1998 Ford Ranger

Engine Performance problem
1998 Ford Ranger 4 cyl Two Wheel Drive Automatic 95000 miles

A little info first. I have replaced the following since I bought the truck with 70,000 miles a year ago.
- Plugs and wires - AC Delco 8 qty
- Air Charge Sensor
- Upper and lower O2 sensors
- PCV Valve
- Fuel injectors
- Fuel Filter
- Alternator
- Throttle Pos. Sensor

So here is whats happenening. In the morning I warm up the truck for 3 or 4 minutes while getting ready to leave. When I start to take off there is a little hesitation in power and a the enginge doesn't run its smothest for a second or two. When I get above 15 or 20 everything is great. Runs smooth no lack in power. Sometimes though when comiing to a complete stop the truck begins to lope and sputter, but only when I am at a complete stop. If I let off the break it stops or calms down. Even if I let off the break for just a second. The truck had died from this issue because I didn't let off the break soon enough or at all. The truck does have almost 100k miles on it. I am thinking Timing belt and maybe cat? What do you think?
October 18, 2010.

Have you checked the idle air control motor to see if it is sticking? Has the check engine light come on? Have you checked for vacuum leaks?

I will check for Vac leaks this weekend. I am not sure how to check the idle air control motor, but they are only about $50. Should I just go ahead and replace it? A long time ago the engine check light came on, but I replaced the alternator and it went off.

Oct 18, 2010.
I hate to say yes without knowing for sure. If you remove it, there is a small plunger on it that moves. If you remove it, you will be able to see if it is sticking or just needs cleaned. I would hate to say spend the 50 dollars and that not be the problem. I hope you understand.

Let me explaine... The Idle Air Control (IAC) valve controls the engine idle speed. The valve is located on the side of the throttle body. This valve allows air, determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed. Here is a picture of yours.

Does the description I listed sound like it could fix the problem you are dealing with?

Also, rather than purchasing one, you can check your own. Turn the ignition switch to the OFF position.
Disengage the wiring harness connector from the IAC valve. Using an ohmmeter, measure the resistance between the terminals of the valve. Due to the diode in the solenoid, place the ohmmeter positive lead on the VPWR terminal and the negative lead on the ISC terminal. If the resistance is not 7-13 ohms, replace the IAC valve. Here is a picture of the electrical leads.

I hope this is helping and not confusing you. Let me know if you have other questions. Just trying to save 50 bucks if possible.


No Problem. I am an old school car guy but I can get in on testing electronics. Its all these damn sensors that cars need to run nowadays. I miss carbs!

Oct 19, 2010.
I replaced the IAC. The truck is running a little more smooth but it does still sputter and die. Only died one today. I will look into the vacume system this weekend and get back to you.

Oct 19, 2010.
Did the IAC test bad? One other question, have you checked the EGR to make sure it isn't plugged with carbon as well as the intake where it bolts?

Let me know. We'll figure it out, and I agree. The sensors are enough to drive anyone crazy. I miss carbs, points, condenser. There were only a few things that could cause a problem and just listening to the engine run would always tell you where the problem was.

Let me know what you find.

Take care,

. After thought. Check the EGR tube to make sure there are no holes in it.