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Thread: e30 325e to 325i swap o2 sensor questions

  1. #1
    Join Date
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    e30 325e to 325i swap o2 sensor questions

    okay, I swapped he e for an i on my 87. it is running pretty good with the exception of a slighly erratic idle. I have a o2 sensor question. the e had a 3 wire o2 sensor mounted near the tranny. the i should run a 4 wire sensor in front of the cat. I say should because I currently do not have the new sensor, and the wiring harness I bought was missing the connector for the o2 sensor so I am also waiting for the connector.
    A couplle of questions. First do I have to weld in a new bong for the o2 sensor in front of the cat or can I just lengthen the wiring since it is already cut and just install the o2 sensor where my stock e had it near the tranny?
    Second, what do the different wires do?
    Third, will I do any harm driving without the o2 sensor for the next couple of weeks?
    Last, do you think the o2 sensor will cure my idle? I know there are no vaccum leaks, however the idle control valve was bad on the donor engine and the shop pulled one from another dead engine for now.

  2. #2
    Join Date
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    1985 E30 325ish
    I'm no expert but ever since I went to an m20 I've never had an 02 sensor and never had any problems with much of anything really. Idles perfectly, drives smoothly. I was told it would not make any difference in my case.

  3. #3
    Join Date
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    85 eta, 59 austin healey
    1. Hehe you said 'bong'. But really, no you don't have to weld a new one in. You can lengthen the wires, all it requires is splicing wires. Very easy.
    2. The extra (4th) wire is a heater wire. The "i" engines have a heater element.
    3. No harm will be done. You will run a bit rich but nothing that will seriously damage anything. I ran without an O2 sensor for a while.
    4. It MAY cure your idle, i would lean more towards the ICV or something intake related.

    I have an extra 4-wire plug from an '87 harness. Keep in mind '87 O2 sensor plugs are different than the rest. What year is your harness? I'm assuming it's an 87...

    My progress thread | BMW CCA #434464 |The Sprite

  4. #4
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    Yes my harness is from an 87. I ordered a new o2 sensor. A 4 wire one. What is the shielded wire? I am thinking the icv. The intake is new as most everything. I will order a new icv tomorrow
    Last edited by Cavi; 08-12-2011 at 11:45 PM.

  5. #5
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    Quote Originally Posted by Cavi View Post
    Yes my harness is from an 87. I ordered a new o2 sensor. A 4 wire one. What is the shielded wire? I am thinking the icv. The intake is new as most everything. I will order a new icv tomorrow
    the shielded wires are for the heater element if i'm not mistaken

    My progress thread | BMW CCA #434464 |The Sprite

  6. #6
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    well I went ahead and ordered a icv and the conector hose. I also ordered a new set of wires, mainly because the set I have now has both tabs broken that hold the wires to the head and they came with the donor engine so I don't know how old they are. The rotor cap and distributor cap are new I had just swapped them on the old engine less than 2000 miles before.

  7. #7
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    Bumping this thread because it's what came up on search and is relevant to my issue. The car is an 86 325e with an 87 325is engine swapped into it. Mine are different than the OP in that I've got a two pin plug and a three pin plug...I'm at work so I can't confirm which is which but I do believe the car is two pins while the engine is three pins. Lumpy idle and the car being gutless up until like 3k could be other issues, but in the meantime I'd feel better about the 02's running properly. Assuming my the car is two pin, can I just buy 86 325e 02 sensors, put them into the 87 325is headers and all should be good?
    Last edited by m5james; 02-22-2019 at 07:32 PM.
    650hp 10 X5///M5
    PERFORMANCE:JB4 w/ meth, stage 2 tune, wrapped downpipes, custom intake
    INTERIOR:AVIN 10.25" screen, Blackvue 550 dashcam, 7" tablet for JB4 logging
    EXTERIOR:Niche staggered 20's or AC Forged staggered 22's, H&R 2" suspension, LED AE, CF front splitter
    325hp 98 BMW 740iL6
    PERFORMANCE:///M5 6spd swap, iron sleeves, L/W Teflon coated & silicone impregnated pistons, Sealed Power rings, 3 angle valvejob, P&P head, perf cams, electric fan, CF intake tube w/aluminium heatshield/wrapped MAF tubing, Magnaflow 14816'd, Eaton M112 in-work
    INTERIOR:Android Dynavin, hardwired V1 above rearview, 12" RE Audio DVC sub, MTX 81000D monoblock, CF silver trim, 5% tint
    EXTERIOR:///MPar staggered 19's, H&R Stage 2/Bilstein HD, custom notched bumper, Shadowline trim, 750iL brakes w/ Axxis pads
    190hp 97 328ci
    PERFORMANCE:Single mass flywheel, ///M3 clutch
    EXTERIOR:Z4///M staggered 18's, rolled fenders, tinted markers

  8. #8
    Join Date
    Dec 2005
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    corpus christi, texas
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    No e30s, again :(
    Your new harness has less pins than the old o2? Mine had more, 4 pins.


    You should gave tons of power now. Whixh diff do you have
    No e30s again.

  9. #9
    Join Date
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    98 740iL, 01 Suzuki TL10
    I'll double check the pins count when I get home.

    Don't shoot me, but...it's got an auto w/ a 2.96 open. GF doesn't wanna learn to drive stick and I've got a 3.73 LSD I'll be swapping in soon enough. Auto aside though , it's terribly slow until like 3-4k then it finally comes alive.
    650hp 10 X5///M5
    PERFORMANCE:JB4 w/ meth, stage 2 tune, wrapped downpipes, custom intake
    INTERIOR:AVIN 10.25" screen, Blackvue 550 dashcam, 7" tablet for JB4 logging
    EXTERIOR:Niche staggered 20's or AC Forged staggered 22's, H&R 2" suspension, LED AE, CF front splitter
    325hp 98 BMW 740iL6
    PERFORMANCE:///M5 6spd swap, iron sleeves, L/W Teflon coated & silicone impregnated pistons, Sealed Power rings, 3 angle valvejob, P&P head, perf cams, electric fan, CF intake tube w/aluminium heatshield/wrapped MAF tubing, Magnaflow 14816'd, Eaton M112 in-work
    INTERIOR:Android Dynavin, hardwired V1 above rearview, 12" RE Audio DVC sub, MTX 81000D monoblock, CF silver trim, 5% tint
    EXTERIOR:///MPar staggered 19's, H&R Stage 2/Bilstein HD, custom notched bumper, Shadowline trim, 750iL brakes w/ Axxis pads
    190hp 97 328ci
    PERFORMANCE:Single mass flywheel, ///M3 clutch
    EXTERIOR:Z4///M staggered 18's, rolled fenders, tinted markers

  10. #10
    Join Date
    Dec 2005
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    corpus christi, texas
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    No e30s, again :(
    I would say swap the diff before getting terribly worried.

    My wife's old 87 325is had a 3.73s with auto as the stock set up
    No e30s again.

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