Upon the suggestion of the dyno tuners, I changed the fuel filter and cleaned the MAF sensor, but the A/F ratio did not improve. Can anyone take a look at the attached A/F numbers and give me a suggestion to try and fix? Car has 96k miles on it, completely stock except for a drop in K&N filter and weld-in straight pipes. Thanks!
have you ran the codes at all? if you have, did you get anything that had to do with IMRC's? if you did clean those cause that can screw with the air/fuel mixtures. it did with my 96 cobra, cause i ran the codes and it registered as on o2 running lean and one o2 running rich. so if you dont want to run into this problem, clean the tb and clean the IMRC's. a simple solution is, to take carb cleaner and take the air tube off, clean the tb, spray some carb cleaner into the port in the tb, then put the air tube on, then turn the car on, and spray carb cleaner into the tube. it cleans some of the stuff up and the air/fuel ratio goes back up slightly. i was getting 225-250 miles to a 3/4 tank and then when the IMRC's became dirty, i was getting 160miles to the 3/4 tank. i cleaned the tb and sprayed carb cleaner into the air tube and i got my mileage back, but my o2's are still reading rich and lean and i still have a check engine light on. so i still have to pull the intake about and clean the runners but like i said, try this and maybe it will work, if not check your fuel injectors....you might want to try putting some cats on the car to see if that is the problem. anyway let me know what happens.
The original cats are still on the car. There is no check engine light at the moment, and I just learned this yesterday so I haven't had time to check codes yet. My fuel mileage is still running around 20 mpg. I'll be running some codes tomorrow and see what turns up.
IMRCs aren't a problem on 99s +. Ford has a TSB for pinging on 01s to reprogram the computer due to lean condition. Maybe your 99 has a similar problem.
