92 Failed Smog....again

I just failed Calif. smog test (second time) The tech. said I might consdider Ox. senser or Cat. converter? I just got some GREAT advice from this web site so I'm back to see if somebody has the magic answere. Are either of these options anything somebody with no experience could do? I passed the visual inspection, the 15 mph (barely) and most of the 25mph test. I failed the last section. I failed by a bigger margin the second time tested??? Thanks for any input you have.

I'm assuming that your fuel mix is running too rich (too much gas into the cylinders), given the tech's recommendations. The catalytic converter removes unburned fuel by chemical conversion and once it's shot the unburned gas (which helps make smog) will start dumping into the air. The oxygen sensor detects how much oxygen is in the exhaust stream. When the oxygen sensor goes bad it causes the engine to run rich (and tanks your gas mileage) which can speed the death of the catalytic converter.

Recommendation: change the oxygen sensors first. The 4.0 liter V6 requires two, and they cost about $50 USD each for aftermarket, but make sure that they have the correct wiring harness. If they don't you'll have to by OEM from the Ford parts department at your local dealer (call them for a price). You can replace the sensors yourself if you have some open ended wrenches and know your way around an engine. After replacing the sensors, let the engine run for a few minutes so the computer can learn the new sensor information and adjust the air/fuel mix.
Replacing the oxygen sensors should solve your problem, unless the cat is fried (unlikely), which is a repair that I would leave to a muffler shop.

Cheers!

Has the check engine light come on at all? There could possibly be some codes stored somewhere in the computer. Have the codes pulled if their are any before throwing a bunch of parts at it. Good Luck and keep us posted

There were a series of somewhat unrelated events that took place. I needed a smog test so I went to Smog Stop. Somehow the tech. set off my alarm (he must have hit the valet switch under dash because I dont use the alarm or have the clicker) This killed my battery but I was able to jump start it for the first three days. Had battery & alt. tested and Kragen Guy said both were good? When I got stranded after work one night I decided to go buy a nice new battery anyway. For some reason I was able to jump start it and drove it home. I out the new battery in and all was well. That is when I found this web site and asked about my tranny fluid & oil mess. The only time any dash lights came on was on my way to work next morning. Check engine light came on as I was pulling into parking lot. I turned engine off and restarted and it was off? In my world that meant problem solved! So the vaccuum modulator got put in and oil & tranny fluid changed. I thought this was my smog problem but I was wrong. My smog "score" actually got worse. The tech doing it said it was unusual to pass the majority of the test and fail on the last little part. I guess I have to find someplace to read the codes or do a smog diagnostic test. I looked at the Chilton and there is no way I would mess with this stuff. So far all the information you have given me has been right on the money. I wish my sons knew how to work on cars. He offered to let me take it to his high school auto shop class, but I think I will spend the money to find out for sure what I need to replace. Thanks again for your advice

You know I had a problem with my 94 Explorer where the Check Engine Light came on and when I shut it off it wouldn't comeback on for a while. My mechanic hooked up the scanner(free of charge!) and proceeded to test it and nothing came up. What he did next was put it through some tests through the scanner so it can play with the engine and it ended up throwing a code for the EGR pressure feedback sensor. I bought the part and put it in myself and it has been fine ever since. For your own info the computer port is under the hood (OBD I) on the passenger side. It will be about two inches long and have a cap on it that says EEC TEST. Idiots at a lot of shops don't even know how to read the computers in the OBD I cars. Find somebody that knows and I guarantee you will figure out your problem. When was the last time you had it tuned up? Replaced air filter? Oxygen sensors? Good Luck and keep us posted

You sure know a lot about cars. I can't remember when I had last tune up. I have only had it for three years. I am trying to find somebody to find out what codes (if any) are saved. I think the air filter is new. I have a hunch that it is going to be the ox. sensors. I have no experience to base it on except I have been studying a lot. I just want to pass smog so I can get my registration sticker. Law changed 1/01/05 that comercial licensed drivers can't go to traffic school and it stays on record longer. There are new school bus driver laws as well and I don't need to draw any extra attention. Besides my son just got permit and I haven't had the pleasure of him driving for me yet?! If it is the Ox. sensors.... do I automatically have to replace both?

You may have to replace both or just one. The computer should throw a code for them. When you own a Ford Explorer your Fix or Repairing Daily, so you learn a lot in ahort amount of time. Good Luck

Suggest that you replace both to save time and aggrevation. If you replace one, which do you pick and if it's wrong one, you may not pass smog. Besides O2 sensors are replaced based on mileage. The exhaust passing thru sensors wear out the material in the sensors. Let us know what happens.