vince21

well, first off im new to the forum but not new to 4runners. I just bought my first 4runner off my dad for $500! He had it for 6 years, and had a 884runner for about 4 years befor this one, there great rigs and i love my new 4runner, its had its problems but for 500 you cant go wrong! Anyway its a 94 4cycl manual, totaly stock except for speakers because old ones were shot! Runs great, however latly ive been having some issuses with it bucking.. It first happend on the highway after just merging and going up a big hill, im used to it being slow and gut less on the highway but once i got over the hill i was in 5th gear going say 100km/h and gave it a bit of gas to get a run for the next hill and it bucked/missed, not sure what to call it. It happens so randomly too, i first thought i was giving it too much gas and it just couldnt take it so it was flooding but, i can accelerate hard 1st thru 4th and its fine till 5th. However, afterwards it started doing it in 4th and 3rd gear, seems like its just when im feathering the throttle coming into a hill, some times with a run so say 90 in 4th for a big one, i was avoiding giving it too much gas becasue i figured it couldnt take the gas, but it still bucked, so had to down shift to 3rd, so at about 3500rpms it continued to buck, soo slowed it down to 60ish at 3000rpms and it was ok, slow up the hill but ok... After several tests the only pattern i can see is hills while feathering the throttle, maybe bumps in the road causeing it at higher speeds, however it even bucked a few times around town while in 1st and 2nd at low rpms (2000) while again lightly on the throttle, when ever it happens in 3rd im lightly on the gas, its only 5th it bucks when i hit the gas semi hard.. I thought maybe it wasnt getting air or something, but it would be worse when accelerating hard up to 4th, and then it wouldnt happen at low rpms in 3rd and lower.. I took one test run up a hill, came in doing almost 100km/h in 5th, didnt baby the throttle, but didnt give it more than it would obviously take, couldnt make the hill no supprise there, so down shifted to 4th at around 90, lots of gas but once again no more than it would take and up it went fine no buck what so ever, BUT as it leveld out put it in 5th just after 90 and what do ya know it bucked, was not flatting it but not easy on the gas, becasue its gutless anyway at thoughs speeds.. At first i thought i wasnt used to driving it, i have been long befor i got my licenes while with my dad in the woods and when i did get my license its all i drove, i recently stoped for about 5months, it was used of and on by my dad but thats it, so i know the jeep inside and out theres no way its just me causeing this. its just not normal...

I know someone will ask whats been done to it so here you go:
Its bone stock, except for replaced parts..
Brake lines gas lines etc..
exuast a few years back
coil
altenator 2 times i think
timing chain or something had chain guid wore out so it wore a hole in the head and when the engine would heat up and water pump would kick in it would run like and what not becasue it was burning coolent, so replaced the head with used head.. this was about 8 months ago maybe, was used for a while by me afterwards, ran perfect, engine makes a ticking noise however but even seems a bit more powerfull than it was befor...
UV joints were also replaces, well one was..
Jeep is really rusted underneth so maybe having it sitting made something worse?
Jeep has 210xxxkm/s

Theres probally more thats been done but nothing thats really relavent to this problem, it seems to happen very randomly, like the fact the brake lights only work everynow and then!

Only conclusion i can draw from lots of searching and tests is the TPS or something going in the driveterrain?

help would be greatly appreciated, i love this rig and i have big plans for it if i can figure this out!! If not im selling or trading my motorcycle for something newer, but id rather keep this rig and my bike... thanks..

myyota

Give it a complete tune up and also replace the fuel filter, and see if that helps, also remove the throttle body and give it a good cleaning.

vince21

i guess me saying jeep is like saying ski-doo instead of snowmobile.. Im just used to saying "jeep" but i guess ill get critisized here casue its a yota forum lol..

when the coil went a few months ago, it was shorting out against the frame, so if it was not touching and not bolted down it ran perfect, but soon as we touched it to the frame it cut out.. could something similar be happening? Seems like everything that goes wrong with this is electrical related, and to make the best of it my dads an electrican and im in thr process of becoming one Anyway thats for the input ill have a look later today!

i bought this for cheap and i dont have money of the knowledge to just jump in and to a complete tune up, ill look for some write ups on what to do but with this rig it was allways dont fix whats not broke so i dont want to get into things that arnt nessary if i dont have to.. sure it well help but i dont have the time or money, it lasted 6+ years with that modo so if i can find this problem it well be good to go again. I know its 16 years old and has 200+ thousand kms so its not going to run perfect, but that buck still shouldnt be there.
thanks for the input though, changing the fuel filter sounds like a good idea!

redhawk427

you might not have to replace the plugs and wires and such. if a plug wasnt firing, you'd think it would be happening ALL the time, not just upon acceleration. although, take your plugs out, one by one(so you dont mix up the wires), and check to see if they are all fouled up. If you find one that is really fouled, replace it and that might temporarily fix it but i dont know for sure. just a guess...if its happening in the entire range of rpms, and at such random times, im wonderin if it could do with your tranny? i dunno just throwin ideas out. im no expert by any means... but basically what im thinkin is..either a plug is being "flooded", by that i mean it isnt sparking OR an injector is messed up? maybe the "buck" your feeling, isnt engine related, but instead just has to do with how your shifting. i guess i got some questions...

#1. Is it fuel injected? (no carburetor)
#2. Are your plugs messed up? This site has great help for diagnosing
#3. How long have you been driving a stick?
#4. Does it happen when you're already in gear. and accelerate?
#5. Are you hearing any "knocking" or "pinging"?
#6. Is your air filter clean?
#7. Is your pcv valve all dirty and clogged up?

I think that should be able to get us somewhere if you answer those. sorry my post is kinda confusing, i was thinking out loud..well thinking and writing lol

vince21

no definatly not shifting, and becasue like i said in my OP, it dosent happen when im accelerating hard.. its usually when im light on the gas but slightly accelerating, or going up a small grade, same with 2nd gear, except its around 25ish km/h that it happens and if you hold the gas there it well buck all day but give it more gas and problem solved. I can see it just being that im going to slow when in 2nd for the conditions but it still didnt do it befor. As for when im in 3rd its around 2500rpms at 50km/h that it usually bucks.. only time i noticed it in 4th was going up a hill, run in at 90 got to the top doing 80 semi hard on gas, and once i start letting up as it levels out bam it jumps.. and for 5th gear its hard to get it to 100 without making it buck, you cant give it no gas at all it seems like, i know its allways been slow and gutless like ive said befor, but it should be able to get to 100 or 110 on flat with out too much trouble...
id think its tanrsmission related too if it wasnt for what happens in 5th, becasue seems like its allways happening when feathering the gas, so maybe somethings loose or shot?

1.yes fuel injected!
2. checking that tomorrow
3. drove first stick when i was 8! so a long time, grew up on manual everything, trust me.. ive been driving this particular RIG lol, for 3+ years now. not counting when i was a kid on the trails..
4.its when im allready in gear yes
5. since the head was replaced it allways made a ticking noise, something like a desil. It ran perfect and seemed more powerfully till this started so ignored that.
6.checking tomorrow
7.checking tomorrow


thanks for the help!

vince21

yeah makes sense, i just allways considerd a truck with no box a jeep never used the term SUV, but makes sense what your saying, ive heard people comment about the ski-doo one, im guilty of that too, guess its were im from

and thanks, thought a tune up would take a lot more, if thoughs prices are right im guessing your being sarcastic, yeah you definatly are.. Coil 15-25? we bought 2 used ones of rigs for parts neither worked paid over 100 i think for one from toyota but thanks for the list of stuff to check, will definatly look that over!

redhawk427

if it's been pinging, then it could be wearing on the pistons because the timing is off. that i believe could make oil and crap start to force past the piston rings and get on the plugs, making them not fire. so definitely check the condition of your spark plugs. and as far as the pinging goes, id probably get that checked out. it may be your knock sensor or something. is your check engine light on?

theMonch

Had a similar problem plaguing my 3.0 for over a year and after doing all of the obvious suggestions plugs, wires, cap, rotor, resetting TPS, fuel filter, injector cleaning, etc. etc. It turned out to be a bad spot in the potentiometer in the Air flow meter. Even though I checked it as per FSM back at the beginning of the diagnosis, it slowly developed a resistive spot that was sending the wrong info to the ECM. I would try possibly swapping the AFM out with a buddies if possible and see if that fixes problem.

The way you can tell if it is the same problem is when it starts to occur, downshift and try to accelerate. This will force the AFM to be in a different position and should clear up the hesitation/miss.

Good luck.

vince21

no check engine lights, it could be what your saying but the problem ive noticed now allways occurs between 50-60 in 3rd usually around 2500rpms on a slight grade. i on puropse made it buck about 10 times in a row to try and see a pattern.. I could go 50 and hold the speed in 3rd then slowly accelerate to around 55 and keep feathering the gas, then when a small grade of something came up or if i just gave it the slightest extra gas, barly enough to notice, it would buck.. Did that a couple times in a row, tried it 20mins later couldnt get it to do it, now if i floor it and i mean floor it from that speed its perfect. So it seems like its 2500 rpms is were its causing trouble, when ever it happens in 4th which is rare, its usually around 2500+ under same conditions. In 5th 2500 is about 90 which is were it bucks, you can floor it and it well buck a bit once or swice around 90 or higher if your going faster when you floor it and after that buck it well go no problem. So the engine must be running strong and fine it has to be something electrical or maybe driveterrain related?
thanks.
thanks, seems like this could definatly be it. When i put i give it extra gas the bucking goes away, it happend in 2nd once and it was bucking and bucking and bucking i was holding the gas steady but as soon as i gave it gas it stoped and went no problem. Same as on hills, like you said i can downshift and it goes away, however if i downshift and keep light on the gas, so its pretty much in the same spot it well buck in that gear too, happend once on one hill. Since then came into the hill doing 90 in 5th bucked right away, downshifted to 4th, lots of gas went for a while with no buck, lots power which is no supprise, so had to downshift to 3rd and up it went slow and steady, but no bucking!

Ill look up some stuff on the AFM to see what/were it is, dont think i would be able to test it with a buddys, but im sure a scrapyard and like 20bux could get one.. Are they easy to switch?

thanks again to everyone for helping!