Found this forum and decided I would post based on the example thread that I read and the shear number of intelligent and knowledgeable responses. Here it goes:
I have a V6 3.0 3VZE ’93 Toyota 4x4 Pickup which has sat for about 5 years. Up until this point, the truck had passed its emissions in Arizona easily. To get the truck running, I had to drop the fuel tank and replace the fuel pump, as it had failed. While the pump was out, I took the time to clean the tank of debris and the gas tar that had formed around the sump and in the fuel pickup and return lines. At this time I replaced the fuel filter and cleaned the line from the filter to the pump with an air compressor (about a 4.5 ft length) where no blockage was found. I flushed the coolant system, changed the spark plugs, air filter, oil and oil filter, some chewed up wires which a rat had damaged and ate through in the engine bay, and some vacuum lines. I have gone through two full tanks of fuel with additives and three full tanks with no additives. The first tank was high test 91 octane with lucas Oil Products upper cylinder fuel treatment (supposed to lubricate and clean fuel system) and the second tank was regular 88 octane with Gummout 10 oz. concentrated fuel injector cleaner. The truck now starts and runs fine with no visible smoke and normal operating temperatures as indicated by the factory installed water temp sensor in the dash.
Now in California, the vehicle has failed with the following numbers at an ASM test:
15mph: [RPM 1684, %CO2 Meas 8.8, %02 Meas 8.1, HC Meas 187 ppm (MAX 92), CO Meas 0.73% (MAX 0.49%), NO Meas 1577 ppm (MAX 533)]
25 mph: [RPM 2721, %CO2 Meas 9.1, %O2 Meas 8.1, HC Meas 62 ppm (MAX 57), CO Meas 0.17% (MAX 0.59%), NO Meas 544 ppm (MAX 786)]
The ignition timing is at 8 deg BTDC (nominal 5 deg).
I should mention that Headers have been installed, but are supposedly CA legal with an EO number manufactured by Downey Offroad and retain all emissions equipment.
Judging by how much tar was in the fuel pickup and return line (causing 100% blockage), I suspect that some or one of the injectors are either leaking or clogged. I believe this would cause the high NO content I am seeing at the 15 mph loaded reading, along with the high HC and CO numbers. If one or more of the cylinders are lean enough to cause a misfire, the HC ppm increases as it is fuel out the tailpipe while in other cylinders the burned lean mixture is causing hotter engine temps, increasing the rate at which Nitrogen Oxide is created.
A question about the numbers: How is it possible that I am passing the loaded 25 mph tests for NO and CO, but GROSSLY over the max limit for NO and over for HC and CO at the 15 mph loaded reading? Is it possible that increased back pressure from the 25 mph test is finally closing a stuck EGR valve? How do we explain what is going on with the HC and CO readings? I am tempted to go out and replace the injectors, but at around $160 per injector it’s not a cheap fix; ESPECIALLY if it doesn’t work.
I had a similar problem with my 93 Corolla. If you have an EGR valve (my car didn’t) get it cleaned. Your high NOX emissions (due to the age of the vehicle) is probably caused by carbon buildup on your pistons, throwing off your compression ratio, and causing the truck to burn rich. My diagnosis? Seafoam the engine, to clean the pistons and get new spark plugs and wires. If you’ve been using THAT much fuel additive, you’ve probably got ash deposits on your spark plugs out the ying yang. If you take your truck to Toyota, they’ll charge you a nice grip ($400+) to clean your pistons, but I’d Seafoam it first, change the sparks, check the Charcoal Canister(you may need a new one) and the O2 sensor, and the then get it tested. If that doesn’t work, Take it to Toyota, with the failed test. It should pass though. The only other thing it could be is the Catalytic Converter, but I doubt it(they don’t wear out, really-it’s just a box of radioactive chemicals with a pipe in it).
This may be a dumb question, but is this a California truck? I believe that up until they switched to the Tacomas, both the 22R and the 3VZ came in either California or 49 state versions. If the truck isn’t a California truck, it’s not going to pass smog there. The emissions sticker should say.
Otherwise, I would agree with scrutinizing the EGR valve. The fuel injectors could be a problem but if you’ve got no other symptoms they wouldn’t be at the top of my list. The other thing I’d suggest is double-checking the timing. Specifically, you should check the timing before you jump the diagnostic terminal and then check it after you do so to make sure that it is in fact changing. A common problem on the later 22R engines was that the TPS would wiggle out of adjustment, and so the timing wouldn’t change at idle like it’s supposed to. Perhaps the same thing can happen on the V6’s.
Also, I disagree with OnyxGold’s advice to take it to Toyota-- there’s not much point to taking a truck this old to the dealer. If you do take it somewhere, an independent mechanic (preferably a Toyota specialist) should be able to do just as good of work for less.
The CO2 reading look a tad low, and the O2 reading look way high to me. I was a smog tech before loaded mode testing, and those two numbers just don’t jibe with a properly running engine. Loaded mode might change things a bit, those O2 readings just don’t float my boat.
Anyway on to the other numbers.
High HC can be rich or lean.
High CO is rich.
High NOX is either lean or misfire.
Your i15mph numbers look like a poorly spraying injector or a cat converter that is not warm enough at 15mph.
I am guessing that you have one or two bad injectors. They are spraying, but not very well.
Retarding the timing (if adjustable) should lower the NOX
One hint after you do the repairs. Go for a 10 mile drive. A hard 10 mile drive. Full throttle starts. high speed. Then take the car to the smog station and don’t turn it off until they test it.
Good luck
Rick