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Rough Idle & Bucking After Installing Head Studs, Turbo and Injectors


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New to the site here, and I've combed through hours of posts, but wasn't able to find any thread that exactly described what I'm experiencing. I also tried everything suggested in the posts below but still haven't been able to resolve the issues. 

 

  • Truck was stock up until Sept 2020, except for:
    • Straight Piped
    • BHAF
    • FASS 95
  • Upgrades done since Oct 2020:
    • Built Towing Transmission
    • Quadzilla Adrenaline
    • ARP Head Studs
    • Borg Warner K27 from Power Driven Diesel
    • 7x.0085 Injectors (popped @ 300 bar)
    • Crossover Tubes
  • Issues: Transmission was done by 3rd party, I installed the Quadzilla a couple weeks later. Truck ran great, with V2 tuning. Ran that for a couple weeks until the turbo, injectors, crossover tubes and head studs were delivered. After installing those, noticed:
    • Bad/Rough Idle. Identical to what @Mopar1973Man describes in his post here
    • Bucking at 40-70 mph, 1200-1800 rpm, under light throttle, 4th gear overdrive locked. Bucking is worse at the low end of the mph range (40 mph). Similar to what Collinst15 posted here
  • Troubleshooting Done:
    • Swapped out injectors for another new set (same style)
      • Mostly improved, but still seems to be there
    • @Me78569 75hp Tow Tune

      • No improvement with bucking

    • Added %5 to 0 psi 4% to 1 psi 3 % to 2 psi and so forth per Me78569’s suggestion from this post

      • Seemed to help the bucking issue a little bit, but still obviously there

    • Completely Unplugged Quadzilla

      • Bucking improved, but still there at 40-50 mph, 1200 rpm, light throttle, 4th gear overdrive locked.

    • Hooked up scan tool, no codes being thrown

 

Still in the process of learning the ins and outs of the Quadzilla tuning, but I can't help but wonder if the issue is mechanical. . . . Any and all troubleshooting ideas welcome, getting desperate :doh:

 

Edited by FCAWdude
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11 minutes ago, Dieselfuture said:

Sounds like injectors to me, what is the engine load the idle. What is your RPM at idle. What is tps input at idle should be zero. 

Have you done WT mod

 

Thanks for responding. 

  • Engine load at idle = 11% +/- 2%
  • RPM at idle = 800 +/- 5
  • TPS input at idle = 0
  • Haven't done the WT mod, but it is on the list of priorities
    • Went through and thoroughly cleaned all the grounds last night

I really hope it's not the injectors. Power Driven warrantied the 1st set and I'm now on the 2nd set. . . I meant to have the 2nd set pop tested by a 3rd party but I needed my truck for a job. Maybe I'll take them out and have them tested just to be sure. I've put about 75 miles on the current set. 

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3 minutes ago, FCAWdude said:
  • Engine load at idle = 11% +/- 2%
  • RPM at idle = 800 +/- 5
  • TPS input at idle = 0

Well this looks good.

Does it still idle rough or you only have bucking issues when driving down the road. I would do wt mod next before I do anything else. It might surprise you on the outcome. Could be something to do with your torque converter cycling.

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1 minute ago, Dieselfuture said:

Well this looks good.

Does it still idle rough or you only have bucking issues when driving down the road. I would do wt mod next before I do anything else. It might surprise you on the outcome. Could be something to do with your torque converter cycling.

 

Okay will do. Going to read over the post again, and try to knock out the WT Mod tonight.

 

The alternator is original. Think it might be a good idea to take it out and have it tested? 

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Test the AC output on the alternator before and after the mod. Make sure to use a good quality voltmeter cheap ones do not work, they give you false reading.

Also make sure you are doing it on a warmed up truck before you shut it down so grid heaters are not cycling and nothing goofy is going on

You really don't want to be above .05vac especially with automatic

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Yup he's got you on the right direction so far. 

 

14 hours ago, FCAWdude said:

7x.0085 Injectors (popped @ 300 bar)

 

You do realized after just about 20k to 30k miles those injectors might drop pop pressure again and be below minimum pop? Dodge FSM minimums are 293 bar. 

 

fuel-pressure-specs.jpg

 

4500 PSI - 250 PSI = 4250 PSI now convert to bar which turns out 293.0272 bar. Going to have a short life span with those +75 HP. Even stock injectors are 310 bar and the only reason why shop pop low is to increase fuel flow but makes the droplet bigger and tends to create more smoke. Hence why I had my 7 x 0.010 popped at 320 bar which is still below the Dodge FSM spec. 4500 PSI + 250 PSI = 4750 PSI convert to bat and that is 327.501 bar. Take a lot longer before I fall under 293 bar. 

 

So in a nutshell... Dodge FSM specs are 293 bar Minimum, Set pop is 310 bar. Then maximum is 327 bar. Closer you are to 300 bar more fuel but smokey. Closer you are to 320 bar the cleaner exhaust but less fuel. Even with my set up and Quadzilla I can get it to pull the tires loose on my truck with just CANBus fuel now. No wire tap.

 

Edited by Mopar1973Man
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  • 3 weeks later...

Update on my situation,

 

  • I have done the W-T mod (reading before the mod was about .06 vac. Now after the mod its about .016 vac)
  • Also did the PCM ground splice repair. 
  • Replaced all the battery cables and upgraded the alternator to a DC power 180amp ( I was already planning on replacing these items)
  • Swapped out the vp44 with a brand new one

After all that it still is "bucking" under light throttle. I can't really tell if it still has a miss at idle, that seemed to be more obvious when it was hotter outside. Also forgot to mention before, the transmission does a weird shift from 3rd locked to 4th. It seems like it jumps out of gear and then will shift into 4th (Again this wasn't a issue after I had the transmission rebuilt with just the Quadzilla on the truck). None of this is a issue when I accelerate hard or aggressive.

 

@Mopar1973Man I get these injectors probably won't last that long, I had already purchased and installed these ones before reading about 7x.010 popped at 320. I would imagine the 7x.0085 should still run fine for the time being. 

 

Any other ideas on where to troubleshoot would be much appreciated. 

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