128keaton

Dad (PO) said that the o2 code light has been on forever, which it has, even after he has replaced it. It smells really rich from the tailpipe, but I get decent MPG for this car (13.4 MPG). Totally mystifying. What could I do to remedy this?

millball

Where'd you get the idea that 13.4 is decent mileage??

My 5 speed 3.0 gets 18-19 MPG, occasionally makes 20.

What are the code numbers that it has set?

scope103

"... replaced 'IT'"? "'IT' smells really rich ...."?

I assumed that the "it" replaced was the O2 sensor. I assume the "it" that smells rich is the exhaust.

Replacing the sensor is very unlikely to cure a code 26. Getting a new mailman doesn't make your bills go away. (You're going to need to verify the code(s); this will get you started: http://web.archive.org/web/201211190...85diagnosi.pdf)

That site gives a list of causes of that code (most of which are actually causes of running rich.) Assuming you have code 26 and nothing else, based ONLY on the age of your vehicle I would first check the ground connection at the back of the head (you don't say which engine you have). Then I would suspect a stuck injector, so I would pull each of the plugs and look for one that's black.

Millball is right. You're not only wasting a lot of money on gas and ruining the air around you, this is the kind of problem that can get steadily worse. And strand you.

Janos01

As far as running rich, Dirty/bad injectors, worn catalytic converter due to age or if the car has run rich for sometime, bad spark plugs can cause this.

scope103

The catalytic converter is downstream of the O2 sensor; it can't cause a code 25/26.

Where you worry about the catalytic converter is where you DON'T have a code but still can't pass a tailpipe emissions test. The input to the converter is "close enough" for the converter to wrap up the last of the loose pollutants, but the converter fails to do that.

Presumably 128keaton is in a corner of the world with no emissions testing; a CEL will cause an immediate failure no matter what comes out of the tailpipe.

128keaton

I think it was 25. I'm gonna get out there in a bit and do some of the other tests recommended in this forum.

as for the MPG, its just a number stuck in my head from god knows where.

Whoops! I meant it smells rich from the tailpipe. The seals and bearings are worn, but I just cleaned the spark plugs and none of them were obviously very black. My injectors do tick, louder since I ran some cleaner through them. I haven't replaced the o2, my dad did like four years ago, before it became under my care.

The injectors were cleaned with two bottles, as for the cat, I wouldn't be surprised. The spark plugs are 6 year old Bosch Lithiums, and they all sparked great when I tested them about a month ago.

I'll check the ground on the back of the block (as suggested by someone else here) and then try to replace the cat. I'll grab the exact code, I just remember looking it up and it was the 'o2 sensor code'. My father said its thrown that for years.

I'd really like to fix this, as it seems I'm spending way to much on gas. I don't have any form of yearly inspections here in TN.

BTW, my engine is the 3.slow with 221k (gotta update my sig)

128keaton

Bit of an update, its now throwing the dreaded 52 code, which is short for 'you are screwed' Last time I checked, it was code 25. I think I might be lucky, because it appears the insulation on the wire right where it goes to the connector has all but fallen off. Apologies for this thread. I wanna get out there and diagnose, but its 30 degrees and snowy outside. Would a knock sensor error cause bad MPG?

scope103

The MOST likely cause of code 52 is a bad "pigtail," which is the wire from the knock sensor itself to a 2-pin connector nestled in with the driver's side injectors. I assume you're referring to the knock sensor side of that 2 pin connector.

The bad news is that the intake manifold has to come off to get to the pigtail. You have a job ahead of you, but the result is likely worth it.

128keaton

Yeah, its allocating the hours and convincing my father to help me. I don't know enough to plow right in and take it off. He has had the engine apart enough to do it, its just cost v.s. benefit. He simply adjusted the timing to counteract the retard from the knock sensor. Doesn't help with the fuel clatter on the highway. Quick question, from the guides it looks like there is a separate connector facing out of the engine. Could I just get by with replacing/soldering the cable that is outside the manifold?

I don't have a huge background mechanically, I can do basic stuff, and I've got a strong electronics background, just don't feel super comfortable tearing apart a car I use for A) going to school, B) going to work. I also carpool, so if I crippled my car, I'd inconvenience other people.

millball

You don't have anything to lose by trying.

Terrys87

iTrader: (1)

I seen you using some Bosch parts. Bosch is good for other brands of autos but not for Toyota. Stick with OEM parts in most cases.

128keaton

I will keep that in mind going forward. The oil filter is FRAM, everything I've ordered has been from OEM (Thanks Principle Toyota, you guys are CHEAP)

They've offered to replace my steering column due to a recall for free.

Also, I've searched around, but I'm having trouble locating information. the knock sensor wire (right between the injectors and under the intake for the upper plenum) HAS a connector. I've looked, but it seems every wire is made to go from the knock sensor to the external face of the block to the connector I speak of. I'm pretty sure the cable is damaged (going from the facing connector to the computer), but I cannot find a replacement. Am I on the right track? Sorry if this entire thread is riddled with uncertainty and stupidity, I don't know much about the 3VZE, but I learn quick.

scope103

You believe the pigtail-to-ECU wire is damaged? That's part of the harness; not a separate part. And damage to that wire can give you a hard-to-fix code 52, because the wire is shielded.

But others have replaced it with simple shielded microphone wire (someone claimed success with RG-59 cable TV wire).

128keaton

Oh, ok. Yes, I took a voltmeter and checked the continuity between the male pins going to the harness and it was pretty low. If Im not mistaken, it would register as 'not connected' on the voltmeter. I'm guessing its this wire, just between all of the work done in the area and the external shielding is coming off VERY easily. I'll get an exact measurement tomorrow and post here before I go modifying factory harnesses.

scope103

Uh, what?

Voltmeters check for voltage. They can only check for continuity if you have a known voltage at the other end (they don't do a very good job of it because they have such high input impedance. Even a very poor conductor (high resistance) will register "continuity" as a voltmeter can detect the voltage without drawing any current to speak of.)

Usually you use an ohmmeter to check for continuity; that will give you a resistance measurement so you know what you're looking at.

And what does it mean when continuity is "pretty low"? Low resistance? Low conductivity (the opposite of resistance)? Low voltage??

Are you measuring BETWEEN the pins to the harness? What voltage do you expect? (I sure don't know; it's probably the input to an op-amp, so you're looking at the input resistor to ground. Or something.)

It's worth measuring the resistance From the pins in the connector to where they connect at the ECM. The shield should have zero resistance to ground, and infinite resistance to the signal wire. The signal wire should have zero resistance back to the ECM, and infinite resistance to ground.

128keaton

Its a voltmeter with an ohmmeter function. By low I mean low resistance. I was measuring the two pins inside the connectors.

I'll check that if I get time tomorrow and the weather lets up.

128keaton

Oh, could someone hook me up with these part numbers:
* O2 Sensor
* knock sensor wire

A buddy kindly bought me the plenum gaskets since he is anxious to work on something, so why not my car? XD

I have a Chilton manual ready to go