Engine/Transmission (1998.5 - 2002) Intermittent RPM fluctuation

[Joe Mc]

Post fix edit: Problem figured out, read full to see what and what.

https://www.turbodieselregister.com/media/1-stumble.6941/

Hope the above link works - a short video that shows what's going on.
Sorry the video is not clocked correctly - don't hurt your neck

Bit of info: Noticed this last week. Only seems to happen at highway speeds. Cruise on or off, power box (Edge Comp) on or off, Trans in OD or OD off, same thing.

What have I tried:

1. Thought possible water in fuel. GDP dual spin on filter system, use Fleetguards, one is water separator. Opened drain on that one and nothing but fuel.
2. Air filter (K&N type), it was dirty dirty, cleaned, let dry overnight, "light" oiling.
3. Fresh Fuel, I don't drive it much and since it had under a 1/4 tank I decided to fill it up with fresh fuel (always get fuel at a high volume truck stop) and as usual added 2 oz of EDT (Everyday Diesel Treatment - Hot Shot Secrets - been using their products for around 10 years).

The video is on the way home from getting fresh fuel.

Thanks in advance.

 

[NIsaacs]

Unplug the Comp. I had an Edge EZ do that, unplugged it and all was well. It was bad and they sent me a new one, problem fixed.

 

[Joe Mc]

NIsaacs,

Thanks for reply. Will give that a try. What symptoms were you having that made you think to unplug it?

 

[petersonj]

After watching the video, I don't see how it could be an engine related problem. You can hear the engine rpm bump up momentarily and see the corresponding rise in rpm's with the tach, but there is no increase in vehicle speed.

If the transmission torque converter clutch is locked (which I think it is), then it is not possible for the engine rpm to rise without increasing vehicle speed. I would be looking at the transmission - TCC momentarily unlocking?

- John

 

[Joe Mc]

John,
Thanks for your reply.

Thinking about what I'm feeling and seeing when this happens, and based on your reply, it makes no sense it would be fueling/engine related.

Bit of past info: Somewhere around 03 & 130k original stock trans began to slip I had DTT built and a few months later I began bolt on mods = Mach 1.8 injectors & Edge Comp. Thereafter, I experienced the hunting for OD between 40-45 mph and installed the DTT box (I believe it taps in at PCM on right firewall and has a recessed screw to set between a certain voltage range) to eliminate hunting, which it did. At present truck has (since 09) 64/14 wastegated HTT & Mach 5s. Late 2020 & about 240k DTT showed not much material left on 2nd gear band and had trans done again. However, I never experienced hunting at any speeds over 40-45?

What's presently happening literally "just" started last weekend. And, happens with OD off as well as on. I'm going to remove, look at and clean speed sensor on rear of trans.

Any other suggestions on what else could be causing and what to check/do are greatly appreciated.

 

[Joe Mc]

Yeehaw!!! Thankfully the "dirty" speed sensor in OD case was culprit. 2,000 rpms rock steady for 50 miles.

 

[petersonj]

Good to hear that it was a simple fix.

- John

 

[Joe Mc]

Amen to that for sure