idle is rough and gas mileage is down

[scrapper]

I have a 94 that is running poorly.I sprayed wd-40 around the engine and have replaced all the vacuum lines,not the plastic ones. It has a new o2 sensor. I have cleaned the mas and the idle control valve.air filter is clean,air filter box is cracked. newer spark plugs and wires,oil fresh. I was wondering where to start? It is not throwing any codes? I was wondering if maybe the timing or the crank sensor. I did not use the spacer tool to set the crank sensor. I am not sure what check to without codes. I was thinking about checking fuel pressure and a compression test. Thanks for some help.

 

[Mikel89us]

Is it hard to start too? Usually, from my experience, the injectors get dirty and one of two things happen.
#1 and most likely, an injector will start sticking open and cause one cylinder to run rich,idle will suffer because that one cylinder isn't running right.

#2 one injector cloggs up and lets less fuel by, then the oxygen sensor sees too much oxygen, and richens the whole system (it doesn't adjust cylinders individually) and then you wnd up with one cylinder running a little lean, and three running very rich.

 

[RonD]

If it has an EGR valve, remove it and see if it is being held open a bit by carbon build up.

On the fuel rail there is an FPR(fuel pressure regulator), it will have the Return fuel line attached and a Vacuum hose.
When engine is at idle vacuum is highest, the vacuum hose pulls open the FPR valve to let unused fuel flow back to the fuel tank, if the diaphragm in the valve leaks, fuel is sucked down that vacuum hose and into the intake, making for rough idle and poor MPG.
Remove this vacuum hose and check it for fuel.

 

[scrapper]

Okay I will try some better gas and run carb cleaner through it. I will check the vacuum line also. I have an old jap bike, that sounds a little like what happens when the fuel petcock goes bad. Thanks will check it out tomorrow after work.

 

[tomw]

Did you repair the crack in the airbox? If it is behind[after] the MAF, it can allow excess air in that the computer is not aware of. That would diddle the mixture.
What does the engine do? Poor idle? Poor performance? Hesitation? Bad mileage? Shaky idle? Too little information for me to make a reasonable suggestion.
tom

 

[scrapper]

The crack is in the air filter box, its the lid is cracked broken on the edge and it does not seal very well. the maf is farther down the line. It idles rough kinda like a vacuum leak. My gas mileage went down about 3-4 mpg. It does seem to have a little less power but the idle and less mpg is really annoying.I am really thinking about making a cold air box and swapping over to a cai. I think a complete box would be very similar to what it has only not broken and I have most everything or can get it for free, much cheaper than the junkyard.
I pulled the vacuum line off of the fuel regulator but it was dry. I'm not sure what the egr vacuum line goes to it has 2 vacuum lines running out of it. I did pull the vacuum line off of the egr and put my finger over it. It seemed to pulse instead of straight sucking. Do not know if it is suppose to do that or not.I have not replaced the big hose on the pcv valve. I notices the vacuum lines that go to and from the I think its a charcoal canister? I think I read that somewhere? are bad but not sure what to replace them with, could not get them from auto zone.
I was also thinking about replacing the upper gasket set on the engine with a complete head gasket set. I was going to get the head checked and some stuff done to it. just dont want the truck down for to long.

 

[RonD]

EGR valve should have no vacuum at idle.
Computer opens it only when engine is under load, i.e. accelerating, pulling a trailer or going up hill.

After engine warms up and is idling, unplug the IAC valve's wires idle should drop down to 500 or engine may even stall, either is good it means no vacuum leak.
If idle stays high, above 750, then you do have a leak, and now is a good time to get for it, with IAC Valve unhooked.

All Ranger since 1983 had CIA, so do it because it looks or sounds better, not for any other reason.

 

[scrapper]

I found this just have to get a vacuum pump. I have one but it doesn't work. The idle is low already and rough, but I can try to unplug the idle control valve.Thanks for some ideas.

http://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-egr-system-1

edit * I have just been reading over this site and it has a lot of different tests you can do. I may just try most of them just to see what condition the sensors are in.

 

[Mikel89us]

EGR valve should have no vacuum at idle.
Computer opens it only when engine is under load, i.e. accelerating, pulling a trailer or going up hill.

After engine warms up and is idling, unplug the IAC valve's wires idle should drop down to 500 or engine may even stall, either is good it means no vacuum leak.
If idle stays high, above 750, then you do have a leak, and now is a good time to get for it, with IAC Valve unhooked.

All Ranger since 1983 had CIA, so do it because it looks or sounds better, not for any other reason.

Ron, that is false, the egr is an economy thing and only works while you are cruising down the road at light throttle. When under heavy load the egr does not operate in order to give max power when needed.

 

[scrapper]

I got an airbox have to install it,even came with a mas.I found a head that I can get. Will be easy to just swap them out.

 

[WarHawk-AVG]

Another thing, try running a pint of marvels mystery oil in a tank of gas for about 3 tanks, you can also try the seafoam in the brake booster vacuum line to see if it loosens up some of the carbon...with no codes it's not sensors, if they were off it would throw codes

SAMSUNG say whaaaaaat?

 

[scrapper]

I replaced the maf and the airbox but not much change in it. I have been busy with brake problems and other things. I'm going to try to check the sensors on it this weekend. I may try the seafoam looked it up on youtube.