91 3SFE Failed Emisison test

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)?:screwy:

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?

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.

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.

"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

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 :nono: but rather a pcv system.

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

Regards,

JOET/CAMRY

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

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?

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

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

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.

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.

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

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

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.

How's the compression? Low compression = worn rings = higher oil consumption = high hydrocarbons.

How's the timing? Timing misset = poor combustion and wasted fuel = high hydrocarbons.

An O2 sensor covered with soot is an indication of poor combustion. How did yours look?

Your sticking idle can't be helping. I would either lube the cable or as already suggested SeaFoam the throttle body or both.

Don't have a compression gauge so can't answer that question. Timing I will double check. The old O2 sensor was soot covered when pulled. I have cleaned the throttle body, seafoamed the engine, fixed the idle and still can't quite pass the emission test.

that 02 sensor helped quite a bit at the 2500.
think your cat might be bad?

Not sure about the cat. I have a parts car and pulled the cat off it so will try swapping that one in this week to see if it makes a difference. The ceramic grid on the "spare" cat looks nice and clean so I am hopeful.

Update: Pulled the cat and found 95% of it's internal packing gone so am in the process of replacing it. Was slowed by one of the exhaust manifold studs pulling out of the head (did it with my fingers: !@#$ I must be strong!) a run to the parts store for a helicoil on Sunday evening only to discover they don't have the appropriate drill bit so I'll get one today. Once that's resolved I'll button it all up and I'm certain I'll pass emissions. Will post the final results.

Swapped in the used cat and finally passed smog with dramatically lower numbers:

1st results 2nd results 3rd results 4th results
2500 rpm test
CO% .72 .78 .67 .21
HC 181 186 146 24
Dilution 14.72 14.15 14.71 15.01

Idle test
CO% .49 .56 .52 .12
HC 377 328 280 23
Dilution 14.69 14.56 14.40 14.79

Thanks for the help. Interesting to see that the engine could almost pass without a cat and equally as interesting to see the drop with a functioning cat.

think your cat might be bad?

I win :bananasmi:boink:

Good call

idmetro - Great to hear your headache is over. It's too bad you had to go to the last resort (cat) to fix it. This is a great thread for others to look at. You showed results of every step you took and quantified them with test results. It's among the best threads on the forum for emissions problems. A big thanks to you.

xfeejayx - When's the party!

idmetro - Great to hear your headache is over. It's too bad you had to go to the last resort (cat) to fix it. This is a great thread for others to look at. You showed results of every step you took and quantified them with test results. It's among the best threads on the forum for emissions problems. A big thanks to you.

xfeejayx - When's the party!

I'm with RIP, thanks for the feedback.

Classes start up again Wednesday, party is every day till then :evillol:

Thanks for the compliments. I have found this forum immensely helpful and hope others might be spared unecessary pain/frustration/expense as well as being able to get more life from their Camry by what I learned.

One thing I should mention is if you find yourself in a similar position you can (at least on a 91) disconnect the exhaust pipe from the bottom of the cat, shine a flashlight in there and get a pretty good view of the physical condition of the cat (all for the $2.50 cost of the gasket). In my case it was immediately obvious that a change-out would be needed. I found it easier to pull the cat, the exhaust manifold and the bracket supporting the cat to the engine block as a unit and then work on them outside of the engine bay.