Please help diagnose problem!

[Diyithedollbaby]

1999 Ford Taurus 3.0L V6
Question: Help diagnose problem
Engine has miss --- Engine light is on.
Retrieved PO 303
Miss on 3 and 6
Checked spark -- OK
Injectors working
Fuel pressure normal
Compression -- normal
140 psi
Only has 10 inches of vacuum and needle bounces
Leakage test on both cylinders (3&6) below 30%
Checked timing -- Cam & crank in time

This vehicle actually belongs to my 83-yr.-old parents---trying to help them by narrowing down the problem. They have already had it at a mechanic, and the mechanic is stumped.

[shorod]

Welcome to the forum!

Why do you suspect there is a miss on both cylinders 3 and 6 since the only code you show is for a #3 misfire? Have you pulled the plugs to see how they look? You might try moving the spark plug to a different cylinder to see if the misfire code follows the spark plug or stays with the cylinder.

When is the last time a tune up was performed? Have your parents used fuel injector cleaner regularly? If your parents are like most 83-year-old Iowans, they drive very slowly and there is a good chance there is a lot of carbon in the cylinders. Before putting new spark plugs in, you might try a cylinder de-carb as described on a can of SeaFoam. Maybe the carbon is absorbing all the air/fuel mixture before it has a chance to ignite.

-Rod

[Diyithedollbaby]

Thank you for responding to my plea for help, Rod!

My parents actually live in Illinois about 3 hours away from me -- I am a transplanted Iowan! Anyway, this car is not driven much -- lots of sitting in the garage, as they have two other vehicles that they drive more often. I will pass on the information you provided and see where that takes them! Thanks again!