SWAP Thread: '91 325i Sedan - S50b30us

[treff-7]

I used OBDII manifolds with bungs on my OBDI motor, and they didn't bat an eye.

They did look over the cat pretty closely - but mine is OBDI, so I had no issue. Like I said - I think you can go a million times, and it is free if you fail (and only $8.25 if you pass) so I say give it a shot.

Wow! It's really odd that it's that cheap! I thought it would cost $100-$150 at least! I will give it a shot and report back.

[treff-7]

The car still has the original M20 in it for the time being. I failed smog a few months back and had to put in a new cat. It's a California approved cat. I'm wondering if I can reuse it when I drop in the S50 that I just picked up.

The aftermarket cats are good for a long list of cars. schröe30er just bought a magnaflow one and it is good for like 2 dozen different cars varying from 1.6l to 6l so chances are yours will work for the s50 but you should look it up. On the other hand it might not be the best flowing cat for that engine but if it works for a 6 liter engine it should work for a 3 liter as well.

[M3PO]

Are the aftermarket cats approved (with an EO number) for the engine you are running? They will ask.

Pretty sure ebay headers won't fly. But the good news (I guess) is that I am living proof that you can go back again and again and again without issue - so you might as well try. The worst the can do is fail you, and you have to go back again with the changes made.

The car still has the original M20 in it for the time being. I failed smog a few months back and had to put in a new cat. It's a California approved cat. I'm wondering if I can reuse it when I drop in the S50 that I just picked up.

[hwy84]

I'm finishing up my s52 swap in a week or two. It will be OBD1 but planning on using the OBD2 exhaust that came with the engine. Welded ports and plugged O2 sensor holes of course. Do you think it will be fine or they really pay attention to the cat?
Thanks!

I used OBDII manifolds with bungs on my OBDI motor, and they didn't bat an eye.

They did look over the cat pretty closely - but mine is OBDI, so I had no issue. Like I said - I think you can go a million times, and it is free if you fail (and only $8.25 if you pass) so I say give it a shot.

[treff-7]

OBD1 s52 with OBD2 cat. Yay or nay?

I'm finishing up my s52 swap in a week or two. It will be OBD1 but planning on using the OBD2 exhaust that came with the engine. Welded ports and plugged O2 sensor holes of course. Do you think it will be fine or they really pay attention to the cat?
Thanks!

[hwy84]

Good job OP, I'm in the same boat. I'm heavily considering buying new injectors and putting in new plugs as well. My HC are too high as well but only minimally like your initial problem.

I will see what I can find out.

Thanks for the inspiration!

What plugs did you end up using? What injectors? Links?

You can do it! :mrgreen:

Start with plugs for sure - cause they be so cheeep. I used Autolite Copper "Resistor" plugs - 3924. Old school tech for old school motor, I guess. Not sure if this really made any difference, but what the hell - 12 bucks for all of 'em.

I went with the stock green top injectors, rebuilt from OK Injectors in Oklahoma. Search for 'em on ebay - 132 bucks for the set of 6 rebuilt, flow-matched, guaranteed for 1 year injectors. Can't beat it.

[phreshkid]

Good job OP, I'm in the same boat. I'm heavily considering buying new injectors and putting in new plugs as well. My HC are too high as well but only minimally like your initial problem.

I will see what I can find out.

Thanks for the inspiration!

What plugs did you end up using? What injectors? Links?

[cmybimmer]

Yeah, only thing is time is not on my side ..

Smog is due on June 10th! lol not good

And thanks man! Its OBD1, just have the plain ol' m50 for now :)

[hwy84]

Congrats man! Im super jealous!

Failed BAR twice so far. passed visual from the gates, but emissions is where the problem is. Im pretty certain i need a new cat, so im on the hunt for a good one :(

Thanks! You already did the hard part by passing viz - now it's just a matter of time.

I'll keep my eyes out for a cat in the bay - are you OBDI or II?

[cmybimmer]

Congrats man! Im super jealous!

Failed BAR twice so far. passed visual from the gates, but emissions is where the problem is. Im pretty certain i need a new cat, so im on the hunt for a good one :(

[hwy84]

Do you think I can pass with the aftermarket cat that is on my car now? The car AND the drivetrain are old enough and have enough miles that aftermarket cats should be okay right? What about eBay headers?

Are the aftermarket cats approved (with an EO number) for the engine you are running? They will ask.

Pretty sure ebay headers won't fly. But the good news (I guess) is that I am living proof that you can go back again and again and again without issue - so you might as well try. The worst the can do is fail you, and you have to go back again with the changes made.

[M3PO]

Do you think I can pass with the aftermarket cat that is on my car now? The car AND the drivetrain are old enough and have enough miles that aftermarket cats should be okay right? What about eBay headers?

[hwy84]

Passed!!

Just to close this out:

I passed the BAR smog test at Evergreen Valley College today (finally).

In case you haven't read the whole thread, I passed the visual no problem, but I had a misfire at idle that made high HC numbers.

After replacing all the stuff listed in the post above, I finally bought rebuilt injectors from OK Injectors on ebay (Their website http://www.okinjectors.com/) and cheap, copper, single electrode Autolite plugs.

The stupid plugs alone seemed to help a lot - smoothing out the idle in a big way - but the new injectors made the most difference. My car ran PIG RICH (like blowing plumes of smoke out the exhaust rich) for about 3 minutes after I installed them - indicating to me that the old injectors had been so clogged up that the ECU was calling for WAY long duty cycles to get the right amount of fuel in the mixture, and the new ones flowed so much better that they were open WAY too long until the ECU adapted.

In any case - I passed, and I am so damned happy I want to drive from here to New York.

Fellow Californians - it IS possible, just make sure you have a clean running motor. The visual part was the easiest part of the BAR process. The dudes at Evergreen are super chill, and as long as you have the right cats, a legal intake (I had a K&N cone with the EO sticker on the strut tower), and a charcoal canister, they won't hassle you. If anything, they WANTED me to pass - Gary at Evergreen is a real car guy at heart, and was super nice to deal with the whole time.

Word up. Thanks for all the help along the way R3v!

[hwy84]

In case it helps for searches...

Update

Leakdown test showed 8-9% across all cylinders (incredibly good, in fact).

Fuel pressure test was a-ok.

I did find a valve cover vacuum leak with the smoke machine (damn you Victor Reinz!) and fixed it.

...No change in idle. :/

So... I went to pop boys, and bought the chepest, hottest plugs that would fit the car. What do you know? Smooth ass idle. Pings like a bastard under load between 4500 and 5500 rpm, but that doesn't matter for the SMOG test.

Gonna test it with these plugs, then swap them back to the NGK bkr6 when i'm done...

[hwy84]

Nope.

Update.

MAF didn't fix it.

Random, frequent misfire at idle only. Mostly just popping/burbling, with occasional hard miss where the engine stumbles and almost dies.

Smooth power delivery all all throttle applications otherwise, and great power, with NO misfires under load.

Have replaced or swapped out the following with no change:

• Injectors (swapped out)
• DME (swapped out)
• Chips (Ebay, Turner, Dinan - no change)
• FPR (swapped out)
• Coils (new)
• Plug boots (new)
• Plugs (NGK OEM)
• MAF (swapped out with known good)
• 02 sensor (new)

I have checked for vacuum leaks and found none.

Continuity on grounds from coils to head to chassis is good.

Cleaned ICV.

Verified O2 sensor is working fine at idle on GT-1.

Compression is even, and high, across all cylinders.

What have I missed? :(

This is all that's standing between me and California legality. I am to the point that I might register my car in a more SMOG stringent zone, so I have to do a roller test instead of 2-stage idle, because the misfire isn't present under load...

...but I'd much rather fix it right.