97 Discovery 1. Just stuck a rebuilt engine into it and its "sweet". HOWEVER!

It dies on rapid deceleration. It's like the rpm's drop and just keep dropping and then it dies. And it's not happy about restarting either.

Checked and replaced most sensors. Water, oil, Throttle position. Didn't replace the mass air but it worked fine before.

Even replaced the throttle body, using the one off my old engine. No difference. But here's the really freaky part. Played the switch and guess game with the 02 plugs, the orange and gray. And it had some interesting results. Orange plug on the drivers side and it dies on deceleration but the engine purrs. Orange plug on the Passenger side and the idle is fine, it no longer dies BUT the engine is rough like a couple wires were crossed kind of rough.

Did the homework, (Thanks LR Forum) and found that the orange plug belongs on the original side which is the driver's side. Which makes the engine purr and makes it die on rapid deceleration. AND occasionally the idle will fluctuate greatly on its own when parked.

Throwing no codes in this mode. No apparent vacuum leaks. o2's were fine before engine swap. Mass air flow sensor was fine. We disconnected the battery to reset the computer. Totally baffled at this point. Any suggestions would be welcome.

 

vacum line on fuel pressure regulator
Idle air control? Bad grounds?
Trans stalling engine? If it dies on deceloration sounds like torque converter is not unlocking

Crushed a wire during engine swap?

Crossing o2 plugs is freaking out the ecm trying to compensate they tell ecm how rich or lean the side of the engine is running

 

vacum line on fuel pressure regulator Checked Fuel Pressure. Will check vacuum leaks with alcohol spray in the AM.
Idle air control? How can you test? Bad grounds? Engine has good ground. Checked.
Trans stalling engine? If it dies on deceloration sounds like torque converter is not unlocking THIS is a possibility. How would we verify it?

Thanks so very much for these. I was running out of directions.

Crushed a wire during engine swap? Nope, checked that thrice.
That's what's so baffling. We've checked all the normal things and can find no faults. It's like marrying an ex-nun. No joy but you're at a loss as to exactly why.

 

IACV should be removed, spray cleaned with carb cleaner, don't move the pintle. Should move by itself when ignition is turned to position 2.

 

Awesome. Thanks so very much. I will try it first thing in the morning. I really appreciate your help. Thanks.
John

 

Sounds like your ECU is all confused, and rightfully so after playing the swap parts game. You might just need the adaptive values reset.

 

care to share how that occurs?

 

never mind, thank you, I found it.