So I have a 1993 LS with stock B18A but I recently was in an accident and now have found a stock 1990 GS loaner shell missing the motor and transmission but everything else is there and both are manual transmissions. My question is what is needed to put my OBD1 swap into OBD0 car that will cost me less money and headaches? Thank you!
if you want to remain obd1, and don’t want to buy anything, transfer the engine and entire harness, ecm, to the 90gs. i’d also delete the abs, using lines from the 93 as well. but that’s personal preference.
Transferring all the OBD1 wiring is not recommended, it would require that you tear down the entire car headlight to taillight and remove 95% of the car’s wiring and transfer it over. IMO this is not really a good option.
But there are 2 really simple options:
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Keep the car obd0. This means you will use all the wiring from the 90 and will need the exhaust manifold, injectors, distributor and ecu for the 90 as well. All of these components will swap to the 93 engine.
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Convert the car to obd1. This is most easily done by buying a conversion harness or two which are very affordable these days. If you go this route you’ll want to use the exhaust manifold, distributor and ecu from the 93 but you’ll still use all the wiring from the 90. You can use injectors from either car, the injectors from the 93 will require some rewiring (and removal of the injector resistor box). The injectors from the 90 are plug and play and require no modification.
There are lots of additional details for these two options available if you search and within each option there are more options for the specifics - e.g. you can use either set of injectors, you can de-pin / re-pin or you can use conversion harnesses…etc.
oh, you have to swap the dash and interior harness too? i did not know. yea that’s a lotta work
There’s no such thing as an “interior” harness. Your car basically has 2 harnesses. The first is the engine harness which is easily removed with the engine. Second is the “main” harness. This is one large harness that has almost all the remaining wiring. It literally runs from your headlights to your tail lights and is not broken down into multiple smaller harnesses which can be removed independently of each other. There is also a small dash subharness which can be disconnected from the main harness and is typically removed with the dash.
Could I use my existing manifold and just run longer wiring?
You could, but you may run into problems with the O2 sensor reading correctly. Do some searches related to the O2 sensor placement and why the 90-91 version is “unheated” and the 92-93 is “heated”. As with most of your other options there are a handful of ways you could tackle it.
i see. so a body harness. and that plugs into the ecm?
the 90-91 manifold bung placement takes readings off of only 2 runners, whereas the 92-93 bung is at the collector, taking readings from the entire exhaust. you shouldn’t run into any problems using the 90-91, but if you have the choice, 92-93 is a more accurate measure
I’m trying to get the guy to search and you keep feeding him misleading info, lol. What you mention is only a minor part and definitely not his big concern. The real issue is placement in regard to how close the sensor is to the head and thus how hot the exhaust gases are at that point. The single wire sensor is designed to be placed where the exhaust gases are hotter. The 4 wire sensor has a built in heater so that it can be placed further down the exhaust stream.
If you :search: :search: :search: you’ll find that the topic was discussed a lot back before obd1 conversions were common, there’s plenty of info out there to help you decide what the best option is for you.
Yes, the ECU plugs into the main harness, then the engine harness also plugs into the main harness.
[QUOTE=Colin;2322679]I’m trying to get the guy to search and you keep feeding him misleading info, lol. What you mention is only a minor part and definitely not his big concern. The real issue is placement in regard to how close the sensor is to the head and thus how hot the exhaust gases are at that point. The single wire sensor is designed to be placed where the exhaust gases are hotter. The 4 wire sensor has a built in heater so that it can be placed further down the exhaust stream.
If you :search: :search: :search: you’ll find that the topic was discussed a lot back before obd1 conversions were common, there’s plenty of info out there to help you decide what the best option is for you.[/QUOTE]
how was my info misleading?
are you under the belief that it’s going to make a difference running a 4pin 02 on a 90 mani? or even a single pin on a 92 mani?
and is a bigger concern than the fact that with a 90, you’re only reading off 2 out of 4 cylinders?
[QUOTE=welfare;2322702]how was my info misleading?
are you under the belief that it’s going to make a difference running a 4pin 02 on a 90 mani? or even a single pin on a 92 mani?
and is a bigger concern than the fact that with a 90, you’re only reading off 2 out of 4 cylinders?[/QUOTE]
Sorry, I guess that didn’t come off right. I got the impression from your post that he shouldn’t worry about it. I just wanted to make sure he does it right to ensure no issues, but it sounds like we’re on the same page.
no worries. and i apologize for butting in on the thread. i know how annoying that can be. so i’ll say my piece and be out; reason i asked of the main harness is that i had replaced one many years ago in my 91 gs 2dr because of a short which had melted a fair portion of it. i did have to remove pretty much the entire interior, save for the dash, but i didn’t recall having to go past the firewall. but it was many years ago so my memory probably deceives me. come to think of it, the car did have to be torn down pretty far to replace it. i may recall removing the bumper as well. long time ago though.
IMHO, OP, and this is just my opinion, i would try and stay obd1. you really want that 4pin o2. reason being is that the conditions for closed loop with a single pin o2 are rarely met. it’s a very narrow range. with a 4pin, about 30 seconds after start up, conditions will be met for closed loop operation, and in an operational system, they will remain met throughout all driving conditions aside from just prior to WOT. honda, like many manufacturers, runs their open loop on the rich side. being capable of remaining in closed equates to fuel efficiency and savings. as colin stated, conversion harness’ can be had for very cheap these days. you can even buy a distributor conversion harness for around 10-20$. extend the 2 fan switch wires to reach the thermostat housing, and you’re set. this is never minding even the greater tuning capabilities of obd1, since i don’t know the objective of this car.
and don’t try and pull the engine, on it’s own, out the top. it’s a real bitch that way, trust me! haha. there just isn’t enough clearance at the apron lol. lower the engine/trans out the bottom. good luck and, as always, have fun
Well for right now I’m just trying to transplant my motor from my nasty shell to a clean body and get it running. As of now I don’t plan on running any other swap anytime soon. Unfortunately I’m going from my current obd1 to this obd0. I would like to sell all my obd1 stuff to make my money back and at the same time convert to obd0 as cheap as possible.
So im probably going with option 1, doing the swap tomorrow. Thanks guys!
4 hours of driving to get an OBD0 distributor, and OBD0 engine harness im close to being done. Im going to drive with no o2 connected for now until i can find a cheap obd0 exhaust manifold.
But I dont have OBD0 injectors, I am running my OBD1 injectors. Can I still bypass the resistor box and stay with my OBD1 injectors?
if they’re high impedence, bypass the box. it should be fine
So I’ve searched but could not find an answer, trying to plug my 90 harness to 93 injector is a no go. It looks like the injectors have some kind of notch in each of the bottom corners?
So many problems, tps sensor, coolant sensor?? I mean what the heck!!!
You will need to swap the obd1 injector plugs onto the obd0 harness and either connect the wires going to the resistor box together or just use the grey block off resistor plug off of your OBD1 harness. I had to do this when I swapped the B18c into my 91 CRX Si. You will need to also convert the one wire O2 sensor to 4 wire and extend the wires to the back of the header behind the engine. One more tidbit is you will need to swap the exhaust from the 92 over to the 90 because they have a different length cat converter and resonator pipe. Also you will need to get an ecu conversion harness because the ECU plugs are different between the 90 / 91 and the 92 / 93. I used an avid AC.JH.003 on my swap.
It may no longer be available, but you will need something like it.
Sorry guys just frustrated beyond belief with this swap!! Had to drive the other day for 4 hours just to buy an OBD0 distributor and trade my OBD1 engine harness for an OBD0 engine harness only to find out that:
- The harness is missing the coolant temp sensor off the head.
- Missing the smaller distributor plug.
- The injector plugs wont fit onto the injectors.
- I also need to buy a thermo fan switch because its different from 90-91 to 92-93
This is the 5th day im dealing with this now I have to miss work because its not done yet! Had to vent, sorry.