Fo by Fo

I drive a 1991 V6 4runner with 4wd and I noticed that when I am going at slower speeds, like in a parking lot or neighborhood and I'm in gear my truck kinda lurches forward just a little bit when I let off the gas. Its not anything that bad, just kind of annoying and doesn't feel right. I have manual hubs but it does this when they are unlocked. Any ideas what this might be? Thanks guys.

TORTIS

iTrader: (1)

i had to replace my TPS to fix that problem.

Fo by Fo

Throttle position sensor?

TORTIS

iTrader: (1)

yes throttle positioning sensor. might need adjustment.

Fo by Fo

I'll defiatly check that out, but I think it may be something to do with the drivline. I noticed with my window down that it makes sort of a clunk noise as I step on the gas and let off the gas as I'm coasting. It sounds like something engaging and disengaging.

Georgiadave

I could also be a worn timing belt causing some cam/valve lag when you let off the gas.

justinking060310

do you have that little round plastic cap(about a 1" circle) on your throttle body? that caused the same problem on mine...

MudHippy

I believe your refering to a dashpot. If it isn't working/adjusted properly it can cause "lurching" exactly as described above.


If your curious about the TPS. Check for codes, if the TPS isn't functioning/needs adjusted it will tell you. I don't suspect so though, I think it's most likely the dashpot.

Fo by Fo

It's not the timing belt, I replaced that pretty recently, my truck isn't running any codes, the check engine light isn't on. It was, but after a tune up (plugs wires, cap, rotor) it went away and is now running MUCH better. This little quirk I have noticed since a bought the truck over a year ago. I checked for the dash pot and I think I see it there, its black right?

MudHippy

Yes, black.

The cover/cap and filter on the front are usually missing, so looks a little different than the pic above.

The adjustment screw is on the piece that the accelerator cable attaches to.

Fo by Fo

Is it that screw suppose to adjusted a certan way? It looks kinda like the one used to adjust the idle right? I adjusted my idle the other day, I wonder if I should have checked my throttle body and maybe cleaned it while I was at it.

MudHippy

Uh-oh!

You didn't try adjusting your idle with the throttle stop screw did you? You'd need to adjust the dashpot the same amount to compensate theoretically. It also could cause your throttle to stick a little when fully closed if misadjusted.

Anyway, to adjust the dashpot first check if it's loose. It's only held on by 1 screw there. Then turn the daspot adjusting screw in towards the plunger on the dashpot a turn or so. Test drive it and see if it worked. You want it turned just far enough in to alleviate the lurching. What the dashpot is doing is helping you close the throttle(let off the gas)slower than you could on your own to prevent lurching. It needs closed inhumanly slow sometimes, just that last little bit before fully closing anyway(practically impossible under some conditions without a dashpot). When you let off the gas too quickly it catches the throttle and gently closes it the last couple millimeters for you. The more quickly you let off the gas the more the dashpot has to work. When done slow enough, the dashpot acts as though it weren't there and offers almost no resistance to the closing throttle. The faster/harder the throttle arm pushes on the dashpot plunger when closing, as when the accelerator is released quickly, the more it resists compressing. This ensures proper throttle closure speed under all conditions. Adjusting the screw on the throttle arm to contact the dashpot plunger sooner when the throttle closes gives the spring that closes the throttle more length of stroke by which it can apply force to/engage the dashpot before the throttle hits the throttle stop(closes fully). This equates to more potential resistance from the dashpot and slower throttle closure is possible.

mikes19984x4

hey, i've been getting a CEL with a code saying "Throttle Position Sensor - Circuit A" on my 1998 4runner sr5 with the 3.4 and 5 speed. i noticed that my motor also has what looks like the dashpot on it also. could adjusting this fix my problem?

MudHippy

No. They don't have any effect on each other.

You need to test and/or adjust your TPS. I don't know for sure how that's done on a 5VZE.

mikes19984x4

oh okay. well thanks for the info. i guess i'll try searching on here for something. if anybody else knows, please contribute.

n4ynu1010

Mudhippy !!!!!!! The pic master and most likely or often this is the problem

n4ynu1010

Here is a walkthru for the TPS test :

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

I would look hard at that (DashPot) as it is a common problem with lurching on deceleration , that was a good idea from Mudhippy previously
Also if dashpot is not problem and you here clunking then please check your driveline (u-joints,center bearing,Trans Mount,drive axle input yolk etc) .
It is not uncommon to have some play in your ring and pinion gears/splines with mileage that will present a little clunk taking up slack in the drive line on acceleration from a coast so that may be just normal .
U-joint is bad if its goes so if they are original at least give them a once over .

In case you need here is the link for the online FSM (manual) :

http://personal.utulsa.edu/~nathan-buchanan/93fsm/

Fo by Fo

I'll probobly take a look at the u-joints, trans mounts, etc. Is there anyway to check for play in the gears without taking apart the differntial? Also, if I spin the driveshaft by hand should there be any play?

Fo by Fo

Oh, I forgot to mention this. I don't know if this has to do with anything but I've noticed since I bought my truck about a year ago the bottom of the tranny has a bunch of transmission fluid on it, like its leaking, but it never drips onto my driveway at all.

n4ynu1010

If you have a Auto Trans and having this lurching problem - have you checked your Tranny Fluid , if low it will do this also , also if it is full and has not been serviced for a long time then the same lurching could be your trans filter is stopped up , just a thought but both of those can cause that lurching problem .
If fluid is low then when you hit gas fluid will move and then get picked up in pan and pressure will build and lurch ...............same thing with stopped up filter , lack of proper pressure at idle or low rpm and then when you raise rpm lurch .
Just something else to look at
As for your leak , I would clean Tranny with degreaser and hose and see where it is coming from - could be many places - fill tube o-ring bad - speedometer drive/speedo drive gear housing (follow your speedo cable) - tranmission cooling line connections - Transmission Pan Gasket - shift rod o-ring/seal - Trans output shaft/yoke oil seal - Torque converter/input shaft oil seal ....................I think thats all of them hehe.
Most common are fill tube o-ring and o-ring on speedo cable/speedo gear housing and the pan gasket .
If any of those fruitcakes tell you the filter never gets dirty in a Auto Tranny .........laugh at them ..........they do all the time especially high mileage and few people ever change them .