A few days ago, my '86 F-150 4x4 (300 I-6, grandma 4-speed) started idling really, really fast (1800 RPM). Not all the time, just some of the time. Anyways, normally she idles at about 700-800 RPM. I noticed that I have also started hearing some kind of clicking noise under the dash. Maybe it is coincidence, but I've also noticed that sometimes when I am setting at a traffic light, idling 1800 RPM, I'll hear that clicking noise and the idle will slow back down to or close to normal. Does this make sense or ring a bell with anyone? Is there some kind of switch or other device under the dash that might cause this? This may also be my imagination, but it seems that, at speed, the truck "gees" and "haws" ever so slightly when I hear this same clicking noise. I just can't help but worry that whatever this is might cause me to be stranded some day if I don't figure it out! If anyone has any ideas about this, any help/advice will be greatly appreciated!

 

is your truck carb or fuel injected?

 

The clicking noise sounds like the EEC power relay under the dash. If it's coming on and off like that your truck can do funny things. I had the same thing happen, although mine would start missing and cutting out insead of getting a high idle. I replaced the relay, didn't help, so I checked and cleaned every electrical connection I could find under the hood. The wires coming off the starter relay were loose. I'm not sure if that was my problem or not, but the problem is gone. Try cleaning and checking for loose connections and see if that helps.


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[font color="green"]1995 F-150 Supercab XLT longbed 4x4 302 M5OD [/font]31x10.50's
[font color="green"]1986 F-150 4x4 300 I6 NP435 [/font]Warn hubs, DeeZee bed caps, '96 XLT bench seat, new paint job

 

The truck is carbeurated, a good ol' 1-barrell.

 

OK, it's 4 months later and I am still experiencing weird things with this truck. The fast idle deal kinda "went away" for a while, but it does reoccur on occasion. Also, I am now having difficulty starting the truck. It seems more pronounced when the truck is hot. Cold starting is somewhat better. She growls and groans when trying to start and had been eventually turning over until yesterday when I became stranded (I knew this was coming). Fortunately, I was close to a long hill, so with a minimum of pushing, I was able to roll the truck off. During one of the grinding episodes I heard that clicking noise under the dash, and today, the fast idle problem has returned. I just can't help but think there is a connection. I believe the battery and the alternator to be good. Today, even though they appeared to be OK, I cleaned and re-greased the battery terminal connections and, at first, that seemed to help. However, after running the truck long enough to get it hot, the non-starting condition returned again. Until I can discover the solution (or replace the truck altogether) I can try to park on hills. This is no problem at home. For now, I am going to go out and poke around under the dash and check for loose connections under the hood. Maybe I'll get lucky!

Also, thanks in advance for any help and/or advice.........

 

Does your truck have airconditioning? If it does there is a fast idle solenoid that causes a throttle kicker on the carb to engage pushing the throttle up so that the truck won't stall. The kicker looks like a small vacumn pod right under the throttle on the carb, some are electric, and others are vacumn but an electrical switch opens the solenoid to let vacumn through on the vacumn models. If you are hearing a clicking noise it is very possible that the eec relay is going bad and activating the fast idle even when the A/C is off. You might also not have air but there is still a fast idle pod that is activated to keep the truck from dying upon sudden deceleration. If this happens again look at the carb to see if the fast idle plunger is up and has been activated. You can disconnect the vacumn line, or wiring if it is electric, so that it will retract and go back to slow idle. Check out Autozone.com and go to the repair link. It has a section just for your truck and you can look at pictures of the carb and where the fast idle plunger is. Hope this helps.

JOe

 

It sounds like two separate problems to me. The no hot start could be a bad starter, cables, battery, or connections.

I'm almost positive the clicking due to a loose wire. Turn the ignition to "on" (engine off) and start wiggling wires under the hood until you hear the clicking. Check the smaller wire coming off the negative terminal. This is where my problem was. The wire is a direct ground to the computer.

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[font color="green"]1995 F-150 Supercab XLT 4x4 302 M5OD 8' bed [/font]31x10.50's
[font color="green"]1986 F-150 4x4 300 I6 NP435 [/font]Warn hubs, DeeZee bed caps, '96 XLT bench seat, new paint job

 

THANKS! Gonna get my tools and go check it out ASAP.........