OK, Super techs I need some help

Question

A 97 Ford Ranger in my shop, idles poorly and bad fuel econmy the complaint.

We have done a complete tune-up, cleaned the fuel injectors, replaced the EGR valve, checked for vacuum leaks, this thing is killing me.

4.0 engine 4 wheel drive by the way.

Bustass or someone help me out

Answer 1

Clean the Mass Air Flow sensor, I'm willing to put money on that being the problem. Two tamper proof torx screws hold it in, sometimes they are filled with epoxy and a small vise grips will remove them.  Disconnect the battery for at least ten minutes to clear the long term memory and force the ECM to relearn fuel and ignition maps.

If it has a K&N air filter installed, toss that in the garbage while you're at it. The oil from those filters contaminates the MAF sensor wires. Despite claims to the contrary by the company I've seen it happen myself...GM has even issued a TSB against the use of aftermarket oiled air filters.

Answer 2

any codes. whats the mileage. need more details please.

Answer 3

Hey Anthony,

    I think that you missed the vacuum leak.

  This motor had a problem with the gasket between the upper intake manifold and the fuel rail, ( the fuel rail is like a seperate plate between the upper intake and the lower intake ). If you remove the upper intake you will probably see part of the gasket is missing, replace with a gsaket from the ford dealer as they have updated this gasket for this exact reason.

May I also suggest that your shop get an information subscription such as alldata, as there is a bulletin pertaining to this, I am not at shop now so I cannot give you the number

  I may add that some of the above answers are very good, but often the mass airflow sensor contamination causes O2 sensor codes P0172, 0173 etc

Answer 4

Some of the others have pretty well covered what to do. Here's what NOT to do. Never, ever clean a MAF with Carb cleaner! CRC Electrical Contact Cleaner or something similar only. Do not actually touch it with anything physically. And never, ever blow dry with high pressure compressed air! Let air dry in a ventilated area or maybe use a fan at most before trying to start vehicle. And don't throw away the K&N filter. Other than all that stuff, Mr. Cool was right that a dirty MAF can and often does cause those symptoms.

Besides the source links below, you might find these helpful too.

http://www.autozone.com/az/cds/en_us/090...

http://www.wellsmfgcorp.com/pdf/Counterp...

Answer 5

Have you checked the EECS?  A sticking purge valve (stuck open) can cause this problem.

Answer 6

See if they can check your IAC sensor, ( idle air control sensor ) This is a missed check point. I would be most concerned about my oxygen sensor. May have two O2 sensors. This is ussually missed in your tune up. They should be changed every 30,000 miles. This sensor guages how much air is mixed in the fuel. This will always cause poor gas mileage and ussually causes poor idling also. I would change the O2 sensor first. IAC is ussually pricey but O2 sensors not ussually.

Answer 7

fuel pressure regulator leaking. pull vacuum line off to see.

Answer 8

Line clamp the vacuum booster supply line to see if idle improves, possible leaking brake booster diaphram. Take a propane bottle and enrich the mixture, does it smooth out? If so too lean, create a vacuum leak, disconnect a vavuum line and see if it improves, if it does, too rich. How many gram is the throttle pulling in relationship to the mila seconds of injection pulse width? What are your 4 gas readings, possible lean missfires. Need more input to go further.