90 Vs. 91??? - Jeep Wrangler Forum

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Wrangler YJ (Model years 1987–1996)
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What is the difference? Im noticing that a lot of parts fit a 91 2.5L 4 cyl but not a 90 2.5L 4 cyl. Whats the difference... ? Help please!:surrender: #1 · Jun 17, 2013 What is the difference? Im noticing that a lot of parts fit a 91 2.5L 4 cyl but not a 90 2.5L 4 cyl. Whats the difference... ? Help please!:surrender: The primary difference between the 1990 and 1991 Jeep YJ 2.5L 4-cylinder engines lies in their fuel injection systems. The 1987-1990 models used a Throttle Body Injection (TBI) system with a single injector, while the 1991-1995 models utilized a Multi-Port Fuel Injection (MPFI) system with one injector per cylinder. Aftermarket parts are more readily available for the MPFI system. Show Less Sort by Oldest first Oldest first Newest first Most reactions #2 · Jun 17, 2013 1990 and before used a carburetor. 1991 and after was fuel injected. #4 · Jun 17, 2013 Incorrect. All 2.5L YJ's are Fuel Injected from the factory. 1987-1990 use a Throttle body Injection setup (TBI), which has one big injector inside of the throttle body. 1991-1995 use the modern Multi-Port Fuel Injection setup (MPFI) which nearly every gasoline vehicle is designed with now. It uses one injector per cylinder, 4 in total, rather than one big injector. Nobody makes aftermarket parts for the TBI, only the MPFI. The change came when Chrysler decided to change the original 1987-1990 TBI design by AMC. Chrysler basically did a lot of re-designing for the 1991 model YJ. 1987-1990 6 cylinders were the carbureted 4.2L, 1991-1995 6 cylinders were the modern Chrysler 4.0 MPFI design. Show more replies 0 Reply #3 · Jun 17, 2013 All 4cly where fuel injected. the 6cly changed to fuel inject from carb in 91.. as for the change in the 4cly between those years, not sure.. could be emmission related perhaps. Insert Quotes Post Reply

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