yotaslave

I own an '86 4runner 22re and it has a lack of power far greater than what is usually characterized by this stock motor(;

When the engine is cold it runs great! But as soon as it warms up, anything more than half-throttle is serious engine bog, in any gear. It's like a switch, one second it's fine full throttle in 3rd gear and the next, immediate drop in power. I have learned extreme throttle finesse but the time has come to fix. I'm pretty certain I've unplugged the temperature sending unit which didn't help. Any suggestions?

HunterRunner0122

I'm having the same exact problem! I haven't had whole lot of time to figure it out but if you find something out before I do please post it. If I figure mine out I will let u know. I'm going to a buddies house this weekend who has a good running 4runner I'm going to swap some parts with to try and figure it out. Good luck!

HunterRunner0122

Does ur temp gauge shoot up to half way (like its already warm) when u have only driven it like half a mile? That's about when mine stars bogging down, after the temp gauge jumps up (but I know it's not at operating temp yet)

yotaslave

Yes! It does do that! I'll be taking a closer look at it tomorrow. I will definitely post if I figure it out

yotaslave

What year is your runner?

HunterRunner0122

It's an 85 but I've got the 22re.

yotaslave

Very nice! I'm jealous, being one year away from a solid front axle.

HunterRunner0122

Yea I had 87 before and a lady totaled it for me so I decided I wanted the 85. It only took me a year to find lol.

yotaslave

So yesterday I unplugged the throttle position sensor, the knocker sensor, the O2 sensor, each separately and drove after each. I even gave her a nice tune up and didn't see anything funky on my old sparks. No change, and every time I let it cool down and kept an eye on my temp gauge as I drove. Sure enough, she ran like a champ up until it reached about halfway, then boooooggggggg. I searched for another temperature sensor I may have missed but nothing I found cured the problem (I even unplugged an injector wire on accident, that was fun!!). I'll keep thinking but as of noe I'm still at a loss. Good luck to you this weekend, let me know what happens!!!

HunterRunner0122

Have u tested your air flow meter (afm) or the o2 sensor? Thanks! I've done everything u have too and no change. have u checked ur check engine light for any stored codes? When I checked mine I got a 2, 5 and an 8, which is afm, o2 sensor and air thermo sensor.

yotaslave

I haven't found a place in town that has an adapter to check any codes yet. Also, mine isn't throwing a check engine light. I haven't tested the afm. I don't think I need to check the O2 cause I unplugged it already with no change...which was very disappointing.

BamaYota1

It's your O2. Unplugging a non functioning O2 will not make a change, because it is faulty in the first place. Run the FSM tests on it, especially the current fluctuation, and it will fail.

You only need a paper clip to check codes. Btw, a bad O2 won't necessarily throw codes.

murphyz

can a vaccuum leak cause this as well? after the engine goes to a Closed loop setup?

yotaslave

How do I check codes with a paperclip?

yotaslave

And how can the absence of an o2 sensor mess up the engine?

stanprophet

When the engine is warm it enters closed loop, it monitors all of the engine sensors to find the correct air to fuel ratio. There are really 4 main sensors that are monitored to correctly reach stoichiometric combustion. The AFM or MAP, IAT, ECT, O2. The O2 sensor monitors left over oxygen in the exhaust after combustion, based on how much oxygen is left the ECM changes fuel maps and begins to adjust the AFR to reach a predetermined value for efficient combustion. Having a faulty O2 sensor will throw the AFR off and cause it to either lean the mixture out, or to add more fuel than what is needed. This can really cause some issues.

Running lean causes increased combustion temperatures, and can lead to overheating. It can also cause hot spots to form on pistons and valves, causing fuel to ignite in heated pores of the metal. Just like taking a torch to them(Worst Case). Running to rich will cause poor mileage, massive carbon build up, and the catalytic converter to eventually melt. In extreme cases it can wash down the cylinder walls causing lower compression and fuel blow by that will eventually cause lower engine problem. Also if the cat becomes restricted it can also cause overheating, since 75-80% of combustion heat is released with exhaust gasses.

Either way, an 02 sensor on an EFI vehicle is rather important.

To the OP:
I have a similar issue, just not as bad. It has been better since I replaced the thermostat that was stuck open. Since I do not have to go above half throttle much I have not really looked into it, but it is on my list. In the next couple of days I will hook my Oscilloscope to the O2 Sensor, and the ignition system and do some testing and let you know what I find.

When it happens are there any weird smells from the exhaust?

I am willing to bet that the AFR mixture is going rich, at least on mine, and causing a lack of power.

yotaslave

Just tested the AFM http://www.4crawler.com/4x4/CheapTri...tml#AFMtesting and statically it tested great, dynamically the E2-VS tested in the milliohm range, far below 20 ohms. This may be our problem, I suggest testing...though I priced the part at $125, ouch!

yotaslave

And as for weird smells...no weird smells, however sometimes I get a good wiff of unburned gas :b

BamaYota1

You can attempt to clean the contacts on the VAFM. Just cut the silicone around the box, and the plastic can be lifted off. Google search adjusting it, and you will find a decent write up. It is a pretty simple device.

I would still check the O2 with an oscilloscope. Iirc, the engine does still read the afm in open loop, but I could be wrong about that.

BamaYota1

And afm's rarely go bad unless they have been opened, so you could score one from a pull a part on the cheap. Just check it before you pay for it. I believe the old 22re Cellicas used the same ones.