7a-fe to 4a-fe conversion questions - Toyota Nation Forum : Toyota Car and Truck Forums

COYOTE556 · 05-01-2005, 10:03 PM

I need some advise. I have a 1994 Geo prizm with a 7a-fe engine. It shucked a rod through the block. I have a 1994 4a-fe on hand and i was wondering if it would work. I know i would have to switch out the ecm, but i was worried about the wiring harness. does anyone know if they are the same? i think the 7a-fe had a knock sensor and the 4a-fe did not, but i was hoping the knock sensor wire was just extra in the harness and if i switched out the ecm, i wouldnt have any problems? any help is greatly appreciated.

Dr Tweak · 05-02-2005, 01:33 AM

Yeah it'd be pretty darn easy. Just check the diagrams for any changes, but for the most part it should be very simple.

***REN69*** · 05-02-2005, 01:40 AM

Question is.. why would you go to a 4AFE? less power and torque..

COYOTE556 · 05-02-2005, 06:49 AM

i wanted to put a 7a-fe back in, however i have the 4a-fe already (free) and i have been pricing the 7a-fe's at junk yards. they are not cheap

toyotaspeed90 · 05-02-2005, 11:10 AM

i'm sure the 7afe wiring harness and ecu will work fine with the 4afe......

mwitt1337 · 04-16-2009, 09:11 AM

I have a 1997 7A-FE and my wife overheated the engine and blew it up. The engine and tranny has about 200K miles on them. I can get a 1995 4A-FE and Tranny with 50K miles on it for $400. It is just a commuter car and i just need to get it running. Can I just pull the 7A-FE engine and tranny and drop in the 4A-FE engine and tranny?

Do I need to change ECM or wiring? I know that the 4A-FE does not have the knock senser and will that cause an engine light to show if it is not connected?