Lowering the HC ppm reading for emissions - 1989 Subaru DL

Any codes? any problem tune up, catalytic convener, burning oil.

i can be, only 2 things, or both.
1: engine running way too rich.
2: dead cat.
(both happens, too)
replace the cat, might be cheaper that full engine diagnosis and repair.
in a real shop we test the cat. using up and down stream tests.
with the 5 gas analyser.
but the truth is a new CAT can hide a very filthy running motor.

hi i have a toyota camry 1992 and it didn't pass emissions its reading 1048 no ppm rpm and it will allow 910

run the fault codes to find the faulty sensor
sensors that control the exhaust emissions are the HO2S ( heated oxygen sensors in the exhaust manifold/s
the O2 sensor ( oxygen sensors after the cat converters ) and the EGR unit that recycles exhaust gas back through the engine to re-burn the gasses

Definitely check the tune-up items. I have also had O2 sensors go bad on these trucks.

How well does the vehicle run?

Assuming that the engine did pass the EGR function test on the emission test results, and the MIL (Malfunction Indicator Light) or check engine light is not on when the engine is running, and if you are not sure when the last time it was that the engine had a complete tune-up, with distributor cap, ignition rotor, spark plugs, spark plug wires, air and fuel filters, then a complete tune-up would certainly help, and if the engine oil and oil filter have not been changed in a while, then they should also be changed before an emission test because long used engine oil traps carbon and it will show up as higher CO on the emission test because the emission analyzer will be able detect the higher CO from the engine oil through the PCV valve.

However, it would seem from those HC readings that there is a vacuum leak, and carefully inspect all of the vacuum lines for any cracks or damage, (especially the vacuum line to the fuel pressure regulator) because cracks in the vacuum lines seem to like to hide underneath the lines.

The emission label under the hood should have the vacuum line routing diagram printed on it, and the vacuum lines should all be checked to be certain that they are all connected correctly.

Here is the firing order diagram for that vehicle to help assist you tune-up the vehicle.

possible but could be head gasket or valves , or worn rings and is by passing the pistons going straight out the end ...or maby settings are wrong ? try carb cleaner and inspect visually air-filter etc.

1993 DODGE CARAVAN 3.0 HCPPM LIMIT 144 READING 172 NO PPM LIMIT 965 READING 1024

have you had the the engine codes pulled and reset?
and if so what are your engine codes?
i dont know of any car that will pass emissions test with the engine light on.
we cure your trouble that caused your engine light to come on and you will pass your test.
later
paul

Do an oil change with 20W50 oil (or one grade higher) to prevent blow by during the test.

You current oil has HC from blow by though the rings.

Do a fresh oil change will lower the HC.

========
Change spark plugs,wires,cap and rotor if they are over 24,000 miles
========

Make the smog check appointment for the EARLY MORNING. Colder air will help the fuel burn better.

========

Clean or change the air filter and pcv valve.

Clean Mass Air Flow sensor with CRC Mass Air flow cleaner or electronic part cleaner.

========

Do a quick wipe down on the wires and cap to take the moisture off.

========

Check spark plug wire contacts for corrosion.

========

Fill the tank to around 3/4.......just in case your fuel pump is weak.

========

Ran the truck for 20+ minutes on highway before the test.

========

Do not carry excessive cargo on the truck bed.


These are the little things I would do to get the HC and CO down.


Please post more information on the comment window.