steanson

OK, is 3 hours of searching enough before just putting it all out there?
My 97 4Runner Limited has...in the last few weeks, seemed to lose it's low-end power, and it seems to have worsened to the point where now it is "missing" or "misfiring" anywhere from 1000-2600 RPMs, usually when I am trying like hell to pull out in traffic or merge onto the highway. *Uhh-huh-uh-uh-uhhuhhhh...huh-huh..* Good Lord, my truck sounds like Butthead. My father even noticed the surging effect while riding with me today, and mentioned that he heard some small "backfires". I have a few little mods, but this didn't happen for some time after: K&N, open air-box (in lieu of the deckplate mod), removed silencers/plugged holes in intake tube.
Any advice would be greatly appreciated.

Oh, one more thing...could the MAF be ANY MORE restrictive!?!? I stood staring at that thing...it looks like the horn to a cheap car alarm. Does anyone make, or can ya swap out other factory MAF and TB with "bigger" toyota parts?

07sbock

When was the fuel filter done last. Also have you run any injector cleaner through it lately?

ciscojay

Have you done a good old tuneup recently? Check plugs, wires, clean throttle body. Seafoam it and then run a can of BG44k when you get down to a half tank. I'd get some and run it hard for a few miles. It'll clean out your cat as well if it might be a little plugged up.

I've heard of guys boring out the TB for a bit more response and maybe few hp, but the only MAF upgrade I've heard of is slapping on the Twin Turbo Supra MAF on an s/c or turbo setup. I heard it doesn't do anything on a NA motor. Search for it.

90vetteman

The MAF is plenty big for our motors. I had the same issue and found out my CAT was going bad. Try disconnecting the exhaust in front of the catalytic converter and take it for a ride. Apologize to the neighbors before you start it up because its going to be loud! Try the basic maintenance stuff too....it couldn't hurt. The other issue that the 3.4 has is the knock sensor. They tend to go bad after awhile and when they do, the computer will pull all the timing out of the engine. You will notice a big decrease in performance and your gas milage drops like a rock.

Good luck!

toytech76

Where have you ever heard that?? I have never seen a 3.4 knock sensor go bad or heard anyone claim the 3.4's have issues with the knock sensors. If you had a bad knock sensor, your check eng lite would come on telling you that it was bad. AS far as the MAF's go, yes, they are pretty restrictive for the 96-98's. You can convert to the 99-02 style airbox and MAF setup. I did the swap and repin myself so I will post the link to my write up about it.

http://www.ultimateyota.com/index.ph...6&topic=3915.0

steanson

Wow, thanks for the good advice...sorry it took so long to reply; I thought I had message alerts and figured everyone was sick of answering a somewhat generic question. I think I may try all of these...it's a 2nd hand 4Runner and I have NO idea what's been done in it's 175,000 miles. Before all this happened I DID notice over time it seemed to knock/ping or had valve clatter when I would accelerate, to the point where I would drive it like a granny until I could get a bottle of octane booster, which, didn't help. I am beginning to wonder if my check engine light is burned out! (Oh, duh, maybe I should pay attention at start-up!) Thanks again, and feel free to continue commenting.

steanson

Oh, and Toytech76 (or anyone else)...do you have comparison photos of the two different MAF's showing their ID? That link to your conversion was GREAT, I am just curious how they compare visually.

bigchris

Definately check your plugs and wires. I had almost the exact same symptoms about 2 weeks ago, serious low rpm stutter and loss of power, no codes. easy tune up items cleared it up.

toytech76

Are you looking for the connector views for both MAF'S? I have another link showing the 2 MAF'S and their connectors.

http://www.ultimateyota.com/index.ph...6&topic=3901.0

steanson

hmmm....I click and click but all it seems to do is open up the thread over and over again, but I see no pics. Actually I was just curious about how much larger the orifice is...like, looking through them... [ o vs O ] so to speak...

90vetteman

It would seem that toytech76 has some issues with my comments but all I do know is that I have had 3 different 4Runners in the shop that had problems with the knock sensor and they never threw codes. It's very difficult to diagnose a problem without actually laying your hands on it, so I was offering up what I knew. As for a bigger MAF, if you have an extra $200 and time on your hands, go for it but if it was me, I'd save my money for some headers. It doesn't matter how much air you can get in if you can't get rid of it. Toyotas design of the cross over tube between the manifolds is very poor. If you are after better performance, start with a set of headers and a good exhaust. JMHO

steanson

Thanks for that...where is the knock sensor located? Is it easy to remove/replace or even test it? This is all really my fault...I knew better than to brag about 175,000 miles without problems...JINX!!

toytech76

hmm..dont know why the pics arnt coming up on the page. The 96-98 mafs are directly in the center of the airstream. The 99-02 maf's are a slim sensor that sits in the side of the air tube on the airbox and are minimally invasive into the airstream. My conversion cost me $50 and an hour of my time. I got the used box complete from a wrecking yard. If you are lucky, it will have the MAF in it. You can use the tacoma or 4runner airbox's. I agree with getting headers, but its the same thing. What good is getting the air out when you can get it in? Opening up both ends would be ideal. You can also eliminate the mechanical radiator fan and get a dual electric fan setup from flex a lite to get rid of the drag on the motor for even more performance. It just depends on how far you want to go. One major reason to swap over to the newer airbox and MAF setup besides better airflow is cost. The cost of a new MAF for a 96-98 3.4 is around $600 from the dealer. The MAF for the 99-02 3.4's is around $130. IMO those numbers speak for themselves. Besides better airflow, its more cost effective to replace the smaller MAF's when they go bad

toytech76

Just make sure you diagnose your problem first beofre throwing parts at it you dont know will fix it. The knock sensors are under the intake manifold and there are 2 of them. They are probably about 200-300 each from the dealer

ciscojay

I had my knock sensors and the pigtail harness for them replaced about 7000 miles ago. There are two on the 3.4L - one for each cylinder bank and located in plain sight, in the block between the cylinder heads, underneath intake manifold.

For me, the CEL did trip and then threw the ECM into safe mode, pulling max timing to protect the motor. Thank you Toyota Engineers! New ones in (my price was $129 ea. discounted from dealer) and runs strong as ever once again.

steanson

This Seafoam...just picked up a can. For this application you guys are talking about dumping it into the gas tank, right? NOT the crankcase, right?
So, I brought home some Seafoam, TB/Carb Cleaner, MAF cleaner (other threads scarzed me outa plain ol carb cleaner)...and a quart of tranny fluid, as it was a bit low yesterday when I checked it...ALTHOUGH I had run it for a couple hours then checked it engine running; should I have let it cooled down a bit? it was way lower than [cold] mark...
I'm getting there, and after all this stuff will come the dealership parts (plugs and wires, knock sensors, etc...
Wish me luck. I SWEAR to never ever ever brag about how well she runs...ever ever ever again!!!

ciscojay

I'd do the seafoam in your induction system as well as the gas tank. BG44k would be better for the fuel tank though. Look up "how to seafoam" on youtube and read the instructions on the can. Be careful and watch how people do it. If you're carbon'd up you'll see lots of smoke. I never did fortunately. Just make sure you pour it in slowly, I personally wouldn't suck it in like some do. Let's not start that thread again, search for it.

steanson

got it...I see now, thanks!
will be clouding my neighborhood in the morning!