Fun with a 3400 Fiero

[MDFiero]

Alright I have myself a situation. I haven't been able to do any work on my 3400 SFI 1986 Pontiac Fiero since the shop that was "supposedly" doing the swap shut down.

Backstory, I bought the car when I was 16, the engine went in my senior year. I was young and naive and had some cash saved up so I went to a "performance shop" to do the 3400 SFI engine swap. Well the shop shut down halfway through the swap and now I have had this car with the engine in and everything hooked up for the past 5 years. My mechanic friends say we can pull the engine, clean it up the right way, and put it back in knowing it is the right way with everything hooked up.

Now I have the time and resources to fix this car up and get it running, which it really isn't ready to do yet. I have the car and the engine is in, but the exhaust is screwed and the wiring harness looks like complete trash.

Here is my problem. I am planning on pulling the engine out and completely re-doing the exhaust as well as the wiring harness. I have the exhaust pretty much figured out, but the wiring harness is going to present the problem.

It is the 3400 SFI engine attached the the 4-speed tranny from the v6 2.8 that used to be in the car. Is there a wiring harness/ECM that I could use as a base to make this easier? I have a feeling that the entire system that this so called "performance shop" used for wiring/ECM is trash, and since I didn't have to pay for it I have no problem throwing it away and going with something that I know will be correct. I don't have much experience with wiring/ECM so this should be fun. Thanks in advance for the help, I am basically just looking for a starting point right now.

[RedZMonte]

What year is the engine/ecu? you can use just about any 3x00 harness from what i understand they are basicly the same.... Depending on if your running a OBDI or OBDII computer. IIRC all the 3400's are OBDII from the factory so it would be best to run a 1996+ harness so that your OBDII computer will work with all sensors like EGR, Knock sensors ect... now the question is what ECU do you need to run the trans? cause that could make it easier to go OBDI and run a 3100 harness/ecu.

S

[IsaacHayes]

I would keep it OBD1, for sake of simplicity and that anyone can burn you a 3400 swap chip that has done them before and you can throw that in and be good.

A harness from a FWD 3.1mpfi engine would be a good place to start with, and the same ECM as well.

You'd just have to swap the knock sensor to an older OBD1, preferably from a 3.4 RWD camaro motor or 3.4 DOHC (lumina, z34) motor. Then you'd run the engine like normal OBDI DIS runs, using only the 1 crank sensor in the block and leave the 24x one behind the crank pulley and cam sensor not connected to anything.

You'd wire in the injector harness to the MPFI wiring of and you'd be ready to roll. Block off the EGR, or if you are REALLY adiment about putting it on, get a "3 tower" EGR from the car you take the wiring harness from, then buy the EGR adapter stuff from the WOTTECH store here for whatever year your 3400 is.

The auto trans in the Fiero is not electronically controlled... So only thing need done there is running the TV cable up to the TB. For that look at 3100 (94-96 era) cars for their throttle body linkage, there will be a spot to hook that up on there, and you can swap the throttle shaft to the larger 3400 throttle body no problem. Also get the throttle cable bracket from a 3x00 car that has the cutout for the TV cable to fit in there. I think I've seen it on a 96 3100 car, but my 94 3100 does not have the cut out. Or you could cut out the hole for it yourself too..

Wait................... 4 speed that CAME with the car?

That must be a 4 speed muncie manual transmission, as the Fiero automatic is 3 speed. Cool. That makes it even easier.

[robertisaar]

Wait................... 4 speed that CAME with the car?

That must be a 4 speed muncie manual transmission, as the Fiero automatic is 3 speed. Cool. That makes it even easier.

keeping it a manual just simplified everything 2-fold...

[MDFiero]

What year is the engine/ecu? you can use just about any 3x00 harness from what i understand they are basicly the same.... Depending on if your running a OBDI or OBDII computer. IIRC all the 3400's are OBDII from the factory so it would be best to run a 1996+ harness so that your OBDII computer will work with all sensors like EGR, Knock sensors ect... now the question is what ECU do you need to run the trans? cause that could make it easier to go OBDI and run a 3100 harness/ecu.

S

The engine is a 3400 SFI from a 2000 Impala I believe. Now as for the ECU/harness I have absolutely no idea.

keeping it a manual just simplified everything 2-fold...

How so?

[robertisaar]

less mechanical connections necessary to have it run correctly...

[ForcedFirebird]

Where are you located? Maybe close to one of us here on the board can help out.

I would use the OBD1 as well.

[MDFiero]

I am in Maryland. What Harness and ECU should I be looking for to use with the engine/trans. I mean like what year and model car should I be looking out for?

[americasfuture2k]

i second, third, forth or whatever with everone about the sticking with OBDI. far easier, less wires and no VATS or PASSKEY or whatever to deal with. or try and bypass.

which 4 speed do you have? the one from a v6 or the duke one? i know one fo the duke ones, one is an economy tranny, the v6 4 speed is just a 4 speed. nothing special. i think there might even be a variation in duke 4 speeds, like a regular geared one. im rocking the getrag 282 in my fiero. love it, but my friends 4 speed from a v6 mated to his 3800SCII does pack a punch. when it was a 2.8, it kept up with my fiero when merlot owned it and had a mild 3.4 in it.

im guessing hes in Maryland guys. just a guess from the big MD infront if Fiero

[ForcedFirebird]

Grab a complete harness and ECM from an early 90's Lumina - ECM #1227727

[MDFiero]

The 4spd is the 4spd-Muncie from the V6. I used to have a 2.8 in it.

[americasfuture2k]

Ooo the underhood ECM.

[robertisaar]

Ooo the underhood ECM.

correct. you will find them on quite a few vehicles...

every vehicle on this list uses a 7727 or a 16149396. you could use a 16149396 in place of it if you can't find a 7727.

L98
90-91 vette only yellow/gray, red, green, brown

LQ1
93 W-car only orange, natural, green, blue
91-92 W-car only orange, white, green, blue

LH0
93-94 W-car only orange, natural, green, blue
90-92 W-car only orange, white, green, blue
89 W-car only black, white, gray, blue

LR8 (2.5TBI)
91-92 W-car only orange, natural, green, blue
90 W-car only orange, natural, gray, blue

LB6
88-89 W-car only black, white, gray, blue

[MDFiero]

So turns out the ECM in the car is from a 99-02 3x00. I had a friend who works at a parts supplier run the part #. So presumably I should just make sure it gets reflashed correctly and find a suitable wiring harness? Will any wiring harness work?

[americasfuture2k]

it is going to need to be trimmed/shortened/lengthened. and finding a good spot to mount the ECM. i suggest getting a NormsFiberglass battery relocation tray because it is the cheapest out there to use and comes with a good length of cable to go from the batt to the starter and to the C500 power distrobution block. and mounting the the ECM in place of the battery. adn maybe the coilpacks in the same location, just shielded and covered of course.