wssup folks! new to this forum…did my very first swap, its a b20 long block swap only on a 90 DA auto
transmission. got a very bad MPG on it and really high rpms…hittin 4000rpm on a 70 mph…kept all the
wirings and ecu to OBD0…everything else is also stock…any ideas??? do i need to upgrade into a OBD1
to get it runnin decently??? its for my wife and she likes that stock smooth ridin…appreciat all inputs
I would say that either your auto transmission is not shifting out of gear properly, or something is slipping. It could be a fluke that it happened as the same time as the swap, but you probably just forgot to hook something up…
Looking in my 1992 Helms manual (that’s the factory manual FYI), it looks as if the Automatic transmission computer has an LED which flashes to indicate any errors. I suspect the 90-91 has a similar “self diagnosis” feature. You will probably want to find that control module and see if it is giving a code. There is also some kind of hydraulic system associated with the automatic transmission that will probably need inspection.
Sorry. I have never worked on, thought about, read about or had any inclination to do any of the above for Automatic transmissions until just now. But I figured that might at least give you a place to start looking. If it were me, I’d start making sure i didn’t miss plugging in a connector of some kind.