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Chrysler Repair/99 Chrysler 300 m, Engine performance


Did you think the bad catalytic converter would cause rough idle, lack of power, high fuel consumption,
And hesitation and vibration ?
I replaced : oxygen sensors, air filter, fuel pump, spark plugs and NO air leak found, isolate the EGR completely, change oil, replace the TPS and IAC, replace the throttle body, ignition coils, also change transmission filter and oil, and NO trouble code is registered ,
This car is running about 160,000 miles and the bad Simpsons started gradually and increases by time,
I made a compression test, all 6 cylinders reached between 120 to 130 PSI, with no difference more than 10 PSI,
please let me know your opinion , you can tel me technically , I'm engineer and I have a big car center service."

ANSWER: Let me think about this and get back shortly.

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QUESTION: Yes Roland , I'm waiting.
Thank you,,,

ANSWER: Hi Essam,
Is the 'no code' based upon the ignition key/odometer readout or the use of a plug-in code reader/diagnostic readout box? If just the key, then I would suggest that you seek more information using the plug-in box.
The catalytic converter could be partially blocked by a loose honeycomb. I believe that a muffler shop can test for that rather than just replacing it as a guess. So do that.
It appears that you have replaced many possible causes but I would stop trying that approach and see what you can find with a diagnostic box. It can give you operational readings that might point you toward the true cause.
Do let me know what you learn and how this gets resolved.
Please read the PS (below) and respond to it.

---------- FOLLOW-UP ----------

QUESTION: Hi Roland,
Actually I used the plug-in box but it didn't fix any trouble codes, only I noted the followings on the screen of the box:
1- when I start the engine in cold the four oxygen sensors readings are going up and down normally but after the engine is heated up the oxygen sensor No.2 on bank 2 (down stream the catalytic) stuck on high reading (0.745 volts) and not moving any more but the other 3 oxygen sensors continue going up-down normally.
2-the long term reading of bank 2 usually is 11 to 12% (means the PCM deliver more than enough fuel)
3-the long term reading of bank 1 usually is around 0.00% (means the fuel is compensated well)
4- some short times the stuck oxygen sensor start moving up-down and in this moment the engine runs fine and the over head console reads very good fuel economy,
Is this means some thing to you,,
Thank you,,

Hi Essam,
I would check out the wiring of the left bank downstream sensor's harness. Pin 1 is black wire and that should be grounded, pin 2 is orange/dark green and that whould have 12V on it from the power distribution center when the ASD is closed (engine running), pin 3 is black/light blue and is sensor ground to pin 43 of the pcm, and pin 4 is pink/white and is the sensor signal wire to pin 53 of the pcm.  Those last two wires go through a light gray 14-pin disconnect at the top rear of the engine. Try testing the continuity while shaking the harness along the pathway that it follows. You may find an intermittent. Also check the fine wires between the sensor and the plug as those are fragile.
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Roland Finston


Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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I have do-it-yourself experience (50+ years) and a library of 100 1982-2012 Chrysler factory shop manuals and 20 multi-manual Chrysler Corp. CD's.

I was voted "Top Expert" 2010-2015, here at AllExperts, and have answered 20,000+ questions.


Five decades as a 'do-it-yourselfer' on domestic and imported cars.

Yahoo Autos Group called The Chrysler Lebaron Club (co-moderator)

Advanced degrees in Physics/bruised knuckles

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"Top expert" of 2010, 2011, 2012, 2013, 2014 and 2015 here at Allexperts. Quickest "average response time" at Allexperts (currently no. 1).

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