91Toy4R

Yo guys,

I don't know if anyone else has experienced this problem, I've used the search but no luck so far. Briefly the problem is that a new oxygen sensor was installed a few (4-5) months after a new ecu was also installed (late 2009)on the vehicle. The new ecu flashed a code 25, the sensor was checked and declared defective and thus replaced. The new one was installed and to date the ecu has not acknowledged it. I bought the vehicle 2 months ago, running fine except that the CEL light was on. The previous owner did tell me about the problem, so there was no deception, but i did thought at time it would be easily rectified by resetting ecu (not successful). Vehicle runs fine regardless (for a 3vze) and my overall mileage usually between 16-19 mpg(i check at every fillup). Could anything be done here or should I just continue to drive vehicle as is? HELP!

91Toy4R

Just an update, last weekend did a 220 mile road trip. My average was just over 19mpg. As i reported originally, the vehicle runs fine otherwise, the only new thing I noticed was a tendency for the engine to quit running whenever the steering was at full lock and vehicle not moving ( as in making a 3-point turn). Could this be another problem and not the O2 sensor?

thook

A code 25 indicates a lean air to fuel ratio.......too much air/not enough fuel. If the ECU was not detecting the O2, you will get a code 21. So, you need to see what code the ECU is giving you at the moment. If it's a code 21, then you need to check the wiring.

However, given the current steering/engine dying issue, sounds like you could have a vacuum leak at the power steering idle up valve.......which would be enough to cause an O2 code. So, verify that code.

91Toy4R

Thanks thook, will be checking same as soon as possible and let you know. thanks again.

aa1911

iTrader: (1)

it's somewhat common for O2 sensors to come bad out of the box but sounds like yours is working; curious as to what the ECU issue was? the most common problem with replacing the sensors is usually wiring it up wrong but if you are getting that good gas mileage I think the sensor is working fine; a short or incorrect wiring will mess up the AFR's and you will get something like 8mpg and the CEL (happened on my taco when I forgot to tape a loose wire end). Why did the PO put in a new ECU? I'm assuming you have the correct sensor as well...

91Toy4R

The old ecu had failed (cracked i think). But i have the old O2 sensor, collected it with the vehicle, just in case. On an aside, this vehicle is strong and sturdy, but i can see why you guys call the engine the 3.slow. My old vg30e pathfinder would have left it in the dust in an acceleration contest, but wasn't as durable (front suspensionwise)

91Toy4R

Ok, I rechecked the codes last evening, and its definitely 21, but on checking the vacuum lines to the idle up valve, and lo and behold, those lines were plugged off. We started tracing some other lines and found those plugged too. I need to check the FSM to see if there is a map of sorts showing vacuum hose layout, then i'll need to check over the entire vacuum system for the vehicle. ( The only ones i disconnected were those to the ADD, i recently installed some MM hubs. Gotta love this site-info at your fingertips.) Will keep you guys posted.

thook

I replied to your PM. I'll copy/paste that message over to your thread here......

thook

Wait a minute.........vacuum lines to the air valve? Your vehicle is a '91. The only lines going to the air valve should be coolant lines, unless you guys in South America have system designs that are different somehow. Are you sure you're looking at the air valve and not something else? There are several vacuum lines going to the throttle body itself, but they have nothing to do with the air valve. Just to be sure, are you looking at the lines that go directly to the bottom end of the throttle body?

91Toy4R

Naw, this is no special South American model, plain ol' USA model imported brand new out of store. I am 3rd owner.
Question- is the idle up valve located on the steering pump or another location?(i checked fsm, which i think depicted somewhere near dizzy, but mechanic disagreed, pointed out vac lines running to location under pump, and those were plugged, by another mechanic probably-we got a lot of guys down here who pretend to be mechs.)
I was just checking for vac layout diagram-but no success, will check site later-any clues? Please forgive my clumsy attempts at posting, kinda new to this.

thook

Good grief. My apologies. I get my hands going in several different threads and lose track of what's going on with who....hahaha! Sorry, sorry.....

Yeah, there are vac lines to the steering idle up valve. I was confusing your issue with the idle control valve on the throttle body. <<<ding, ding>>> Regardless, looks like you found the problem there. How does the vehicle behave with those unplugged, now?

The code 21 means the ECU's detecting a problem in the circuit. Let me find the page that goes over testing at the diagnostic port to see if you're even getting an O2 signal.

BTW, does the wiring harness for the O2 look factory or spliced in? The connector at the O2, that is?

91Toy4R

Will check and get back to you

thook

Here's some instruction for O2 operation and verification. It's kind of a lengthy read, but informative.....

http://www.autoshop101.com/forms/h58.pdf

Do you have a volt meter? Or, would you have your mechanic do this?

91Toy4R

Yo thook,

Hope you had a good weekend, and thanks for the tips you sent, I wasn't able to do much this weekend(wifey had other plans), but I was able to start tracing some vacuum lines.
What is now certain, is there are no vac. lines from PS pump to manifold.
With reference to the first thumbnail photo on the attached link(trouble uploading photo), one hose connects the two ports (5,13) for the PS, the hose tightly fitted no 13 and with a loose fit on 5, creating a controlled airleak(smooth idle at 500rpm). With 5 unplugged-the engine would have a very low and rough idle (300-400 rpms) and with 5 plugged-no idle whatsoever. I found what i think to be the air control valve on the PS pump, but it appears damaged with no discernible way to connect vac. lines. Lets say that i have to live with this scenario-should i plug port 5 and adjust idle otherwise?

I have another pic that i tried to upload with no success, but it shows a small black container by the brake master cylinder with two hoses on top with designations-'VAC' and 'ACT' (assuming it means actuator). the one to 'ACT' is plugged. Do you know where this is supposed to lead or connect to? None of the vac. layout diagrams i consulted make any mention of it.


https://www.yotatech.com/forums/f116...e-help-209069/

thook

PM sent.

If you can't get another PS up valve right now, adjusting the idle to compensate is going to be a detriment to your mileage.....if you can live with that. What's more, I'm not sure how much you will have to adjust the idle up to compensate for the steering load. I've never had to do this, myself.

Let's see if we can get you some pics going of the up valve situation. If I look at it, maybe I can determine if it's repairable somewhat. Then again, maybe you could just avoid tight turns????