Motor keeps idling at 1900 rps after pushing the first speed, bad consumption

[fabianoliver]

hello good evening!
I have a 94 explorer 5 speed manual.

The engine behaves strange in some situations:
If I go push hard in first gear, and then I put the engine into neutral, it keeps idling at 2000 rpm.
If I turn it off and on, it idles normal, at 600.
If I drive slowly without accelerating too much, at traffic lights the revs drop to 600.

When driving between gears, the rpm do not drop to 600, they remain at 1300.....
If I release the accelerator, the engine continues pulling slightly (it goes at 1300 revs) for a few seconds, and then drops, and you feel that the engine slows the truck.
I already changed injectors, air and gasoline filter, I cleaned butterfly and changed the IAC valve, spark plugs, and cables.
What could be happening? consumption in the city is BAD,
10.5 miles / gallon.
In freeway seems ok: 19
what can happens? Any ideas?
i want the truck as others cars, as soon as you take off the foot off the accelerator, the engine stops pulling.
Cable in the butterfly seems relaxed, doesn't sticks
Any ideas?

Thanks!!

 

[410Fortune]

Intake manifold air leaks
It takes the iac a minute to compensate idle
So the mas air flow sensor is metering the incoming air, the oxygen sensors measure the outgoing air. Any air that enters the system between the two is called “un metered air” and the computer has a hard time to compensate… it is very common for a 4.0 from 94 to have leaky intake gaskets.
A visual inspection of the base of the intake plenum can help, any buildup of soot?

Check all vacuum lines and feeds, no leaks allowed

Also 02 sensors wear out over time and get lazy

Any check engine light?

 

[LG57]

Also, Check the intake air tube for leaks on the bottom side. They wear under there over time.

 

[410Fortune]

That’s right oh man
We had a 92 explorer one time no matter what we did high idle… finally found the large crack on the underside of the accordion Section of intake tube
Those old 3 piece ones were the worst!

Good call… un metered air =super high idle

 

[fabianoliver]

Intake manifold air leaks
It takes the iac a minute to compensate idle
So the mas air flow sensor is metering the incoming air, the oxygen sensors measure the outgoing air. Any air that enters the system between the two is called “un metered air” and the computer has a hard time to compensate… it is very common for a 4.0 from 94 to have leaky intake gaskets.
A visual inspection of the base of the intake plenum can help, any buildup of soot?

Check all vacuum lines and feeds, no leaks allowed

Also 02 sensors wear out over time and get lazy

Any check engine light?

Hi 410Fortune.
A mechanic has changed the injectors, and they use new gaskets for the manifolds i'll take to them about that posibility.
I've no O2 sensors installed in the truck, just a Ford plug on each sensor cable.
I would like to check for vacuum leacks, but i don't know how to start to do it....
No check engine light on.

 

[fabianoliver]

Also, Check the intake air tube for leaks on the bottom side. They wear under there over time.

Hi LG57, i'll dismantle it and check, some weeks ago i take it off cause i change the raditor, and it seemed fine, but honestly i didn't look any crack, may be it has ! thanks

 

[410Fortune]

It needs 02 sensors to run
You cannot cheat the upstream sensors

 

[fabianoliver]

It needs 02 sensors to run
You cannot cheat the upstream sensors

Hello 410, take a look on the thread i've posted in february about the lack of O2 sensors in my truck....

WTF!, no O2 sensors in my 94? someone take them off?

Hello all. I've my 94 since some months now. I've worked on it a lot, but has never bought new O2 sensors to update them. As the truck is consuming a lot in the city, i've decided to buy a new pair of O2 sensors now, thinking may be they needed to be changed. I'm bring them from USA, here parts...

www.explorerforum.com

 

[410Fortune]

That never happened here in USA! They were all shipped with sensors here

So odd that they did not have then in south America and then your truck is drinking fuel! I wonder why they didn’t just install the sensors?