V6 replaced into car that was a Supercharged V6, now chugging at idle, what's wrong?

[Luke Johnson]

So the bottom end from my supercharged V6 VY series II seized, and yesterday we installed a 'normal' non supercharged V6 into it. Had a few issues during install, such as EGR valve tube doesn't seem to have an equivalent on the supercharged exhaust assembly so we just blocked the egr valve at the intake manifold end. Also we broke a sensor on the right side (when facing the motor) header meaning that we had to hack together the wiring to connect that sensor to the loom. There is also one 'loose' plug on the right hand side of the main loom near the firewall, it seems to go to a vacuum advance on the supercharged motor but can't seem to find the equivalent on the non supercharged manifold that is in there now.

Had some other issues such as the connection to tailshaft spline alignment, ended up removing that whole rubber connection and reinstalling it back after sliding the mini shaft into the gearbox. Also, installed the linkage upside down (several times!), couldn't figure out why the gears were shifting backwards

Ok, to the main point.... it starts and run pretty decent at high revs, but chugs heavily at low revs and tends to stall if a slight amount of acceleration is not applied. We have tweaked the idle cable a bit but you can tell even at 1000revs that something isn't quite right. Also, the check engine light / warning is on. I'm feeling like it must be on of the sensor connections in the loom that is throwing things out, because we seem to have all the vacuum hoses connected properly. One other thing is that we did a 'join' on the main fuel line into the manifold and perhaps we have restricted the flow a bit.

So... I realise it sounds like a few dodgy things, but I'm pretty sure that just one of those will be causing this chugged. At high revs and high speed it actually goes really nice, it feels smooth and grunty.

Please help me fix the chugging, or it is going to go to a mechanic and $$$... Thanks!

 

[Luke Johnson]

A couple of other things: it has new plugs, good leads, good alternator, good battery. New oil, new coolant etc.

 

[SweetWagon]

Did you change the memcal? Tune will be way off otherwise

 

[Smashfist]

It's not gonna be happy with you blocking off the EGR without computer adjustments to suit. Explains why it runs like a bag of crap at low RPM/low throttle situations - that's where it's going to adjust fueling due to EGR usage.

 

[Luke Johnson]

Ok, this is the memcal/computer from the supercharged version, connected to the non supercharged one. How do we make it right? Does a mechanic have to do this retune with some fancy computer, or can I do it?

 

[EYY]

I can't see why it would idle any differently. The tune should be close enough for the ecotec at idle as they'll have similar fuelling requirements when the s/c engine has the boost bypass valve open (light throttle driving/reversing/idling).

At higher rpm, it'll be injecting way too much fuel in and running too rich for the ecotec, so I'd assume that you'd be mainly noticing problems at those revs.

Either way, having it retuned is the best thing to start with.

 

[Luke Johnson]

At higher rpm, it'll be injecting way too much fuel in and running too rich for the ecotec, so I'd assume that you'd be mainly noticing problems at those revs.

At this stage it seems the opposite is happening (problems at low revs not high), so does mean it is probably some other issue like vacuum or fuel flow or a sensor problem?

 

[Bowen]

Hmmm wonder if your loosing vacuum perhaps one of the vacuum connections you didn't put on goes to the vacuum ball and is subsequently making you loose vacuum from all the other vacuum points.....

Supercharged tune also has 2 deg more base timing advance but should be fine ....

What sensor did you break? It wasn't the speed sensor was it? Car will stall and run like poo without speed Input

What's the code your getting? Could be an indication of what's going on...

 

[SweetWagon]

Ok, this is the memcal/computer from the supercharged version, connected to the non supercharged one. How do we make it right? Does a mechanic have to do this retune with some fancy computer, or can I do it?

Memcal from a VT V6 should work, get one from a wrecker and try it.

 

[Decicrate]

If you have replaced the supercharged engine with a non supercharged engine and have not changed the tune to a ECOTEC then that will be the issue.

The supercharged engine runs a bigger injector than the ECOTEC, and the whole tune will not be right for the ECOTEC..