trouble shooting

[pcav]

just bought a 1992 Ranger 4x4 4.0 auto.....any engine familiar folks out there to answer questions???

 

[snoranger]

just bought a 1992 Ranger 4x4 4.0 auto.....any engine familiar folks out there to answer questions???

There's a bunch of us.

 

[pcav]

There's a bunch of us.

High idle in neutral. Sporadic revs when shifting into reverse or forward it will rev higher or even lower sometimes

 

[pcav]

High idle in neutral. Sporadic revs when shifting into reverse or forward it will rev higher or even lower sometimes

And thanks so much for replying

 

[Uncle Gump]

I would be looking for vacuum leaks to begin the process...

 

[pcav]

I would be looking for vacuum leaks to begin the process...

Actually I just looked around under there and I only see a few vacuum hoses

 

[Uncle Gump]

Yep... those are the ones. Start checking...

 

[pcav]

Yep... those are the ones. Start checking...

So I just unplug them individually as the engine is running to look for a difference in the RPMs?

 

[Uncle Gump]

Not exactly...

I like propane... carb cleaner will work also.

Lightly release either on suspect areas below the throttle plate while running and note the areas that change engine RPM.

 

[pcav]

Not exactly...

I like propane... carb cleaner will work also.

Lightly release either on suspect areas below the throttle plate while running and note the areas that change engine RPM.

Gotcha

 

[Denisefwd93]

There are way MORE then a few vac hoses & connections, ?

 

[pcav]

There are way MORE then a few vac hoses & connections, ?

I need all the help I can get

 

[Denisefwd93]

You will need a multimeter a code reader and some rudimentary knowledge easy to obtain with the internet these days, The forum experts I'm sure, will chime in at some point my first thoughts are throttle position sensor. Listen to Gump he knows his stuff, and how to cook shrimp in many many ways ?

 

[91stranger]

I don't understand how you want us to help you but don't tell us what the issue is.... Are you just looking for 4.0 specific issues or do you have an actual issue? Please be more specific when posting to help us help you.

 

[Bill]

So I just unplug them individually as the engine is running to look for a difference in the RPMs?

If you unplug them the engine will start running rough or stall because you are creating a huge vacuum leak. However, you can unplug individual lines at the vacuum port on the manifold and put a cap over the port to prevent a vacuum leak. You can buy vacuum line caps at most auto parts stores. I'm not familiar with the ports on a 92, but I'm assuming there are normally a few or more vacuum lines connected to several ports. You can disconnect them one by one, but a cap over the port on the manifold and take it for a test drive. If you find one of the lines may have a leak you may have to check for a T in that line that splits off for different devices/sensors. These tests may turn on the check engine light on OBDII vehicles (95 and later). I don't know if that is the case on a 92. Don't overlook the possibility of an intake manifold leak, a leak in the power brake booster diaphragm, leaking throttle plate hinges, or anywhere along the air intake plenum between the air filter and where it connects to the throttle intake, in addition to the PCV valve and its tubing that connects to the intake manifold.

This website has vacuum diagrams. Maybe someone who has a 91 thru 94 4.0L can tell you, or post a picture of the vacuum line port locations.

https://www.therangerstation.com/how-to/engines-fuel-systems/ford-ranger-engine-vacuum-hose-diagrams/

There are other issues that can cause your problem. Just do a search for surging engine or high idle. But, checking for vacuum leaks is the first step.