Solved Rough idle on cold start - what to try next ?

[davem]

I've been battling a 'rough idle on cold start' for quite awhile (couple years) ... I lived with it long enough and am trying again to resolve it. Typically, its running good after a few miles down the road once warmed up. I dont recall the exact engine codes, but I know it included lean conditions and misfires.

I have a 2001 XLT V-6 with 147,000 miles.

2-3 years ago, I replaced plugs and wires.

A week ago, I had upper and lower intake gaskets replaced. The codes have been reset and the CEL is not lit up. Its running better, but will still die if I dont work to feather the gas pedal on a cold start.

I've read many posts to get an idea of what to try next. Do I need to wait for the CEL to come on ? I assume its just a matter of time until it comes on, but I gotta ask: How can I have this bad start-up idle and NOT get the CEL to light up ? Does that alone help pinpoint the cause ?

With my current condition, of bad idle at cold start, and no CEL, which of the following (which I've ran across in my forum searching), if any, make sense to pursue:

IACV
IAT sensor
MAF
Engine Coolant Temp sensor (this is a new one for me, but very intriguing)
PCV elbow
Cannister Purge Valve
ignition coil
fuel pressure
O2 sensors (could they be bad, but not throw a code ?)
other ?

Am I being unrealistic about achieving a good cold start idle ? I get that its 12 years old and all, but a buddy of mine drives a 18 year old rig that idles just fine.

I dont want to spend a ton of money obviously, but hope I can make some improvement from what I have.

Thanks.

 

[lobo411]

I have a 2001 XLT V-6 with 147,000 miles.

What engine?

 

[davem]

What engine?

4.0 L SOHC

Sorry, I thought there was only one V-6 available in 2001.

 

[davem]

My cold idle issue - resolved !

I want to thank everyone who posted suggestions on how to fix my rough cold idle issue on my 2001 XLT V-6 4.0 SOHC (148,000 miles).

After getting my intake gaskets replaced (upper and lower), the problem has not re-appeared in approx 3 weeks, and that includes a great start and idle at -22 F (air temp) here in MN this morning.

This forum is a great source of information - thanks for your help on this problem (and others through the years).


Dave

 

[Turdle]

I merged the "solved" thread into this one and then marked it as solved. This will help others.

 

[swshawaii]

12/18/2013

A week ago, I had upper and lower intake gaskets replaced. The codes have been reset and the CEL is not lit up. Its running better, but will still die if I dont work to feather the gas pedal on a cold start.

1/6/2014

My cold idle issue - resolved !

After getting my intake gaskets replaced (upper and lower), the problem has not re-appeared in approx 3 weeks, and that includes a great start and idle at -22 F (air temp) here in MN this morning.

What fixed the "dying"? :scratch:

 

[davem]

When I returned to the shop, a few days after having the gaskets replaced, the CEL had eventually come back on. The shop said it was a cylinder 6 misfire and replaced the spark plug.

Personally, I struggled with the spark plug being the solution (the plug was only 2 years old) and that the (small) shop just happened to have the plug
on hand.....

I believe that a plug wire simply was not firmly in place after the gasket repair and that over the course of a few days, got looser and looser. Note that right after the gasket install, it ran good, but got worser and worser over the next few days.

After the plug was replaced (believe that if you want), but before the really cold weather hit, I did spray some carb cleaner into the throttle body and cleaned it up a bit - I'm no expert, but I would not classify it as real dirty.

Maybe I'm giving too much credit to the gasket repair ?

 

[swshawaii]

Good idea cleaning the throttle body, should be considered preventative maintenance. Another is idle air conrol (IAC) valve cleaning. Probably the most simple and often overlooked cause of a rough or stumbling idle, but almost never throws a CEL or trouble codes. Third is mass air flow (MAF) sensor cleaning. All this involves is spraying with electrical contact cleaner, or specific CRC MAF cleaner, and not touching the delicate filaments. For best results, remove the throttle body to clean.

IAC Valve Cleaning
http://www.mysporttrac.com/mysporttrac/projects/CleaningIAC/CLEANING_IAC_MOTOR.htm

MAF Sensor Cleaning
http://www.explorerforum.com/forums/showthread.php?t=350613

Throttle Body Cleaning
http://www.mysporttrac.com/MySportTrac/projects/ThrottleBodyCleaning/Throttle_Cleaning.htm