Rough idle and hard start solved...

12-05-2007, 12:02 PM

I remembered reading on TDR about a little wire that rubbed bare when I first got my truck three years ago...well, I found it, and it was bare. I found I had looked at the WRONG wire then...I had looked at the wire with the connector, it was the OTHER wire!

The wire is part of the AC circuit, but IIRC it is also part of the CPS (crank position sensor) circuit. You can see the oil filter right above the wiring...the wire rubs a bolt head on the AC compressor and runs to a AC pressure sensor next to the AC compressor. I ran a little RTV over the bare spot, added a piece of convoluted tubing, and ziptied it up a little better.

I had a intermittent rough idle, and a very lopey high idle. After I fixed it, it coughed and stumbled, just like it does when you replace the CPS. It completely cured my rough idle, intermittent hard/bucking start, and lopey high idle.

If you can see the pictures, it is a VERY small bare spot.

This is one of those things I had put away into the "ah-ha" files so long ago and, for whatever reason, decided to look a little deeper tonight since I was already there.

My power is back to normal, with very little smoke. Rough/hard start is gone...idle is normal. Things runs like it did when new...I also gained between 2 and 4 psi of boost. The thing acted like I was losing an injector and like the timing was retarded...

http://i174.photobucket.com/albums/w...e/IMG_1941.jpg

http://i174.photobucket.com/albums/w...e/IMG_1942.jpg

http://i174.photobucket.com/albums/w.../IMG_1945A.jpg

steved

12-05-2007, 12:04 PM

As a side note, this caused NO codes to be thrown...just poor running.

steved

ah64id · 12-05-2007, 12:43 PM

wow.. good find... something else to put in the headbone.

__________________

05 3500 QC LB NV5600 4X4 SRW
Pricol's (EGT, Boost, DP, FP, Oil)
Amsoiled, BMK-11
GDP MK-2+ w/ Cat 2 mic
Smarty Jr Revo

DORKWEED · 12-05-2007, 01:52 PM

This should be a sticky in the 3rd gen area IMHO!!!:thumbsup Good job as always Steved!!

Dad · 12-05-2007, 03:17 PM

Nice work..

Makes you wonder how many parts have been swapped at Dodge dealers across the country looking for that..

12-05-2007, 03:28 PM

Quote:

Originally Posted by Dad98.5

Nice work..

Makes you wonder how many parts have been swapped at Dodge dealers across the country looking for that..

Thanks, but I want to stress that I only used the information someone else provided to find this problem...I didn't find it on my own, although the last time I read that thread was over 3 years ago.

I'm quite sure there has been a lot of time and money spent in vain trying to locate this problem...I know when it is bad, it causes a no start/no run condition.

steved

AlK · 12-07-2007, 12:50 AM

steved,

Thank you for posting this. I took a look at my 2006 and everything was ok. Just to make sure that the wires will never rub against any metal surfaces, I took two pieces of 5/16" rubber hoses(1 about 2" and 1 about 6") and cut them length wise on one side and slipped them over the electrical wires.

__________________
2006, 2500, 4x4, QC, Black, Auto, Leer Cap

ynots57 · 12-07-2007, 09:17 AM

Gotta love this site........... Thanks for sharing this info steved,

__________________
2005 3/4 SRW 48RE QUAD L/B 4x4 AEM AERO

BBRam · 12-07-2007, 09:27 AM

Quote:

Originally Posted by DORKWEED

This should be a sticky in the 3rd gen area IMHO!!!:thumbsup Good job as always Steved!!

Sticky it is. Thank you Steved, Great piece. :thumbsup

__________________

03-3500, DRW, QC, 4x4, R850 BD Twins, BD IC Boots, BD Billet Flexplate, Full Billet DTT Trans, Lockup Switch, SMARTY TNT-R / TS MP-8, Wicked Diesels Eliminator Fuel System & Coolant Bypass, Floor It Stage 3 CP3 & Rail Cap, BIG Stix's by FTE, ARP Head Stud's, Springs, Fluidampr, ATS ARC-FLOW, Mag-Hytec, AFE, Boost, Drive Pressure, Pyro, Fuel Pressure, Tran's Temp, Rail Pressure Gauge, GDP Ladder Bars, GrandRock 7" Miters. (R/T .021, 60' 1.76, 1/4 ET 13.03 @ 102.05 mph)

July 2009 Cummins Forum ROTM Winner

95 1500 Sport 2wd Cummins Drag Truck under construction.

"In search of the Magic Dyno"

BearPaw · 12-27-2007, 01:52 PM

I know what I'm going to be doing this weekend. Thanks.

__________________
2006' QC Shorty, 6 on the floor, Smarty Jr. Pyrometer, Kore HP Series, Thuren Track-bar, 35X12.50X17 Toyo Open Country MT, DIY Steering Box Stabilizer, ThingstTo come: BHAF, CAT back and Home brew intake horn.

***05610on24s*** · 12-30-2007, 12:36 PM

Mine has been doing the rough idle and hard start for a while... It doesnt do it all the time though. I had talked to a diesel mechanic that i know and he actually told me about this. I just have been to damn lazy to look at it. Well, i did the other day, wrapped it, and cleared it from the AC line... Since i have noticed that it idles smoother and sounds better. As far as boost gain... If i get in it all the way with my TST, im holding 40psi......which is all i wanna get out of my stock and what my TST is set to limit at.... No fuel pressure guage yet to tell anything there... But like i said, it sounds better and idles smoother since i fixed this problem....

Very nice write up steved.. you actually made me remember about the wire and go fix it... Thanks

__________________
05 w/ 07 Metal, SRT, Flares, DiPricol, II PS62 on ATS, AD150, MBRP, TST, 6.5" lift, 8 Bilsteins, 22's on 37's... Next up... Tranny
Redneck Engineering Low Curve, 6" out 0" up, Custom Paint, 100" RevTech, 6 Spd, 3" Primary, Billet Concepts Controls, MC Motorsports Reaper Wheels, DNA Sprockster

BighornCTD · 01-02-2008, 07:13 PM

Well I am crossing my fingers on this one. My truck has been plagued with the same symptoms which the dealer has never been able to fix for the last 20K miles.

Last weekend I was under the truck investigating a coolant leak and decided to look at this. All I did was pull some slack in the wires so they weren't up against the compressor. It was cold and I was laying in my driveway so I didn't put on any loom yet, but I will as soon as I get it pulled in the shop. I couldn't get a good enough look to see bare spots, but will look closer to see.

So far it seems to be running much better, like it was new again. And my overhead is reading 20 mpg (should be about 18 hand calc'd) which would be a record for me driving to work and back. :thumbsup Funny thing is this has been an intermittent problem...maybe changing oil filters has disturbed the wire enough to make it either better or worse?

__________________
2006 2500 QC SWB 4x4
5.9 CTD, G56, 3.73TR, no mods.

12-05-2007, 12:02 PM	#1 (permalink)
Guest Posts: n/a	Rough idle and hard start solved... I remembered reading on TDR about a little wire that rubbed bare when I first got my truck three years ago...well, I found it, and it was bare. I found I had looked at the WRONG wire then...I had looked at the wire with the connector, it was the OTHER wire! The wire is part of the AC circuit, but IIRC it is also part of the CPS (crank position sensor) circuit. You can see the oil filter right above the wiring...the wire rubs a bolt head on the AC compressor and runs to a AC pressure sensor next to the AC compressor. I ran a little RTV over the bare spot, added a piece of convoluted tubing, and ziptied it up a little better. I had a intermittent rough idle, and a very lopey high idle. After I fixed it, it coughed and stumbled, just like it does when you replace the CPS. It completely cured my rough idle, intermittent hard/bucking start, and lopey high idle. If you can see the pictures, it is a VERY small bare spot. This is one of those things I had put away into the "ah-ha" files so long ago and, for whatever reason, decided to look a little deeper tonight since I was already there. My power is back to normal, with very little smoke. Rough/hard start is gone...idle is normal. Things runs like it did when new...I also gained between 2 and 4 psi of boost. The thing acted like I was losing an injector and like the timing was retarded... http://i174.photobucket.com/albums/w...e/IMG_1941.jpg http://i174.photobucket.com/albums/w...e/IMG_1942.jpg http://i174.photobucket.com/albums/w.../IMG_1945A.jpg steved

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12-05-2007, 12:04 PM	#2 (permalink)
Guest Posts: n/a	As a side note, this caused NO codes to be thrown...just poor running. steved

12-05-2007, 12:43 PM	#3 (permalink)
ah64id Local Rotor Head.... Join Date: Sep 2006 Location: Idaho Posts: 3,282 Thanks: 12 Thanked 54 Times in 45 Posts ah64id's Truck Pics	wow.. good find... something else to put in the headbone. __________________ 05 3500 QC LB NV5600 4X4 SRW Pricol's (EGT, Boost, DP, FP, Oil) Amsoiled, BMK-11 GDP MK-2+ w/ Cat 2 mic Smarty Jr Revo

12-05-2007, 01:52 PM	#4 (permalink)
DORKWEED Banned Join Date: Dec 2005 Location: "The Peoples Republic of Illinois".....behind enemy lines Posts: 2,166 Thanks: 0 Thanked 0 Times in 0 Posts DORKWEED's Truck Pics	This should be a sticky in the 3rd gen area IMHO!!!:thumbsup Good job as always Steved!!

12-05-2007, 03:17 PM	#5 (permalink)
Dad Administrator Join Date: May 2007 Location: Indiana Posts: 5,273 Thanks: 18 Thanked 114 Times in 40 Posts Dad's Truck Pics	Nice work.. Makes you wonder how many parts have been swapped at Dodge dealers across the country looking for that..

12-07-2007, 12:50 AM	#7 (permalink)
AlK Cummins Fan Join Date: Jan 2007 Posts: 41 Thanks: 0 Thanked 1 Time in 1 Post AlK's Truck Pics	steved, Thank you for posting this. I took a look at my 2006 and everything was ok. Just to make sure that the wires will never rub against any metal surfaces, I took two pieces of 5/16" rubber hoses(1 about 2" and 1 about 6") and cut them length wise on one side and slipped them over the electrical wires. __________________ 2006, 2500, 4x4, QC, Black, Auto, Leer Cap

12-07-2007, 09:17 AM	#8 (permalink)
ynots57 Diesel Head Join Date: Mar 2007 Location: Southern OR Posts: 2,632 Thanks: 10 Thanked 20 Times in 19 Posts ynots57's Truck Pics	Gotta love this site........... Thanks for sharing this info steved, __________________ 2005 3/4 SRW 48RE QUAD L/B 4x4 AEM AERO

12-27-2007, 01:52 PM	#10 (permalink)
BearPaw Cummins Enthusiast Join Date: Nov 2007 Location: Utah Posts: 252 Thanks: 0 Thanked 2 Times in 1 Post BearPaw's Truck Pics	I know what I'm going to be doing this weekend. Thanks. __________________ 2006' QC Shorty, 6 on the floor, Smarty Jr. Pyrometer, Kore HP Series, Thuren Track-bar, 35X12.50X17 Toyo Open Country MT, DIY Steering Box Stabilizer, ThingstTo come: BHAF, CAT back and Home brew intake horn.

12-30-2007, 12:36 PM	#11 (permalink)
*05610on24s* Cummins Nut Join Date: Sep 2006 Location: Terre Haute, IN Posts: 336 Thanks: 0 Thanked 1 Time in 1 Post 05610on24s's Truck Pics	Mine has been doing the rough idle and hard start for a while... It doesnt do it all the time though. I had talked to a diesel mechanic that i know and he actually told me about this. I just have been to damn lazy to look at it. Well, i did the other day, wrapped it, and cleared it from the AC line... Since i have noticed that it idles smoother and sounds better. As far as boost gain... If i get in it all the way with my TST, im holding 40psi......which is all i wanna get out of my stock and what my TST is set to limit at.... No fuel pressure guage yet to tell anything there... But like i said, it sounds better and idles smoother since i fixed this problem.... Very nice write up steved.. you actually made me remember about the wire and go fix it... Thanks __________________ 05 w/ 07 Metal, SRT, Flares, DiPricol, II PS62 on ATS, AD150, MBRP, TST, 6.5" lift, 8 Bilsteins, 22's on 37's... Next up... Tranny Redneck Engineering Low Curve, 6" out 0" up, Custom Paint, 100" RevTech, 6 Spd, 3" Primary, Billet Concepts Controls, MC Motorsports Reaper Wheels, DNA Sprockster

01-02-2008, 07:13 PM	#12 (permalink)
BighornCTD Cummins Fan Join Date: Jul 2007 Location: Montana Posts: 57 Thanks: 0 Thanked 0 Times in 0 Posts BighornCTD's Truck Pics	Well I am crossing my fingers on this one. My truck has been plagued with the same symptoms which the dealer has never been able to fix for the last 20K miles. Last weekend I was under the truck investigating a coolant leak and decided to look at this. All I did was pull some slack in the wires so they weren't up against the compressor. It was cold and I was laying in my driveway so I didn't put on any loom yet, but I will as soon as I get it pulled in the shop. I couldn't get a good enough look to see bare spots, but will look closer to see. So far it seems to be running much better, like it was new again. And my overhead is reading 20 mpg (should be about 18 hand calc'd) which would be a record for me driving to work and back. :thumbsup Funny thing is this has been an intermittent problem...maybe changing oil filters has disturbed the wire enough to make it either better or worse? __________________ 2006 2500 QC SWB 4x4 5.9 CTD, G56, 3.73TR, no mods.