Replaced throttle body and still doesn't go 30 miles an hour
My car has 135000 miles.
My car has an automatic transmission.
The vehicle could have a clogged catalytic converter, the fuel filter and/or injectors could be plugged and there are other possibilities in the fuel, ignition, and air induction systems. It is also possible that your vehicle has entered "limp mode" which is set by the PCM if the transmission would be damaged by higher speed operation. The first thing to do is determine if any diagnostic trouble codes have been set and stored by the PCM and their meaning. YourMechanic performs a check engine light diagnostic to retrieve these codes and then uses those codes to track down (i.e., individually test) the failing component. If no codes have set, the engine can be diagnosed on a scope to determine if the issue is confined to one or a couple cylinders or if there is a "global" problem such as you might get with a failing fuel pump or ignition coil or, as noted, a clogged catalytic converter. If you desire that the problem be diagnosed and repaired, please set up a mobile diagnostic with YourMechanic and they will promptly dispatch a certified Mechanic right to your location.
Have a car question? Get free advice from our top-rated mechanics.
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%