Need tips on removing O2 sensors from 1994 e32 740i with M60 engine

[LysanderSpooner]

Today I drove my car up on some ramps hoping that I could change out my two upstream O2 sensors as easily as I changed out the ones on mom's e39 525iT... WRONG.

On the 740 they are located on top of the exhaust down pipes, just rearward of the transmission mounting bracket and tucked up nice and high in the cramped space near the end of the transmission tunnel. There is *almost* enough room to get the open end of a 22mm wrench on them at the proper angle, but not quite.

To make matters worse, the original ones (which look quite OG to me) seem to not really be 22mm across the flats as they should be, but rather 21.05mm. I say this because the 22mm wrench fits quite loosely, to the point where it slips off quite easily with the little bit of purchase I can get on them given the cramped quarters. The fit is so loose in fact that they really seem like they just *must* be 21mm, but my 21mm (Snap-On) wrench won't go. So they must be 21.05 or thereabouts. Wierd.

I did a pretty fair bit of searching here and elsewhere and came up with not a single link to even some remote page on some random website where some other poor soul like myself cried his eyes out over what a bitch this seems to be, and how to make the best of the situation. And no, I don't think there is room in there for an O2 sensor tool socket adapter thingy. But I could be wrong.

So tomorrow I will have another go at it, getting the car a little higher in the air so that I can try any or all of the following:

- Dropping the whole exhaust system lower to create more clearance
- Removing the transmission mounts and raising the transmission slightly higher at the rear
- Cutting a massive hole in the transmission tunnel from above and then welding it all back up aftward

If anyone has any better ideas, I'm all ears.
(And they say your ears and nose never stop growing... yikes.)

[shogun]

Should be similar to the 750, get the car up in the rear, maybe drive on 2 ramps, disconnect the exhaust at the rear and the middle hanger, let it drop a bit by weight of the exhaust, I used a small scissor jack at the rear end to support/adjust the dropping, then you have just enough space to get onto the O2 sensors. Pics http://infinitier.ddo.jp/e32/page/ma...inte_50707.htm

The scissor jack also helps to lift the exhaust again to install the bracket after the O2 sensor replacement, especially when you do the work alone, the exhaust is quite heavy.

Important: mark the wires/connectors for each sensor before you start, otherwise you will mix up the 2 connectors and you will not know which one goes where.

[Cactuar]

The hanger bolts for the rear muffler snapped in half when I tried to remove them on my 735.
Your hangers are equally as old so I suggest you use a liberal amount of penetrating oil and let it work through the rust before attempting to remove them.

[Sansouci]

Once you get clearance from dropping the muffler, see if you can get a proper pipe wrench (Stilson type) on the flats.

[LysanderSpooner]

Should be similar to the 750, get the car up in the rear, maybe drive on 2 ramps, disconnect the exhaust at the rear and the middle hanger, let it drop a bit by weight of the exhaust, I used a small scissor jack at the rear end to support/adjust the dropping, then you have just enough space to get onto the O2 sensors. Pics http://infinitier.ddo.jp/e32/page/ma...inte_50707.htm

The scissor jack also helps to lift the exhaust again to install the bracket after the O2 sensor replacement, especially when you do the work alone, the exhaust is quite heavy.

Important: mark the wires/connectors for each sensor before you start, otherwise you will mix up the 2 connectors and you will not know which one goes where.

Thanks shogun, I knew if anyone could come up with a link to some obscure website (in Japanese no less) it would be you! haha

I'll be putting her back up in the air today, wish me luck!

- - - Updated - - -

The hanger bolts for the rear muffler snapped in half when I tried to remove them on my 735.
Your hangers are equally as old so I suggest you use a liberal amount of penetrating oil and let it work through the rust before attempting to remove them.

Luckily I've been through the whole exhaust hanger routine before, so mine are not going to be frozen in place. A bitch to deal with yes, but snappage will (hopefully) not be a part of the equation...

- - - Updated - - -

By the way, I did find a couple videos on doing this to an e38 7 series... this must have been one of the top complaints from the dealer networks, because on the later e38 models those suckers stick out sideways and are so easy to get to you could almost just drive up on a curb, crouch down on the pavement, and reach them with one arm.

[shogun]

Testing + replacing oxy sensors on E32 730 V8 M60 I posted with pics in 2008 here http://www.bimmerboard.com/forums/posts/472541/

Note http://www.bimmerboard.com/forums/posts/473149

[LysanderSpooner]

GOOD NEWS:

So yesterday I was finally able to get the new (OEM Bosch) sensors installed by (a) propping the exhaust up with a jack, (b) removing the 8mm nuts (13mm hex) from the two rearmost exhaust hangers, (c) lowering the exhaust with the jack until it is almost hanging on the midships rubber mounts, (d) removing the O2 sensor wiring bracket, (e) loosening both exhaust hangers that clamp around the exhaust and secure it to the transmission case and sliding them out of the way, and (f) removing the exhaust brackets from the transmission case (2x13mm hex bolts each).

I also wedged the handle of a ratchet between the exhaust and chassis to create just a little more room to work. All of this combined allowed me just enough room to get my 22mm spanner on them at a proper angle.

Re-installation was pretty straightforward, paying special attention to get them in tight enough to compress the crush washers. This was nearly as difficult as getting them out in such cramped quarters. I reconnected the wiring with the sensor on the right plugged into the plug on the right, and left to left. More on that later...

I should mention that my reason for replacing the sensors were a random Check Engine light and lumpy idle, especially when cold. Otherwise the car runs fantastic.

The stomp test was showing codes 1212, 1213, 1222 & 1223, all O2 sensor related. I realize that there is surely more going on than just bad sensors, but I wanted to be able to rely on them to help me sniff out these other problems, whatever they might be. The old ones had at least 80k on them, and I have smog test coming up.

Things I have recently done trying to improve the idle include:

- Replaced all vacuum hoses and the bung on the PCV valve
- The "washers under the intake bolts" trick to re-compress the intake gaskets
- Cleaned the ICV with B-12 Chemtool
- New MAF

The spark plugs are fairly new. The coils and boots are not. The injectors could have 260k miles on them without being serviced. I have a pile of the previous owner's records somewhere that I need to dig through.

NOW TO THE BAD NEWS:

I was excited to start her back up and see the CE light go off while idling, but the idle was no better and the light soon came back on and stayed on solid all the way home (~15 miles from where I was doing the work). By the way, it was a cool night (for San Diego anyhow, maybe high 50s) and the coolant temp barely got above the blue mark on the gauge. So I will be replacing the thermostat just in case.

Then this morning the car ran worse than ever, even stalling once after a cold start, which it has never done. I subsequently saw shogun's link (thank you), so today I swapped the connectors so that they crisscross (who knew?), but that has hardly made a difference. Even after clearing the codes the same ones came right back after a few miles.

So I guess my question is, does it make sense that the car would run worse with new sensors? Particularly if there are air leaks, clogged or leaking injectors, coils on the fritz, etc.?

Looks like it's going to be a busy week under the hood for me...

[shogun]

no crisscrossing the O2 sensor sensor wires, see my note above. Make it as it was originally installed and I hope you marked them. Maybe someone with an M60 can tell you exactly. Or test, disconnect one sensor after the other and then test on the DME.
DME pins: M60B40 V8 engine 740 E32 cylinder row 1-4 are pins 13 (black-white) and 40 (yellow), for cylinder row 5-8 12 (black-white) and 39 (yellow)

Remove the cover from the MOTRONIC plug, insert the plug again, the pin numbers you can read then or count them. Please check again in the Bentley Manual or in the wiring diagrams the correct pins. Let car idle till the cats are at operating temperature.. Check with a voltmeter. The voltage should fluctuate between 0.2-0.8 V. within 1 second at least 1 time. The faster the better the oxy sensor is responding. Older ones get 'lazy'. In case the voltage is constant, the corresponding oxygen sensor is defective. In case the voltmeter is at 0.45V, then wait till engine gets warm and the voltmeter starts to fluctuate. Then it should start regulating/fluctuating.

Checking at the MOTRONIK is easier. cables on our oxy sensors: heated oxy sensor: schwarz/black - Signal, grau/grey - Masse/ground*, 2x weiß/white for heating of the oxy sensor.

https://www.bimmerforums.com/forum/s...left-and-right

[LysanderSpooner]

SUCCESS!

It turns out that (on my car at least), the wires go right/right and left/left, meaning the sensor plugs into the connector on the same side rather than crisscrossing. This was what I initially thought must have been true... I just couldn't imagine Germans making them cross over just to mess with our minds... LOL

Shogun's warning about making sure to keep track of which one goes where is still valid though, because unless you are the original owner of your car, you never know if someone didn't cross the wires coming into the bracket from the main harness. My guess is that they all left the factory without crossing though.

In any case, my car is now running great, and the CEL is slowly fading away as the computer compiles fresh data. I never did a hard refresh by disconnecting the battery, so it has just taken a little time. Woot!

[LysanderSpooner]

So I spoke too soon...

This morning I got in the car and it started right up and idled beautifully... for about a minute. Then the CEL came on again and it started back to the same lumpy idle. Now I am getting the same four codes again too (1212, 1213, 1222 & 1223).

I'll be back at it tomorrow, ugh.

[shogun]

1212 Oxygen (O2 or Lambda) Sensor 2 (cylinders 4–6)
1213 Lambda Control System Bank 2: The ECM has been unable to maintain Lambda (fuel mixture or fuel trim) on Bank 2 (cylinders 4–6) of the engine.
1222 Lambda Control System Bank 1: The ECM has been unable to maintain Lambda (fuel mixture or fuel trim) on Bank 1 (cylinders 1–3) of the engine.
1223 Coolant temperature sensor

so if the coolant temp sensor is broken = it will make the DME believe the coolant is cold and always run a rich mixture. Maybe one of the causes.
Concentrate on the intake system, intake air leaks, fuel pressure regulator, etc.

Test data temp sensor http://www.e32-schrauber.de/bmw/s-tempsensor.htm

added: read this thread from the E34 forum, same codes, good ideas to solve https://www.bimmerforums.com/forum/s...213-code-issue

[LysanderSpooner]

Shogun, thank you so much for those links, particularly the second one. It turns out that I did not in fact have a 1223 code, but rather a 1221 for the other o2 sensor. Chalk that up to poor note taking I suppose. This means my temp sensor was fine, though I still may replace the thermostat if the car continues to run cold on the freeway at night. Your analysis of a rich condition due to a falsely low coolant temp reading made perfect sense to me, and I was about to pop for a new sensor but when going back through my notes I found the error in my error codes, haha.

The real issue turned out to be a severely (horrifically?) deteriorated vacuum hose to the brake booster. I decided to check this after reading through the second link you gave.

IMG_7369.JPG

(Next on my shopping list is a new cruise control cable...) ;-)

Long story short, the car runs better than it ever has in the 5+ years I've owned it. The CEL is off, no more codes in the stomp test, braking and shifting are noticeably better, and I am going to guess that my gas mileage goes up too.

Man, what a relief. Off to a star certified smog station now.