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Chrysler Repair/'03 Town & Country rough idle when cold


QUESTION: I have an 03 Town & Country with a 3.8L V6 (220K miles).  When it is cold the engine runs a little rough.  It idles fine, just that you can feel a slight roughness to it.  Once warm, it idles smooth.  Not sure what is causing this.  I have a new air filter, plugs, wires and have cleaned the throttle body.  On a side note, I also have seen over the past few months that the MPG have dropped from an average city MPG of 17 to 13-14.  Not sure if the two are related.  Any ideas what could be the issue (MAP, IAT, coolant temp sensor, O2 sensor)?  My main concern is the lower MPG, but the rough cold idle is annoying.  I have replaced the fuel pump (and filter) twice in the last 4 months.  Original started howling, first replacement would not prime the system without bouncing the ignition key a few times before start up (worked fine for the first few months).  Current pump starts the engine immediately.  Otherwise the engine is running really good (after warm-up).

ANSWER: Hi William,
There is probably a fault code stored in the engine control module. Try the ignition key: "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see if the mileage is replaced by a 4-digit number preceded by a P. If so let me know what you find. If not, then get a fault code readout using a reader that plugs into a socket under the dash by the steering column. Some nationwide auto parts stores will do that for free (e.g. Autozone) or an independent shop may charge around $40.
Once we have fault code numbers we can go from there.
Please read the PS (below) and respond to it.

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

QUESTION: Roland, I guess I should have mentioned that last week the only fault codes I had were for Gross and Small Evaporative Emissions System leaks.  Both of these were fixed by replacing the gas cap and a worn hose on the carbon canister.  There are no codes or check engine light at this time.

Hi William,
With no codes it is difficult to focus on any specific part. The miss may get worse and set a code (check engine light would come on), but otherwise I would look over the vacuum hoses that are connected to the intake manifold for possible loose connection; and then the other part that may cause this (or hard starting, or dying when coming to a stop) is the exhaust gas recirculation valve (egr) being gummed up and not closing to a dead stop. So you could try spraying some WD-40 on the stem of the valve. It is possible that in '03 and on there is no egr valve (I have a note in my '02 that says this may be the case) so if it doesn't show on the underhood sticker you don't have one.
So check out those possibilities and keep checking for a fault code.

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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.

I answer questions seven days a week and respond to you in about 30 minutes. "Maxed Out" means I am answering another question, briefly unavailable, or asleep overnight, so try again later.

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)

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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