91 3SFE Failed Emisison test

[idmetro]

My 91 Camry with 195,000 miles on the clock just failed its emission test with elevated HC readings of 337ppm at idle versus a max allowable of 220ppm; HC is also elevated at 2500 rpm (181 vs. max 220). Thoughts on the likely culprit(s)?

[KimMG]

catalytic converter
O2 sensor
improper air/fuel mixture
Have you checked for any codes?
When was your last tune-up?
Do you have the results from the last emmissions test to compare?
How's the car running?
How's the fuel economy?

[RIP]

All the above. Hydrocarbons are the "chuncks" in the emissions. High HC indicates incomplete combustion and can have many causes.

If you don't have any error codes and you haven't done a tune up lately I would change the spark plugs, air filter, and check the PCV system hose between the valve cover and the throttle body for blockage. The PCV system is there to limit HC emissions. Consider changing the plug wires and distributor cap/rotor if you have one. A cat converter that isn't hot enough can make you fail. It is most efficient when it's hot so make sure you've put plenty of miles on it before you test. Wouldn't hurt to leave it run right up to the test.

[idmetro]

I believe I might have the results from the prior emission test. I'll see if I can dig them up. Haven't checked for codes yet. Car running ok but has developed habit of not idling down when throttle released; you can manually get it to go to idle by nudging the linkage but no apparent bind point. Fuel economy down a couple miles per gallon from typical but the weather has been quite cold so a decrease was not surprising to me. Has been approx 30K miles since last tuneup. Will also change oil as it is due.

[Mike Gerber]

"Car running ok but has developed habit of not idling down when throttle released; you can manually get it to go to idle by nudging the linkage but no apparent bind point."


Clean out the throttle body. That is the usual remedy for any type of sticking of the pedal/cable. If you are not sure how to do it yourself, do a search for "throttle body cleaning". It has been covered numerous times.

Mike

[JOET/CAMRY]

Originally Posted by RIP

All the above. Hydrocarbons are the "chuncks" in the emissions. High HC indicates incomplete combustion and can have many causes.

If you don't have any error codes and you haven't done a tune up lately I would change the spark plugs, air filter, oil and PCV valve. Consider changing the plug wires and distributor cap/rotor if you have one. A cat converter that isn't hot enough can make you fail. It is most efficient when it's hot so make sure you've put plenty of miles on it before you test. Wouldn't hurt to leave it run right up to the test.

the 1991 Camry 3sfe motor does have a distributer cap and rotor. it does not have a PCV valve per say but rather a pcv system.

Your slipping RIP. doesn't your 1987 Camry with a million miles on the clock have a 3sfe 4 cylinder motor?


Regards,

JOET/CAMRY

[RIP]

Yup ya got me. Is that better (see post #3)? Thanks for watchin my 6.

[idmetro]

Thanks for the info. I'll start my work on the items previously mentioned.

I have a parts car (same engine and year) that I can pull from. My daily driver was made in Japan but the parts car was assembled in the US. Are the fuel/emission parts interchangeable?

[KimMG]

For parts interchangeability, look at the parts numbers on the parts you want to trade. There were some differences between the assembly lines.

[caguy714]

Hey, mine pass easily when I changed new distributor around $140. It passed easily because in California, we have to smoke check every 2 year, the year in between we need to only buy sticker. But when I check with a buddy in his shop, I got high HC or Unburned fuel, I changed the new distributor, because I water sprayed the engine and killed it. It passed easily. Good luck

[xfeejayx]

when in doubt, seafoam it. Can help the throttle body sticking (seafoam deep creep), and will clean up your combustion a little bit (the regular stuff), especially if you have never done it before, and especially since you have so many miles and aren't getting complete combustion. ToysRme wrote an excellent how-to. Search the camry forum.

[blu88notch]

Go in with new oil.
Pull your air filter
Make sure your plugs aren't worn
Add 2 quarts of Methylhydrate to about 6 gallons of 87 octane.
Beat on it and bring it in hot, and let it idle while wiating for test.
Pass.
Worked for my 200,000 mile 89.

[idmetro]

Update:

New cap, rotor, wires, plugs, air filter, oil change, pcv line was obstructed - cleaned it out, egr valve clogged - cleaned it out, cleaned up the throttle body. Ran the car down the highway for 25 minutes to make sure it was warm and retested it, did not pass. I did note that when I pulled the old plugs the depsits on them were whitish not tannish as I had expected. Ideas on where to go from here?

1st results 2nd results
2500 rpm test
CO% .72 .78
HC 181 186
Dilution 14.72 14.15

Idle test
CO% .49 .56
HC 377 328
Dilution 14.69 14.56

[blu88notch]

Methylhydrate. It's one "snake oil" that works.
2 quarts to a 1/2 tank max.

[idmetro]

Originally Posted by idmetro

Update:

New cap, rotor, wires, plugs, air filter, oil change, pcv line was obstructed - cleaned it out, egr valve clogged - cleaned it out, cleaned up the throttle body. Changed the O2 sensor (3rd results).
1st results 2nd results 3rd results
2500 rpm test
CO% .72 .78 .67
HC 181 186 146
Dilution 14.72 14.15 14.71

Idle test
CO% .49 .56 .52
HC 377 328 280
Dilution 14.69 14.56 14.40

Results headed in the right direction but still not there.