mikes19984x4

okay, so several months back, i had to get a new crank and balancer put in my 98 4runner sr5 4x4 that has the 3.4 and 5 speed. this came about when on a road trip, a "knocking" noise started coming from the front of the motor. at first, i thought it was a rod or something of that nature, but when i took it to the local shop i've always used, it was found that the balancer had actually "loosened" on the end of the crank, which in turn caused the damage to the crank. after getting it back, it ran like a top and still does. however, when i try to rev up to the rpms where max horsepower is reached (i believe its 4800-ish), it will absolutely not rev past 4000 rpms. i am 100% sure it will not rev past 4000, b/c i've tried to do it in every gear except 5th, as i would be doing well over 100 miles per hour if i tried that. could someone tell me why this is occuring and if there is something i can do to fix this, b/c it's annoying knowing my truck can never reach its max power.

mikes19984x4

come on guys, somebody has to have some kind of info that'll help me out...

Yota Runner

I wouldn't think that a new crank and balancer should have effected the rev's in any way as long as it was all stock specs.....did they screw with anything else?

mikes19984x4

no, just a new crank and balancer were added, along with various new seals and an oil change, which were needed. also, if it helps any, a friend of mine who is into dirt-track racing mentioned something about a "crank trigger" or something like that? does anyone have any more info, b/c it will be greatly appreciated.

mikes19984x4

anybody else have any info/help?

mt_goat

X2, its most likely something else. How long since you checked the plugs? Any codes thrown? Fuel filter old?

mikes19984x4

the only code that is thrown is one that says "Throttle Position Sensor - Circuit A", but the CEL comes on and off at random intervals with that one and it does does casue any change in the way the truck performs. the fuel filter, plugs, and wires are all new, as i had a tune up done to it about 3 months before the trip to the shop for the crank, so i know it's none of these things. is it possible for a technician to actually "reprogram" or "reset" what the ECU will see the rev limiter as?

ciscojay

Sounds like you need to get a decent OBDII scantool, like a BR-3, that can show throttle position %. You should be around 75-80% at WOT, you may have a bad TPS, based on what you just posted. You may actually only be hitting 60% or so, and you're not squirting fuel to make max power. BR-3 is the scantool that Gadget and Brian at URD recommend, since it has all the features that most $300 scantools have and the BR-3 is only about $90. The only caveat is that you need a laptop to use it. It's trick software though, shows almost everything in realtime as you're driving. Your problem may not even be related to the crankshaft issue, but who knows until you diagnose and isolate.

mt_goat

I'd start there, the nice thing about OBDII is it tells you where to start looking.


Not on a Toyota, at least not without installing a piggy back computer.

ciscojay

You may simply have a loose throttle cable...check it out.

mikes19984x4

thanks for that info guys, its really appreciated. however, a big questions for me, as i'm currently a college student, has to be is there any way or place i can take my truck and get it scanned with the BR-3 like you all are saying to do? only asking b/c of financial status, but if it's not, then i'll start savin up for the BR-3. so, that code could be causing my problems after all?

MTL_4runner

Absolutely.

mt_goat

Some of the major Auto parts stores will pull codes for free. Autozone is one of them. You could at least get the code that way, next time it pops up.

mikes19984x4

awesome to finally be able to narrow down this problem to a specific area. thanks again. so after doing more research on here, i found some posts about how to test the TPS with a volt/ohm meter. i'm guessing if the resistance is not correct, it is telling the motor it has already reached its rev limit, thus causing the "cutting-out" and "bouncing" of the motor?


and yeah, the code that was pulled was definitely the P0120, saying "Throttle/Pedal Position Sensor - Circuit A Malfunction". and i didn't think the rev limiter could be "reset" via the ECU, as my ride definitely does not have any type of piggyback module...

mikes19984x4

okay, so new question about testing the TPS with a volt/ohm meter : i found on here a post about how to do this test, but it says to apply a vaccum while testing. anybody have any suggestions on how to do this? i really need to know so i can get this problem fixed ASAP! once again, any and all help is greatly appreciated...

mt_goat

You can buy a little hand held vac pump/tester at the auto parts places. You just pump it up to the vaccum needed and test away. Probably about 15 inches of vaccum would be needed. You might get lucky and find a store that will loan one out, but the cheap plastic ones don't cost too much.

MTL_4runner

You can either use a hand actuated vacuum pump or just open the throttle by hand and forget using vacuum at all. The idea is just to see that when the throttle is opened, the correct resistance results and there are no discontinuities or spikes in the readings either.

mikes19984x4

awesome man. i'm wanting to fix this really bad, but right now i'm just interested in seeing if when the gas pedal is fully depressed, what kind of resistance i will get from testing with the volt/ohm meter and compare that reading to what the other posts say should be within specs. good to hear that i can simply do it while just holding the throttle wide open. so now i just gotta find a volt/ohm meter to use, as mine is about 220 miles back at home (didn't think to bring it to college with me ) does the autozone loan-a-tool thing include volt/ohm meters?

lexustech

if that is ok,i would also check to see if your mass air flow sensor is dirty,have seen dirty hot wire cause engine not to go past a certain point

mikes19984x4

okay, i haven't tested the TPS as of yet, but will do so as soon as i can get my hands on a multi-meter. as for the MAF sensor, what is the "hot wire" on it, and should i just go about cleaning it with some CRC electric parts cleaner as some other posts have stated . i'm very interested in getting my 3.4 back to the way it was pre-"going into the shop" and if anybody else has any kind of info on this, it will be greatly appreciated...