RPM fluctuates/rough idle when fans turned on??? [Archive] - Jeep Commander Forums: Jeep Commander Forum

: RPM fluctuates/rough idle when fans turned on???


Chapman89
01-20-2011, 10:22 PM
Before anyone crucifies me (Jeep5253) I did search around the forums a good bit typing in "idle surge" "rough idle" "rpm fluctuate" etc!

Here's my problem, it only occurs (from what I've noticed) when the fans are on regardless of heat or a/c.

When idling at a complete stop or when in park the rpm's set at about 500-600. Every minute or so the Jeep will get a light shake from the engine and the RPM's will rise and fall between 700-400 and then back to the normal idle.

It sounds like it has to do something with a sensor but I am unsure. PCV? IAT sensor?

I appreciate the help!

jeep5253
01-20-2011, 10:31 PM
Who, me ?:)

robby
01-20-2011, 10:33 PM
Well....for whatever it is worth, and I assume you mean the cabin heater fans, my 07 4.7 displays the same behavior.....actually, the cabin fans don't have to be on....it still displays that behavior.

Sort of when the better half is in the store and I'm in the Jeep, in Park, listening to radio/waiting situation.

Finding this occured only idling while parked.....since new and now at 37k with no changes, I decided it is the nature of the beast and I decided the odds of my determining the cause/correction was nill.

That being said, when in gear, say, at a light, it is stable.
I suspect, that when the engine is unloaded, it hunts for a ideal fuel mixture....this is seen as a idle fluctuation of 2 hundred RPM or so.

Rob

Chapman89
01-20-2011, 10:44 PM
The only reason I am wondering is because I've never noticed it before. It occurs both in park and in gear at a light. Is there anything I could clean for the heck of it? I'm just about to turn 50k so I'm probably due a good cleaning of the engine.

SAL-XK
01-21-2011, 04:06 PM
My 4.7 does the exact same thing.

Chapman89
01-21-2011, 05:19 PM
Sounds like it's normal then, that works for me! haha

On a side note I did wash the entire engine bay/radiator during my tow hook install (PITA btw!) and I think a couple pounds of mud washed out. My driveway looks like a trail.

robby
01-21-2011, 06:25 PM
Well, I am telling you what my 4.7 does.......I think it would be more helpful if some 5.7 owners report in.

Since it occurs in gear, it may be looking for some attention.....possibly throttle body cleaning or IAC concern.
Could even be a coolant temp sensor reading out of range.
The best approach in my opinion is to get a good diagnostic, done in real time, with a Starscan or a independent shop using the All-Data programs.

At this time, nothing is far enouph out of range to set a light or code, but a good diagnostician might see something on the screen.

If, however, you start hearing from HEMI owners with the same concern, I would avoid getting to concerned unless someone found a fix.

Rob

filipiak1
01-21-2011, 06:47 PM
I would look into a throttle position sensor (TPS). It's $25ish at the local parts store. Bolts with a torx screw/screws to the driver side just below the air intake. 10-15 minute change. Something you could do yourself and it will probably cure your problem.

My 06' 4.7 would ramp up and down while in Park in the morning when I first started it. Not under load (Drive), but in park. Mine started out doing the same thing and then it went over the 1000 RPM range.

I changed mine with about 38,000 (45,000 now) and no problems since.

Good luck and keep us posted.

Chapman89
01-21-2011, 06:53 PM
I'll take a look at the throttle body tomorrow to see if it could stand to be cleaned.

Edit: After reading some more threads it sounds like it could be the IAC going bad. I noticed today when coming to a stop the slight hesitation and rpm stumble as some described.

Mongo
01-21-2011, 07:00 PM
Like any problem, the first thing to do is check for stored DTC's.

Have you replaced the spark plugs when the maintenance schedule says too?

Eroded spark plugs will cause rough idle, loss of power and even stalling.

Ignition cables will degrade with use and time as well, I think they are called for replacement at 60k miles/5 years, if you've got more than 5 years on ignition cables with less than 60k, I'd consider replacing them.

Check your owners manual, Chrysler has been equipping some of their vehicle with suppression ignition cables instead of the more common resistive cables, the suppressive cables often can last the life of the vehicle.

Cleaning the Throttle Body, especially the IAC circuit, can help.

The Hemi has an Hydraulic Fan doesn't it? Something I was shocked, I guess its something they've doing on trucks for years, I've never seen it on cars. Could the fan be causing the load that drags down the idle and makes it rough? Its supplied by the PS pump, maybe there is something with the PS and fan that needs correcting.

Chapman89
01-21-2011, 07:04 PM
Spark plugs were changed at 35k to Champion Double Platinum.
As I said previously, I'll give the throttle body/IAC a look tomorrow. I believe the Hemi does have a hydraulic fan however I am unsure of any PS issue.

Mongo
01-28-2011, 08:09 AM
Spark plugs were changed at 35k to Champion Double Platinum.
As I said previously, I'll give the throttle body/IAC a look tomorrow. I believe the Hemi does have a hydraulic fan however I am unsure of any PS issue.
There are threads on this board, as well as half the cars built today, about using other than OEM make/model of spark plug. A lot of engines today use a DIS that share coils, a.k.a. as a wasted spark system. This causes a reverse current flow on half the plugs, and that can cause a lot of unexpected results with the plugs, like half of them erroding twice as fast, if NOT faster. Double Platinum should avoid that, but I wouldn't rule it out, considering how many posts you see about people complaining about spark plugs, and everyone concluding that the OEM make/model plug work the most trouble free. I also sense that people are using super cheap and inaccurate gauges to set the plug gap and that may be more at the root of the problem, with people gapping plugs to the wrong gap.

A fairly extensive hydrualic system, like driving a fan off the Power Steering, could create quite a load on the motor, and heavier loads on a motor at idle will cause it to run rough. If its really cold weather, cold PS fluid at a higher viscosity might be increasing the load on the PS pump drastically. Personally, I change my PS fluid every 30k miles, yes, overkill I know, BUT, if I had a hydrualic fan driven off the PS pump, I would worry that fluid is suffering a lot more sheer stress than typical PS fluid, and degrading accordingly, maybe fresh fluid would help out that PS system and hydraulic fan run with less resistance. BUT, its a pure guess on my part. I suspect this hydrualic fan is the reason Jeep specifies a special fluid that is also hydrualic fluid for the PS, only available from the dealer.

06h
01-29-2011, 09:50 PM
I have a 5.7l with 17k miles that does it when you turn on the front and rear fans to high, wipers on high, all heated seats on, head lights on, hazards on and cabin lights on. When you rev the motor is stops and the lights brighten but when you stop the lights dim and starts a shutter. I think I narrowed mine to the charging system, just waiting for the idiot light to come on letting me know the alternator failed since the dealer says its fine.

Is the alternator of adequate size?

robby
01-29-2011, 11:01 PM
I believe the alternator is in the 130 amp range.....quite enouph for the various loads.
In the situation you describe 06h, the output is probably right at break even when idleing with all the components running.
Trouble is, alternator output is still R.P.M. dependent, so, no matter how much field current the alternator recieves, the output won't rise past break even till the engine speeds up.
What you are feeling is the alternator is at its highest resistance to rotation and the load is being felt throughout the vehicle......usually it is belt vibration on the no load side of the belt.

Rob

MrMustang
02-24-2011, 10:15 AM
I have a 3.7L V6 and I have been having the issue of the idle getting rough for a few seconds at stoplights, dropping to 500 rpm on the gauge, then going back to normal at 600 - 650 on the gauge.

Yesterday, it died after I came to a stop in rush hour traffic, as well as, this morning as I was backing into the daycare center driveway.

Has anyone with the 3.7L had this issue? Is there an IAC and /or TPS for this model?

Any info is appreciated.

MrMustang
02-26-2011, 12:20 AM
So, I found out the throttle position center and other related electronics are actually integrated into the throttle body assembly. They cannot be replaced without replacing the entire throttle body assembly. Has anyone done this?

MattTucker
02-28-2011, 07:56 AM
I have the 3.7 v6 and experienced this "rough idle" / "shutter" while sitting in a drive-through this morning (while in gear). RPMS dropped quite a bit, then back to normal. This was the first time I have experienced this.

--Matt Tucker

MrMustang
03-03-2011, 10:50 AM
I have the 3.7 v6 and experienced this "rough idle" / "shutter" while sitting in a drive-through this morning (while in gear). RPMS dropped quite a bit, then back to normal. This was the first time I have experienced this.

--Matt Tucker

For a minute there, I thought I was the only one who had experienced this issue. I have been trying to devise a plan to work on it, but I am not sure where the issue lies. I found that the throttle body assembly is under $200, so I am thinking of changing it out since it contains the electronics for the IAC and TPS.

Has anyone else experienced this?

MrMustang
03-13-2011, 12:39 AM
For a minute there, I thought I was the only one who had experienced this issue. I have been trying to devise a plan to work on it, but I am not sure where the issue lies. I found that the throttle body assembly is under $200, so I am thinking of changing it out since it contains the electronics for the IAC and TPS.

Has anyone else experienced this?


I take that back Matt, I think we are the only two with the issue. Have you had a CEL or any other issues with it?

medina111178
04-03-2012, 12:45 PM
Ive done some reading also and found that it could be due to a loose vac line. but mine does the same thing but not all the time. thanks for all who posted possible fixes will be sure to check them all out.

rhobll
04-04-2012, 10:05 AM
For a minute there, I thought I was the only one who had experienced this issue. I have been trying to devise a plan to work on it, but I am not sure where the issue lies. I found that the throttle body assembly is under $200, so I am thinking of changing it out since it contains the electronics for the IAC and TPS.

Has anyone else experienced this?
You can purchace both the IAC and TPS for the 3.7L, at Partstrain.com Or i'm sure you'll find it at your local car store. After cleaning the throttle body, I removed the IAC and cleaned it. Lots of carbon. The TPS does not come in contact w the inside of the TB, so nothing to clean there.

thance
04-04-2012, 04:28 PM
So, I found out the throttle position center and other related electronics are actually integrated into the throttle body assembly. They cannot be replaced without replacing the entire throttle body assembly. Has anyone done this?

UMMMM.... I've replace the TPS in my wifes 3.7 2002 Liberty without having to change the whole TB. Did they change the manufacturing process for the Commanders?

redrockXK
04-04-2012, 10:10 PM
you should try some sea foam. after 130,000 miles in my commander it started idleing a bit rough and that sea foam fix the problem. i even got better mpg.

BrendenV
04-05-2012, 01:29 AM
you should try some sea foam. after 130,000 miles in my commander it started idleing a bit rough and that sea foam fix the problem. i even got better mpg.

+1. I use seafoam in all my engines from lawn mower to boat to commander. It really works!


Sent from my Autoguide iPhone app

Kale
11-08-2012, 04:27 PM
2006 jeep commander would idle rough then stall out

Kale
11-08-2012, 04:54 PM
My 2006 jeep commander would idle rough then stall out while in drive or park. There wasn't any check engine light on at the moment also. I had it towed back to the house to work on it. After a couple of hours of trouble shooting and multiple restarting the engine, I was able to generate a check engine light. The diagnostic machine indicated that it was the crank shaft position sensor (can be easily mistaken for the camshaft position sensor) a $20 part at the local auto parts store. The sensor can be access from underneath the car on the passenger side. Remove the splash guard to allow more room to work (4 bolts, use 13mm socket). Only one bolt holds the sensor in place, again, use the 13mm socket, unplug wire harness from sensor. Compare old sensor to new one to be sure that they are the same. Lubricate the O-ring on the new sensor before installing. Be sure to clear or erase any problem codes with the diagnostic machine so the check engine light would turn off. My jeep runs perfect now, this is my first experience with a sensor that would intermittently work. Most of the time it would work or don't work. This repair is very cheap and easy to do. Let me know if this posting helps anyone. Thanks.

CommandA.R.
11-08-2012, 09:29 PM
i had the same problem with my 2006 4.7L commander limited at 82k miles. it would idle between stall and 2k RPM. then one day driving 2 hours from columbus ohio it stalled while driving 75 in the middle of the highway and i got a check engine light. so i took it to the dealer ship and they tried checking the the computer but couldnt find anything. they told me to take it to a jeep specialist at a Jeep/Crystler dealership. the specialist told me that since jeeps are known for having major electrical wires run through the doors, and that jeeps have a problem with getting water on the inside of the doors, that there was alot of decay and corosion of the wires. so i reccomend taking it to a jeep/crystler dealership and have a specialist check it out. also call crystler to see if your jeep has had any of the factory recalls done to it. best of luck.