I looked up online what it was called when a car jerks forward the stops over and over and I guess it’s called surging. But apparently there is no engine code for it so my mechanics say they can’t do anything about it. How do I fix it, or how do I explain it so that they will know what to fix? Just what is going on here?
You need to find a more experienced mechanic. There was a time when cars did not have computers, did not store trouble codes. Yet capable mechanics could fix whatever was broken.
Your car may have a serious vacuum leak, or the problem may be due to a faulty MAP or MAF sensor. Maybe there’s a transmission problem. Find a mechanic willing to test for these situations even without a clue from the computer.
Manual, or automatic transmission?
Surging can be caused by a number of things that can set a code. What kind of car and how many miles on it? Occurs at all speeds and idle? If the car is actually jerking forward I don’t consider this a surging problem though.
(Some possibilities include an air leak, weak fuel pump, fuel filter, EGR fault, ignition fault, etc., etc.)
Add to that list - timing. Your computer may be trying to correct the idle, it overshoots due to bad timing, and then it drops low. Then the cycle repeats…