Older Model m20 Swap

[CleanE/NoCut]

Hello R3vlimited, this is my first post here and I need to know some info. I have a 87' 325i 5-speed that has an engine that is in poor condition, one that would cost too much to rebuild so I am interested in buying a 325i 91' m20 engine that I found. To do this swap I know that I need to change the wiring harness so that the rpms would work (heard the rpms dont work when you change the engine to a newer model engine, not completly sure if this is true) but could someone please tell me or make a list of exactly everything I would need for this swap. I really want this car to be on the road asap, THANKS! :D:D

[Bretts85E30]

If ur just swapping the engine and not the harness u don't have to worry about anything just make sure the sensors are all in the right spots
If u plan on doing a harness swap then there are plenty of write-ups on how to do it just gotta bypass the c104 connector next to the dme

I personally didn't have to when I swapped to the early I harness it was just plug and play minus making a c101 adaptor for the square to round style.

[CleanE/NoCut]

So is it worth changing the wiring wiring harness? It seems like it is possible to do without a harness change

[MR 325]

If your 87 is a 325i then swap that harness on to your new engine. Problem solved.

The only other thing you'll need to do is swap the water pump on the new engine to a early model pump.

Anything you do beyond those two things is up to you.

[TobyB]

But don't plug an 87 body harness into a 91 engine harness- that will result in smoke....

I seem to remember that pin 20's the offender, but it's been a while.

So swap the harness, the waterpump (buy a new one!) and probably the thermostat
housing (IF there are a different number of senders) and be happy.

t

[CleanE/NoCut]

Well who here actually tried it? Cause one person is saying I should keep the 87' harness others say I need to switch it with a new 91' one. I am still not completely sure.

[golde30]

use the 87 harness, makes your life easier.


also, wtf is up with your user name man, sounds like yer pushing pills.

[MR 325]

Well who here actually tried it? Cause one person is saying I should keep the 87' harness others say I need to switch it with a new 91' one. I am still not completely sure.

This is not complicated. Use the 87 harness and you will have no issues.

[CleanE/NoCut]

I thought the name is catchy, I'm not pushing pills haha. Do I need to put the 91 dme/ecu for the new engine?

[SpecM]

bub, the engine is 100% the same

swap the LONG BLOCK and keep everything else the same (harness, DME, sensors)

you can use the 87 w/p on the newer engine but it would be a good idea to buy a new one (buy one for an 87)

also replace timing belt, other belts, hoses, rear main seal, etc...

[MR 325]

You can use the 91 DME with the 87 harness if you'd like to.

[CleanE/NoCut]

Is there any advantage using the 91 dme or will the 87 work just as well

[Bretts85E30]

More codes and stomp test I believe

Although I can't get the stomp test to work in part due to no check engine light wired into my
Harness swap and no light on my early model cluster.

Would make life a helluva lot easier to figure out if I still have problems that would trigger a code on a 173 dme

[CleanE/NoCut]

The 91 engine, the car it was in was automatic, so I heard swapping the new 91 automatic dme would make the car shift wierd. Anyone know what I should do?

[SmokeE30]

Automatic and manual cars used the same DME there won't be any issues