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Chrysler Repair/rough idle: '01 3.3L


QUESTION: I have a 2001 Grand Caravan with 3.3 l engine.  It threw po401 code, so I cleaned out the carbon from the egr tube, the egr valve was replaced 2 years ago and seemed clean.  This solved that code, and idle seemed fine till the next day, when
really rough idle and stalling once warmed up.  
Now it throws a po172 code only.  Seemed to idle fine when I started it in th morning, cold outside, at 1000 rpm, then once warmed up, rough again and idle fluctuates between 500 - 700, and stalls sometimes when starting warm after running for awhile.
I cleaned the EGR valve with throttle body cleaner, stem seems to move freely with  screwdriver pressing from the bottom.  When I turn the valve upside down, something inside rattles, like a loose coin. Checked the lower vac hose to the valve while revving the engine and can feel the vacuum. There is some movement I can see in the area where the slit exposes the diaphram.
I read that I should check the PCV valve, but didn't do that yet, since it seemed quite difficult to reach, being located on the rear intake cover.

I took off throttle plate and cleaned IAC with carb cleaner, and still rough idle throws po172 (rich, bank 1).  Could that be from a faulty IAC.  If I unplug the IAC while it is idling, will that tell me if the IAC is good (i.e. change in idle speed will occur).  I thought if it was IAC, it would throw a specific code for that.


ANSWER: Hi Gary,
Kevin sent this to the Question Pool and I recognized that we had exchanged info about a week ago. Did you check out the code 0172 pages that I sent you?

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

QUESTION: Yes, thanks, I did get them. This code has a lot of possible issues related to it, so tough to narrow down.
I thought that the rough idle might indicate a faulty IAC, so tried cleaning throttle body and IAC first, but it didn't solve the problem, so I am wondering if the IAC might be bad, and how to check it. It doesn't throw IAC code po505 though.

ANSWER: I doubt the IAC is the issue unless it is listed on the 0172 procedure. Do those things on that procedure that are the least demanding/costly first.

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

QUESTION: Hi Roland,

Thanks for your previous responses.

I checked the wiring harness connectors to the IAC, and there is no power at all, so I'm thinking short somewhere or relay etc.  Can you help me track this down?  Wires are all taped together to difficult to follow just one bad circuit.  Is there a tool you would recommend to check circuits without damaging wiring?

Also, the 2006 Caravan I just purchased uses the oil filters that fit 2007 and up Caravans.  Any idea why my van would have a 2007 engine in it?  Date of manufacture is 06/2006.

Lastly, my key won't open the drivers door when I stick it in and turn it.  It just turns freely 180 degrees each way.  For the back latch, the key goes in but won't turn.  The fob device work to gain entry, but would like the physical key to work as well just in case the fob fails.


Hi Gary,
The IAC motor on the throttle body is operated by varying low voltage signal from the PCM as it perceives the need to change the idle air passageway opening. So you could measure the voltage between the two wires at the plug as you rev the engine, request a.c., allow the engine to warm up, etc. which should cause a need for a passageway correction.  You could probe through the insulation of each wire with a fine straight pin and then attach the two leads of a digital volt-ohm meter to the pins and observe the varying voltage which is probably in the range of a very few volts. Also, you could verify the connections of the those two wires at the PCM plug 2(gray color): the violet/dark green wire at the IAC pin 1 goes to pin 49 at the PCM plug while the violet/light green on pin 2 goes to pin 57 of the PCM plug. You would put the volt-ohm meter on "ohms" setting and expect a reading near 0 ohms if the wires are good, measuring while the engine is shut off.
I can imagine an oil filter housing change to the '07 model year in 6/06 due to a part shortfall.
On the locks you will need to remove the door interior panels enough to remove the handle. I can copy the procedure from a manual I have on a CD and attach the pages to an email I would send to you directly. I am a bit busy for the next 5 days but can get to that next Tuesday. If you would tell me you email address then I will be ready to send the pages. When you list your email don't use the @ symbol but instead use "At" or the address will be automatically erased from your question.

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Roland Finston


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 1982-2011 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)

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