1984-1991 bmw 3 series oxygen sensor replacement connector located behind the passenger side shock...

1984-1991 BMW 3 Series Oxygen SensorReplacement

Replace an old oxygen sensor on your E30 for better gas mileage.

Written By: Andrew Bookholt

1984-1991 BMW 3 Series Oxygen Sensor Replacement

© iFixit — CC BY-NC-SA www.iFixit.com of 10

INTRODUCTION

Use this guide to install a new oxygen sensor. Oxygen sensors on this vehicle wear out about every60,000 miles. Replacing an old sensor will help your car run better and stronger while warm and willprovide better fuel economy.

The specific oxygen sensor part number varies among the 318i, 325e, 325i, and 318is models, so besure you have the right sensor for your car before you start the job.

TOOLS:Oxygen Sensor Wrench (1)

PARTS:Oxygen Sensor (1)



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Step 1 — Oxygen Sensor

Before beginning, make sure theengine is cold. Like, sitting for hourscold. You'll be working directly nextto/on the exhaust downpipe and mayget burned if you're not careful.

Start by locating the oxygen sensorconnector. On this 325i, it is acircular connector located behind thepassenger side shock tower andbelow the (unused) battery tray.

Step 2

Unscrew the oxygen sensorconnector (lefty, loosey) and unplugit from its socket leading to theengine harness.



Step 3

Next, locate the oxygen sensorbody. It'll be screwed into thedownpipe about a foot past theexhaust manifolds.

If your oxygen sensor has a heatshield on it, now is the time toremove it. Use a screwdriver to pryit off and set it aside.

Mine is long gone. I have no ideawhere it went.



Step 4

Before attempting this step, assess how rusty your oxygen sensor is and how long it has beensince it was replaced. If it looks very rusty, or if you live in a rainy/salty climate, soak the sensornearest the downpipe with a penetrant like PB Blaster every few hours for a whole day before youtry to wrench it off. You definitely don't want to strip this thing.

Thread the oxygen sensor wires through the slot in the oxygen sensor wrench.

With the socket seated as best you can on the hex head of the oxygen sensor, use all the strengthyou can muster to crack it free from its prison in the downpipe.

Luckily, mine broke free pretty easily. It'll happen pretty abruptly so be careful-my hand required acouple band-aids after smacking it against the manifold.



Step 5

Grab the body of the sensor andunscrew it from the downpipe.

You'll need to use your other hand tofeed the annoying length of wireattached to the sensor in thedirection you're unscrewing it so thewire doesn't get all tangled.

Once it is free from the threads, pullthe sensor body out of the downpipeand remove it from the vehicle.

Step 6

Next, locate your new sensor. Youremembered to buy it, right?

Before reading the next bullet, readthis one. The threads of this oxygensensor come with anti-seize gooppre-applied. As you remove theprotective cap, don't get any anti-seize on the tip of the oxygensensor. Don't touch it either. It'llmess up the readings from thesensor if the anti-seize or other junkis vaporized in the hot exhaust gasstream.

Carefully remove the protectiveplastic cap from the tip of thesensor.



Step 7

If your sensor didn't come with any anti-seize on the threads, be sure to apply some to makereplacing it in the distant future a bit easier.

The second picture shows the grimy old sensor. I'm not really sure when it was replaced last, butjudging from the buildup on it I'd say replacing it sure won't hurt anything.

The little slits in the side of the sensor tip are where exhaust gases enter. For more information onoxygen sensor operational theory, check out the oxygen sensor Wikipedia page.



http://en.wikipedia.org/wiki/Oxygen_sensor#Automotive_applications

Step 8

Carefully insert the tip of the oxygensensor into the downpipe and tightenit by hand.

Feed the wire attached to the sensoraround in the direction that yourotate it to avoid it getting all twistedup.

Step 9

Use the oxygen sensor wrench totorque down the oxygen sensor.



Step 10

Insert the new oxygen sensorconnector into its socket on theharness attached to the chassis.

Twist the connector barrel clockwise(righty tighty) to lock the connection.



You did it! Enjoy your new found increase in gas mileage!

This document was last generated on 2017-07-17 11:14:37 AM.

Step 11

Since this particular oxygen sensorcan be used on many vehicles, thecable is a bit too long for thisparticular vehicle.

If the cable has too much slack, itmay contact the hotmanifolds/exhaust pipes and thewire insulation can melt. All kinds ofbad can result from that, so followthe next two bullets.

Luckily, Bosch is awesome andincludes two zip ties to keep thecable folded on itself to take up anyslack.

Fold the cable on itself and use zipties to keep it folded. Trim the endsof the zip ties if you desire.



1984-1991 bmw 3 series oxygen sensor replacement connector located behind the passenger side shock...

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