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WTEC II help-- hesitant downshifting

ArmoredCTP

Member
22
48
13
Location
Waukesha/Wisconsin
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

Well-known member
Steel Soldiers Supporter
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Camp Wood/LC, TX
Codes stay in memory. Everything points to throttle modulation not being communicated to the WTEC.
 

ArmoredCTP

Member
22
48
13
Location
Waukesha/Wisconsin
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

Feo, Fuerte y Formal
Supporting Vendor
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Location
Mason, TN
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

Well-known member
Supporting Vendor
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Location
Stratford/Connecticut
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

Well-known member
3,185
6,477
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Location
Port angeles wa
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

Member
22
48
13
Location
Waukesha/Wisconsin
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

Well-known member
Supporting Vendor
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645
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Location
Stratford/Connecticut
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.
 
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