Hi! My car has intermittent episodes of stumbling or stalling at low speeds. No codes and car never acts up in the shop. New MAP sensor, spark plugs and wires, idle air control valve, PCV valve and alternator. Battery tests fine. Very frustrated and scared to drive the car! Always starts up after stalling.
A clogged catalytic converter can cause that. My 99 Corolla was bugging down all the time and the cause was a bad CC.Well, after 20 years you can expect something like this happening.
I had an issue where when the vehicle was stopped it would vibrate and when stopping quickly the engine would stumble and sometimes shutoff.
It turned out to be a half inch to one inch crack in the base of a vacuum hose. I wrapped electrical tape around the cracked part and reinstalled it. There was also a different vacuum hose that was not seated on fully so I pushed it all the way on. Looking at them it would not seem they could cause such an issue though when I made the adjustments at least half of the vibration went away and it would not stumble or shutoff when coming to a quick stop.
I’d recommend closely checking every part of every vacuum hose and doing a proper fuel pressure test which you can rent a gauge at a lot of auto part chain stores.
Thanks for the reply! We did check for a vacuum leak, but nothing turned up. Currently the hypothesis is that the problem is caused by the plug-in for my pay per mile insurance-sounds far-fetched, but the car has been running fine since I cancelled it!