Very rough running engine -- RPM's jump while idling

[Deadkid9110]

Getting the ranger started is easy enough, but keeping it that way when cold is a whole different ball game. The engine revs high and low while it's idling. It will run normal for a little while, then rev high for a few seconds and then the idle will go really low, then it will even itself out and run steady for about 5-10 seconds; Then the cycle repeats itself. When the engine is cold, it dies when the RPM's drop (No matter the temp, could be 100 degrees or -30). When the engine is warm, it stays running, but still bounces.

I took it to a local mechanic, and he tuned the carburetor and lowered the idle speed, it sounded just fine after he did that. Then I started driving it, came to a stop sign, and it started acting up again.

It is a 2.8l V6 Carbureted Engine

Any helpers? It would be much appreciated, as I would like this to become my Daily Driver. Thanks!

 

[enginepaul]

If you have the stock computer, which from what you describe is probable; pull the codes and start there. If you aren't sure about some of them, post them and maybe we can help.

 

[Deadkid9110]

Sorry for adding in details I knew nothing about. The engine is carbureted, no computer; or IAC for that matter.

 

[kimcrwbr1]

Put a new PCV valve in it and does the dizzy (distributor) have three wires or 6 wires coming out of it. Some pics would help also both sides of the engine and front of the carb.

 

[dangerranger83]

These trucks came from the factory with a feedback carb, exhaust emissions stuff, etc... that is all controled by the computer. If it lacks a computer then somebody has been under the hood of her.

 

[roadhawg]

I have a 99 Ranger with the 4.0 V6 that does the exact same thing. I still don't know what is causing it but it seems like these two vehicles have the same problem. This is a problem which is caused by a defective part that both of these Rangers have. Does anyone have any idea what probably is?