3100 to 3500 swap not Going Well - help

[Joseph Upson]

Dude, did not know about the twist and I assume it may need the exact gauge to ensure proper flow if the TWIST makes that much difference. Any idea on what Gauge of wire to use. and if I did get them reversed does anyone have a PIC of the plugs and what wire goes to which in each side. I will replace the wire end to end, I spliced into it last time to extend. But since this seems to cause some issues, I will replace the whole thing and twist 9 times per foot

Once I do this I will try the other items, GROUND (assume you mean the Engine ground and those are in place on each side of Engine to TRANNY bolt.
Are there other grounds. Plug wires are all new and separated best as possible with the clips and such.

Thanks
Rick

That's 9 twists per foot minimum, going over is fine.

[malibuRick]

SUCCESS !!!!

well, I guess the wire was it. got one from a 3400 put everything back on and she fired right up and idled smoothly. Dang Wire, can't believe that was the root of all my ills. Lessons Learned. Thanks everyone for all the feedback and assistance in the SWAP. Glad to have her back on the road.

[IsaacHayes]

Sweet... So how fast is it???

[Guest]

I tried a used ECU also just for grins, it would not even start so I dont think it was good.

The ECU is likely fine. You would need a TECH2 to program the ECU for proper VIN verification. The newer OBD2 GM ECUs, BCMs, even the radios need to be programmed when swapped into a different vehicle through the use of a TECH2.

[malibuRick]

Where can i get TECH2

I tried searching briefly and could find no place to purchase such a re-programmer. Can you suggest a site or location to purchase one.

[Guest]

LOL....

GM dealership

Bring about $20 000, IF they'll sell you one, which they won't.

[malibuRick]

hehe, $20,000

wouldnt need to fix this car if I had an extra 20K laying around - hehe. Oh well, it seems to be running fine. Except I am getting O2 sensor issue and Check engine light coming on. I replaced both O2 Sensor. 180K miles and 10 years, figured it was about time for some new ones. Driven for a bit but light ECU will not take code away, Do I need to reset the code. I thought enough sampling and the ECU would correct the O2 sensor codes???

Using the EXTERNAL Trigger, should advance or retard the timing a bit? Would that adjust the fuel rich/lean mixture in the exhaust? Assuming the ECU still thinks it has 3100 in there with the 3500. But same injectors and sensors and figured it would give similar exhaust readings in the O2.

Any suggestions? Catalytic converter? Code is for BANK 1. thought that was the BEFORE Cat, but replaced both. Still get code.

Rick

[Superdave]

I wouldn't mess with the trigger's timing at all, you might end up hurting the engine. The VE is different between the 3100 and 3500 since the heads flow so much more, the ECM should be able to handle the fuel trims well enough but if you want the most out of it tuning will be needed.

FWIW, i run less WOT spark advance on my 3500 then the original 3.1 used.

[IsaacHayes]

Make sure your wires aren't cut/damaged for the O2 sensor circuit as well......

DHP or HPT would allow you to tune the current ECM to get the most out of it.