Hey guys, love your stuff here. You guys rock!!! So here's my problem, I have a 2001 4Runner SR5 2WD with 169K on it and my horsepower has definitely dropped off quite a bit from when I first got it with 52K on it. I have been pretty good about my routine maintenance. I wanted to go through what I've done so far and see if you guys can help me narrow it down a bit. So here's what has been done recently: Spark plugs, fuel filter, plug wires, cleaned the MAF sensor and throttle body, Seafoam treatment in the gas tank, crankcase for 1K mi then did another oil change, and in the PCV hose. I've also used numerous fuel/fuel system treatment products like gumout and STP. My truck is still running good aside from the horsepower issue. It idles good, cranks up just fine, no CEL and still gets good gas mileage.

I'm just missing that pin your head back feel when dropping down two gears to pass on the interstate. Now it's more of a gentle sway which is embarrasing compared to how hard the poor thing is trying. I remember when I first got it that I would be going up hill on cruise and I'd have to cancel it cause when it dropped down two gears I would almost rear end the person ahead of me! If you weren't ready for it, it'd kinda freak you out.

I'm not sure what to try next. The coil packs are original so I may try that next. The front O2 sensor is original too and could prolly stand to get replaced as well as the catalytic converters... gotta save up for that tho. I'm no expert (barely a novice!) so I look forward to any feedback as to anything I might have left out or what is most likely the cause. Thanks again guys and have a good one.

 

Could be a clogged/bad cat check it and see what you got there

 

i would definately say that the cat is clogged... i was having a similar problem at 134k miles and i put a high flow cat and a flowmaster on and it fixed the problem

 

If the cat is clogged, your engine might run a little warmer.

 

I knew you guys would nail it! My truck has been consistently running smack dab in the middle of the temp gauge. I can't recall if that's normal or not, can anyone else confirm what a normal running temp would be? BTW, I just did a radiator flush a couple of months ago and it didn't have any affect on the temp.

Hey cRoW, where'd you get your parts from???

 

Mine sits right dead center.

 

How about if he were to core the cat and run a URD o2 simulator. Howwould it sound, any different?

Aaron

 

Huh, wierd. Mine is dead center too. Well the cats do have nearly 170K so I might move them to the top of my list. Can't seem to find any Magnaflow cats for my 01 4Runner though... Anyone else upgrade theirs, got some part numbers? I have the 01 model with 2 cats, first one being the Cali version.

 

that might be tough to find.. i welded my exhaust all up so it kinda fell toghther with a little molten metal..

 

Yeah, I'm more of a direct fit type of mechanic wannabe! lol

 

then it'd be great for the environment and it'll be REALLY quiet.
try it.

 

Quiet huh? I somehow doubt that one, as the the enviro yeah not such a good contribution.

Aaron

 

Once I read the title first thing in my mind was the cats. You can get them online at carparts.com that's where I got mine and had them welded from a muffler shop across the dealership. According to my scan gauge parameters I am running at 180F-195F depending on conditions. Or in the instrument cluster. I wouldn't recommend gutting the cats at all. States now are getting more strict on it and some auto repair shops from what I've heard is being required to report cats that have been modified. Our shop has not yet been required to but SC is a little slow on emissions related stuff.

 

i kind of had the same problem with my 86 4runner. i would have no power and couldnt take it out of 50mph but the engine was great ..come to find out it was my brakes locking up so just check if your brakes are hot after driving, if so it could be the master cylinder or front brake calipers need to be rebuilt....

 

Ok guys, I finally got around to replacing both Cats, along with the Air/Fuel Sensor and new Denso plugs and Denso wires. The problem still persists! I have no horsepower when I get on the freeway and the truck just seems sluggish all around. I know this isn't the strongest truck but I remember how much pep it had when I got it. Any suggestions are welcomed since I'm out of ideas! Thanks guys and I love this site

 

at a 169 miles normal maintenance should included both the front and rear AFR/O2s', TPS, take out the injectors and get them professionally cleaned and checked, knock sensors wires harness replaced, timing belt, take off the intake and TB and clean it well, replace "D" gasket with "O" gasket for better throttle reposonse. Air filter.....ETc...

I say this because even though sensors arent throwing codes they start to get sluggish and out of spec. Same thing with the injectors--they get clogged and start squirting an ugly pattern.

What kind of oil do you run and how often is it changed? I havent seen any 3.4s' with valve gunk unless the oil wasnt changed regulary so i wouldnt worry about valves. Muffler?? is it rusting out??

 

Cool, that gives me a lot of new things to try. I think I'll start with the TPS and the rear O2 sensor. While I'm at it I may try cleaning the MAF sensor again.

I use Castrol Syntec Blend and change it every 6K miles. My muffler is showing some signs of rust but it is still intact. Thanks again.

 

the stuffing inside the muffler start to break down and clog the system.......also, FYI-- the rear O2 doesnt affect performance but they go out also.......I am just one of those people that if i am in there--then i'm going to replace it. More or less....

AND--i am not saying its the be all end all, but Mobile 1 @ 10k oil changes treated me very nice.....builder on my motor said he could tell the oil was changed regularly--then i told him i changed it every 10k--

 

I do seem to get a decent amt of airflow coming out of the motor even at idle but replacing the muffler has been on my list, maybe in the spring when it warms up again I'll go at it.

I like the sound of changing the oil every 10K miles!!! That's next on the list as well. lol Do you use a specific filter to last those 10K miles?

I have suspected the timing might be off, might be time to have the dealer run some tests on it. They run specials near spring time as well. Thanks again for the great responses!

 

ODBII was invented just for cases like these. All the stuff you replaced was probably just fine, and could have been tested with an ODBII computer and an infrared thermometer.