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PT Suddenly Runs Rough

 
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  #1 (permalink)  
Old 17 Dec 2010, 10:39 am
Young Cruiser
 
Join Date: Nov 2003
Location: Oklahoma City, OK, USA.
Posts: 50
Default PT Suddenly Runs Rough

Until last night, my PT (2004, non-turbo 2.4l, 5 speed, 103,000 miles, timing belt, water pump, plugs, & wires replaced at 95,000 miles) ran well. Suddenly my check engine light (CEL) came on and I noticed it running rough. I then noticed that the temp gauge was higher than it normally ran but it wasn't in the red. The CEL started blinking so I drove about a mile to my destination and killed it. the only code that came up was P0172 (bank 1 running rich). I let it sit for about an hour (I stopped to eat) and though it started, it continued to run rough. The trip back home was about 10 miles with no change in the problem (CEL continued to flash but would occasionally remain solid for a few seconds). At home, codes P0172 & P0344 (cam position sensor) were returned. I previously changed the cam position sensor at about 99,000 miles because the CEL returned the P0344 at random although the car ran well.
I left it alone overnight & went to check it this morning and found that my antifreeze was about 1/2 gallon or more low. I don't recall it overheating or boiling over before so I'm not sure what happened with that. Nevertheless, I'm at a loss where to start looking for my problem and whether the low antifreeze was a cause. Is it possible that it overheated and messed up the engine causing it to run rough now? The oil looks OK and the exhaust is as clear as it can be. I'm just at a what the heck moment here.
Do you have any ideas where to start looking or what to start trying? I'm not afraid to work on my car (I changed the timing belt, water pump, plugs, & wires successfully) but I don't want to just start replacing things at a whim.
Thanks in advance for any suggestions.
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Poncho Villa
2004 Base Model PT Cruiser, 5 Speed

Last edited by Poncho Villa; 17 Dec 2010 at 10:46 am. Reason: spelling
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Old 17 Dec 2010, 12:33 pm
Obsessed Cruiser
 
Join Date: Sep 2001
Posts: 27,743
Default Re: PT Suddenly Runs Rough

When you replaced the Camshaft Position Sensor last time, did you use a genuine Chrysler part or one from an auto store. After market sensor either don't work or don't work very long.

When was the last time you checked the antifreeze? Could possibly be a reason to run rough if it just happened.

From PT Do-It-Yourself.net:

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. Diagnose the faulty circuit, and repair the cause.
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Old 17 Dec 2010, 07:53 pm
Young Cruiser
 
Join Date: Nov 2003
Location: Oklahoma City, OK, USA.
Posts: 50
Default Re: PT Suddenly Runs Rough

Quote:
Originally Posted by CREWZIN View Post
When you replaced the Camshaft Position Sensor last time, did you use a genuine Chrysler part or one from an auto store. After market sensor either don't work or don't work very long.

When was the last time you checked the antifreeze? Could possibly be a reason to run rough if it just happened.

From PT Do-It-Yourself.net:

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. Diagnose the faulty circuit, and repair the cause.
The sensor I purchased from Auto Zone. I'll look for the genuine MOPAR part especially after reading a few posts about the poor quality of aftermarket sensors.

As for the antifreeze, I haven't checked it since I replaced my water pump & timing belt ~ last March. After the replacement work, I checked the antifreeze nearly every day for about a week and topped it off in the overflow bottle until it seemed to remain at a consistent level. Clearly I need to be more vigilant with my cars! It's interesting though that I've not noticed any leaks or the telltale scent of coolant.

After refilling the radiator and driving it around a little this morning (with the same problem ), I let it cool then restarted it without the radiator cap to check for bubbles. I didn't see any bubbles but I suppose that a head gasket leak isn't entirely ruled out.

I agree 100% with your last comment about diagnosing the faulty circuit and repairing the cause. I've considered over the past couple of years purchasing a PC-based scanner (I think it's called Auto Tap or something like that). If you have any suggestions for a cost-effective scanner, I'm game to learn more about how my car runs! It's really a fascinating idea except that this is my daily driver and I don't like being without it!

I really appreciate your comments and suggestions.
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Poncho Villa
2004 Base Model PT Cruiser, 5 Speed
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Old 18 Dec 2010, 01:06 pm
Young Cruiser
 
Join Date: Nov 2003
Location: Oklahoma City, OK, USA.
Posts: 50
Default Re: PT Suddenly Runs Rough

Just to follow up with some progress notes. I decided to check spark and compression so I removed the upper intake then all four plugs. Plugs 1 - 3 looked clean but plug 4 was grey and wet (fuel wet I believe). I then grounded each plug in turn and had my dear sweet wife crank the engine while I observed the plugs for spark. Interestingly, only number 4 was not sparking. That explains the wet appearance. I swapped the plugs and wires around to make sure it wasn't just the plug and wire and found that all four plugs and wires were capable of sparking but not on the number 4 post of the coil. It's odd to me that it's just one post and not at least two posts that are cold as I thought 1 & 4 were tied together while 2 & 3 were tied together (not that they would spark simultaneously but that they were somehow sharing the same sparking mechanism).
After seeing the lack-of-spark issue, I didn't check compression though I will check it later just for giggles.
Now that I've narrowed the issue down to fire in number 4, I'm interested in what I can check or do next. I'm guessing (though guessing worked poorly for me in school all those years ago) that the computer may have something to do with telling which plug to fire. Is there something in the circuitry that I can check to try getting fire to number 4? Is it possible the coil can go bad on just one post? I'm just not sure how the system can be prejudiced against just one cylinder but I'm eager to learn.
Thanks in advance if you've got some insight!
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Poncho Villa
2004 Base Model PT Cruiser, 5 Speed
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Old 18 Dec 2010, 01:26 pm
Obsessed Cruiser
 
Join Date: Sep 2001
Posts: 27,743
Default Re: PT Suddenly Runs Rough

I'm not sure how exactly everything works but I do know everything is computer controlled and the computer relays and sensors. Lots of things to go wrong. From what you said, the easiest way to try something (and I hate throwing parts at a problem) is put in a new OEM coil and do the same tests you just did. No need to upgrade the coil, the OEM Chrysler part is well capable of throwing enough spark to take care of anything the PT puts out or needs.
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Old 18 Dec 2010, 02:17 pm
Young Cruiser
 
Join Date: Nov 2003
Location: Oklahoma City, OK, USA.
Posts: 50
Default Re: PT Suddenly Runs Rough

Quote:
Originally Posted by CREWZIN View Post
I'm not sure how exactly everything works but I do know everything is computer controlled and the computer relays and sensors. Lots of things to go wrong. From what you said, the easiest way to try something (and I hate throwing parts at a problem) is put in a new OEM coil and do the same tests you just did. No need to upgrade the coil, the OEM Chrysler part is well capable of throwing enough spark to take care of anything the PT puts out or needs.
That sounds like a good plan. I'll let you know what I find.

As for your point about "hating to throw parts at a problem", I think you and I may be related!
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Poncho Villa
2004 Base Model PT Cruiser, 5 Speed
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Old 18 Dec 2010, 04:59 pm
Young Cruiser
 
Join Date: Nov 2003
Location: Oklahoma City, OK, USA.
Posts: 50
Default Re: PT Suddenly Runs Rough

Knock on wood, my PT is running well again. After replacing the coil, I immediately reassembled the plugs, wires, & intake to start it and it fired right off. Woo hoo! In my haste, I didn't get to check the compression but I wanted to check it more out of curiosity than necessity.

A code P0113 came up after starting the car but I think it was because I had the IAT unplugged at the time. It should disappear after a few more cycles methinks.

Many thanks Crewzin'!

Cliff Notes:
Car suddenly began running rough & initially threw code P0172. Continuing to drive the car it threw an additional P0344. The car idled rough with an obvious misfire. I checked for spark and found that the coil did not spark on cylinder 4. Replaced the coil and all is running well. Code P0172 (rich condition) was likely due to no fire in cylinder 4 and P0344 may be due to the Auto Zone cam position sensor that I installed at about 99,000 miles.
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Poncho Villa
2004 Base Model PT Cruiser, 5 Speed
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Old 18 Dec 2010, 05:03 pm
Obsessed Cruiser
 
Join Date: Sep 2001
Posts: 27,743
Default Re: PT Suddenly Runs Rough

Great. Just in time for a Happy Holiday. Good luck.
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