AHHHH I Failed Ontario Emission Test?

Question

I have a 1993 Toyota Pickup, 22RE I4 engine with EFI. 300Km...Good compression,no oil burning, 5 speed manual.
FAILED HC Test limit 66ppm reading 209....PASSED HC Curb Idle Test limit 200/ 129
FAILED CO% limit 0.37 reading 8.34.........PASSED CO% Curb idle limit1.00/0.18
PASSED NO limit 968 reading 36................N/A
RPM @ 2525.............................................RPM @ 867
Dilution 17.4.............................................10.3
These results seem to indicate a very rich mixture at higher RPMs. Prior to testing I did a complete tune up including new NGK Iridium plugs (correctly gapped), wires, distributor cap and rotor, PCV valve, air and fuel filters. I set the timing to specs (with Dianogtic terminals jumped). I changed the oil (synthetic) and filter. The exhaust system was shot, so I replaced the Cat and muffler with new Magna Flow low restriction (2 1/2") parts. I reused the original front pipe with the O2 sensor in it....a header and new induction system will follow when I have $$$$. I did not adjust the valves as they are not noisey.
Since the test I have tested everything I can think of that would give high HCs and COs.
This truck uses an Air Suction system (Passive/Pulse air system, not an air pump)...it is working properly.
I've tested the Coolant Temperature Sensor both in the truck and on the bench...it's OK.
I've tested the vacuum switching valve for the high temperature line pressure up system....OK.
The fuel pressure regulator seems to be working properly, but I don't have a gauge...?
The Dash Pot filter is clean and it works OK.
There are no codes stored in the ECM. It is not an OBD-II system.
When I tested the O2 Sensor initially (after warm up) I was getting readings of 150-200mV @ idle, 800-900mV @ 2500 RPMs. Later it jumped to 500-600mV & 900-1400mV...?
My Haynes Emissions Manual says to watch for a voltage drop when you disconnect a vacuum line(too lean)..it did, and a voltage increase when propane is added through a vacuum line(too rich)..it did.
Do you think the O2 Sensor ($200) is Boffed?...or is the ECM not adjusting the fuel mixture?...or could the Magna Flow Cat be at fault?...too low back pressure maybe?
HELP!

Answer 1

Change the stinking O2 sensor and hope you haven't screwed up your new cat. $68.99 at Auto-Zone. If you take care of your CO you will get rid of the HC issue. You probably needed all the above repairs however your looking in the wrong direction. With a CO problem you want to examine your fuel related systems. Since you don't have trouble codes it can be hard for a do-it-yourselfer. If by some chance the oxygen sensor doesn't do the trick then you may be looking at vacuum leaks, leaky injectors, most likely a bad computer. I would start with the O2 sensor, remove the plugs and let them dry over night. Get in the truck and get it hot. Drive it hard for about 40-50 miles then head straight to the emissions test and leave it running. You've done good with most of your checks. From the test and readings it sounds like your O2 sensor is lazy. I bet the truck sits before the test is ran and the vehicle hasn't fully warmed up staying in open loop causing it to run rich.

Answer 2

You clearly have a fuel control problem.
Assuming that the temp sensor is indeed within spec, check the thermostat. It should be running at something close to 200° F (check at the thermostat housing). If less than 150° F, replace the thermostat.
The NOx reading is low, but check anyhow—
Is there possibly an exhaust leak upstream of the O2 sensor? If so, the O2 sensor will believe the trucklet needs more fuel.
Is the PAIR unit still pushing air downstream after full warm-up?
The PAIR system should disable itself after warm-up, but if it is still active, again the O2 will see a very lean condition and add fuel.
Another area to check is the injector(s). If there is one or more that the pintle will not close well at higher RPM, it could dribble, or draw excess fuel.
Finally, if the O2 is slow, or lazy, or locked for whatever cause (poor engine ground) It could drive the engine rich though as a rule, this will only generate a 5% or so CO reading.
You said your dilution was 17.4%. That seems a bit high to me, but we measure differently down here. If the oxygen level is more than 1.5%, check for air in the exhaust stream. It shouldn't be more than 1.5%, and less than .02% is desirable.

Happy Motoring

Answer 3

You gave plenty of info. I would change the O2 sensor if it is the original, maybe you wanna replace the EGR .An Ol trick in the USA was to disconnect a vacuum line just before inspection.Just disconnect one that allows the engine to continue idling.Another trick was to add a quart of pure Alcohol to an almost empty tank of gas.But then , these cars were carbureted and none of this computerized stuff.Now adays with these newer cars, even a loose gas cap can change the way an engine runs.Good Luck

Answer 4

Your exhaust is throwing off the jetting! and yes change the O2 sensor.