Diagnosing shake at idle (not fpr)

[fl0w3n]

02 LB7 ZF6, lotta miles, hard ones too.

New Bosch FPR when I got it, really smoothed out the idle compared to now. Before it was lopey, now it’s just shakey.
Injector rates don’t seem too bad with EFI Live, and checking with TorquePro app it’s just about the same numbers.
Passenger motor mount was shot, replaced that and it just barely helped. Haven’t done driver or trans mount yet.

I was thinking it was maybe the DMF in the ZF6, but reading up about that I don’t think it would be as driveable as it is if it was broken. Although I do hear a rattle at idle

I am suspicious of the harmonic balancer, either being spun on the crank or just missing chunks. I’ve got a new one, as well as a key repair kit on its way, I’ll do the water pump and check while I’m down there. However, in the video the balancer looks steady.

Can I get some ideas and help on diagnosing?

Screen shot of balance rates
https://imgur.com/a/RIxMtZ8.jpg
https://imgur.com/a/5CBigy1.jpg

[YOUTUBE]M32ApAs2YTE[/YOUTUBE]
[YOUTUBE]rh5rR2eObvQ[/YOUTUBE]

 

[Burn Down]

Injectors is my guess. How many miles on them? Who’s injectors?

I have a little shake with my ii injectors in my 05’. I have run a bunch of seafoam and optilube, the shake is almost gone. My balance rates looked pretty good with 5 being at-5 when I first got it. Now it’s at -3, gotta love ii...

 

[fl0w3n]

Injectors is my guess. How many miles on them? Who’s injectors?

I have a little shake with my ii injectors in my 05’. I have run a bunch of seafoam and optilube, the shake is almost gone. My balance rates looked pretty good with 5 being at-5 when I first got it. Now it’s at -3, gotta love ii...

No idea who’s injectors, previous owner said they had been replaced but I doubt they were some quality units or “done right”.

350k miles on the truck. Previous owner said cp3 only has 20k miles on it, again not sure brand or quality of the part that was installed. It’s an old farm truck, worked hard and put away wet type life.

What is ii? I’ve run AC Delco upper injector cleanse through, and throw optilube in the tank for now. I’m planning on trying AC Delco again soon. I think the truck sat for a while, and now that I’ve been using it and logging some miles it seems to be waking up a little. But the rates look good from what I’m reading, except a random 6.8 reading on one of the torque pro screen shots.

 

[Burn Down]

II (industrial injection)... lb7’s are hard on injectors, plan on doing them soon. Any white smoke cold or warm? Tuned or stock?

 

[fl0w3n]

II (industrial injection)... lb7’s are hard on injectors, plan on doing them soon. Any white smoke cold or warm? Tuned or stock?

My plan is LDS sac45s soon.

No white smoke, no fuel halo in oil when I drop it on a white paper towel. Stock.

It seems like signs point to the injectors being OK... but I’ll be replacing them eventually any ways.

 

[Burn Down]

What does the cam and crank sensor signals look like? Does it smooth out just off idle?

 

[Brent@LDS]

I would shut off each injector individually and see if the shake goes away.

 

[fl0w3n]

What does the cam and crank sensor signals look like? Does it smooth out just off idle?

Good question, I forgot to bring that up. Idle is right around 600rpm and if I bring it up to about 8-900 it gets a tiny bit rough and just a little stumbly I feel like. I’ll try and make a video of that. At cruising or freeway speed, I can’t discern any shake over the general rough ride the shot suspension provides. Seems to cruise up to 85mph without much complaint. Another reason I’m hesitant about it being balancer, I feel like it would get worse with RPM

How can I check cam and crank sensor signals? Will torque app do that?

I would shut off each injector individually and see if the shake goes away.

I assume I’ll need to do that with EFI Live? My friend is the one who had it on his laptop, I’ll need to do that next time I’m at his place.

Unless there’s another way to do it?

 

[Burn Down]

I use a scan tool for the crank/cam signals. Not sure what your app shows? Efi or a scan tool can shut the injectors off individually.

 

[DAVe3283]

Your balance rates look OK, but the warning sign is the main fuel rate is only 4.6mm³. It should be almost double that for a stock tune, I believe. What that means is your injector are all in similar condition (balance rates tell how uniform injectors are), but overall condition is poor. They all appear to be weeping fuel, and the computer is compensating by reducing the desired fuel amount.

My numbers come from an automatic in neutral. The ZF6 might have less parasitic loss in neutral, but I wouldn't think half. I think worn injectors are your problem here.

 

[Tothemax]

bet its the dmf I have changed several that where still being driven with a shake like that and worse.

 

[fl0w3n]

Your balance rates look OK, but the warning sign is the main fuel rate is only 4.6mm³. It should be almost double that for a stock tune, I believe. What that means is your injector are all in similar condition (balance rates tell how uniform injectors are), but overall condition is poor. They all appear to be weeping fuel, and the computer is compensating by reducing the desired fuel amount.

My numbers come from an automatic in neutral. The ZF6 might have less parasitic loss in neutral, but I wouldn't think half. I think worn injectors are your problem here.

That makes a lot of sense. I was kind of suspecting that.
Like I’ve mentioned I have been figuring on doing SAC45s, so it’s not crushing information to hear that. I think I’ll still try AC Delco one more time.

With that being said, if all injectors are pretty evenly worn, why would it be causing the shake?

 

[fl0w3n]

bet its the dmf I have changed several that where still being driven with a shake like that and worse.

How can I check to confirm?

 

[Tothemax]

you can take the starter out and use a flash light and a pray bar to see if the ring gear moves side to side. there is usually a lot of iron rust dust when there broken

 

[DAVe3283]

With that being said, if all injectors are pretty evenly worn, why would it be causing the shake?

Because they are weeping fuel all the time, not just on the compression stroke.

Check the DMF, maybe that's it. I'm not very familiar with the manual trucks, so that could well be the issue.

Sent from my Cat S60 using Tapatalk

 

[fl0w3n]

you can take the starter out and use a flash light and a pray bar to see if the ring gear moves side to side. there is usually a lot of iron rust dust when there broken

Okay sounds easy enough

If it is shot, can I replace it with a single mass and keep what ever clutch is in there now? Current clutch is coming up on 100k but feels fine to my foot.

Because they are weeping fuel all the time, not just on the compression stroke.

Check the DMF, maybe that's it. I'm not very familiar with the manual trucks, so that could well be the issue.

Sent from my Cat S60 using Tapatalk

Oh that makes sense.

Neither am I. Just trying to learn, appreciate everyone’s input so far.

 

[WVRigrat05]

Your balance rates look OK, but the warning sign is the main fuel rate is only 4.6mm³. It should be almost double that for a stock tune, I believe. What that means is your injector are all in similar condition (balance rates tell how uniform injectors are), but overall condition is poor. They all appear to be weeping fuel, and the computer is compensating by reducing the desired fuel amount.

My numbers come from an automatic in neutral. The ZF6 might have less parasitic loss in neutral, but I wouldn't think half. I think worn injectors are your problem here.

What should main injection rate be?

 

[DAVe3283]

What should main injection rate be?

For a LB7 with the Allison (what I am familiar with) I believe it is 8-10 mm³ in neutral, and 10-13 mm³ in drive. I would imagine a ZF6 truck would be similar to an Allison in neutral, maybe a hair lower. These are all with the A/C off, on the stock tune. And I am just going from memory. But 4.6 mm³ is quite a bit low for sure.

Newer engines might be different, and adjusting the timing and fuel pressure at idle throws those numbers off. What I like to do on aftermarket injectors is after getting the tune dialed in pretty close, write down the fuel rate in park and drive, then use that as the baseline for future checks. The big thing is if the main rate goes down over time, the injectors are weeping extra fuel or hanging open. If it goes up over time, there is extra load on the engine or combustion efficiency is going down (injectors not opening right, lower compression, etc).

 

[fl0w3n]

For a LB7 with the Allison (what I am familiar with) I believe it is 8-10 mm³ in neutral, and 10-13 mm³ in drive. I would imagine a ZF6 truck would be similar to an Allison in neutral, maybe a hair lower. These are all with the A/C off, on the stock tune. And I am just going from memory. But 4.6 mm³ is quite a bit low for sure.

Newer engines might be different, and adjusting the timing and fuel pressure at idle throws those numbers off. What I like to do on aftermarket injectors is after getting the tune dialed in pretty close, write down the fuel rate in park and drive, then use that as the baseline for future checks. The big thing is if the main rate goes down over time, the injectors are weeping extra fuel or hanging open. If it goes up over time, there is extra load on the engine or combustion efficiency is going down (injectors not opening right, lower compression, etc).

What are the symptoms of air being introduced into the fuel lines?

When I did my FPR the rubber lines at the fuel distribution block right there were pretty crusty and cracked, I tried using some tubing from the parts store to replace them but the bends were too tight. I’ve since ordered the correct AC Delco replacements, as well as the two rubber lines at the filter head. I just haven’t had time to tear into it and replace them. I also don’t have a lift pump yet. These are high on my priority list but just haven’t gotten to it

 

[DAVe3283]

Generally air in the lines will cause issues building rail pressure, and if bad enough can effect the idle. If there is that much air, it shouldn't drive well at all, it would fall on its face when you gave it throttle on the road.

Fixing the lines is a good idea regardless. But I don't think that's the main issue causing this. You'll find out, I suppose.