Not sure what this is or where I should look for this, BUT. 1994 XLT 4.0 4x4 manual trans, and whenever I go over a bump, pot hole, RR tracks, etc. My check engine light will flash on for about a half second and my RPMs jump about 300-500. Thought maybe my foot my accidentally hit the gas more, but no, even does it out of gear. Changed out the TPS (Motorcraft) and IAC (UK, Motorcraft UA) Evap purge sensor, and still does it. Plugs / wires changed last year trying to trouble shoot this and I am at a loss for figuring it out. ANYONE who has had this issue AND fixed it, I would greatly appreciate knowing what you did..

 

No real electrical reason for that issue that I can think of, you could check the connector on Crank sensor and EDIS-6 module(spark module) but I would expect a code to be set for anything electrical causing it

I would say its mechanical issue
RPMs go up when more air is let in
Obviously throttle linkage
PCV Valve
Power brake booster
Any vacuum hose

Can you reproduce it by hitting engine with a 2x4 or rubber mallet
Or moving around hoses/wiring in engine bay

 

I'm pretty sure I don't want to start smacking anything under the hood with a 2x4, I might create more problems than solving. Vacuum I'm going to check with throttle cleaner. I didn't check the PCV, nor have I replaced it since I bought it and it looks like it's factory. The linkage I did tighten up the linkage about 4-5 days ago and it hasn't happened since, but I've been gentle. I still may have 1 or 2 threads to tighten it for no slack. And I upped the idle a tad too far, which I have to bring back down from 900 to about 750.

 

LOL, wasn't talking full swings

Just see if its the vibration from hitting a bump that's causing the issue, something to stick or unstick
Can't be a metal bar or hammer, wood or rubber only