of determining engine load. When engine load goes up, intake vacuum drops. Vacuum is highest at idle and drops during acceleration and wide open throttle.

The computer uses the MAP sensor's input to vary ignition timing and the fuel mixture. So a MAP sensor problem may cause drivability problems such as surging, poor fuel economy and performance.

MAP sensors either generate a voltage or frequency signal as engine vacuum (load) changes. Vacuum leaks can cause problems with the sensor's reading, so check for leaks and the sensor's vacuum connection to the engine.

How to check: a MAP sensor's voltage or frequency output should change when engine vacuum (load) changes. If you don't see a change, the sensor is probably bad and should be replaced.
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Old 27 May 2011, 09:38 pm
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Default Re: Car misses at 3800 rpm

Wow, that is the best explanation of the MAP sensor I've ever read. Good job Crewzin!
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Old 28 May 2011, 06:05 pm
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Talking Re: Car misses at 3800 rpm

The problem is solved ,seems I just needed to reboot the computer.I figured I would take the car to the dealer on Monday and have them run a scan on it. I still had a few things to do like an oil change, and front brakes. I disconected the battery to clean up some corrosion on the terminals.After putting everything back together I started the car low and behold no check engine light ( thought the bulb was gone) pluged in the diagnostic tester read no faults. So i fugure by unhooking the battery and hooking it back up I must have fixed it. Been driving all day still no problems.
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Old 08 Dec 2013, 08:17 pm
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Default Re: Car misses at 3800 rpm

I have. 2006 and it misses also at about 4000 rpm I replaced the plugs and plug wires and it seemed to cure it. Then a few days ago the kid left it unplugged for 3 days at -32c and when she tried to boost it she crossed the cables and melted the booster cable (btw she is billeted on a farm about 100 miles away). It warmed up today to -27 so I drove out there and started it.
The CEL light was on so I plugged in my bluetooth OBD and took the car for a drive and the miss returned. With the OBD I was able to monitor the engine vacuum, and it dropped from 22 to 10 as the engine reached about 4000 rpm.one fault code was cam sensor and the other was power train low voltage.She gets to come home next week and then I will try to see if resetting the ecu by disconcerting. The battery
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