When I crest the top of a hill and let off the gas pedal, the check engine light will come on in my '94 Villager (Quest with different badges). I read the code and it was throwing a code 51 fuel injector circuit fault, which made sense as it would idle a bit rough on one cylinder at idle occasionally. I rebuilt the motor recently (for other reasons) and replaced the bad injector while I was at it, but now with the new injector, I've still got the code 51 thing when I let off of the accelerator. I'm wondering if this might not actually be an injector circuit problem, but perhaps an 02 or MAF that's slightly out of spec. Thoughts?

http://www.nicoclub.com/FSM/Quest/1994- ... est/ec.pdf

start at EF & EC page 127 to put a volt meter on the plug terminal to see if power is running through the wiring or maybe find an open wire...

did you check if the old injector was OK? putting an ohmmeter on the injector to see if there's continuity or not? (EDIT: just read your other posting ~ ok now just concentrate if the wiring is bad or not)

maybe swap that injector to another location & see if it's an injector problem or a wiring problem?