I have a 1990 ford aerostar that has a problem that starts after about 40mph. It will start shuddering until I push the accelerator a bit or I let off of it. If I slightly tap the brake it quits also until I slow down or speed up, usually happens between 40mph and 50mph. I have seen on other threads people having the same problem, but no cures. People have been told to check the maf and iac. Can someone tell me where these two sensors are located? Not sure what else to check. Could this be a fuel injector problem or a sensor problem? It idles really rough also. I do not believe it has anything to do with the suspension or front end related. Tires are good also. Thanks for any input.

 

Are you sure it's not your front end?
I recently had a simular problem and found it to be a right tierod end and an upper control arm bushing problem. More noticeable when going over speed bumps or pot holes.- Andrew

 

Also, check your air intake hose that connects to the engine to make sure it's tight. Mine kept slipping off and would make for a rough idle and eventually would cause the engine to stall. I guess it confused the air control module.

 

My explorer had that exact same problem. The CEL finally came on so i took it to the dealer and The MAS, intake manifold gasket and 2 O2 sensors had to be replaced. They also tired to blame the problem on the front end but i declined to send it to the specialist, its bad enough the repairs were over 1,000 bucks.