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Yes. He is good at fabrication stuff but as far as working on vehicles he tries to work as fast as he can and always ends up having to tear it apart at least twice before he's done because he forgot something. But that's another story for another day. I'm not sure what the vane position looked like. It was pretty late when I got home. I'll have to plug in my cs and see if it shows me that either tonight or tomorrow when I get a little time.
 

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I have been following this thread for a while, I have a 2005 LLY 3500 with warm rough idle and was very rough when coming down to idle after rev for a second or so, rough idle only occured after ECM demanded idle pressure down to the 4350 area (Warm). Actual pressure coming down to idle after rev dropped to about 3300 for a second when ecm demanded 4350. I did fix this issue by replacing the injector reading negative balance rates both in park and drive but not out of spec. The suspect injector only read negative 2 in neutral and the worst I saw but only briefly was negative 5 in drive with foot on brake. I was told by the guy who helped diagnose and repair the issue that he has seen many injectors that read in spec balance rates cause alot of issues. When the truck is up to operating temp now I have no more rough idle and after rev the acual pressure drops barely below less than 100 after rev. This issue was very sensitive to air temp as well as the operating coolant temp of the engine. Seemed to never occur until ECM demanded lower idle rail pressure due to being up to operating temperature. Makes sense beacause the bad injector was bleeding pressure when the ECM was demanding them closed and the regulator was in pressure reduce mode causing rail pressure to briefly drop too low until the regulator caught up. It had no effect when cold because demanded pressure was much higher when cold so the rail pressure bounce had no effect on idle.
 

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Well I was waiting til I knew for sure the injectors fixed my problem. Truck seemed to be doing awesome and unfortunately on Easter morning I woke up from my apartment in Ohio to see my truck wasn't outside. This was at 4am, just before 10am the county dispatch called to tell me they found my truck 2hrs south in West Virgina.

From what we can make out they took my baby for a joy ride, dogged and flogged it, wrecked the front and swiped the passenger side. At the end of it all they got it stuck in a creek or mud hole from what the cop said. I guess that wasn't enough so the left the truck in gear, and left the truck running wide open and spinning the tires.

They made off with around $1200 in tools I had in my truck along with my PPE Xcelerator, and my Bully Dog Watch Dog Monitor. It's been almost two weeks and everyone keeps saying they think the trucks blown up. Thank god yesterday I called the shop were the truck is being repaired and they said she's purring like a kitten. They did go ahead and send it to the local Chevy dealer to check it over. But so far jokes on them. They thought they was gonna blow up my truck and 325k miles later and a couple worthless thieves and she's still purring!!!

I'm hoping I get my baby back soon but only time will tell. More than anything I wanna find the low lives responsible for the rape of my baby..
 

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Dang NO-GOODERS!!!
Hopkins that sucks!! But I gather from the beginning of your post you actually changed your injectors and it fixed the problem? All or a few? And where did you get them?
 

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Just 3, I believe #4 was my problem child. At idle after warm it wouldn't command #4 to do anything except when you gave it gas.
 

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I have been following this thread for a while, I have a 2005 LLY 3500 with warm rough idle and was very rough when coming down to idle after rev for a second or so, rough idle only occured after ECM demanded idle pressure down to the 4350 area (Warm). Actual pressure coming down to idle after rev dropped to about 3300 for a second when ecm demanded 4350. I did fix this issue by replacing the injector reading negative balance rates both in park and drive but not out of spec. The suspect injector only read negative 2 in neutral and the worst I saw but only briefly was negative 5 in drive with foot on brake. I was told by the guy who helped diagnose and repair the issue that he has seen many injectors that read in spec balance rates cause alot of issues. When the truck is up to operating temp now I have no more rough idle and after rev the acual pressure drops barely below less than 100 after rev. This issue was very sensitive to air temp as well as the operating coolant temp of the engine. Seemed to never occur until ECM demanded lower idle rail pressure due to being up to operating temperature. Makes sense beacause the bad injector was bleeding pressure when the ECM was demanding them closed and the regulator was in pressure reduce mode causing rail pressure to briefly drop too low until the regulator caught up. It had no effect when cold because demanded pressure was much higher when cold so the rail pressure bounce had no effect on idle.
X2

The GM specs for balance rates are really only good for warranty work IMHO. If you want your truck to run optimally I would suggest aiming for a max of +/-2 in drive. The key is to make sure your largest balance rate number is positive not negative (since negative is always a leaking injector whereas positive can be related to deposits/sticking or differences in cylinder pressures).


Just 3, I believe #4 was my problem child. At idle after warm it wouldn't command #4 to do anything except when you gave it gas.

Sounds like you figured out your issue, definitely not normal.
 

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Well, I seem to have inadvertently gained some headway on my rough idle over the holiday weekend. It was time to replace my AirDog fuel filter, so I replaced it with the CAT 1R-0751 filter. This was simply a maintenance item I by no means expected any increased performance from this, but it actually ended up making a huge difference. I didn't notice much at first except it was MUCH easier to keep a steady throttle down a ridiculously rough dirt road. Then on the highway I noticed my shifting had improved drastically. I had always thought my truck seem to defuel too much on shifts cause a rocking horse type of effect. Well that was gone it now shifts much smoother. My mileage took a nice step in the good direction as well went from 16.5 on my 300 mile trip to my parents house to just over 18 on the trip back (yes these are hand calculated not DIC #'s), which had in my opinion worse conditions for fuel mileage. I know fuel mileage has too many factors to put much weight into, but still. Now after a few days of driving I can certainly say it idles smoother and I have not had the lopey idle, yet anyway (fingers crossed).

I really can't explain why this filter change would have any of these affects other than maybe the CAT filter is able to flow more volume than the standard AD filter. I know the AD filter at 15,000 mi would be a bit dirty, but even when I initially put the AD filter on new it didn't run like it does now. So we'll see how it does. I don't know that this is the root cause of my issue, but thought I would pass along the info.
 

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Well, I seem to have inadvertently gained some headway on my rough idle over the holiday weekend. It was time to replace my AirDog fuel filter, so I replaced it with the CAT 1R-0751 filter. This was simply a maintenance item I by no means expected any increased performance from this, but it actually ended up making a huge difference. I didn't notice much at first except it was MUCH easier to keep a steady throttle down a ridiculously rough dirt road. Then on the highway I noticed my shifting had improved drastically. I had always thought my truck seem to defuel too much on shifts cause a rocking horse type of effect. Well that was gone it now shifts much smoother. My mileage took a nice step in the good direction as well went from 16.5 on my 300 mile trip to my parents house to just over 18 on the trip back (yes these are hand calculated not DIC #'s), which had in my opinion worse conditions for fuel mileage. I know fuel mileage has too many factors to put much weight into, but still. Now after a few days of driving I can certainly say it idles smoother and I have not had the lopey idle, yet anyway (fingers crossed).

I really can't explain why this filter change would have any of these affects other than maybe the CAT filter is able to flow more volume than the standard AD filter. I know the AD filter at 15,000 mi would be a bit dirty, but even when I initially put the AD filter on new it didn't run like it does now. So we'll see how it does. I don't know that this is the root cause of my issue, but thought I would pass along the info.

It would be very hard to catch a new "bad" fuel filter without watching the lift pressure all the time but hopefully you have finally solved your issue once and for all. Thanks again for the update.
 

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Rough Idle When Warm

Has anyone else resolved this?

I too have a stumble at idle, in neutral and park only, after the truck is over approximately 170 Deg F and have been trying to figure this out for over 3 months. My symptoms are exactly the same as others on here... "Everything is great, idles fine, until you get it up to operating temps (around 185) then it is still perfectly fine while in gear, but the second you put it in Park or Neutral it starts loping pretty bad. According to Torque App, rpm's jump from around 660 to 690 then back and forth. Then you can stick it back in gear and goes back to idling within an rpm or two of 680 like it should."

A little history.....
05 LLY - Chevy Silverado 2500HD Crew Cab 100K miles.
Completely Stock, No Modifications.
In February, a gas station sold me 20 gallons of water due to a problem with their underground fuel tank. Clerk said no problem with the fuel...They have been selling it right along. (But didn't say I was the first one that morning). Had it towed home and dropped in the driveway. By the next morning, everything had frozen solid due to low temp of 11 Deg F that night. Dealership installed new injectors, new CP3 pump, cleaned the tank out, flushed lines, etc. I have installed a new sender/float in the fuel tank and a new fuel filter housing due to seeing some bubbles in the fuel system with clear tubing installed. Dealership checked everything with a Tech II and assures me that it's normal for some of these trucks to shake like this. They did notice that the VSS showed 1.5 mph while parked and that idle was about 10rpm higher than commanded.

Any ideas would be appreciated.
 

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They did notice that the VSS showed 1.5 mph while parked and that idle was about 10rpm higher than commanded.
I noticed this exact same thing using my CTS to monitor these parameters. Mine hasn't acted up since my above post, but it used to do that. I have no idea why it would though. It appears to me that the problem is a fuel issue, but may be different for each of us. Like the above guys found injectors fixed the problem and for me possibly a bad AD fuel filter might of been the culprit.
 

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I have noticed that as my engine is heating up, the balance rates seem to be working correctly and the idle is smoothe. When the temp gets to 160 Deg F, the balance rates turn off and the rough idle starts. The balance rates are all zeros in park and neutral. Does anyone know what changes in the ECM or FICM at this temperature?
 

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I have noticed that as my engine is heating up, the balance rates seem to be working correctly and the idle is smoothe. When the temp gets to 160 Deg F, the balance rates turn off and the rough idle starts. The balance rates are all zeros in park and neutral. Does anyone know what changes in the ECM or FICM at this temperature?

It's not the temperature that screws up the balance rates (although that may relate to your rough idle) but the reason the balance rates don't display is that the RPM is out of range for displaying them so the ECM will read all 0.0 across the board (06+ trucks will display balance rates even while driving).
 

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I am also having the rough idle issue in only park and neutral, I will be rebuilding my filter head and replacing filter to see if that fixes mine. Will post if it fixes it.
 

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I believe mine was either wiring or injector. Since the new motor has went in I havent had any lope at idle.

My "knock" did come back but I actually thinkb its related to my hydroboost. I'll confirm this once I replace it.

Its weird that depending on the fluid level and what the truck is doing I have the knock. My balance rates have always been awesome.

Only 1, 3, & 8 right now have negative numbers. None of which are over -1.0 normally they are about half that. All other are +0.8. Not one injector is +/- 1.0.

Ive seen a lot of LLY threads about knock and no one ever finding out what it was. I honestly think this go round mine is hydroboost related. Hopefully this eveningn or Monday I can confirm this.

Sent from AutoGuide.com App
 

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It's good to hear some feedback on this problem. I recently bought an 05lly with 120k. Started having this issue this week. Only does it in park/nuetral when warmed up. The truck was ppe tuned by previous owner and has a 3.5" straight pipe side exit exhaust. Other then that it's stock. I don't even know if the kid left the stock tune on it. It has a efi live dsp5 switch that doesn't seem to do anything. For starters I'm going to service the fuel system this weekend and see if it makes a difference.

Any input is appreciated
 

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I came across a new observation on mine this past weekend. Mine hasn't shown symptoms for quite a while until this:

When I filled up I was running late and didn't have time to put in my additive (Stanadyne Performance Formula). The first part of the trip was 80 miles and as soon as I pulled off the highway and stopped the lope was right back and as bad as it has ever been. I continued to run that tank out and it consistently loped bad. The next fill up I went back to putting in my additive and after a short drive it was like magic it basically quit lopping and hasn't done it since. I should note both fill ups were at the same station that I have used for years.

So it appears my additive has a big affect on whatever the problem is. Really don't know what it could be though. Just another piece of the puzzle.
 

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I came across a new observation on mine this past weekend. Mine hasn't shown symptoms for quite a while until this:

When I filled up I was running late and didn't have time to put in my additive (Stanadyne Performance Formula). The first part of the trip was 80 miles and as soon as I pulled off the highway and stopped the lope was right back and as bad as it has ever been. I continued to run that tank out and it consistently loped bad. The next fill up I went back to putting in my additive and after a short drive it was like magic it basically quit lopping and hasn't done it since. I should note both fill ups were at the same station that I have used for years.

So it appears my additive has a big affect on whatever the problem is. Really don't know what it could be though. Just another piece of the puzzle.

Brent you already replaced your FPR though, right?

Does your actual vs demand rail pressure go up and down with the lope?
 

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I seem to be having the same issue. Last night I had less then a quarter tank and when I got home it was loping in park before I shut it off. This morning I drove to get fuel and at that time I put my additive in. After driving multiple places today it hasn't acted up once.
 
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