1998 Ford Explorer Chugs on Inclines and Cloverleaf

[CynthiaK]

Hi,
As the title states, my explorer chugs and loses power on inclines and when circling on a cloverleaf.
I changed the fuel filter and fuel pump about a year ago for unrelated problems.
I have cleaned the MAF. The hoses all look in good shape.
Any suggestions on what it could be?
Thank-you!

 

[410Fortune]

Any check engine light?
How many miles on the rig?

The fact that you went straight to the fuel pump you replaced a year ago is funny to me. A parts store fuel pump is lucky to last a year. I would consider checking fuel pressure just to rule it out as the cause

Chugging up a hill is usually a fuel demand issue
You have good instincts

 

[CynthiaK]

No check engine, 260,000 KMS.
Also, new air filter.
About to:
check fuel pressure (thank-you!)
check spark plugs/wires
check ignition coils
check purge valve solenoid
clean throttle body

I bought a spare fuel filter just in case but have not replaced the one I just replaced a year ago.
I am also wondering if it could be the filler cap? Cheap replacement cost even if that is not the problem.

Anything else I should check?

 

[410Fortune]

Don’t use solvents on the throttle body only wipe it clean

You can clean the mas air flow sensor

The gas cap is not usually the problem

Do you hear a vacuum sound when you remove the gas cap or anything like this?

With the ohv a miss or
Lack of power is usually a fuel supply
Issue or something in the ignitions (plugs and wires)
Keep an eye on coolant level
Any excessive use of oil or coolant should be noted

With no codes, no check engine light, then all the hoses and emissions stuff should be Allright otherwise the computer will tell us

 

[CynthiaK]

Don’t use solvents on the throttle body only wipe it clean

You can clean the mas air flow sensor

The gas cap is not usually the problem

Do you hear a vacuum sound when you remove the gas cap or anything like this?

With the ohv a miss or
Lack of power is usually a fuel supply
Issue or something in the ignitions (plugs and wires)
Keep an eye on coolant level
Any excessive use of oil or coolant should be noted

With no codes, no check engine light, then all the hoses and emissions stuff should be Allright otherwise the computer will tell us

I used to hear a vacuum sound but no longer do.
I already cleaned the MAF with MAF cleaner and yes, I will just wipe out the throttle body with a dry cloth.
Coolant and oil levels are fine, no oil in the coolant.
One other thing - when I start the vehicle, no matter cold or warm weather, it is now roaring to 2000 RPM which it never did before.
If I drive it say to a store, go in and shop and then come out and start it, it only roars to 2000 RPM sometimes.

 

[410Fortune]

That’s too high of an idle
Something is not right

You likey have some major air leaks in the intake or egr system or a faulty iac valve

Does the check engine light illuminate when the key is first turned?

 

[CynthiaK]

That’s too high of an idle
Something is not right

You likey have some major air leaks in the intake or egr system or a faulty iac valve

Does the check engine light illuminate when the key is first turned?

It comes on when the key is in position 2, like all the other ones do, but goes away as soon as the engine starts.

 

[CynthiaK]

From the internet:
The Idle Air Control (IAC) valve in a 1998 Ford Explorer regulates engine idle speed, especially when the engine is warming up. A faulty IAC valve can lead to rough idling, stalling, or a high idle. Symptoms of a bad IAC valve include unsteady idle speed, hard engine starts, engine stalls, poor acceleration, and a persistent check engine light.

I have high idle (only on start that does drop back down after a few minutes) and intermittent poor acceleration.
If I drive the vehicle before the idle drops down, shut it off and restart it, it sometimes runs rough, but not always and I don't get an engine light.

 

[CynthiaK]

I tested the IAC valve and it is working.

 

[410Fortune]

Test fuel pressure and inspect plugs and wires

 

[Turdle]

What is throttle position sensor voltage at idle?

Check this several times, key on engine off. Pull throttle open, let it snap back to idle checking to voltage for spike, or, high voltage at idle intermittently

 

[1998Exp]

No check engine, 260,000 KMS.
Also, new air filter.
About to:
check fuel pressure (thank-you!)
check spark plugs/wires
check ignition coils
check purge valve solenoid
clean throttle body

I bought a spare fuel filter just in case but have not replaced the one I just replaced a year ago.
I am also wondering if it could be the filler cap? Cheap replacement cost even if that is not the problem.

Anything else I should check?

If you don't have an oscilloscope it's practically impossible to check the quality of the spark. Be aware that if more than say 5 year old, the plug wires are very likely to have developed pinholes in the insulation, especially in the area close to the exhaust manifold, and are robbing you of spark energy. That's a well-known issue with this older system that gave me repeated grief. Motorcraft has newer type wires, with much more durable silicone insulation that installed some time ago and they work great. Make sure to use the heat shields and keep the wires as far as possible from the exhaust heat.