VegasNaturist

Okay, let me explain. Truck is at a stop, idling fine. I put it in gear to take off, and just above idle (say 1,000 – 1,200 rpm) it bucks and won’t rev any higher. I can feather the throttle and stay just above idle, and it runs okay. Soon as I press the throttle more, it starts bucking and I loose any speed I accumulated. By bucking, I mean it rapidly revs, drops out, revs, drops out, etc. Similar to if you let the clutch out too fast. If I hold it in the “sweet spot”, which is barely on the throttle, I can accumulate some speed and actually upshift to as fast as she’ll go within the RPM’s available. No load, she seems to rev fine.

This created quite an adventure this past weekend as we were in Saline Valley in Death Valley NP, roughly 60 miles from pavement. I was able to nurse her out of the valley by using low range and a steady foot. Once we got to CA 190 and did the ceremonial airing up, we proceeded. Since it was mostly down hill, we actually got some speed built up. When I got to the bottom at Panamint Valley, It just wouldn’t climb the next steep grade. I pulled over, pulled the ECM fuse for a moment, and reinstalled it. After that, it improved a little, and we climbed at like 25 MPH. Ultimately, at very low speed, I nursed her all the way to Pahrump NV. We stopped for a fuel and potty break, and I had her shut down for about 20 minutes. I also pulled the fuse for the halibut. After that she ran better (not like she used to, but) and we made it over Spring Pass and down hill into Vegas. As we were crossing the valley home, it started it again, a little at a time, until it was as bad as it was in Death Valley.

Not sure if pulling the fuse made a difference, or just shutting it down and letting ‘something’ cool for a moment was the help. The longer she sat, the better it went.

Truck has, within the last year, a new VAFM, igniter, coil, plugs, wires, cap & rotor, reman injectors, Toyota fuel filter, TPS ohm’ed good, fuel pump tested optimal, and the truck has been running great! I intermittently had the same issue last year, and couldn’t definitively find the issue by testing everything. After installing all the above parts to fix a no run issue (ended up being plugged injectors due to a burst Autozone fuel filter), this issue disappeared and the truck has been a DD ever since. Now it’s back.

Opinions? Advice? Help?

Sorry for the length but I wanted to kind of show the circumstance as well…

John

blake.nemitz

ground??? at a loss here

blue_CA_yota

I was gonna say TPS until you said it ohm'd in spec..
Does the truck run hot? Like it's going into some kind of limp mode? (resetting the ECU somehow fixes it).. EFI Temp sender? On a 22re its just below the throttle body, has a green plug IIRC.. You can ohm test that as well.. I don't know the specs for it though.. Will check for you..

I'm curious too.. this is wierd..

Check engine code?

VegasNaturist

Actually, I'm contemplating the TPS even though it ohmed good. Possible dirt/crap making an intermittent connection on the "off idle" contacts giving the ecm conflicting info about throttle's actual position?

Oh and not running hot at all and no codes...

blue_CA_yota

disconnect the TPS and see if the truck runs better..
I was gonna say TPS cause I had same issue last year.. Had to use LOW range to get up my driveway..
Do you want me to post full EFI specs?

VegasNaturist

WOW, you're quick! I have the specs in the FSM but thanks... I'll try disconnecting it and see what happens. But first, gotta go to that job thing.

John

blue_CA_yota

Yea I've heard that before I'm procrastinating while studying for exams.. I'm using any excuse I can find to not read 980 pdf slides haha..

When you get the chance, drive the truck, and when it starts acting up, unplug the TPS and if that cures it, blamo!! TPS adjustment or replacement is in your not so distant future..

subarubie

Here is my thread, it sounds like some of the problems I was having..A no cost fix for my problem......https://www.yotatech.com/forums/f116...-fixed-228628/




Let me know if it works for you..

Numbchux

Sounds a bit like a clogged cat. although they don't usually cause actual bucking as much as a massive power loss.

VegasNaturist

Thanks Subarubie, I actually read your post when I did a search, just hadn't got that far yet (haven't really had time to check stuff out since we got back). Will definitely look at that!

Why does everything cost $100 +?

John

VegasNaturist

Thanks Numbchux, (with a handle like that, wouldn't want to get on your bad side LOL). I'm assuming (yea, I know) the cat is good as the truck just passed NV smog. And it had great power on the way out to the hot springs.

John

vital22re

iTrader: (2)

water in the tps will make it act like this.

VegasNaturist

I was thinking trash/dust/dirt, not much water here in the desert though. I drove the truck yesterday and i was acting up again. I disconnected the tps and it made no difference. Did some more checking and found the pick up coil in the distributer ohm'ed out of spec. I ordered one from 1sttoyotaparts.com (PN 19250-35180 if anybody is interested) and we'll go from there.

Thanks for the input though

John

VegasNaturist

Pickup coil arrived Friday, and was installed Saturday morning. Drove across town to a friends house, roughly 60 miles round trip, and the truck ran flawlessly. Let's hope this cured the issue. Because the issue wasn't constant, only time will tell...

John

spooner29

i seem to be having the same problam with my 86 carbed i cant figure it out

Dmac297

I'm having a similar issue of my 88 toyota pickup efi starts bucking at light throttle only when loads are applied stereo, headlights, blower, motor, wipers ect. but clears up fine when you get above 1500 -2000. But once you let off to maintain a speed and the rpm drops down it starts to lurch and buck. Check TPS ohm rates in spec went through and did light tune up fuel filter, plugs, cap, rotor, wires, ECT. Still at a loss timing is dead on idles great runs fantastic above 2 grand can't seem to pinpoint this.

VegasNaturist

Holy Thread Revival Batman! Let me first say I no longer own that truck. We turned to the dark side and bought a Jeep Wrangler Unlimited Rubicon. I did however figure out what the problem was with my truck. I had bought that truck from a friend who bought it new and drove it for the longest time. The last few years he owned it, it sat in his driveway untouched. I pretty much completely restored the truck mechanically and we were still using it for off road fun. We were out in Saline Valley in Death Valley National Park when it started acting up again. This time though, whenever it acted up, it felt like fuel starvation, and I could hear the fuel pump (in tank) clicking. After getting the truck back home (story in itself) I dropped the fuel tank to replace the fuel pump, thinking it was bad. Instead, I found the fuel tank had rusted while the truck was sitting all those years. The rust would break loose while driving and clog the sock inside the tank, causing the fuel pump to cavitate, and it literally was fuel starvation. After a while, the rust would settle to the bottom of the tank and the truck would be okay, till it got stirred up again.

I replaced the fuel tank, pump, and sock and never had the issue again...

John