Thats what I was affraid of. ,,,

Hopefully you'll fish something out this weekend with the Tester...

Have you checked the fuel pressure? One item I forgot to include was the fuel pressure adapter. You disconnect the high pressure line from the injector rail and insert the adapter. It has a schrader fitting on it where one can check the fuel pressure. If you need it, let me know.

does a monty have a fuel pressure regulator that is electrically controled? i need to look and see where it is located if it does have one. fuel pump and filter already changed to i guess this would be next in line.

Vacuum controlled. Under the throttle body. Behind the coolant hoses that go to the ISC.

well as of yesterday i'm a the proud Grandpa of little 7.5lb Levi Lathem. the roofers should have the construction dumpster out of the way soon so i can get the montero out of the garage and get back to trying to figure out the problem on it. the tester i borrowed will single out the MAF sensor to see if it is out of spec. and does anyone know how thw fuel pressure regulator works? does more vacume make less fuel or what?

Congratulations Walker!

If you want to meet up sometime, you can try parts off my truck to save some moolah. My cell # is 706-340-1273.

Not sure how the regulator works. Frank will know the answer on that one.

The injectors require a certain pressure above atmospheric pressure for good atomization of fuel.... normally around 36 psi.

Inside the regulator is a diaphragm and spring that moves in relation to the amount of intake vacuum.... or pressure differential between the intake runners and atmospheric pressure of 14.7 psi.

When the engine is idling, intake vacuum is high and pressure differential increases - which if uncorrected would spray more fuel/constant pulse as compared to when the engine is at WOT. At WOT there is no (or very little) vacuum in the intake - only atmospheric pressure. At idle, base fuel pressure is assisted by intake vacuum, since the injector is spraying into a vacuum. IOW, the relative pressure differential is greater due to the vacuum in the intake runner.

The regulator allows more fuel to bleed off to the return line when intake vacuum is high - and conversely it clamps down on the return volume to increase fuel pressure as vacuum declines.

The ratio is 1:1 on a N/A engine - 1 psi less vacuum = 1 psi more fuel pressure. This way, the injectors are seeing the same differential pressure no matter what the engine is doing - which allows the ECU to use a constant multiplier for fuel calculations, based on engine rpm and load.

If you add forced induction into the equation, the intake becomes pressurized (under boost) to an extent greater than 1 atmosphere (14.7 psi) and the regulator must be able to allow an even greater pressure to be applied at the injector to maintain the same differential... so volume of fuel and good atomization for fueling calculations can be accomplished.

That explanation sounds a little convoluted, but maybe it'll help you understand how it works.

Frank

ok i got it now and thats exactly how i thought it would work. my brother in-law is a master tech with ford and he is betting on a damaged or dirty MAF sensor. he told me how to clean the one i have but i may just try and get some readings before and after then might just replace it if i cant get good readings off of it. this might make sense as it acted like it backfired under load shortly before this whole problem started. so i will start with the MAF sensor when i get back at it. as of right now i'm on the way back to the hospital to see the newest member in my family.

Holy Moly they are proud of the MAF sensors at all the parts houses.

If you want to try replacing the MAF sensor, either get one from a junkyard or swap in a known good one from someone else's truck.

If you get it from a junkyard, try asking the price for the entire filter housing - some might not know there's a $400 sensor inside and will charge you for only the housing. <img src="/forums/images/graemlins/wink.gif" alt="" />

Or you can go here and pay about $8.

Frank