HAH! Rough idle cured...thanks to TDR!

[steved]

Well, we will see if these pictures show up...



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I remembered reading about a little wire that rubbed bare when I first got my truck three years ago... well, I found it, an 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 IIRC, but 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. I hope this cures the major smoking pig I am driving... and brings my power back up to norm...



So I want to thank all of those that had found this problem so long ago! You saved me a potential break down on the side of the road!



steved

 

[steved]

OK, bear with my poor photo corruption... here is the bare spot pointed out.

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steved

 

[steved]

Hmmmm, boost is up between 2 to 4 psi at cruise... no hard start... and less smoke! Plus it runs like crazy now! I'd really like to see what my EGTs at higher elevations are now...



That was definitely one of the problems I was experiencing... it acted like I had retarded timing or a bad injector.



steved

 

[DPKetchum]

Well just DARN! Thats in my file also.

 

[BSwope]

Im gonna have to check this out as well, my truck seems to have timing rattle even when the TST is turned off, im gonna get my truck on the lift and check this out!! Thanks for the pics and write up!!





Thanks again

Buddy

 

[wcjp]

What a great find. I'll have to check on mine this weekend. At the very minimum add some insulation to avoid heartache later.

 

[steved]

After driving for a couple hundred miles...

It didn't fix all the issues, but the truck hasn't ran this smooth and with this much power in some time. I'm back to breaking tires loose on tar strips under WOT in 5th (which it hasn't done for some time)... the thing just glides down the road, it is noticeably much smoother running. And I don't have as much "valve noise" at cruise... which leads me to believe it was affecting the timing. It is also much more responsive!

And again, I found this from reading someone else's posting about the same problem a few years back... that's where I'm drawing all my info of the CPS/AC being connected somehow, and the fact that this problem exists. I was under the impression this was fixed in 2004. 5, and only affected the older trucks; mine must have been missed.

It is definitely worth looking into, for the very least to prevent sitting along the road somewhere.

steved

 

[JCrockett]

My buddy found this info out over at the DTR, there were no photos in the post but I figured it out from the descriptions and your photos confirm I put the wire loom on the correct wires. My truck has 29k on the clock, and I didn't see any copper showing. How may miles on your truck Steved when you noticed the problem.



Thanks for the photos

 

[steved]

I've had a rough idle that has been intermittent for at least two years and probably 70k miles. I'm surprised it didn't cause more issues than it did, like leave me stranded in the mountains two weeks ago (the way my luck runs... ). The power loss, well, I attributed that to a flash I had within the first year or so of owning it. The changes probably came on slow enough, that I would not have noticed them when they actually did take place...





steved

 

[steved]

I will add that the truck has 140k on it... I had the symptoms for probably 70k.



steved

 

[steved]

Hmmm, I was happy getting around 20mpg... I'm getting well over 20mpg highway after fixing this (I assume it was running retarded timing?).

The last three consecutive tanks (I took a ride to North Carolina for an M37 engine) were 23 mpg, 25 mpg, and 21 mpg! And that is hand calculated, filling the main tank so the fuel is into the filler neck using the auxiliary tank for a consistent "fill"...

I am still amazed at all the problems this bare spot caused!

steved

 

[HOBrian]

Steve, what did you use to clean the wires before you fixed them?? Great find!!!!

 

[steved]

I didn't clean them... I simply placed some RTV over the bare spot and wrapped it with convoluted tubing. My truck has some much grime under it, cleaning is like polishing a turd.

steved

 

[HBarlow]

Steved:

Thanks for a good report on a problem solved. My '06 also has an intermittent rough idle.



Could you provide a little reference info for interpreting your photos? The first photo you posted looks like it was taken from under the truck with the lens pointed upward at the bottom of the oil filter. The engine block is to the viewer's left. Is that correct?



Is that the back of the alternator we see at the bottom of the phots you posted with the arrow pointing to the bare spot?



Harvey

 

[p-Bar]

Steved be careful using RTV , make sure it is rated for electrical. It is corrosive to copper. The liquid tape in the electrical dept at Home Depot would be a good choice. Thanks for reminding us all again about the wire issue.

 

[steved]

Steved:

Thanks for a good report on a problem solved. My '06 also has an intermittent rough idle.



Could you provide a little reference info for interpreting your photos? The first photo you posted looks like it was taken from under the truck with the lens pointed upward at the bottom of the oil filter. The engine block is to the viewer's left. Is that correct?



Is that the back of the alternator we see at the bottom of the phots you posted with the arrow pointing to the bare spot?



Harvey

This was laying under the truck... looking up at the oil filter... the engine is on the left... that "plug" on the side of the engine is the block heater.



That is the AC compressor, and its power feed connector in the second picture. The smaller set of wires with the nick run to a pressure switch in the AC system located near the passenger side frame rail.



steved

 

[HBarlow]

Steved:



Thanks for the reply and further explanation. I'lll get under my truck today with a bright light and look for a similar problem.



I didn't see what caused the bare spot on the wire. Had you already moved the harness away from the fixed object it was riding against?



I'll report if I find a similar problem.



Harvey

 

[steved]

Steved:



I didn't see what caused the bare spot on the wire. Had you already moved the harness away from the fixed object it was riding against?



I'll report if I find a similar problem.



Harvey

The bolt holding the AC line to the compressor... it has a sharp edge on its "crown" that the wire in question rides against...



IIRC, in the original thread they stated this should have been "fixed" by DCX, but I'm not sure...



steved

 

[WKruger]

Check engine light come or set any codes?

 

[steved]

Check engine light come or set any codes?

Nope...



steved