I’m hoping someone here can shed some light on this issue I’ve had with my truck for the last few years. Only when towing something, and only when in OD with the RPM’s under 2K….if I slowly roll into the throttle and start to build boost, over about 50% throttle the engine will shudder and shake. It will continue to do this until I give it enough throttle that it downshifts and the RPMs jump up….then it pulls like a train. Fuel pressure is good, HPOP numbers are good, FICM voltage is good, Boost is around 20psi when it starts doing it. The ONLY time it does this is when the truck is at low RPM’s in Overdrive.

I had an injector fail on me early this year, so I replaced them all with “premium” 155/30 injectors, and also added a KC stage 1 Jetfire turbo and new custom tune….and the truck still does the same thing. Under 2K, in OD, when towing and when I slowly roll into the throttle…..stumble/buck/shudder.

I did a bunch of research online over the weekend, and it sounds like torque convertor shudder is common in these trucks? IF that is the cause, is there any type of fix or way to increase transmission line pressure to keep the locked up torque convertor from shuddering/slipping? Or do I just need to replace it?

The fact that it only does this in OD when the convertor is locked up leads me to believe that’s the issue…..anything else it could be?

 

It's an engine miss. I wonder where you got the information that torque converter shudder is common with these trucks. I've never seen a 5R110W transmission have torque converter shudder. But I've seen several 6.0L engines with misfire that people mistake for torque converter shudder.

 

What would cause a miss like that if it's not fueling related? It's got good fuel pressure, and all brand new injectors(old injectors had same issue)...and a new turbo, with new tune. HPOP pressure and FICM are good.

What would cause the miss? Something to do with compressor stall at the turbo from too much load at too low an RPM?

 

I'm a transmission guy, not an engine guy. I can tell you that what you are describing is not a transmission problem. I do no know how to troubleshoot the engine problem.

 

So there is no way a 5R110 transmission could ever shudder when the torque convertor is locked up in OD.....like other transmissions can do?

 

It is possible, but I have never seen one do it. Maybe yours is the first.

 

A simple google search shows all kinds of 6.0 powerstroke type forum posts regarding torque convertor shudder........it doesn't seem impossible at all. Unless everyone of those trucks is dealing with a misfire issue....and not a convertor issue.

At this point...I don't know what else it could be. If it was an engine problem...you would see it in the form of codes, or oddball FICM, HPOP, or other sensor readings.

 

Unfortunately, there are quite a few 6.0L engine issues that do not result in codes.

 

Agreed. But if there has an ICP, HPOP, FICM, etc, etc issue...you would see it in the PID numbers you are monitoring.

The one common denominator here is that it only happens when the convertor is locked up and in OD. If it was FICM, HPOP, FUELING, ICP, etc related.....wouldn't it happen in all of the gears?

 

Do you have a spare FICM to throw into it for a trial? FICM voltages really don't tell anywhere near the entire story on FICM operation.

 

Unfortunately No, I don't have a spare FICM laying around. If it was the FICM, wouldn't the problem pop up in multiple gears, most likely in the higher RPM ranges? Why only OD gear? Doesn't higher RPM under high load tax the FICM more than lower rpm low load conditions?

 

Could be that a weak cylinder isn't compensated for as well at low rpms (or low fueling) as it is at lower or higher engine loads. Who knows.

Many people have access to a "known good" FICM for troubleshooting purposes. Same with IPR valves. The reason is because codes are not thorough enough and definitive troubleshooting techniques are not readily available to the average user. "laying around", lol.

Best of luck with the mystery.

 

That's when the load is highest and misfire tends to show up at higher loads.

I suggest you replace the torque converter. That will eliminate torque converter shudder as a possibility. Either that will fix it, or prove that the problem isn't torque converter shudder.

 

O was just going to type "highest load".

 

I'll probably get my monitor setup to keep an eye on the Torque Converter Slippage PID......that's a much cheaper way to figure out it's not the TQ instead of loading up the parts cannon with a new one and shooting it at the truck. Ha!