I have a 97 ford ranger. 4c. And it runs great except when I have to get on it hard it runs really rough. I put computer on it and it said idle sensor so I replaced it. That did work so I was checking the back coil pack and it seemed lose. But when I unplug it the motor never misses a beat. So what should I check next?

When was the last time you put spark plugs and spark plug wires on it? If they are getting old, you may want to start by looking at them. When you had the codes checked, were there not any codes present for a misfire? If so I would start there. If not, let's talk about these coils.

Because this motor has two coils, you can unplug either one of them and it will seem to run fine, at least at idle. How old are your plugs and wires? It may be time for a tune up. If you are confident your plugs and wires are good, it may be time to check out your coils. To check that coil out, try and get a hold of an hei spark tester.
You may be able to find this at your auto parts store. To use it, first make sure the coil you want to test is securely plugged in and bolted down. With the engine off, unplug one spark plug wire at the spark plug and plug this tester in. The clamp part of it needs to be connected to a good ground. Once it is plugged in and connected to ground, start your truck. If your coil and plug are delivering good spark to that cylinder, you will be able to hear this tester sparking. It will sound like a loud cracking noise. Rev your truck up and listen to ensure that your coil is still delivering spark. If it does, shut it down, plug your plug wire back in, and move on to the next cylinder.

If you hear the loud crack of the spark on every cylinder, your coil is working properly. Hope this helps. If this doesn't pan out, there are more things you can check.

If you have checked your coils and wires, and everything looks ok. It is time to talk about fuel delivery. The easiest thing to do to start out is replace your fuel filter. Most auto parts stores have a loaner tools program. If yours does, borrow a fuel pressure gauge. Sorry, I don't have one of those to take a picture of. Under your upper intake manifold, you should see a shiny silver colored pipe that sits on top of your fuel injectors. Somewhere along this pipe, you will see a valve cap very similar to the valve cap on your wheels. Unscrew this cap, and connect your fuel pressure gauge here. Make sure you have the hoses routed so they won't get caught in any moving parts, then start your truck.

With the engine ruining at idle, the fuel pressure gauge should read about 39psi. Shut the truck off. Go ahead and route this gauge so that it is not going to get caught in any moving parts, then feed it out of the engine bay so that you can see it and gently close the hood. I suggest you use tape to secure this gauge to the windshield.

Take the truck out on a test drive. Find a safe place, and then accelerate as hard as you can in your truck. Your fuel pressure should go up, not down, as you accelerate. If your fuel pressure rises from its level at idle, you are done with this test.

If your fuel pressure drops while accelerating, you have a fuel delivery problem. While you still have the fuel gauge hooked up, move it back to where you can see it in the engine bay. Along that fuel rail, you should also see a small silver colored canister with a vacuum hose running to the top of it. This is your fuel pressure regulator. With the engine running, disconnect the vacuum hose from the fuel pressure regulator, and plug the vacuum hose with a golf tee or a pen. Your fuel pressure should go up when you disconnect the vacuum hose. If it didn't, it is bad.

Assuming everything is ok there, I would look at the fuel filter if you haven't replaced it already. It may be clogged and unable to allow enough fuel to flow through to supply the motor. After you replace the fuel filter, test drive it again. If it is good, good. If your fuel pressure is still doing under acceleration, you most likely have a bad fuel pump.

Right before summer. I changed the wires and plugs and put the idle control sensor on.. think for the advice. I'm working 6/12s so I'll have to try all this sunday. Thx again and happy new years

Ok. Finely got time to change the fuel filter. And it's still acting up. The funny thing is that if I drive it grandma style it runs fine. It's only when I get on it and come to a stop it either dies. Or it will run like it's on one cylinder and then within less than a min it idles perfect..

Try cleaning your MAF sensor.

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1999 Ranger 4.0 and extreme Snap-on tool fetish

Instead of cleaning the maf I bought a new one. And it's made it better but it's still wants to try and die if I Rev it up. Now it will idle almost to were it sounds like it's run on 2 cylinders and then it will idle back to normal.

Clean your iac.

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2006 Ranger. 2.3l 5 speed
Air box mod and throttle cable mod.
Tri-fold tonneau cover. VHT taillights. Tinted corner lights.
fog lights.black headlights.
LED driving lights, dome, 3rd breaklight, LED tailgate light bar and LED foot wells. LED tails.
4.10 stock gears[/COLOR]

My Build:

http://www.fordrangerforum.com/proje...ger-build.html

I finally got time to put a new iac on and it not running rough now but now it's at a higher idle. I've so far changed the idle control sensor, the maf. And the iac. .. lol what's next?? And thx guy for all the help

How high is your idle currently? You have changed a lot of parts out on it. Wouldn't be a terrible idea to disconnect your battery for a few minutes, then reconnect and take it out for a drive. When you disconnect the battery, it causes the ecu to lose stored information like fuel trims, and when you hook the battery back up and drive it, it will have a chance to relearn itself from the factory settings. Worth a shot, and free to do

Ok I did all of that and it started kinda rough the started do alot better then before I drove it back to work it started doing it again. So I'm wondering if when I pulled the catilic converter if that's the reason it's acting up.

Possible. Does it not have a cat on it now? Another thing you could try is to disable the egr valve and see if it runs better. Next to your throttle body on the back side you should see a silver valve that has a vacuum hose connected to it, and on the bottom there should be a pipe that runs down to your exhaust manifold. Pull off the vacuum hose and block the house off with a golf tee or small bolt. Take it for a drive and see if you have any improvement

Ok. Thx. Try it tomorrow