Need help with hydrocarbons at idle

'92 Ford Taurus 3.0L

AZ standard reading for idle Hydrocarbons is 220.

First reading @ idle 310
Changed air filter, PCV valve and dumped a bottle of 91% rubbing alcohol in gas tank because I was told it would help.

Second reading @ idle 423
Took car to shop where they checked for vacuum leaks and an overall check. They said everything seemed fine but to run the gas with the alcohol out and refill with chevron gas and add octane booster, which I did, also changed oil.

Third reading @ Idle 628

Now I'm at a loss and I don't know what to do. I need to pass emissions test but don't have a lot of money to spend on more repairs/fixes. Any ideas (just short of getting rid of the car)?

Any help/advice will be greatly appreciated.

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Rubbing Alcohol? Really? My understanding is that the mythbusters debunked that one...

Okay, first, there could be numerous causes. I would ask how many miles are on the car, and what the maintenance was like (religious, or ...well.... y'know )...

The reason is because the first cause is the worst. low compression from worn cylinders/rings.
Of course a lot of things a little wrong w/ the engine can cause this, most all of them aren't worth fixing (given the vintage)

Did you try cleaning your Mass air flow meter (sensor)? If it's dirty, it can tell the computer incorrect things... leading to a lean or rich A/F mix.

Did you check the ECU for codes? some codes which contribute may not kick your check engine light...

O2 sensor is obvious.

Maybe your catalytic converter has gone bad? (it is 17 yrs old)

If your spark plugs (one or more) are worn out, they may cause incomplete ignition in one or more cylinders...

The list goes on, but I would suspect one or more of those is your culprit.

Good luck! Good hunting!

Thanks for the feedback!

It has 113,426 miles and the maintenance is normal but not religious.

The mechanic I took it to the second time said the spark plugs were fine and he didn't get any miss fires when checking it out. He even tried pulling the vacuum lines while it was running to try to lean it out but it wasn't working and he suspected the rubbing alcohol was the problem.