Reader Question: Hey Austin,
Here is a quick question for you.
I have a 1998 Ford Escort ZX2 (5-speed Manual). Intermittently, when I hit a bump on the highway my “Check Engine Light” goes on for a moment and the engine feels like it downshifting and the momentum of the car “pulls back”. Then almost immediately, the light goes off and the car drives like normal.
The problem appears to be getting more frequent.
What do you think it is?
I wish I had a quick answer. I have seen and heard some strange complaints over the years, but you are in the top 5 strangest! Ha!
This could be something simple though, since it only happens when you hit a bump and will eventually correct itself I can only assume something is loose or has a bad connection.
I would open the hood and start from the front of the engine and work my way to the rear, lightly pulling on all electrical connections and rubber vacuum hoses and connections looking for anything that is loose or broken.
Make sure you get under the vehicle to check the connection at the oxygen sensor, which is screwed into the exhaust pipe. You might be able to reach it from under the hood.
If you feel comfortable doing so, you might want to do this with the engine running and someone sitting inside the driver seat watching for the check engine light. Do not pull on spark plug wires or touch spark plugs while the engine is running though they will bite you. You can however use a wooden yardstick to bump and push on sensor connectors with the engine running.
If you do not find anything under the hood you might want to try gently pulling and pushing on the under dash wiring inside the vehicle. If you can get access to the computer, I would lightly tap and tug on the computer itself with the palm of your hand while the engine is running.
This is commonly referred to as the “Tap test” and a computer with an internal problem will fail when it is lightly tapped when the engine is running.
The last thing I would look at would be the check engine light bulb itself.
The instrument panel can be easily removed and the bulb inspected or replaced. The onboard computer can malfunction if the check engine light does not operate.
Keep me posted, will you?