WTEC II help-- hesitant downshifting

[ArmoredCTP]

Hey everyone!

My M1081A0 with WTEC II has a downshifting issue that I think I know the answer to, but can't confirm definitively.

My trans downshifts fine when slowing to a stop, although it sometimes takes a little coaxing with brake pumping to nudge it out of each gear. It is, however, very reluctant to drop a gear when I accelerate from a slow cruising speed.

I was cruising in 4th at about 25mph yesterday coming up on a red light. It turned green, so I floored it, but it stayed in 4th, and even upshifted to 5th after a few seconds. It did the same climbing a short hill. I usually can't do more than 20mph or so climbing hills, and the constant upshifting at the worst time doesn't help.

I read how to get pull codes from the controller, so I tried today with the truck shut off. Not a single code! Are the codes that get stored erased once the truck is shut off, or do they stay there indefinitely? I tried pulling them a day after driving, so maybe that has something to do with it?

I have a feeling it's the TPS, but I can't be sure. Would checking for codes after driving and before shutting down help? Anything else I should try?

 

[NDT]

Codes stay in memory. Everything points to throttle modulation not being communicated to the WTEC.

 

[ArmoredCTP]

Codes stay in memory. Everything points to throttle modulation not being communicated to the WTEC.

At least it sounds like more of a mechanical adjustment than replacing expensive sensors.

I confirmed that it does throw a code when I unplug the TPS. Still no codes plugged in.

 

[simp5782]

I had a 1084 do this. It was like it would shift when it didn't need to but when it needed to it couldn't make it's mind up. Flooring from a dead stop it wouldn't do much of anything.

I turned the fuel screw up a few turns and adjusted the wastegate rod and it acted much better

 

[Suprman]

Sometimes the throttle cable is out of adjustment and you arent getting full throttle with the pedal down. There is a procedure in the tm to adjust the tps.

 

[Ronmar]

You can tell the WTEC controller to re-calibrate the TPS(real easy using keypad and pedal), but as Suprman mentioned, you want to make sure the cable is moving the sensor correctly with pedal application.

 

[ArmoredCTP]

Thanks for your help, everyone!

I think I my problem is a combination of a choked fuel system and huge ratio difference between 2nd and 3rd. I took it out for a spin a couple more times, and found that the engine just isn't revving fast enough on takeoff, no matter what gear its in. The problem seems to be a clogged fuel system that seriously delayed acceleration.

The problem has always existed, but has gotten far better since changing fuel filters a couple years ago, filling up with premium diesel containing detergents, and dumping Seafoam in at every fill up. It's waking up after a slumber since Summer '19, and I mostly forgot about the problem. I think the fix is to just keep driving it and let the fuel system keep cleaning itself out.

I also noticed a pretty big difference in gearing between 2nd and 3rd. That, coupled with low power, would explain why going up hills can be a pain. It still struggles a bit going up hill, but it would still probably take a lot of convincing from the sensors to get the transmission to shift to 2nd on a grade. It does downshift from 4th to 3rd when I start climbing, but still climbs fairly well enough for me to not worry much about it.

Again, really working the engine fueled with a lot of detergents is probably my best move at this point. I will also back off that fuel screw. My Dad has an M35A3 he did that to, so I have the triangular bit to use for that. I plan on driving my truck plenty this season, so if anyone wants an update in the next month or two, I can do that!

 

[Suprman]

Some older cat motors need the injector/rack adjusted. They are just sluggish. Sometimes your throttle cable is out of adjustment and you are not getting full throttle.