Help Rough Idle LLY

[b_r_a_d_79]

I am working on a 2004 LLY/ZF6 truck. The truck idles rough as can be but does not seem to always do it. The balance rates on every injector go back and forth between -7 to +15 when acting up. It will slightly start to lope before the rough idle and seems to do the rough idle when it gets to operating temps. There are no codes in the truck but I have found out that some codes are turned off using efi live when I had the maf unhooked and it didn't throw a code. Known modifications are EFI (unknown tuner), CTS insight, and egr Blocker Plate. Truck has 142,000 miles. I have swapped out the ficm, maf, done the ice pick, and the return rates test. Both banks are returning less than 20ml. When the truck is running correctly injector balance rates are good. If the truck is idling rough I can touch the throttle and idle straightens out. I am uploading a video to youtube right now and will post the link as soon as it finishes uploading. Hopefully someone has ran into similar issues.

 

[Awenta]

Flash back to stock. Check the harness by the alternator?

Sent from my SM-N910V using Tapatalk

 

[Bonestock]

I am working on a 2004 LLY/ZF6 truck. The truck idles rough as can be but does not seem to always do it. The balance rates on every injector go back and forth between -7 to +15 when acting up. It will slightly start to lope before the rough idle and seems to do the rough idle when it gets to operating temps. There are no codes in the truck but I have found out that some codes are turned off using efi live when I had the maf unhooked and it didn't throw a code. Known modifications are EFI (unknown tuner), CTS insight, and egr Blocker Plate. Truck has 142,000 miles. I have swapped out the ficm, maf, done the ice pick, and the return rates test. Both banks are returning less than 20ml. When the truck is running correctly injector balance rates are good. If the truck is idling rough I can touch the throttle and idle straightens out. I am uploading a video to youtube right now and will post the link as soon as it finishes uploading. Hopefully someone has ran into similar issues.

This definelty sounds like the famous injector harness issue. Check for rubbed wires where harness is stretched injectors #2 adn #7 mainly. Also check the wiring by the ficm that is zip tied down the the alluminum bracket. Make sure your ice pick fix was performed correctly. Good luck.

 

[b_r_a_d_79]

The wiring looks good next to the FICM as well at the injector connectors.

 

[Burn Down]

Ck the 3 ground wires at right front of the engine. I had a loose one that would make mine run like sh*t and then perfectly fine.

 

[b_r_a_d_79]

I'll take a look at those in the morning. Thanks

 

[weazel]

Just throwing it out there to check also, FPR... Had one make one of my lly trucks idle and act funny. Don't know if that's what your problem could be, but while you're checking, might as well add that to the list.

 

[b_r_a_d_79]

the FPR was my first thought but I've never seen balance rates act this way.

 

[b_r_a_d_79]

Installed a new FPR in this truck still no change. Also took a ecm I had and tuned a stock tune for this truck and installed it in the truck as well with no change

 

[weazel]

Do you have a way to post up a video of it running? Curious to see what it's doing exactly..

 

[b_r_a_d_79]

I never was able to get my video to load up to you tube but I found a video of what looks like to be the same issue. Heres the link.
https://youtu.be/WzKMKosGFDo

 

[Chevy1925]

have you watched the crank/cam signal for irregularities?

could also be the dual mass fly wheeling causing you issues (if its still a stock clutch in there)

 

[b_r_a_d_79]

yes the crank and cam sensors seem to be reading properly.

Would the flywheel issue only occur when the truck is to operating temps?

 

[Chevy1925]

yes the crank and cam sensors seem to be reading properly.

Would the flywheel issue only occur when the truck is to operating temps?

that i dont know as i have not worked on one with this issue but i know that damn dual mass can cause all kinds of headache and weird issues.

 

[weazel]

When you push the clutch pedal in, does the idle get better, like in that video? Or does it stay the same?

 

[WVRigrat05]

When you push the clutch pedal in, does the idle get better, like in that video? Or does it stay the same?

I was gonna so the same thing, acts like the flywheel.

 

[b_r_a_d_79]

It stays the same no matter in gear, neutral, clutch engaged, or disengaged. The only time it goes away is when below operating temps or if any throttle is given but it does not have to raise rpm. Like if the ecm sees any throttle percentage at all.

 

[WVRigrat05]

You say the balance rates are jumping all over? I'd really play the the harness and see if it quits. Is it a certain injector doing it or more than one?

 

[b_r_a_d_79]

Every injector bouncing back and forth when idling rough

 

[WVRigrat05]

Never had that issue. You have a spare ficm you can swap out?