12HT engine sensitive throttle Kangaroo hops on low RPM

Submitted: Sunday, Aug 04, 2013 at 14:58
ThreadID: 103561 Views:5930 Replies:3 FollowUps:4
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When I am driving at low speed the engine jerks on low RPM on 2nd or 3rd gear resulting in kangaroo hop jerks.

I even got the cable pull at 90degrees to the pump arm and problem still persists.

Was suggested on another post to try moving or fitting another ball end further out from centre on the pump arm but my mechanic couldn’t figure out which ball is this as couldn’t locate it and he doesn’t know what type of ball to fit on it .

Was also suggested to get a heavier return spring for the manual gear guys.... where shall I place this?

Will hand throttle work? Is there any particular recommended brand or specs to look for?

I had also read on internet to check power train/.. which components of this should I check? Would snugging up of the pinion of differential help?

I read in another post suggesting to take apart the flyweight assembly inside the governor and tighten them back to spec will help?

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Reply By: Ross M - Sunday, Aug 04, 2013 at 17:51

Sunday, Aug 04, 2013 at 17:51
Naveed Merchant
I think I originally suggested the new ball and arm extension.
You have to ask yourself why a mechanic can't recognize or find the ball in question and fit an old piece of carby arm, complete with ball, and attach the throttle cable to that.
It may not give you, (may not), full throttle but you will never need it anyway because unless you are going to try and drive at 160kmh then it won't matter.

The new Ball has to be further away from the OE throttle arm pivot.

Who ever suggested tightening the pinion bearings, I presume tighter than spec preload, is off their heads and don't know it will destroy the front pinion bearing an then the diff.

Don't believe what you read on the internet and therefore don't believe me either. You decide on that one.

The internals of the pump governor and fuel rack sliding resistance of 4oz is a techo thing to set and most don't know how.
Find a pump service centre for that.
Ross M
AnswerID: 515898

Follow Up By: Ross M - Sunday, Aug 04, 2013 at 20:26

Sunday, Aug 04, 2013 at 20:26
Have you checked the engine mounts are ok and not letting the engine move under higher torque loads?


Is the throttle cable one nice curve and unrestricted or kinked or caught on something else in the engine bay?
FollowupID: 795201

Follow Up By: Naveed Merchant - Sunday, Aug 04, 2013 at 21:05

Sunday, Aug 04, 2013 at 21:05

Mechanic recently overhauled the engine after oil pressure issues and i guess he fixed it well on the mounts and the cable is curved and smooth. I will still check on engine movements during torque.

I will also send governor to pump service centre to recheck this out

I had seen some added suggestions on:




and dont know if these will help?
FollowupID: 795206

Follow Up By: Naveed Merchant - Wednesday, Aug 07, 2013 at 02:53

Wednesday, Aug 07, 2013 at 02:53

I got the internals of the pump governor serviced and there is a huge improvement .. but still jerks a bit on low rpm....
FollowupID: 795319

Follow Up By: Naveed Merchant - Tuesday, Aug 13, 2013 at 14:40

Tuesday, Aug 13, 2013 at 14:40

Went to pump centre and has improved but ii guess its still not set to toyota standards.I wanted to know what is the toyota standard setting for this pump for its coarse and fine idle speed set screws in the governor housing.
FollowupID: 795669

Reply By: The Bantam - Monday, Aug 05, 2013 at 18:10

Monday, Aug 05, 2013 at 18:10
I don't know exactly the cause of the problem but it is far from uncommon in larger diesels with a bit of age under them.

Its a problem progressing from idle to power....its called "hunting"

An old Mack tipper I was driving had a shocking case of it especially when hot comming off a high speed ( 80 pluss Kmh) run.

It was embarasing comming up the drive on the way back to the hard stand going Burp Burp, Burp, Burp.....it would even do it with the foot right off the throttle.

The boys in the workshop had it one weekend and when I got in it Monday morning, It went an extra 10Km an hour faster ( it would nearly do the speed limit on the freeway) and progressed from idle to power smoothly....what they did I have no idea, but it had nothing to do with the diffs or gearbox.

Some diesel pump adjustments is my guess.

AnswerID: 515961

Reply By: Naveed Merchant - Tuesday, Aug 06, 2013 at 18:02

Tuesday, Aug 06, 2013 at 18:02
I am today with mechanic and going through all the checklist suggested here in this post.

I just read an interesting post some years back suggesting to install a device thingy to dampen the lower swing of the throttle actuator arm. This is found in cars with petrol fuel injection.. they have a dampener device which has a spring plunger that travels slowly, as if in oil, and it slows the snap back of the throttle arm at the bottom of the swing.

Any idea which vehicle or engine model of this dampener work on 12HT? The picture of this is shown here http://forum.ih8mud.com/diesel-tech-24-volts-systems/232329-kangaroo-engine.html

Any idea where i can find compatible small "shock" absorber in the linkage system. So when I plant my foot down, the damper absorbs the punch and delivers a smooth accelerating vehicle. Also probably dampens offroad pedal wobble.
AnswerID: 516014

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