FED UP. electrical wiring woes inside M30 related

[Mr. Burns]

My m30 swap has been hit and miss when it comes to drivability...my birthday passed, and my car failed the smog test MISERABLY.

Long story short, I used my factory M20 harness when I swapped in my M30.

I ran into TPS sensor issues (reading WOT) when supposed to be at idle, reversed that reading, and worked well for awhile...ran pig rich.

Eventually just coughed and died even when trying to turn over. Plugs are charcoal....

I've purchased a legit M30 5spd harness, and will be removing the M20 harness.

I'll be doing this in hopes of resurrecting my project to run properly in order to pass the smog test legitimately.

the TPS issue should be resolved, plus the wire fitment I would assume would be a little cleaner/tighter.

has anyone else given up on their M20 wire harness with M30 engine and swapped over?

I feel so aloooooone:(

[Ether-D]

Well, I went and bought a basket case 944 instead of tackling the wiring on mine, so that tells you how I felt about it. But all hilarity aside, the m20 harness shouldn't be a problem unless there's something wrong with it physically. I'm only repeating what I've read on that though.

[EatsHondas]

My m30 swap has been hit and miss when it comes to drivability...my birthday passed, and my car failed the smog test MISERABLY.

Long story short, I used my factory M20 harness when I swapped in my M30.

I ran into TPS sensor issues (reading WOT) when supposed to be at idle, reversed that reading, and worked well for awhile...ran pig rich.

Eventually just coughed and died even when trying to turn over. Plugs are charcoal....

I've purchased a legit M30 5spd harness, and will be removing the M20 harness.

I'll be doing this in hopes of resurrecting my project to run properly in order to pass the smog test legitimately.

the TPS issue should be resolved, plus the wire fitment I would assume would be a little cleaner/tighter.

has anyone else given up on their M20 wire harness with M30 engine and swapped over?

I feel so aloooooone:(

The M20 harness is easy mode. No modifying except for wire lengths, and there's barely any of that.

How are you sure you don't just have regular old E30 problems unrelated to the engine swap? The M20 forum is full of people who can't troubleshoot their stock setup. I would go back to the diagnostic basics before radically changing your hardware.

[Mr. Burns]

I have. Fuel pump, flow, cat, spark,maf,iac,etc etc.

Im looking into megasquirt at this rate...considering I may boost in future

[Mr. Burns]

Furthermore...to add to the issues...

Body harness plug(c101) is female on e30.

My M20 harness fit perfectly with its male c101.

M30 harness is female engine harness C101...what gives.

[lukeADE335i]

It sounds like you're having normal Motronic issues... don't give up (the Megasquirt will be a world of pain vs just troubleshooting the Motronic).

If it runs pig rich at all times, are you sure the spring in your AFM is adjusted correctly? Also, is the O2 sensor working correctly? Are the injectors leaking or stuck open? Is the thermo switch for the Motronic working? etc.

I ran mine without the O2 sensor for a while and it ran ok, just on its base maps, but with a properly working 02 sensor, it was a noticeable difference in drivability once the computer had adjusted the injectors.

I've had mine on the dyno to check emissions, AFRs etc. and the Motronic 1.3 worked perfectly with the M20 harness.

The best Motronic troubleshooting guide I've found is here:

http://www.hiperformancestore.com/motronic.htm

Good luck! It'll work out :)

[Mr. Burns]

It sounds like you're having normal Motronic issues... don't give up (the Megasquirt will be a world of pain vs just troubleshooting the Motronic).

If it runs pig rich at all times, are you sure the spring in your AFM is adjusted correctly? Also, is the O2 sensor working correctly? Are the injectors leaking or stuck open? Is the thermo switch for the Motronic working? etc.

I ran mine without the O2 sensor for a while and it ran ok, just on its base maps, but with a properly working 02 sensor, it was a noticeable difference in drivability once the computer had adjusted the injectors.

I've had mine on the dyno to check emissions, AFRs etc. and the Motronic 1.3 worked perfectly with the M20 harness.

The best Motronic troubleshooting guide I've found is here:

http://www.hiperformancestore.com/motronic.htm

Good luck! It'll work out :)

it's not MAF as I've swapped them out, O2 sensor is the proper one and (supposedly) working correctly
haven't put any thought or research into the injectors tho...

thanks for the link:D haven't checked that one our yet

[lukeADE335i]

The link mostly focuses on e28s, but it all applies to the Moronic 1.3 system too.

It's a comprehensive step by step to troubleshoot the Motronic.

[Mr. Burns]

BOOM! RESOLVED!!!! traced back to simply a loose connection at the fusebox....

didn't need to replace the harness afterall.

[Ether-D]

Yes!! Good to hear man.

[quickervicar]

Awesome

[lukeADE335i]

Good stuff! I love it when problems turn out to be simpler than first thought :)

[Mr. Burns]

Hate to be posting this but the problem id back.

Here's a video of its behavior.

https://vimeo.com/142938357

Is realize the video kind of sucks...
But it idles great however when gradually increasing throttle it hiccups and it's like the tps hits a flat spot between 1300rpm to about 3000rpm



Also at WOT it's like it hits a brick wall.

Values:

Air fuel mixture is stuck at 50%
O2 sensor readings arent fluctuating properly... go from 0.450mv to 0.520mv...




I'm open to anything now.

It's not mechanical it's electrical

[quickervicar]

Just thinking out loud here, so forgive me.

The engine only measures the air passing through in two places, correct?

1) AFM on the way in
2) O2 sensor on the way out

If the AFM is stuck at 50%, I'd start tracing that down.

What injectors are in this thing? My 535i ran pig rich when I swapped out larger injectors without a software change. (long story)

[Mr. Burns]

I'm a bit of a cad.

I was running a m20 tps the entire time, the wires were simply reversed thinking it would work.

On a whim I plugged in a m30 tps (265) and all went well.

My guess is the incorrect tps was giving the open loop o2 readings.

So legit....this is finally resolved fir good now.