Is it hard to adjust the valves on a 91 camry v-6?They were never adjusted yet and it has a little over 200,000 miles on it.The only reason I ask is even though it run good it seems my m.p.g. has dropped from 26 to 18 and it flunked the last emmission test putting out too many hydrocarbons.The mileage drop might have been that I put some stuff in the tank that was supposed to increase my mileage but instead seems to have decreased it.

 

Iwouldn't look to valve adjustment to solve the emissions failure. If you're not getting excessive tapping noise then leave them alone - it's a daily driver not a race car. Excessive hydrocarbons is unburnt fuel. Changed air filter recently? When was your last tune up? What stuff in tank? How old is O2 sensor?

 

Thanks for the reply Pedro.On my last check yesterday I was at 25 MPG which seems to be normal.I did take it to a shop with an exhaust analizer and they did get it to pass emmissions but would not tell me what they did to get it to pass without putting any new parts on it.I gave it a full tuneup before taking it to them except for the oxygen sensor which has been on for probably 100,000 miles.I did'nt change that because I did'nt get any check engine light.Is there an easy way to check if an oxygen sensor is good or not as I do'nt like to buy parts if I do'nt need them.I know that excessive hydrocarbon is unburnt fuel and would like to improve my emmissions and mpg if possible.Other then the emmissions the engine runs and sounds great.Going strong 201,000.

 

When was the last time you did a compression test? If your exhaust valves are leaking slightly then that could be the source of hydrocarbons. I'd do a compression test. It's a 91 with 200k so I don't think there's a lot you can do. You can search internet for O2 testing but with 100k on it you may want to just replace. How long are you planning to keep this car? 25mpg is not bad, I doubt you'll be able to cost justify trying to get it higher.