My first EFI swap- a few questions

[Phill]

I am in the process of swapping a 3.1 into a '76 Chevette and have some computer questions. The Engine/ ECM are from a '90 Cavalier Z24 with a 5-speed, the tranny I plan on using is a non-computer controlled auto from an S-10.

First of all, how much of what was originally connected to the ECM is needed? Obviously I need all the engine wiring, but there was alot of stuff connected to the ECM that seemed unnecessary. (brake light, A/C stuff, vehicle speed). If it needs a signal from this stuff, is there a way to bypass that?

Second, the ECM had been stripped off the car, so obviously I plan on getting one from the same car but will anything '90-ish with a 3.1 work? Is there a better one to get?

I know I'll have tons more questions later but this is it for now. I'll try and get a cardomain page up for this car, it should be a pretty cool little toy

Thanks, any info is appreciated
Phill

[sharkey]

you are going to need an ecm from a 89-91 2.8/3.1l, best to find a j body. this ecm is a 7730. try to find one fromn a 5 speed.

there is a lot hooked to the ecm, but some wont be needed. you will need to hook all of the sensors on the engine up, this includes
-map
-tps
-coolant sensor (the 2 wire one, 1 wire is just for the gauges)
-intake air temp
-iac motor
-injectors
-knock sensor

you will not need to hook the a/c pressure switches up, however, if you are going to use the ecm to controll an electric fan (its a good idea, no dealing with a clutch fan or temp switches), you will need to ground the a/c fan request wire or the fan will run all the time. if you get a non a/c ecm, no worries about doing anything with this.

the power steering pressure switch does not need to be hooked up.

i would hook up the check engine light from the ecm. many people wouldnt, but if there is a problem, you can diagnos it. same thing with the diagnostic plug, id put it in. if its in you can hook a scan tool to it to read for codes and the data stream (write the vin number down from the car you get the ecm from, you need it in order for the scan tool to comunicate with the ecm)

what tranny are you planning to use and what year is the vehicle its out of??? if you are going to use a tranny with lockup (like a 200c, 200-4r, 700-r4) you can use the ecm to trigger lockup, but this would require a vss input. if you are using a 700r4, most have en electronic speedo, and you would be able to hook this right to the ecm you are using. if this is something you are wanting to do, i can tell you more info on how to wire it up.

[Phill]

Thanks alot. The tranny will most likely be a 4-speed from an '86 S-10. I think it's a 700r4(don't quote me on it...). I'd prefer not to have the ECM hooked to the tranny if I don't have to. If it's an electronic speedo will I still be able to hook up a mechical speedo?

For a lockup torque converter I'll probably use the Chevette setup (as long as it just needs +12v) as it's extremely simple- just needs vacuum and brake switch hooked up.

As for the diagnostics port and check engine light I definately will hook those up. A have an '88 YJ with a 4.0L swapped in and the the guy who did it didn't hook up the check engine light- what a pain in the @$$! Especially when it already has one!

Thanks for the info
Phill

[sharkey]

iirc, an 86 s10 will have an electronic speedo. there are converters out there to convert the signal to a cable drive speedo.

[Guest]

Mechanical speedo in the '86 '92 IIRC was the change over to electronic VSS in the S-series pick-ups/SUVs.

I used a gear adaptor that seems to come on ALL S-series, and modified one to accept a VSS sensor from a late '80s FWD manual tranny, from a Cavalier IIRC. Which BTW you should try and match as closly as possible, VSS to the ECM you are using, there were some variations on PPM between models even from the same year.

[Phill]

Thanks guys. First off, this may be a stupid question but what does IIRC stand for?
Second, will there be any problems if the computer doesn't have a VSS input? I want as little wiring as possible (I hate wiring so I decide to build a multiport Chevette... duhhhh). Wait a second- does that stand for If I Remember Correctly?
I haven't gotten too good of a look at that tranny so I dont know if it's got a speedo cable (I hope Raven's correct- that would simplify things) But if it doesn't have a speedo cable, I could swap out the tranny tailstock for one that does, yes?

Once again thanks for all the help guys. This project should go way smoother now
Phill

[bszopi]

Wait a second- does that stand for If I Remember Correctly?

There you go..

[Guest]

You'll still be able to drive it, but the mapping will never compensate for accekl enrichment, or decel stall saver, and many other little variables that the VSS has control over or at least has an effect on. The VSS is not hard to wire, it's two wires, the harder part is making an attachment that will actually drive the VSS and if need be, the speedo as well.

[Phill]

HMM... Guess I really should hook that up then. I'm interested in seeing how you modified that adaptor piece (what was the purpose of those anyway?). I should be able to rig something up- I have access to a fully equipped machine shop with 3 CNCs and no work to run on them.

I'll see if the VSS is still in one piece on that Cavalier and play around with it a bit.

http://www.cardomain.com/ride/2499331/1 Here's a link to the cardomain page.

Phill