VY starts, stalls immediately after engine swap

[twentyfouroz]

Hola. Log time lurker, first-time poster, multi-dunnydore owner. The issue I have today is with my 3.8L VY wagon. I found a low km Ecotech last year, and on Jan 2 2021 I swapped out my leaky 290k+ chugger. The job itself was a %^$#ing nightmare ( stripped and snapping studs and bolts, random parts missing, etc. ) but by C.O.B Monday I had the old-new motor on the mounts and mostly connected back up. I drove the car in on the Friday before... so at that stage, EVERYTHING worked fine. Fast forward to Tuesday and there's no way it will run. It kicks and fires, sometimes I can rev it almost to 1500 RPM and it sounds fine... then it shuts off. First thing I thought was air leaks, so I eradicated that as an option. Then, because it backfired sometimes I thought maybe I had crossed plug leads. But they were fine / correct. Then I thought maybe coil pack, so I swapped that... no difference. Next I wondered if it was the immobilizer, but I got a new battery for the remote and did the reset trick ( disconnect battery, turn on headlights ). No change, and the padlock on the dash goes "out" when I turn the key. In between, the starter failed... so I got another one. I also replaced the plugs. All my "mates" said it was the CAS for sure, so today I replaced that. 4 hours later it was all back in. No change.

Now I am kinda nowhere, because I think I've gone through all the logical things that could be causing the issue. I could easily throw away $1500 replacing parts ( fuel pump, both CATs, ECU, BCM, various sensor) and still not get it running because I never got to the bottom of it.

Is this some weird ECU thing where the map is off? Or it's forgotten the engine timing? As far as I can see all the peripheral stuff is fine. I'm through the looking glass now. Anyone had this happen? What did you do? What fixed it?

 

[krusing]

Sounds like a Vac leak to me, but that would be the first thing to look for,
Or the vac hoses not installed correctly.

You should be able to swap out a motor of the same type and should fire up ok,
but,
Did you use the original SENSORS from your old Motor ?

 

[twentyfouroz]

Sounds like a Vac leak to me, but that would be the first thing to look for,
Or the vac hoses not installed correctly.

You should be able to swap out a motor of the same type and should fire up ok,
but,
Did you use the original SENSORS from your old Motor ?

*mostly. The coolant temp sensor and canister purge is not the old one, TPS, MAF, Crank Angle, CPS, both 02's are the old ones. Plenum, Injectors and fuel rail also off the original (running) engine.

 

[krusing]

*mostly. The coolant temp sensor and canister purge is not the old one, TPS, MAF, Crank Angle, CPS, both 02's are the old ones. Plenum, Injectors and fuel rail also off the original (running) engine.

that shouldnt effect it,
I was thinking the CAS, Knock Sensors, the CAM Sensor/s, IAC and TPS as you mentioned above.
Hmm, VAC Hoses sounds like 1 of the issues.

 

[twentyfouroz]

that shouldnt effect it,
I was thinking the CAS, Knock Sensors, the CAM Sensor/s, IAC and TPS as you mentioned above.
Hmm, VAC Hoses sounds like 1 of the issues.

Well... you were on the money. It was a leak... a bad one... but not what you'd expect! Probably a rookie mistake on my part, but this morning I was just looking all around the engine and just asking myself if I had missed something. I went and had a look at the old engine, and suddenly it hit me. I looked on one side and I could see a weird mismatch between the plenum and the intake manfold. They didn't match! Then I started thinking... I swapped over the throttle body, plenum and injectors but left the manifold in place on the new (old) motor. I immediately grabbed a 6mm drive and pulled the top off, and there it was.... the port that lines up with the manifold going... nowhere! I poked a screwdriver through it, and sure enough... it was completely open! All that air was by-passing the MAF and just going in through the port. I made a plug and sealed it up ( will do a better one later ), reconnected the battery, one crank... VROOOOOOOM! Runs smooth AF now.