S50 swap issue.

[dhof14]

Hey everyone looking for some insight to my issues with this swap. I have an s50b30 from a 95 m3 into my 89 e30.

Now using the 413 red label DME idle is steady (750ish) until after a few minutes then it will rev itself to about 1200 rpm then drop and throws an oxy sensor code pulled from my Peakse reader, (note stomp test is no worky) After the code the car runs like absolute crap lots of hesitation, and I noticed its fouling my plugs. (blacks them out, not wet)

This is consistent, it does it every single time.

I tried another DME a 506 sliver label with a Eurosport chip that is supposedly for stock S50. It idles like shit, its lumpy like if i had a big cam. If i disconnect the ICV it runs fine after. (assume this means it defaults into open loop?) I still get the same Od code from the Peakse and same result.

Things ive done so far:New o2 sensor, New maf, new fpr, rebuilt injectors (stock green tops), ebay headers, CPS sensor tested, Compression test was near perfect, smoke test showed a leak, but already replaced the hose, Timing has been double checked, cleaned the ICV.

Engine is a stock S50, used getrag 260 with M20 flywheel and clutch, used a garagstic wiring harness adapter.

Im not sure where to look next, can anyone please give me some suggestions?

[st.petebiodiesel]

So with obd1 an o2 sensor code doesn't necessarily mean the o2 sensor is bad. It just means its seeing an o2 reading that is well off the normal range. This can be caused by a vacuum leak.
M/S50 commonly leak from the icv fitting that clips into the the intake manifold plenum. The tabs break off and it often dislodges itself.
Also the vacuum port on the bottom of the throttle body for the evap canister. Most people forget to plug that port.


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[dhof14]

So with obd1 an o2 sensor code doesn't necessarily mean the o2 sensor is bad. It just means its seeing an o2 reading that is well off the normal range. This can be caused by a vacuum leak.
M/S50 commonly leak from the icv fitting that clips into the the intake manifold plenum. The tabs break off and it often dislodges itself.
Also the vacuum port on the bottom of the throttle body for the evap canister. Most people forget to plug that port.


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i figured its out of its range. It has a new o2 bosch sensor. Ill recheck the ICV locations, I have that purge valve tb port plugged currently.

[dhof14]

Rechecked the ICV fitting and hoses nothing found. ICV still moves freely, checked o2 heater element wiring and that has 12v....

[Eliminare]

I had a similar issue when I did my swap. I had my MAF sensor backwards. It might sound stupid, but it's worth checking if you haven't already.

[dhof14]

*solved*

turns out the throttle stop screw had left the butterfly too far open. Thus letting too much air in at idle. Can't believe I missed that.

turned the screw and it runs smooth with no CELs

[haaken675]

it's always something simple seemingly...At least you didn't throw parts at it to find out that was the issue like I always seam to.

[dhof14]

well back to square one. Its different now. It idles from 500 to 900ish back and forth, Peakse showed a code of oxy sensor and lamba control 1. I fixed my stomp test, DME flicks code 1221 at me. Again this is a brand new bosch sensor.

I sprayed around and my revs steadied when I sprayed at the oil filter housing??? I replaced that gasket during my build and theres no oil leaking?

I attempted to disconnect the o2 sensor and there was no change whatsoever, Changed my plugs as well for fresh ones that helped the idle a little bit.

Any ideas?? im lost

[dhof14]

Update: not out of the waters completely until I run the car some more, however, I rechecked my intake vacuum lines and found a crack in one of the lines from crankcase to intake elbow. Seems that PO had some 90 degree elbow that was hose clamped in there. I performed another smoke test and tada! smoke like a mother out of that ghetto rigged piece. Used realoem to spec out the correct part.

Idle is less lumpy after a few minutes its completely stable until i give it another rev and then it searches, I assume this is due to the DME relearning, or I got another leak. Note: it has no more hesitation while revving.



I performed fuel pressure test: 40-45psi (bouncy idle) 50psi while revving within spec according to Bentley book.

DME temp sensor: 4.99v book calls for 5v

Oxygen Sensor: BRAND NEW SENSOR, heater had the correct 13 or 14v BUT the grey and black wires where not fluctuating with idle, was steady at 0.3v Went ahead and changed o2 with an old one, and the 1221 seems to have disappeared.

MAF test: perfect hot film glows

going to test the rest of the sensors for assurance, but big step in the right direction


Cliff notes: Carb test does not always work, in my case it did not, GET A PROPER SMOKE TEST DONE! The crack wasn't even that big but it caused a shitstorm of problems showing the sensitivity to the system. GET YOURSELF A BENTLEY BOOK ITS ON THE INTERNET FOR FREE!

[jayuuey]

Did you double check vanos install/timing? Maybe it could be off a tooth.

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