Driver ignoring unknown problem ----- Car guys will probably laugh

So, I have a '97 Ford Explorer Sport. Others have refrered to it as the death mobile, but I like it. It’s paid for and it has the big three:

1) Turn Key - Start

2) Push Gas - Go

3) Push Break - Stop

Here’s the new issue:

When driving primarily on the highway, I feel and hear this loud Thump and notice that the RMP’s drop significantly and then come right back up.

When it first happened, it scared the crap out of me. Now it has been happening for quiet a while and I have just gotten used to it. (Probably not the safest thing to do.) We just got back from a weekend car trip and I have come to accept that I need to get this issue at least identified and possibly resolved. Any ideas out there.


- Loud thump that is more felt then heard.

- RPMs drop to almost nothing and jump right back up.

- Usually at higher speeds 65-70.

- Possibly related to road surface bounce andor bumps.

Well, it should scare the crap out of you! While this is just a guess, just the possibility of a broken motor mount should get you to a mechanic a.s.a.p.

It almost sounds electrical to me. Not always easy to find except when it breaks down fully. Maybe a faulty ignition switch like you turn on/off engine while driving?

Just another maybe…

If the vehicle has a rollover protection system that shuts the fuel pump off in the event of an accident or rollover…and I think it does…that may be malfunctioning and shutting the fuel pump off in response to a simple bump. At highway speeds you’re drawing more gas, so the effect of a momentary fuel supply interruption would be more noticable.

Lots of possibilities but a bad AC compressor comes to mind. The clutch on it engages (it’s normal when it does that) and the compressor doesn’t want to move,then it seems to break free, then works as usual. It’s a maybe. The other possibilities could be serious ones.