Guys,

I'm stupid when it comes to pulling codes and such. Will any/all codes that come up make the check engine light come on? Or do I just have to check it periodically?

Reason I ask is I recently read a post where someone mentioned their gas mileage jumped from 13mpg to almost 20mpg. Someone told them it was probably due to a bad O2 sensor he replaced.

Can mine be bad and I'll never know until I pull the codes. The light has never come on as long as I've owned the truck (10 years). It works though. No matter how hard I try I can't get my truck to get over 14mpg. It doesn't smoke, or use any excessive oil. The tailpipe looks spotless, yet it won't get over 13-14mpg. It doesn't matter if it's city or highway driving, whether my foots in it or not. It just won't happen.

BTW, it's a 94 F150 Supercab auto with a 5.0 and 3.55's...... It's equipped with factory mass air too.


Thanks,

John

 

Not all codes will light up your check engine light, don't feel bad mine only gets 14 to a gallon and 12 in the winter, I just can't seem to get any better or worse gas milage.

 

To answer your question the answer is no. Just check it every once in a while. Because your Truck has OBD1.(on-board Dyagnostic generation 1) all vehicles with EFI before 1996 will have this setup. On OBD1 The Check engine Light will only come on when a serious malfunction occurs and the vehicle feels like it wants to leave you on the side of the road. The problem is the computer will not store the malfunction like the OBD2 system will. On OBD2 (vehicles 1996- present) the Check engine Light would come on if there is a malfunction in the and the malfunction occures more than once than it is stored in the computer making it easier to pull up codes better than the OBD1 system.
the Way to check if your O2 sensor on your truck is bad is to hook up a scan tool. The scan tool will read the truck's computer on start up the truck will run open loop for about 5 minutes after it should switch to closed loop. If the computer doesn't switch to close loop than the o2 sensor is bad.

You have to consider that the truck has a lot of weight and a 5.0 302 v-8 isn't a gas sipper. with a good tune up ( Plugs, Filters, and clean throtle body) and with a new o2 sensor you might be able to pick up to 17-18 mpg the best you can get with this truck.

 

Thanks guys,

What kills me though is my truck used to consistently knock down 16-17 without a problem. It's got a recent tune up.

Can I use some Seafoam Deep Creep to spray down the intake tract, throttle body and all? I'll also check the MAF to see if it's dirty or not.

I hate to do it, but I may even ditch the last cat and do a homemade cat back with a nice Flowmaster and get the exhaust shop to bend up a 3" pipe. Maybe get a k&N too.

I hate to spend any large money on it since it'll be getting sold HOPEFULLY sometime next year. I want a PSD!!!

 

What do i need to do to scan it for codes? How do i do it as well?

 

www.fordfuelinjection.com they tell you how to do it, its pretty easy you just have to be able to count fast. You only need a piece of wire and a paper clip for a jumper