96 explorer 4.0 with low fuel pressure?

Those symptoms sound more like the MAF sensor or IAC valve. Both can be cleaned (carefully).

Here are instructions for cleaning the MAF:

-Paul

Not sure what you are asking, because I don't see any problem with your fuel pressure. Fuel pressure is regulated ABOVE the manifold. That's the purpose of the vacuum hookup. In any case, if the engine only stumbles at idle, the problem is not with fuel delivery -- the demand for fuel at idle is very low. Did you check the IAC?

Hello Paul:) Thanks for the response!! I have replaced the IAC(probably didnt need to:)). Cleaned the Maf a few times. No check engine light. Did all the 02 sensors. New fuel filter,temp sending sensor(computer),coolant temp sensor(gauge),thermostat,catalytic converter,egr valve,dpfe(egr pressure sensor),air filter,camshaft position sensor,removed and cleaned throttle body,new platinum pulgs. Yesterday I checked the fuel pressure and came up with the low pressure. Truck runs perfect with exception of the idle issue. Thanks again Paul!! :)Nel

Brand new Iac. I thought fuel pressure remains the same whether at idle or at higher rpm?? Thanks:)Nel

I checked the manual for my 94 4.0L OHV engine. It gives three specs for fuel pressure:

Key on, engine off: 35 to 45 psi. Engine idling: 30 to 35 psi. Engine idling, vacuum hose disconnected: 35 to 45 psi.

It also says that the pressure should drop by 3 to 10 psi when going from key on, engine off, to normal idle pressure.

The vacuum hose mentioned is connected to the fuel pressure regulator- I guess they want more fuel pressure at full throttle than at idle.

-Paul

Sounds like you've eliminated a lot of things. One other possibility- a manifold vacuum leak. Those can be tough to find. Check the usual suspects (hoses and their connections) and then there is the nasty one- the lower manifold seals.

Explorers have had problems with bad lower intake manifold seals, so much so that the factory paid to have them replaced. I haven't experienced that myself, just read about it. Maybe someone who's experienced this problem will describe the symptoms and any troubleshooting tips they learned.

-Paul

Let's try again: Fuel is injected into the manifold. Hence what counts is not absolute pressure, but the difference between the regulated pressure and the pressure in the manifold. That's what stays (reasonably) constant. At idle, the manifold pressure is low (high vacuum), so to compensate for that, the absolute regulated pressure drops. At full throttle the manifold pressure rises (low vacuum), so the absolute regulated pressure has to go up. The regulator uses the vacuum hookup and a diaphragm to accomplish this trick. Hope it's clear now.

Just came back from mechanic and he sprayed some carb cleaner around upper intake..engine did funny things. Said to take off intake and examine it as it is plastic. I am going to do that now. Just got a gasket and am keeping my fingers crossed that the intake is not cracked. Thanks and Ill keep you posted!! Thanks again:)Nel

Yes that has cleared it up!! Thanks for making me understand! I am used to my 71 460 big block mach1..its an alcoholic...just keeps drinking and never complains or breaks down!!:)Nel

Ah- I'll have to remember that technique. So if you have a manifold leak, the carb cleaner gets sucked in thru the hole, changing the idle. Interesting...

-Paul

Did the upper manifold gasket tonight. Old gasket was really flat and hard. Cleaned up plastic intake really good and inspected for cracks. All I found was a little scratch near one of the gaskets nothing to really worry about. Also used gasket maker (hitemp) everywhere but over the gaskets. It is much better now!! I should have done the lower since I was already there but oh well..next time. Only thing I cant figure out is my parts store (advanced auto) gave me a FELPRO brand gasket and in the box were 6 gaskets but the 4.0 v6 only uses 3. I looked at the outside of the box and it says 1996-1997 upper intake gaskets QUANTITY 6. Why?? I also sealed off the IAC with the gasket maker and tomorrow Im doing the throttle body. Thanks everyone!! :)

I have a 2000 explorer at around 70,000 mi it had all the problems you described. Thanks to Google Groups I found that these explorers tend to have problems with the lower intake manifold gaskets. I got the Ford Dealorship to replace it free even though it was passed warranty. I read that you replaced the upper, but the lower may be the culprit.

Do you think they would replace a 1996 with 100k?? Thanks :)Nel