I don’t know whether its a transmission or an engine problem, but
when I’m in ‘coast’ mode, not accellerating or decellerating, things go into hiccup mode - quick jerks, several a second, back and forth. Feels like when you are towing a trailer and the play in the hitch causes the jerking.
My garage has been treating it as an engine problem, the bill is nearly $600 so far, with wires, fuel filter, and intake manifold ‘o’ rings… what should we consider next?
A new tech/shop. Sounds as though he’s searching. Perhaps like a faulty tranny VSS (Vehicle Speed Sensor).
Need more info.
Add year, engine size and mileage.
Tranny fluid level up to the proper mark? When was the last service?
When the vehicle is stopped and in PARK, does the engine run smoothly?
When picking up speed, does it run smoothly? How about during DE-acceleration?
From a stop, when accelerating does the tranny shift harshly or smoothly?
Has the tranny ever shifted out of gear when coming to a complete stop?
As an extreme answer, maybe even engine mounts.
What year? How many miles? Any Check Engine Light on?
Info like this helps to narrow the possibilities down a bit.
By wires, I assume you mean plug wires. Were the plugs replaced at the same time? If not, there better be a good reason why not since misfiring plugs can kill plug wires, coils, etc.
Offhand, it sounds like someone has been guessing a bit here. The fuel filter would obviously not cause this and any perceived intake sealing problem can be easily verified with no guess work at all.
What’s extreme about it? There’s almost ALWAYS a shortness of necessary info on here.