RSR

I've got one I purchased as a spare from one of the yota yards in Colorado that I'll sell. $20 plus shipping. PM me if interested.

RJR

It is possible to be a bit more scientific about all of this. The O2 sensor and the diagnostic port can supply a lot of info about rich vs lean operation if you make the right measurements.

Here are a couple of good links for explanations of how all of this stuff works and where to make the measurements.
http://www.autoshop101.com/forms/h25.pdf Pages 11-15 describe how the injector control works and how the O2 sensor and the catalytic converter work together to keep emissions down.
http://www.autoshop101.com/forms/h27.pdf Page 13 describes how to use the VF terminal on the diag connector to figure out lean vs. rich.

In a nutshell, here's how the system works.
- The ECU has a "map", or table, of injector times based on air flow, air temp, rpm, and coolant temperature (those are the main ones.) It uses this map to calculate optimal injector timing for engine conditions. It recalulates the injector times pretty much on every revolution of the engine. Generally, if the sensors are all working properly and the injectors are stock, the engine will run well with this information. It will not, however, necessarily pass emissions.

- To pass emissions, the cat converter has to be operating with just the right mixture of combustion products. It is designed to work well only if the mixture is at the 14.7:1 air:fuel ratio, the stoichiometric ratio. That's the air/fuel ratio where there is just the right amount of oxygen to combine with all of the fuel and burn it completely. Page 14 of the first document I referenced shows how fussy the cat is with respect to air/fuel mixture. The purpose of the O2 sensor is to get that mixture right so the cat can do its work. This only happens when the engine is in "closed loop" mode, which requires the O2 sensor be warmed up and the engine running above idle but not at full power. That's why they use 2500 rpm for the test, and nowadays put the vehicle on a dynomometer.

You can measure the VF terminal under those conditions in two ways. With the T (or T1) terminal open, the voltage will tell you if the ECU is trying to enrich the mixture (voltages near +5V), or trying to lean it out (voltages near 0V). Nominally the value should be near 2.5 volts. If it is not, something in the system is biasing the mixture away from nominal. These values are "learned" from the O2 sensor over several hours of operating time.

With the T1 terminal shorted to E1(ground), the VF terminal will track the O2 sensor output. This should be oscillating between 0 and 5 volts, at a rate slightly less than once/second . If it is stuck at 5V, the O2 sensor thinks the mixture is too rich and is telling the ECU to lean it out. If the voltage is stuck at 0V, the O2 sensor is telling the ECU the mixture is too lean, and needs enriching.

Gevo, since your smog test indicated a too rich condition, the O2 sensor output should be stuck at +5V. If it is stuck at 0V, the O2 sensor is suspect and is probably the cause of your problem. If it is oscillating properly, it means your cat is not doing its job even with a perfect mixture going into it (if the cat were healthy and the mixture going in was correct, you'd pass smog.)

If the O2 output is indeed at +5V, it and the cat are likely healthy. Something is causing the ECU to put too much fuel into the system. Among others, the following things will cause the ECU to improperly enrich the mixture: (essentially, all of these things cause the ECU to operate on the wrong part of the "map" which tells it how long to pulse the injectors.)
- Coolant temperature sensor giving an inaccurate, cold reading. Colder engines require richer mixtures to run well.
- Air temperature sensor giving a cold reading. Cold intake air requires a richer mixture because it doesn't vaporize the fuel as readily.
- AFM set wrong. If the ECU thinks more air is entering the engine than is actually happening, it will inject too much fuel.
- Injectors too large for the engine. The ECU determines proper injector timing based on a specific injector design. If that changes, it has no way of knowing it needs a shorter time. It can "learn" a new setting from the O2 sensor, but the range of learning is limited. Once it hits the limit, the engine is essentially in open loop mode all the time and will fail emissions.
- Vacuum leaks also distort the information the ECU receives, but normally that would cause a lean condition, so is likely not your problem.

I think if you measure the VF terminal both with T1 open and T1 shorted to E1, you'll know a lot more about where to look for your problem. Report back here if you want more help interpreting the results.

Good luck at getting past this hurdle!

Gamefreakgc

Before changing your VAFM readings, grab a sharpie and mark where it was at before. You don't want to be guessing when it comes to fuel trims, long-term rich or lean will eventually have effects on your engine, such as premature cat failure or leading to spark knock.

PS: It's probably not timing, or electrical. Your throttle body is probably sticking open because it's dirty. And it's supposed to idle up a little anyway, like maybe 100-200 RPM. Now if that happens when you press the brake, that's another issue.

Gevo

EDIT: RJR (not Gamefreak)

thanks for that explanation! Yes, i meant to do the 02 sensor work as well, it was mentioned here to me, but I put it later on the to do list and ran out of time. Sat morning I will test the outputs of the 02 sensor and see where to go from there.

The 02 sensor is new, the cat is new... Engine temp sensor is new... but I have all the old ones to swap out and see if I get different results.

Thanks again!

PS: I still suspect the ECU itself being broken to some degree since the VC and E2 lines were shorting for a while... If I can find someone with the same one to swap and test... that'd be nice.

Gamefreakgc

Not about to take credit to the O2 posting that was RJR. He's right though, I've done half those tests he described in chasing my own air/fuel ratio issues. It helps if you have a good multimeter that refreshes quickly (or an old analog voltmeter), if not then it's not quite so accurate.

Gevo

Lol. I meant RJR! Sorry man.
I would love o get an analog multimeter

Gevo

Alright! I got home and took my time to read through your post again RJR, first of all I really appreciate your and everyone else's time that you put in here with thorough and clear descriptions...

Furthermore, the quoted portion below is very useful information for me because at this point I am pretty sure that mechanically everything is operating properly and that the problem is the ECU is spraying to much fuel. I'll start by checking the O2 sensors readings, and go through it before I take it to the mechanic...

If you guys have more ideas to add to the quoted list below, please list it!

Gevo

Guys, one more thing I want to throw out there.... I purchased the Denso platinum spark plugs... I keep reading that the best ones for this engine are the regular cheapo Densos... I was thinking can this have anything to do with anything?

Gamefreakgc

Platinum plugs wouldn't be enough to make you not pass smog. They still work just fine.

Gevo

Fyi: I had a few minutes today and tried to see quickly what kind of values the ecu is getting for O2 readings... well the not so great quality digital meter didnt show anything practical. It was about 100mV. I ordered an analog multmeter yesterday so ill test again of course.

I assume if there was no signal or incomprehendable signal (or short?) from O2 the ecu would show a code right?

RJR

The O2 sensor is only operative when it is quite hot, above about 750 degF. So, if the engine wasn't fully warmed up, you should expect to read roughly 0 volts. The ECU knows this and ignores the O2 sensor until the coolant temperature sensor tells it the engine is warmed up.

If you measure the Ox1 terminal on the diagnostics connector, that is a direct connection to the O2 sensor. That should go between 0 volts and roughly 1 volt when it is working. However, it is a very high impedance source, and a lot of analog meters will load it down and give low readings, and also cause the ECU to complain.

If you measure the VF pin on the diag connector, with T1 shorted to E1, that is a buffered and amplified version of the O2 sensor signal. You should see it going back and forth between 0V and 5V, and it will drive any reasonable meter just fine.

Gevo

RJR, I read through most of the documents you linked. At some point it was just interesting for me..

I let the car heat up to its normal operating temp, then held throttle at 2500rpm for about 90 seconds then tested the O2 signal voltages. I feel it can still not be hot enough to operate if operating temp of th O2 is above 700.

Thanks for your thoughts on the multimeters.. this should be fun

RSR

If you're trying to test at idle you might not be getting a reading too.

Not sure of the electrical here, but the 02 sensor is only being read when off throttle and before 70% or WOT. Otherwise it's ignored and factory tables are used to calibrate air/fuel ratios. See the discussions on the flamethrowers for instance and adjusting your rig for optimal A/F ratios.

Imagine there's a troubleshoot in the FSM, but haven't looked. Just a couple ideas that might help. (Then again, maybe not. )

RJR

Sounds like you did the measurement correctly. Mine operates fine under those conditions and gives valid readings. Given that the measurement technique is correct, it's a good indication the O2 sensor or the wiring is defective. If the O2 sensor puts out near 0V, it's telling the ECU that the mixture is too lean. In that case the ECU will dutifully enrich it, causing you to fail emissions in the way you have. A working O2 sensor should not put out 0V while the smog test is showing excess HC and CO.

I would expect the ECU to throw a code, however, if the O2 sensor is stuck at some low voltage. You might want to pull codes even if the CEL isn't on, just to be sure.

To be sure of not loading the O2 sensor with a cheap voltmeter, make sure you also measure the VF terminal with TE1 shorted to E1. That will give you the buffered version and tell you exactly what the ECU is seeing.
Then, remove the short on TE1 and measure again. That tells you what the ECU is trying to do to the mixture. If it is near 5 volts, the ECU is trying to enrich the mixture as much as possible. If it is near 0, it is doing its best to lean it out. If it's near 5 volts it's a good indication that the ECU is getting bad data from somewhere.

Gevo

RJR, yesterday I tested with both the terminals shorted and not shorted. To be sure it is heated properly, I'm going to go for a long drive and try the test again.

So, to further understand the system, if the O2 sensor isn't quite heated up properly and I test the terminals at the data-link, what voltage should I expect to see? Usually when the multi-meter is showing a few hundred millivolts it's telling me that it's getting no information at all. Would this be the case if the O2 sensor isn't heated to it's operating temp? Or would I be reading some other information at the data-link that would tell me O2 sensor isn't in the loop yet...? I don't recall reading anything about this question in the texts....

RSR, every idea is helpful in that it makes me think!

RJR

Your voltage reading will depend somewhat on the quality of your voltmeter and where you connect the ground lead. I measure about 50mV with an Agilent hand-held with the ground connected to E1 on the diag port when the engine is cold. If you connect your meter ground to the frame somewhere, you could easily pick up another 100mV of ground variation in the system.

If your engine coolant was up to temperature and you ran the engine at 2500 rpm for 90 seconds, I would expect you to see voltage out of the O2 sensor. It's possible you're not making connection in the diag port. The connector sockets on my port are all filled with dielectric grease, so sometimes it's hard to see if I'm in the connector or beside it.

If you put the meter on the Ox1 terminal, you should see voltage pretty quickly. That's the direct connection to the sensor, and it heats up fairly quickly, since it is basically sitting in the red-hot exhaust stream. On the other hand, when you measure the VF terminal with T1 shorted, you're getting the ECU processed version of the signal. If the ECU is running open loop (engine still cold, or at idle, or at full power), the ECU sets that voltage to zero regardless of what the O2 sensor is doing. At 2500 rpm warmed up, though, it should track the O2 sensor (except the range is 0-5V instead of the 0-1V you would see at the Ox1 terminal).

What might be helpful is to get about 8 feet of twin-conductor solid wire, 22 gage or so (left-over garage door opener control wire works great) and run it from the diag port Ox1 and E1 terminals into the cab. Hook it to your voltmeter there, get an assistant to do the driving (so you don't crash while focusing on the voltmeter!), and go for a drive. That way you'll be able to read the O2 sensor under actual driving conditions. You definitely should see activity while under partial load, cruising, etc.

I've attached a diagram with a bit more detail about the diag connector.

Gevo

RJR, thanks for the info!
I had previously found a very helpful link for the diagnostic connector.
http://pinoutsguide.com/CarElectroni...c_pinout.shtml

I think i will take your advice about wiring my multimeter to the diag port and driving with it. I have plenty of wire to use (leftover from my many other projects and hobbies)

As soon as im finished with this paperwork, I can take couple hours off work

Gevo

So im about to take a drive with the multimeter rigged up etc. But I wanted to mention again, how does the ecu keeping the PAIR reed valve on fit into all this? On cold startup the pair valve was on. I unplug the vsv and it goes off. What kind of malfunction or perhaps wiring issue would cause this and how would it relate to rich condition.. other than overall messed up ecu...? And t add, after the engine warms up the pair valve seems to g go back to normal operation...

Gevo

I have data. Im going to write it here and add as I get more data.

When connected to Ox and E1, I get 100 mV, multimeter doesnt chirp to note that its getting any voltage. This is during any driving condition.

Pulled over and connected to Vf1 and E1 and shorted E1 to TE1. When at idle voltage shows 4.9, anywhere but idle it shows 140mV. It takes 5 to 10 seconds of idling before voltage goes to 4.9. When adding throttle it changes to about .5 V then goes to 140mV.

Update: I unshorted TE1 and E1 and left VF1 and E1 connected. The whole time it was showing 144.4mV And during hard acceleration it would go to 147mV.

I dont know if 144 mV is meaningful actual data or it is just some residual noise in the system.....

Next step. I will go home swap old O2 sensor in and see what happens with these numbers.

on the way back home I connected the E1 and Ox terminals just to see if I will get the same reading. I did not. voltmeter is at 2.5 mV and is not budging.

RJR

Something sure seems wrong with those O2 sensor numbers. The sensor or the wiring could be suspect.

The 144mV across VF1 and E1 with TE1 open is probably the ECU signaling that it's running open loop, which is consistent with an inoperative O2 sensor. The puzzler is why you're not getting a code.

Sounding more and more like an open sensor/wire