RPM's jump up and down?

[smc]

I have a 92 eb. When I first start it up when it is cold, the rpm's jump up and down almost dying. When I am on the interstate, and around 65mph, the rpm's will jump from 2.2K up to 3.0K and back and forth. It is really annoying. Lastly, when I put the thing in part after driving anywhere, the rpm's will start increasing to about 2.5K. I know it should not do this. Does anyone have a suggestion? Thanks. Shaun, Indiana.

 

[rocket01]

I have an eb'92 as well with similar symptoms. When it's cold out especially it idles rough and almost stalls when intially accelerating. Whilst driving down the road however, it is not that noticable. So far I have tried changing the oxygen sensor and have reset the computer (removed battery). The engine light comes on intermittenly as well. If you get some suggestions as to what to do let me know also.

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[Maniak]

Your first symptom sounds like the AIC. If the AIC isn't working, the Idle will be very low, to the point where it will blip the trottle to keep it running. An easy way to check if the AIC is working is to turn on the A/C when the vehical is warm. If the idle goes up a little the AIC is working. Another way to check is to disconnect the AIC and then start the explorer. If the idle is lower with the AIC disconnected then your AIC is most likely not the problem.

Now your problably asking what is the AIC (Air Idle Control).. I've also heard it called IAC (Idle Air Control). When standing in front of your motor look just right of your intake manifold. It will look like the bottom of a can when standing in the front of the vehical. It bolts to the side of the intake plenum with two 10mm bolts. I have a picture of it here somewhere.. If I find it I'll put it on my web site so you can see what I'm talking about if you don't see it. Checker/Autozone type stores don't carry it, but a NAPA type store does. It cost me around $75. If you can't afford it right now you can remove it from the plenum and then remove the 2 screws that are holding it together. Once apart you can clean it will all kinds of chemicals.. I used carb cleaner and brake cleaner and it cleaned it up enough to keep it working for a few weeks until I got the money to replace it.

I have no idea what would cause your second symptom. I don't think its the AIC since it is only used at idle, but you never know...

Mark

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Mark
mark@legendz.com
http://mark.legendz.com
Off-Road and Motorcycle Information, Pictures and Movies

 

[smc]

Thanks for all the replies. I will try checking the AIC control and see if that is the problem. I have changed the Oxygen sensor and the thermostat to see if those were the problem, but it was not. I am really hoping to figure something out soon and when I do I will let you know. Thanks again for the reply.

 

[reedr]

smc

Had the exact same symptoms in my '91.
Bad TPS (Throttle position sensor)
Ford dealer needs "calibration code" from
label inside door jam...about a $40 part.
Rick