terminator

iTrader: (1)

First off, I have a 96 4Runner Limited with the 3.4 4x4. The replacement engine has @ 66K on it, body has 225K. About a month or so ago I had to drive it from NC to KY and back, no problems at all with any stuttering, ran strong and fast, well maybe not fast but fast enough! Yesterday I hit the gas hard to pass and it acts like it's hitting a rev limiter, this only happens under hard acceleration. As long as I don't mat it to the floor it's good but when I do it stumbles like a stutter box at the drags. I let off and give it gas easier and it runs great.

Does anybody have an idea of what's the culprit? I've been told fuel pump and filter possibly, clogged converter, MAF could be bad. There is NO CEL though so I'm lost.

Thanks
Jason

Brasson

Does the 96 have a distributor or is it coil packs? I had a similar problem on an old 87 nissan pickup once and strangely enough when I took it in, they diagnosed and replaced the distributor cap and rotor.. that was a very neglected truck though as I was about 16 at the time..

Yota Runner

pull the all the boots on the plug wires and check for cracks. Roll the end of the boot between your fingers with a little pressure, there should be no cracks or splits. If there is you should replace them. When I baught mine it was doing the same thing and that was the culprit. It wasn't even cracked or split bad but it doesn't take much to make it run crappy! At least its a start for diagnostics

terminator

iTrader: (1)

Well a shop hooked it up to diagnose it and @ 4K the MAF goes apey so they're thinking that's the issue. I'm having it replaced, well I'm replacing it so I'll post up if it runs fine afterwards.
Thanks
Jason

terminator

iTrader: (1)

OK, Deathcougar sent me a used MAF and I still have the isse, plus I now have a CEL but I think that's b/c I forgot to plug it in before I took a test drive. What a test drive also! I haven't looked at the boots yet but when the engine was replaced they were replaced. I'm going to put on a new fuel filter and check the plugs out along with the boots. No distributor, coil packs.

alexh2

My 98 Taco 3.4L was doing that for years aong with a slightly rough idle and finally it progressed to a cylinder misfire code. I pulled the injectors and found one that was twice the specified resistance.

Haven't put it back together yet so I don't know if the power loss at high load/rpm will go away.

After finding the bad injector, I pulled the plugs and the plug in the bad cylinder was quite a bit lighter than the rest but I'm not sure if I would have noticed it otherwise.

Although I just re-read your post and you say it stumbles so it sounds more like ignition. Mine didn't really stumble, it just felt like somebody instantly reduced the throttle by about 1/3.

terminator

iTrader: (1)

Well I have no CEL so nothing to follow there. I went out and bought the wires, boots, plugs, PCV and fuel filter today. I'll start with the valve and the fuel filter and go from there, you know, cheapest to most expensive I guess.

alexh2

terminator,

I just got my injectors back in - pretty big job on this truck.

As I said above I located a bad injector. The resistance was twice the spec. truck runs/idles better than it has in years.

I did run it a few times at full throttle up to red line and I felt no loss of power through the whole power band. I have to think it was the injector because the power loss was very noticeable before.

The theory would be that a weak injector would show up as a slightly to very rough idle. However, at power the cpu could compensate for the weak injector by turning up the output of the other units. It would do this based on feedback from the o2 sensor and of course it has no way of knowing that there is a weak injector unless it gets so bad that it detects a total miss. However, at full load, the injectors would max out and result in a loss of power, like fuel cut was hit.

You can easily check the passenger side injector resistance by pulling the connectors and measuring the resistance. It should be about 14 ohms at room temp. Just be extremely care not to break the connectors. The drivers side are not accessible.


If you don't find a problem there you might be able to check the resistance of the drivers side injectors by pulling the connector on the ECU but it won't be fun.

The other way to diagnose this might be to check emissions if you have access to a friendly shop. I had to smog my truck about 6 months ago and it barely passed NO which can indicate a lean condition.

My truck was like this for several years. Hopefully I didn't burn the valves too bad on that cylinder.


Good luck

terminator

iTrader: (1)

Well I don't know how to measure resistance, don't know how to use an ohm meter at all. I did replace the plugs, nothing to report there, wires and boots, PCV (just to do it), and fuel filter and it still does the same thing. I found a new coil pack that the PO gave me, new Toyota one actuall so I might put it on each one to see if it eliminates the massive stutter. If not then I may have to take it somewhere.

alexh2

I understand, I probably spent almost as much as just taking it to a good shop especially when you consider how long I lived with the problem.

During the period of a couple years I must have pulled the plugs, wires and coils 3 or 4 times. I was convinced it was an ignition problem and was pulling my hair out trying to find something wrong with the ignition.

Also, I'm not really crazy about working on a fuel injected cars fuel system. There are so many joints on the fuel delivery system and a problem with a $1.00 O-ring or gasket could be your life.

Good Luck

terminator

iTrader: (1)

I got a call yesterday afternoon from the mechanic and he said he tried everything and can't locate the problem. He then hit a website (I don't remember it but will see if I can get it) where mechanics post up about issues they have and what they found and how they fixed it. He typed in the miss and found a post where there is a similar situation, miss at 3500+ RPM. It states that sometimes after a timing belt change a cam or crank bolt will come loose and the pulley may become damaged and this somehow makes the engine act up. Sounds like a potential fail safe to me but I may be wrong so I told him to go ahead and tear it down and see if that's the problem.

I'll keep this post updated with what the mechanic finds out and with any luck the bolt will only be loose and he'll only have to re-torque it and all will be good and the miss will be fixed. Potentially there could be some pulleys and removal of the front end of the engine but we'll see. Praying for an inexpensive fix right now.

terminator

iTrader: (1)

Well the bolt that holds the crank pulley was loose. He re-torqued it and drove it, still stutters. He came back and said there's play from it wobbling so we're going to replace the pulley, and the keyway as well as the timing belt since it's off. HOPEFULLY, this will fix the problem but I won't know until he gets the parts and re-assembles it which should be first of next week.

mikes19984x4

holy crap, this sounds just like my problem...if you type 3.4 rev limit in the search box you'll probably find it...now my truck runs fine, but will not rev past 4000 rpm for some reason...

terminator

iTrader: (1)

I'm guessing you haven't found out the cause yet from your thread?

mikes19984x4

that'd be a big negative...i haven't been on here in about 2 months, but several guys were saying since at one time i got a CEL that was related to my TPS that it could be my problem. but i checked the resistance in the TPS as the fsm says to do and it checked out fine. i'ts weird because my truck starts, idles, and runs fine. but once it gets to 4k rom, no matter if at full throttle or bearly pressing it, it WILL NOT rev past 4k rpm and starts to make the truck sputter like and it sounds just like when a drag car is hitting their preset rev limiter before hey take off...and i know before my crank pulley came loose which caused a knocking sound and the trip to the shop that my truck WOULD rev past 4k rpm b/c one time i thought i was for sure going to be hit in traffic but i punched it and it definitely went past 5k rpm...

terminator

iTrader: (1)

Well the mechanic found that the keyway on the crank was damaged from the loose pulley and since the Crank Position Sensor is located right in the same area it could be sending bad signals. He's going to put it all back together and call me back when he's done, keeping the fingers crossed here.

terminator

iTrader: (1)

OK, turns out the damaged keyway on the crankshaft was causing the CPS to send false signals causing the stuttering. New keyway, gear, belt etc. and she's back to normal again. The bolt that loosed on the crank pulley/balancer damaged the keyway, I'll get pics of the keyway and post them up so anybody with this problem will have a start. That or you may have a bad CPS.

DeathCougar

iTrader: (23)

This is a very common problem. The timing belt will be replaced, and often times people don't torque down to the proper setting (217ft lbs) then it will wobble, and do exactly what happened to you Terminator. I have sold countless harmonic balancers because shops don't follow proper torquing procedures.

terminator

iTrader: (1)

The shop that put the pump/belt on said they didn't have to remove it for the install. Then in another email said they pulled the pulleys and accessories from my engine to swap on the replacement one. They're obviously at fault but are refusing to cover anything under their warranty. I'm beyond PO'ed right now and I'm fighting with them via BBB and now the KY Attorney General's Office. I've also posted about their lack of support. Thanks though.

DeathCougar

iTrader: (23)

Ey yi yi. Thats BS on their part. You absolutely HAVE to remove the front balancer to replace the timing belt. Sorry to hear that with the shop