i got '99 problems...

[eevee]

but my toyota is now less of one, thanks in part to this forum

still having some weird issues [see below], would definitely appreciate suggestions! first, a little storytime

so a few years ago i was taking an asvab practice test which included automotive knowledge in one part. my scores everywhere else were normal to well above average, but on this section (unsurprisingly) i totally bombed it. i made a mental note then to one day learn how cars work. when my vehicle started acting up recently, i decided it was a really good time to start doing some research. now i kind of actually understand what is happening under the hood. i just took another practice test and my automotive scores have drastically improved to above average

:dancin:

my brother got a new car and handed me his 1999 4runner limited (3.4 v6 4wd ~250k), which started having serious trouble getting to 20mph or above when it was flat and literally could not make it up any significant incline. i just wasn't getting any power and i was getting a lot of shaking/shuddering so i decided to start learning as i go. honestly, a good bit of my time and certainly frustration has been dealing with seized bolts (and screws) which have apparently just been rusting for 20 years - getting hold of a line wrench was a profound experience. codes revealed some misfiring (later i learned of a lean mix P0171 code, could have been happening all along and i just wasn't told). here's what i've done so far and how successful each step has been...

1. replaced fuel filter (no significant improvement)
2. replaced spark plugs/wires (no significant improvement)
3. replaced coil packs (slight improvement)
4. cleaned maf sensor, replaced air filter (huge improvement)
5. seafoam spray (slight improvement)

while these steps have taken it from completely dysfunctional to reasonably functional, it's still not doing what i know it's capable of as far as acceleration or top speed. it seems to be intermittently not shifting normally and could be some kind of torque issue among other potential problems. here are a few things i'm considering next...

• replacing throttle position sensor
• replacing upstream 02 sensor
• replacing maf sensor
• checking ignition timing
• checking vacuum
• cleaning injectors
• checking fuel pump

thoughts, suggestions, or tips would be greatly appreciated... thanks!

 

[pokeyman]

check your catalytic converter it may be plugged up.

 

[NissanTechJake]

If you have a lean shift code like that one of two things is going on here.

Either the MAF is out of calibration (which is why cleaning it helped significantly) and causing erratic fuel trims.

Or

You have an air leak

If your code reader has live data and you can look at fuel trims, anything outside of + or - 5% is out of normal range.

 

[drallan]

2nd on checking the Catalytic Converter. I haven't had this happen to my 4runner, but had an old s10 that would bog under load, and could barely get up a hill. Felt like I was driving a go cart with a speed limiter on.

Other option could be to clean the MAF again, especially if it helped. Sounds silly, but when i first got my 99 I did the whole, plugs, filters, fluids, MAF, etc. change. It ran better, then got worse. apparently a piece of debris had dislodged and was stuck to the MAF. Looked like a dust bunny caught on the wire.

 

[eevee]

so the catalytic converter is not very old but i did do a backpressure test which revealed no issues there.

the hoses and stuff could probably be replaced pretty cheaply so i might do that... are there any kits/combos or anything out there for that?

thinking i might just go ahead and replace the maf sensor, although i could try to clean it again.

on another note, can anybody recommend some general preventative maintenance? in addition to the things i've already mentioned... the timing belt and water pump were replaced just before i got it. probably a good time to do an oil change, any other thoughts?

 

[weekendclimber]

Had a similar issue and at the time didn't have space to tear into it. Took it to a reputable shop and it took them a week to diagnose. Was the MAF sensor. Replaced that and it was back to normal. Same year as yours.

 

[garn79]

so the catalytic converter is not very old but i did do a backpressure test which revealed no issues there.

the hoses and stuff could probably be replaced pretty cheaply so i might do that... are there any kits/combos or anything out there for that?

thinking i might just go ahead and replace the maf sensor, although i could try to clean it again.

on another note, can anybody recommend some general preventative maintenance? in addition to the things i've already mentioned... the timing belt and water pump were replaced just before i got it. probably a good time to do an oil change, any other thoughts?

yes, an easy DIY is the breather valve on rear diff. located at top of diff just a bit to DS; apparently can cause rear axle seals to leak if it gets plugged. Cheap part, cheap maintanence vs axle seal replacement.

 

[eevee]

cool, i'll check into it. i believe my brother had some rear axle issues just before handing it to me, so that might actually have been replaced as a part of that but i will definitely find out