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P0301 code - was IAC valve

 
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Old 07 May 2012, 03:08 pm
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Default P0301 code - was IAC valve

2007 2.4L non-turbo, automatic transmission, 97,000 miles

This has got to be one of the most frustrating little problems I have ever had the misfortune to involve myself with. Part of the original problem (mentioned in my IAC thread) was the rough, surging idle when the air conditioner was running. That was corrected with the new radiator fan assembly. Now the idle is much smoother, doesn't surge, but is still a little rough. The car will run for miles on the highway without throwing a code, but when you get into town and idle, it is throwing P0301. Not immediately, but soon.

I have replaced the plugs, coil, wires, air filter, manifold gaskets (both at the block and between the two halves), and am almost through one tank with fuel injector cleaner. This little engine runs great on the highway, the problem is at idle. I have switched injectors between cylinders, switched spark plugs and wires between cylinders, put the old coil back on, and can not make the code change cylinders. I am unable to detect any other possible sources of manifold leak that would only involve #1. I haven't checked compression yet, but it runs so good otherwise that I can't believe it's a compression problem. Temperature is rock solid at about 1/2 way up the guage.

Here is one interesting symptom that I only noticed today, because it's the first time I tried to wind up the engine sitting in the driveway. When it's sitting in park idling, and you slowly bring the revs up, as soon as it hits about 3600 rpm it cuts completely out, then back on again immediatly when the revs drop just below 3600. It's almost as if it has a rev limiter on it. It will continue on and off as long as you are holding the revs near 3600. However, on the highway, this little engine will wind up to 5000 (as high as I cared to go) when acccelerating down the highway and not skip a beat, which is why I never noticed the issue previously. Do these little cars have a no-load limiter on them? Or am I maybe looking at a PCM problem that is at the root of all of this?

As much as it chaps me to do so, I'm just about ready to patronize my local dealer's service department while I still have any hair left.

BTW, I have assumed all along the #1 is at the 'front', meaning the end with the timing belt, air conditioner, etc.
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Last edited by Wingerbill; 07 May 2012 at 05:17 pm.
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Old 07 May 2012, 03:24 pm
cruserdad1976's Avatar
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Default Re: P0301 code - was IAC valve

if you are asking do they shut down at a set RPM yes they do mine will shut off at about 105mph
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Old 07 May 2012, 04:15 pm
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Default Re: P0301 code - was IAC valve

[QUOTE=Wingerbill;425864]2007 2.4L non-turbo, automatic transmission.This has got to be one of the most frustrating little problems I have ever had the misfortune to involve myself with. Part of the original problem (mentioned in my IAC thread) was the rough, surging idle when the air conditioner was running. That was corrected with the new radiator fan assembly. Now the idle is much smoother, doesn't surge, but is still a little rough. The car will run for miles on the highway without throwing a code, but when you get into town and idle, it is throwing P0301. Not immediately, but soon.[QUOTE]


Quote:
When it's sitting in park idling, and you slowly bring the revs up, as soon as it hits about 3600 rpm it cuts completely out, then back on again immediatly when the revs drop just below 3600. It's almost as if it has a rev limiter on it. It will continue on and off as long as you are holding the revs near 3600. However, on the highway, this little engine will wind up to 5000 (as high as I cared to go) when acccelerating down the highway and not skip a beat, which is why I never noticed the issue previously. Do these little cars have a no-load limiter on them?
Yes sir you are correct. All PTs have a park/neutral rev limiter.

Quote:
BTW, I have assumed all along the #1 is at the 'front', meaning the end with the timing belt, air conditioner, etc.
Yes sir, you are right again.

Jerry

Last edited by wwpptc; 07 May 2012 at 06:21 pm.
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Old 09 May 2012, 08:59 pm
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Default Re: P0301 code - was IAC valve - now update

PT is at the Chrysler dealer, the phone call from the service tech is "very low compression in #1". About the only thing I didn't check, mainly because my compression guage is 'old school' and won't reach far enough down the deep spark plug hole. Time to upgrade, I guess. I'm letting them pull the head to tell me what is wrong, and will probably let them do all the resultant work as well. Not that I can't but time is at a premium right now. At this point, I am hoping for 'best case' scenario, and it's just a slightly burnt valve. It runs so good off of idle that I can't believe it's a major hurt, but I guess we will see.

Any 'ball park' guesses as to what this (including replace timing belt and water pump) should run dollarwise?
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Last edited by Wingerbill; 09 May 2012 at 09:01 pm.
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Old 14 May 2012, 09:54 pm
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Default Re: P0301 code - was IAC valve

I now your pain. I have a 2002 cruiser that has 125k miles. I have been fighting code po303 I changed coil, wires, injector for #3 cyl., and plugs. Then I went and had the motor what they called decarbonized, just in case it was a carbon problem. I also had low compression on cyl#3. it was only around 90, but checked it the next day and it was to 130 to 150. Some of the fine fellows on this forum said it could have been carbon on one of the valves, and could have come off allowing the valve to close thus bringing up the compression some. Mine also runs great off idle, but runs rough in gear at a stop.I am going to go thru the rest of the gas that's in the tank since the decarbonization was done to see if it works or not. If not i guess the head job with belt and water pump is next. Please post what the dealer finds .Price around where I am at is from $900 to $1200 to have the work done
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