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I am usually passive in this forum and try to figure things out by reading and studying yotatech, 4crawler, marlincrawler forum and all other sources in the www.
Story first:
I own a 1992 Toyota Hilux, xtra cab, 4WD, 5 gear manual, with the 3VZE 3.0L V6 in it.
I bought the truck about 4 years ago in Arizona, fixed it up in Minnesota put a self built slide-in camper in the bed and lived in it for about 2 years, travelling 60 000 miles through the US, Canada and Alaska.
I usually like keeping my travelbuddy up to date. That means - I listen to him, fix malfuction codes in case they appear, use my greasegun regularly and try not to be too hard on brakes, clutch, drivetrain, powersteering and so on..
When coming into California 2 years ago I layed the truck off and kept it at a friends place.
Now, 2 years later, I'm back from germany and I'm trying to put some life back into it.
I did a timing belt job (gosh, that idler bearing was worn out), put a new marlin crawler cluth into it serviced front and rear brakes and am just trying to get it registered in California.
And here is my problem...
That truck would bring me save around most of the continent, never brake down on me and given some tlc be an amazing travelbuddy.
Now DMV - or actually the smog test place - would tell me that its not in good shape..
I keep failing the 15 mph test due to high HC and high CO. I went 3 times already (of course doing major diagnostics and fixes in between) and failed all 3 times..
Seems I do have "incomplete combustion" when being in lower rpm and I do wonder where that my come from.
TEST 1 - all perfomed on 2nd gear and with 1950 lbs rear axle weight (my camper is still sitting on the truck)
After that I did some work on the truck including:
new sparkplugs
new sparkplug-wires
new distributor rotor + cap
new catalytic converter
new PCV-Valve
measured VAFM and intake temp sensor - it is in specs
measured TPS and it is in specs
tested PAIR system with the worksphop manual and I think it works as supposed to
EGR works fine - no NO
went for 2 more tests and slightly worse results...
LATEST TEST - all perfomed in 2nd gear and with 1950 lbs rear axle weight (my camper is still sitting on the truck)
I sometimes do get a code 22 on my dash for about 2 seconds within the first 3 minutes and when the engine is cold. I measured resistance in the engine coolant temp sensor and it is in specs..
I hope its not due to bad compression... But bad compression would result in bad numbers for both, 15mph & 25mph, right?
I do wonder if the weight of the camper is bad for the test?
The technician tells me it doesnt matter, because the dyno-roll is not doing too much of a resistance and the extra axle weight is also being taken into validation at the DMV for setting my individual boundarys..
Any ideas what could cause high O2, HC and CO in lower rpm's only?
thanks you so much already and keep an cruising - or crawling.. ;P
I have a federal version truck, so there is only the one O2 sensor that is right in front of the cat.
I did measure the O2 resistance and it seems to be in spec. (5.8 ohm)
But somehow, I dont get the fluctuating current reading when I try to measure the "Feedback Voltage" between VF1 and E1... It just shows 0.5 Volt constantly on my digital multimeter..
I was wondering if the ECU would throw me a check engine light code when something with the O2 Sensor would be wrong?
would a broken O2 sensor not also mess up the 25 mph reading at 2700 rpm?
A broken O2 sensor is just bad, bad, bad. Why your truck would pass at 25mph I can't say, but I wouldn't expect it to pass at all.
So I'd start with the complete diagnostic on that sensor. http://web.archive.org/web/201003261...01heatedox.pdf One possibility is that the heater in the O2 sensor is out, so that it is not measuring anything at 15mph, but is barely coming alive at 25mph.
In general, high O2 indicates an over-lean condition (e.g, vacuum leaks). If high enough, it can cause mis-fires, which will give you the high HC. http://www.cygnusx1.net/Media/Supra/...taTech/h56.pdf (I'll bet you could hear the mis-fire, if you weren't so used to it. )
There's a good chance it's the O2 sensor. O2 sensors get sluggish in their old age, and don't respond as fast as they should, particularly at low rpm/power when the exhaust isn't as hot. You may or may not get a code under these circumstances. The ohms test only tests the heater circuit, not the actual sensor itself. Get a new Denso ($45 + shipping from Rock Auto), and you'll probably be good to go.
Thanks scope for that tech-manual on emissions! the chart with emission-gases and the ratio depending on lean or rich mixture is amazing and very helpful to see those numbers!!
I just ordered a new O2 Sensor and a new intake manifold gasket (since I reused the old one when I replaced the PCV-valve and valve-cover-gaskets).
I'll keep you posted about my next readings.
due to the over-lean condition...
I doublechecked all the vacuum and intake hoses and made sure there is no leaks that could cause very lean conditions.
question here..
When I bought the truck it would leak power steering fluid, so I replaced the steering gearbox.
I would still have to refill the power steering reservoir even though the pressure hose, return hose, pump and gearbox would be dry.
What I figured out back then was, that this little airvalve that idles up the engine when power steering pressure applies - would be leaking.
So the intake manifold would basically suck power steering fluid through that little airhose, that is supposed to just rise the idle, into the intake and into the combustion chamber!!
Hating that because of 2 little failing O-rings in that valve my engine would suck power steering fluid - I took that valve apart and welded it shut - and I took those hoses out and put vacuum plugs over those openings.
So - the Intake manifold opening for the "idle up hose" is now plugged and so is the little pipe that is connected to that "intake-box" that sits right next to the VAFM.
Plugging up that hoses would be fine, right? - Just wondering, cause the smog-technician gave me a hard time, saying the vacuum hose would not be routed as manufacturer-specs and that alone could fail me the test...
...
Plugging up that hoses would be fine, right? - Just wondering, cause the smog-technician gave me a hard time, saying the vacuum hose would not be routed as manufacturer-specs and that alone could fail me the test...
Yeah, that'll do it. Just tell the California-licensed smog technician that some guy (girl?) named scope103 said "yeah, sure, that's okay ..."
I believe that the your truck will run okay with the idle-up blocked off, but that really doesn't matter vis-a-vis smog. If they want all the original vacuum lines, then you need to supply that. Of course, adding vacuum lines that do nothing is pretty trivial, unless you threw away the control valve. Or, you could get a replacement valve from RockAuto for about $67, and then you can be back to stock.
right! I did pull that valve at a pick'n'pull a couple of months ago, but I'm not gonna put it back in. I dont like the fact, that a little O-ring leaking results into power steering fluid being sucked into the intake..
IMHO - thats not the smartest engineering toyota did here...
My O2-sensor arrives tomorrow. Ill keep you postet.
"Power steering fluid" (actually you better be using ATF in the power steering system in these Toyotas) is just oil at heart, and cleaner with less additives than most engine oil. Doesn't hurt the engine at all to burn a bit of it any more than the oil that gets sucked in through the PCV valve or that sneaks past the rings. It just goes up in smoke when it hits the cylinders. No need to get on Toyota's case for this one.
"Power steering fluid" (actually you better be using ATF in the power steering system in these Toyotas) is just oil at heart, and cleaner with less additives than most engine oil. Doesn't hurt the engine at all to burn a bit of it any more than the oil that gets sucked in through the PCV valve or that sneaks past the rings. It just goes up in smoke when it hits the cylinders. No need to get on Toyota's case for this one.
^^ I agree.
You could also complain that having coolant passages in the intake is stupid or how a head gasket needs to seal combustion, coolant, and oil.
Plus, an "o" ring is not that expensive to replace.
ok. taking it..
I wasnt aware of how bad that fluid could be for the engine and maybe rusult into wearing piston rings or creating buildup around the valves. And since I never felt that the 3VZ-E needs to idle up at all for keeping the powersteering strong - to me that little valve was just useless and only creating pain.
back to topic though.
still waiting for my O2 sensor, but I used the afternoon yesterday to diagnose my engine coolant temp sensor and to check my timing.
Coolant temp sensor is in specs.
I know there is plenty of "timing threads" out there but there is something else I ran into.
My timing was set at about 13 degrees BTDC.
So I connected the TE1 and E1, fired up the engine and set my timing to about 8ish degrees BTDC.
When the engine idles (its set around 800 rpm) the timing is spot on!
As soon as I open the trottle a little the timing sets off and advances to - I would say about 20 to 25ish degrees BTDC
Im wondering if that is supposed to happen that early? I get that the timing wants to be earlyer in higher rpm's, but to me it appears the timing moves too early - right after idle..
I also wonder - Isnt the ECU supposed to keep the ignition timing at exactly 8 degrees, since the TE1 and E1 are connected...
Im just wondering if I did something wrong here, or if that my be showing me issues about some kind of ECU-failure..
I know there is plenty of "timing threads" out there but there is something else I ran into.
My timing was set at about 13 degrees BTDC.
So I connected the TE1 and E1, fired up the engine and set my timing to about 8ish degrees BTDC.
When the engine idles (its set around 800 rpm) the timing is spot on!
As soon as I open the trottle a little the timing sets off and advances to - I would say about 20 to 25ish degrees BTDC
Im wondering if that is supposed to happen that early? I get that the timing wants to be earlyer in higher rpm's, but to me it appears the timing moves too early - right after idle..
I also wonder - Isnt the ECU supposed to keep the ignition timing at exactly 8 degrees, since the TE1 and E1 are connected...
Im just wondering if I did something wrong here, or if that my be showing me issues about some kind of ECU-failure..
I think that's normal behavior. Mine does the same thing. I'm pretty sure the timing is only fixed when two conditions are true:
1) TE1 is jumpered to E1
2) The TPS idle switch is closed.
If timing were fixed at +8 deg regardless of rpm when TE1 is shorted to E1, the engine simply wouldn't run much above an idle, and if it did you'd likely have flame shooting out the exhaust as the late fuel ignition resulted in fuel burning well after the exhaust valve opened.
Basically you are trying to get as close to 1.0 as possible. Enter your numbers into the calculator to see if your are running a bit rich or a bit lean. Odds are you are running a bit rich and need to adjust your VAFM spring about 2 -3 clicks lean. BUT- don't open your VAFM until you've done a tune-up, checked your O2 sensor(s), and seafoamed the carbon out. As a last resort, if you have to adjust your VAFM spring, use a razor or knife or box cutter to slice (carefully) the silicone from the plastic cover on top of the air filter box. They don't like you tampering with your VAFM so make it look like you never did **ALWAYS MARK (with a sharpie) WHERE THE ORIGINAL SETTING IS!** then adjust the spring to where you need it to be.
Then reset your ECU computer by pulling the fuse or pulling the positive cable of your battery, waiting a few seconds, then plug it back in. Take it for a drive for at least 10 miles.
spec for the timing in the 3VZE is 10 - they will give you about 2 degrees either way so adjust your timing accordingly. Also adjust your idle to where it is 800 RPM when hot.
How would adjusting the VAF affect lambda? The ECM takes readings from the O2 sensor, and adjusts the mixture (via injector open time) to drive O2 to a minimum value. This is all without any regard to the VAF reading.
The VAF does provide the base number in air flow changes, but if the setting of the VAF is off then it's just a matter of learned fuel trim.
If the ECM is unable to use learned fuel trim to bring the mixture to the right place, then the problem is definitely not in the VAF. Unless someone has already tampered with it after it left the factory.
I think there is a reason why Toyota so carefully sealed the VAF.
As scope103 says, no need to adjust the VAFM, at least not yet. (However, do test it for proper operation. If the VAFM has "dead spots" in its range, it could cause mixture problems by causing the ECU to operate on the wrong portion of the fuel trim map. Adjusting it won't fix that, however.) The ECU should be able to pull the mixture into control based on the O2 sensor. If that's not happening, there are two signals that can help sort out what's going on.
1) VF1 - this signal is the learned fuel trim. In closed loop operation, it should be 1.25, 2.5, or 3.75 volts. If it is stuck at or near 0v, it means the ECU thinks the mixture is rich and has reached the limits in trying to correct it. If it is stuck at or near 5 volts, it means the ECU thinks the mixture is lean and has reached the correction limits.
At this point you know what the ECU thinks.
2) The next step is to check the O2 sensor output. If it is stuck high (around 1V), it means the O2 sensor thinks the mixture is rich. If it is stuck low (near 0V), the O2 sensor thinks the mixture is lean.
I would suggest warming up the engine, running it at 1500 rpm (where you have the problem), and looking at both of these signals. Here are the possible combinations.
- VF1 betweeen 1.25V and 3.75V, O2 sensor switching between (approximately) 0v and 1v about once/second. This is proper closed loop operation. If the engine is failing HC or CO emissions under these circumstances, the most likely causes are a bad catalytic converter, or a misfiring cylinder.
- VF1 at 0v, O2 at 1 volt -- ECU and O2 sensor agree the mixture is rich. It could mean the O2 sensor is giving bad data to the ECU. It also could mean you should look for something dumping in excess fuel (leaky injector, cold start injector stuck on, etc.), or a faulty sensor causing the ECU to operate on the wrong portion of the fuel trim map.
- VF1 at 5v, O2 at 0V - ECU and O2 sensor agree mixture is lean. It could mean the O2 sensor is giving bad data to the ECU. It also could mean you should look for a vacuum leak or a plugged injector or a faulty sensor.
- VF1 at 0v, O2 at 0V - ECU and O2 sensor disagree. ECU thinks mixture is rich, O2 sensor says it's lean. In this case it's likely the O2 sensor is not communicating properly with the ECU. Look for faulty wiring to the ECU.
- VF1 at 1V, O2 at 1V - ECU and O2 sensor disagree. ECU thinks mixture is lean, O2 sensor says it's rich. Again, The O2 sensor is not communicating properly with the ECU.
How would adjusting the VAF affect lambda? The ECM takes readings from the O2 sensor, and adjusts the mixture (via injector open time) to drive O2 to a minimum value. This is all without any regard to the VAF reading.
The VAF does provide the base number in air flow changes, but if the setting of the VAF is off then it's just a matter of learned fuel trim.
If the ECM is unable to use learned fuel trim to bring the mixture to the right place, then the problem is definitely not in the VAF. Unless someone has already tampered with it after it left the factory.
I think there is a reason why Toyota so carefully sealed the VAF.
I stand corrected !
Doing a quick lambda calculation on both of his smog tests, I get--
Test 1 = Lambda 1.002 Cat eff = 75%
Test 2 = Lambda 1.002 Cat eff = 0%
which leads me to believe it's not fuel trims or air/fuel mixture, but a bad o2 sensor or bad cat as stated earlier in this post. Thank you... always happy to learn, even if I learn from my mistakes.
That's a good article, @GO_BLUE. Thanks for sharing it. Unfortunately, the IM240 test used here in Colorado reports emissions in grams/mile, not % or ppm, so I don't know how you'd calculate lamba from that information. Seems like you'd have to know grams/mile of total exhaust to figure that out.
Thank you guys for all the amazing help and info on that topic!! Not only in this thread I find soooo much helpful info on keeping my truck alive and I would say you guys definetely help me becoming a better mechanic!
The Lambda-Calculator is awesome and should maybe somehow make its way into a "sticky thread" so its going to be found since its an amazing diagnostic tool. What do you think?
Yesterday 2pm my Denso O2 Sensor arrived. Installation - after having some pain getting the old one off - was done in about 15 minutes and I could reset the EFI and fire it up.
Getting under the hood and playing with the throttle body and rpm's I think I could tell already that the engine sounded a bit different. Maybe I make this up now, but I had the impression the "combustion sound" (not the valves or the injectors) sounded a little "lighter" or "higher"..
Anyhow, I hooked up my multimeter and went for the full O2-sensor diagnostics and - BAM - It was working closed loop operation!
I drove a couple of miles to make sure there is no malfuction coming up and I went for the smogtest:
After telling him that Scope said "its totally ok to have those vaccuum lines for Aircondition- and powersteering-idle up taken out" he agreed with that and we went for the dyno-run.
PASSED WITH FLYING COLORS
The technician was pretty impressed and said - "Wow, thats very clean now!"
So emissions is done now and I finally can go to DMV. - thanks guys!!
Anyhow, out of curiosity I put those numbers into the Lambda-Calculator and was surprised about the readings.
To me it appears that the Lambda-value was better with the broken O2 sensor and would be more off with the new one.
Here is the reading from the last Test that made me pass emissions:
At 15 mph the lambda value is still VERY lean (between 1.116 - 1.206)
At 25 mph the lambda value was spot on (1.002) with the broken O2 sensor and is now a little lean (1.021) with the new O2 sensor.
I'm wondering if this could be an indication for a vacuum leak somewhere around the intake?
I'm also wondering how the ECU figured out a good mixture with a broken O2 sensor and has trouble getting the right mixture with the new one..
Not being hypocrit here. I'm happy the truck runs well and I passed smog - just trying to understand whats happening.
Congratulations on getting back on the right side of the emissions laws. Those are great numbers! Thanks for sharing your final results. You are welcome to all of the advice from here - it was a pleasure dealing with your situation, because:
1) you gave a clear statement of the problem with supporting data.
2) You approached the problem methodically,
3) you did the tests we asked you to.
In other words, you were a model client. Wish everyone was so easy to work with.
I'm not a lambda expert, but my guess is that the test facility might have some slight errors in the measurement of O2 and CO2. Since those gases aren't part of the "pass/fail" criteria, the stations might not be too strict about accuracy for those measurements. They will affect the lamba calculation, however.
I just replaced my original O2 sensor on my '94. Emission readings have been creeping up over the past few years, but not to the point of failing yet. I'm taking it in later this month, so it will be interesting to see how much improvement there is with the new sensor.
05-28-2018, 04:05 PM
;P
**ALWAYS MARK (with a sharpie) WHERE THE ORIGINAL SETTING IS!** then adjust the spring to where you need it to be. 
