1st Problem: While driving our 1997 Ford F150 (4.2 V6-Automatic) along at constant speed, suddenly the feeling of being tapped from behind or hiccup occurs. Constant speed can be at 45, 65, 55, doesnt matter. Happens randomly. Seems to be getting more frequent. The Engine Light is not on. Engine starts fine. No hesitation on acceleration. Any ideas on what this could be?

2nd Problem: Wipers turn on by themselves and sometimes will not shut off. Could this be a ground wire problem with the wiper motor.

 

Now that you mention it, mine does that under power. I've got the V6 with the 5 speed, but it doesn't seem to happen very often (I didn't even remember until I saw your post). Hiccup, maybe, or like its catching its breath. Not a big lurch, but noticable. Had a buddy at a repair shop (not a Ford dealership) put it on the computer because the check engine goes on and off from week to week. Light was because of vacuum leak in emissions system, but no reading about hiccup under power.


About the wipers, I think Ford had a recall for that, check for links to recall sites.

Fabman

 

Could it be the fuel filter causing the problem?

 

Don't know, I've had the truck for 2 years and 22,000 miles and I changed all the filters and plugs when I bought it, but I don't remember exactly when the problem started.

 

Could be a misfire

 

I would vote for the fuel filter, just had mine changed at 13,000 miles and it made a noticeable differance. I did not have the symptoms that you have but at very low speed just crawling along in traffic I would sometimes have a surging effect. Since the change I can notice a better pick up especially at low end.

 

As for the first problem, try the fuel filter first, if that doesn't work then change plugs and wires. I had the same problem with mine. Did the fuel filter first,no change, then did the plugs and wires and voila! No surging.
Good luck with it.

 

I have the same problem with my 1997 F150. (4.2) auto. 89000 mi.
Recently, (last couple of weeks) I have noticed the same hiccup while driving at 45+ mph. It seems to be occurring more frequently. The truck idles fine and runs great at speeds lower than 45. It's driving me nuts!

Last year I replaced the coil. In the last two months I have replaced the Fuel filter, plugs and wires and recently, after the check engine light came on, Autozone checked the code and told me that I need to replace my egr. Instead of buying a replacement, I cleaned it and put it back on. The truck seem to run fine until recently the check engine light came on again and the truck runs like crap at 45+ mph. What's the deal?