1997 4runner 3.4l lacking power

[Blitzkrieg]

I have to second the partially plugged cat. If your exhaust bolts/flanges arent totally shot try unbolting the cat and taking it for a quick drive and see what it does.

I'll third that.

Other culprit could be dirty fuel injectors.

Reset the ECU by disconnecting the battery negative cable for a couple minutes, drive the truck for a while and make sure it's not showing a check engine light or throwing error codes.

 

[Blitzkrieg]

The bolts aren't being cooperative so I might just cut it out and see how it drives. Would a clogged cat be worse when it's cold?

Soak the bolts with a penetrating oil.

Be careful about cutting it out. If the cat is good you are essentially ruining it and a new one is not cheap. Also, here in Colorado and I am sure in California you will fail the AIR inspection if you are missing the cat.

 

[fun_runner]

The bolts aren't being cooperative so I might just cut it out and see how it drives. Would a clogged cat be worse when it's cold?

Or, alot of times its easier to remove the oxygen sensor in front of the cat.

^ :hello:

 

[zerocirca]

Yeah I totally didn't think to do that. You think the o2 sensor hole will let off enough pressure to notice if the cat is clogged?

 

[fun_runner]

Yes.

 

[1985taylor1925]

I had similar issues with my truck a few years ago and it was a bad injector. But if that was your issue you should be seeing a code. Still possibly something to consider if the issue isnt in the cat or pcv as mentioned

 

[zerocirca]

A partially plugged catalytic converter will cause those symptoms. How many miles are on it? Has the timing belt been done? Maybe the old belt jumped a tooth and is throwing the timing way out of whack?

If the belt is good, the exhaust isnt plugged and you've done all the maintenance stuff then the only way out now is the S/C. :cheers:

So I finally figured it out. The problem was the timing was messed up. Actually the crankshaft gear. So I decided to change the timing belt and when I took the belt off I noticed the crankshaft gear had some play in it which was alarming. I took it off and the woodruff key holding the gear on the crankshaft was warped and ground down. The slot in the crankshaft gear was severely bored out which allowed it to have some play which in turn messed up the timing. Replaced that gear and timing belt, now it runs top notch!
Thanks fun_runner and everyone else that chimed in

 

[KMcCormick24]

Im having the same issue

I know my 4runner has two bad knock sensors. My question is will that affect the performance of the car? It runs perfectly fine. Im also considering replacing the catalytic converter I know that can cause some engine choking. The car has almost 260,000 miles on it and I don't know if the cat has been replaced ever. I haven't replaced the knock sensor mostly because I cant afford the $1200 repair and don't know how to do it myself. So i guess the real question is which one will affect the cars performance more?

 

[imagemaker]

If the Cat was bad, wouldn't there be a code?

 

[imagemaker]

Im having a similar issue..Im having a similar issue. 2000 4runner 3.4 motor. Replaced air box,(potential stripped screw on the MAS) replaced MAS, Replaced TPS, replaced IAC, Replaced ECT, Replaced brake booster ( as per Dealer diagnosis) , checked vacuum lines for breaks. New plugs. No codes. Been to 4 shops, all the incorrect diagnosis. The problem is exactly the same and has not presented itself differently after each repair.
Runs fine on start up. As it approaches normal operating Temp, it will seem to lose power. If you come to a stop and accelerate it bogs down, back fires through the air box. Does the same thing if restarted after 30 minutes. When the issue occurs , if you pull over and restart the vehicle it will return to normal operation

 

[19963.4lsr5]

If your knock sensors are bad I can see the ECU removing timing to prevent a knock condition. You will feel that as a loss of power.


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[JBurt]

Have you looked at the o2 sensors? Just a thought.

 

[Oliver4R]

So I finally figured it out. The problem was the timing was messed up. Actually the crankshaft gear. So I decided to change the timing belt and when I took the belt off I noticed the crankshaft gear had some play in it which was alarming. I took it off and the woodruff key holding the gear on the crankshaft was warped and ground down. The slot in the crankshaft gear was severely bored out which allowed it to have some play which in turn messed up the timing. Replaced that gear and timing belt, now it runs top notch!
Thanks fun_runner and everyone else that chimed in

Ugh... I hope that's not the problem on mine. I don't want to dig into my engine that deep. May have to though...