Was trying to follow the l67 swap walkthrough to put a l36 into a 97 monte ls with the 3100. found a donor 3800 with complete tranny and wiring/pcm from an 01 imapala... yep learned later that I picked a HARD one. physically fit with the small mods just like in the walkthrough. then started wiring... got the pinouts from the 97 c100 and the impys strut tower plug, but no one can give me the pinout for the plug that goes from the underhood fuse boxes through the firewall, so i am trying to trace from the fuse box and try to figure where they go on the c100. can't even get it to roll over, think the main problem are 3 wires on the monte, 2 are for tranny park signal and one for theft deterrent. To the point where I am looking for any light at the end of this tunnel. Would the wiring harness from a 99z34 work with an 01 impala 3800, if so, would i use the pcm from the impy or the z34? can the harness and pcm i have be used with what i have? Any thoughts would be appreciated.
Thanks.

 

I'd just get a harness from a 98-99 Z34 or LTZ - it's the same engine, but you may want to see if the gear ratio in the tranny is the same (which it SHOULD be)

You should probably use the Impala PCM, but a Z34/LTZ PCM may work also.

 

thats why im keeping the 3100 til it dies

 

I finally found a harness, 98 monte carlo z34 with the 3800, i have the pinout diagrams for my 97 3100 c100 and a 99 3800 c100, does anyone know if the 98 and 99 c100 have the same wiring?

 

OK, heres where I am at. Got a 98 z34 harness and pcm. C100 plug was identical wire for wire. Couple of issues:
The temp sensor has three wires on the engine and two on the harness, hooked up the black and yellow left the green unhooked.
Alternator has 2 wires on the alternator and 1 on the harness, hooked up the red and left the orange unhooked.
Have 2 O2 sensors hooked up but have a plug for a third on the wiring harness ?? left it unhooked.
Tranny linkage reads a gear off (park is reverse), gonna try to swap the arms from the old tranny to see if it brings it back.
tranny kickdown cable needs to be reworked to fit the new throttle linkage and the throttle only pulls about 90% wot.

heres the biggie: ran it multiple times, smooth idle, quick start, all good.I drove it up to the lift to put some exhaust on. At this point I left. Some friends/family welded the stock 3.1 exhaust to the 3.8 downpipe. Now I get a call saying it won't start, it just backfires. I'm thinking it is basically one of three things: They may have tacked it on the car, could possibly have fried my one-day-old (to me) PCM, or maybe the tiny 3.1 exhaust is just way to restricted or plugged for the 3.8 to run (??) or maybe some fluke s thing like a bad wire connection or something. Anyone have any insight on the exhaust restriction/collapsed thought?

Anyone have any solutions to any of these conundrums?
Thanks again

 

Another day and some more money:
Pulled back the exhaust a little, no change. Seems like it basically has no spark, one spark as the key is released. (pulled plug and got same thing grounded on exhaust)
Checked cam and crank position sensors as the haynes manual said, checked good. Have power to the icm but when i pulled the coils and tested across the coil signal terminals nothing until the key was released, then one signal which was causing the backfire. Got another ICM from a junkyard but no change.
Still thinking either the icm or pcm got fried from welding the exhaust without unhooking the battery.
One possibly odd thing though, the ignition relay buzzes when the car roles over and a few seconds afterwards, i tried swapping out a couple of them and cleaned the terminals. If we turn the key until it is about to role over the relay starts buzzing. tried checking the connections as well as possible.

Ideas?

 

sounds like the engine is just dead or something to do with the crappy alarm or maybe the starter is too small?

 

starter or bad engine will not cause the ignition alarm to chime when turning over... sounds like wiring to me.

1st: check all fuses. i know sounds simple but there are a lot of them. chances are something isnt right.

2nd: i used a 98 Z harness for my swap recently and there were only 2 O2 sensor connectors on it. what is this 3rd connector you speak of?

3rd: have you tried unplugging the battery for a while and seeing if you can start it? id say leave it unplugged for 1-2 hours then try.

4th can you turn it to key on and get an OBD2 scanner to read for codes? if you cant read codes from the PCM then the PCM could be dead or a wire is loose or bad.

5th: if the temp sensor on the 2001 L67 doesnt match the sensor on the 98Z harness go to junk yard and get a sensor from a 98/99 l36 as it will match the harness and work with the PCM. figure out what that 3rd connector is that you think is an extra O2. if you can get a pic post it i should be able to identify it. if not i can post a pic of my harness that i used. Trans range switch.... if this isnt correct, it will keep the car from starting cause the car wont think it is in park or neutral... you can try to start it in N? these cars dont have trany kick down cables... not sure what your looking at, but it could be the cruse control cable. it should fit fine and if not it isnt critical for the car to run. also the 98/99 3800 throtle cable is diff then the 3100 and 3.4 DOHC. i got mine from a police 9c3 car.

6th: try disconnecting the MAF and the O2 sensor... this should push the computer to run in limp mode. this along with trying to start in neutral should help rule out some variables.

also i have a zip file with all the info i used for my harness to do the swap. if you PM me your email i can forward it to you. it is 20+mb so i cant post it or PM thru the board.

 

So it turned out it was two things, we had a loose ground to the ignition relay and the PCM was bad, probably actually from us swapping them back and forth and whatnot.
Here's the kicker, ran it for a while then started putting it all back together, went to swap out the tranny linkage when the dang thing snapped inside the tranny case. 7 hours later, we hope we have it back together right and the car is waiting to be reassembled.

It is the cruise cable, needs the plastic spring loaded clip, got one, but would have to cut the end off and find a way to put a new end on.

The engine harness has a place for 2 02 sensors, but the 97 monte has the downstream sensor wired into the body harness so it is already hooked up.

Good idea on the temp sensor, might even be able to pull it from the 3.1.

 

the body harness will not connect the the pcm. so the rear O2 will never talk with the pcm and apear to be missing. if you can connect your harness to the body harness or just use the harness and remove the left over 97 harness then you should be golden.

i did what ever i could to removed the 96 harness in my car and use the 98 Z stuff. there are very few frankenstien areas of my car. i did this on purpose so if i were ever to break down the car would basicly be no different then a 98 Z or 98 GTP (once my topswap goes on.) when my DOHC died and it was towed to a local shop, when i poped the hood they scratched their heads clueless on what did what on the engine as if it came from outterspace!!!!! i spent an hour with them trouble shooting too before my wife that i just married the day before demanded we rent a car and get on with our honeymoon! if i had the 3800 it would have been a no brainer to figure out. so this is why its best to have it as stock as possible.