Someone, one of the genius previous owners, cut the wire from the upstream oxygen sensor and left the sensor screwed in. It wasn't to splice in a new sensor they just drove it like that.

I've bought a new sensor but I cannot for the life of me find the connector in the harness for it! I have tried to trace the harness around the engine bay without luck. Can anyone help me out with a picture or diagram?

 

When you say "upstream" o2 sensor, are you implying you have two sensors? As far as I know, the never had more than one. The connection to it is located near the firewall on the passenger side of the car. There should be a 2-prong connector along with a separate single wire connector.

I have seen some 240s (I think pre-88) with the oxygen sensor in the exhaust manifold but most of the later models had it in the front of the cat. What year is your 240?

 

Just just below your windshield wiper motor , you should find the wires there.

 

Yes, sorry to confuse you. I realize they had only one but to me it would be the upstream as I'm used to having more than one. In my 1990 the sensor is located in the manifold.

That being said, I figured the connector(s) would be close enough, and I looked at that spot just above on the firewall but can't locate anything. I'll take another look and see if I can get a picture later this evening. That's why I'm confused!

 

it's two connectors, a round 1 pin for the signal, and a square 2-pin for the heater wires. should be right under or next to the windshield wiper motor on a 240.

 

Here is if what I am working with... Is this right?

 

yeah, that looks like it. except I think mine were held in place by that clip thats on the top of the firewall, above the heater hoses.

 

The connectors are already connected but not to the oxygen sensor, as you can see. That's my confusion. You think someone swapped the manifold with an earlier model car? Seems like maybe it is down on the exhaust as a wire is run down the firewall.

 

O2 sensors are generally pretty close to the input of the catalytic converter.

 

Trace that wire down to see where it runs. If it runs to an oxygen sensor in the cat then just leave it be (unless it need replacement). It could be like you said that someone replaced the exhaust manifold with an earlier model.

 

It has to be what it is, since it is already connected. I just never took the time to check the exhaust because I saw the sensor at the manifold. I'm thinking now maybe someone had this car boosted at one point (if that's the case, I am praying for an oil bung for oil return setup hidden away... that would be awesome). I'm going to definitely do a thorough check all over the engine bay for weirdness. Good thing I ordered the correct sensor part number for 1990 though!

 

Replacing my oxygen sensor. Wondering if I have the right part. 1993 240 wagon.
The electrical connection on my Bosch sensor (0258003308) fits the plug going into the engine manifold. It is the opposite of the plug going into the passenger side assembly. Also the wire harness seems to be a few inches short to reach from the cat to the passenger wire harness. Does this make sense?

 

does your 93 have 'pulsair', aka a B230FD engine, or is it a B230F w/o pulsair? apparently those use two different OX sensors. The "pulsair' system has a "F" shaped rubber hose that goes over the valve cover near the front of the motor, and connects to small pipes that come out of the exhaust side of the head just below the exhaust manifold, and connect to some vacuum fittings on the intake side.

B230F, no pulsair, Volvo part 5601753 or 3501753 - Bosch 0258003034
B230FD, pulsair, Volvo part 6842910 - Bosch 0258003308

afaik, that plug in the rear facing side of the exhaust manifold is for EGR, the OX sensor should be threaded into the lower part of the downpipe just forward of the catalytic converter. there may also be another fitting in that general area with a plug, thats for inserting a exhaust gas probe in front of the cat for engine diagnosis.

looks like you got the sensor for a Pulsair B230FD engine.

 

here'sa diagram of pulsair, if you don't have this stuff on your engine, then you don't have pulsair.... however, i've also heard of B230FD engines where the pulsair has been removed and the air ports on the side of the head plugged... (because it doesn't work real well when it gets old), this would still require the B230FD OX sensor.

 

We have the B230F.
Thanks for that information. I was not aware of the engine difference.
We recently lost our mechanic but really want to keep the car. So I'm having to go back to school, as it were, to learn how to do all these things.
We have a 240 Classic #1086. Trying to keep it on the road.

 

93 240 wagon.
Okay, here's where I am. Need some help.
There might be more to the story, but I think these are the essentials:
1. Car was running rough. Stalling at times. Seemed random. Check engine light was on.
2. Took to a friend/mechanic who told me the codes said it was the O2 sensor and Air Mass Flow whatchamacalit.
3. I ordered both parts. Got the wrong oxygen sensor (see earlier post). Got the correct one this morning. Installed it.
4. Started the car. Still ran rough. Did not stall on me, but the idle speed was erratic and low.
5. Went on to the AMF. Changed it out.
6. While working on that, thought I would take a look at the air filter. Very clean, but I noticed that the bottom clips were not right and it looked like it may not have been sealed properly. Fixed.
7. Started car. Turned over. Gave a slight bang, and then died. Tried it several times. Same result.
8. Thought maybe I had gotten the wrong AMF part, since the store had ordered me the wrong O2 sensor. I did notice that the inside configuration of the AMF was slightly different.
9. Put the old AMF back on the car. Started. Same result. Slight bang, and then nothing.

Is there something I could have done to the air flow in removing and reinstalling the hoses? It doesn't seem that complicated. Since I was working around the ignition wires, could I have knocked something loose? Would that result in the above?

Help!

 

I came back to the car after a few hours. It cranks now but won't start. Battery seems strong. But there's no ignition taking place. I'm thinking that in working on the air intake I goofed up something in the ignition wiring under where I was working. I'll start diagnosing that, but if anyone has any suggestions, please send them along.

 

I'd start from the basics. Is it fuel or spark? Shoot some starting fluid in the intake, see if it starts...
Best to take a compression test first if you have the gauge.

 

its possible you knocked the distributor out of whack, or the hall sensor wire... wait, 93 doesn't have hall sensor, it uses a crank position sensor (CPS) instead, so belay that.

ok, other than the distributor cap and the spark plug and coil wires, there's really no ignition wiring near the intake manifold. you might verify that pin 15 of the coil is getting full battery voltage when the ignition is on...

what *is* under there includes the idle air control valve (IAC). if the hoses to that are badly split, the engine will get way too much air when the throttle is closed, and this air won't be going past the MAF aka AMM (mass air flow meter, also called air mass meter) so the ECU (fuel injection control unit) won't inject any extra fuel to go with that air. I always recommend having a new set of the little IAC hoses on hand whenever removing the IAC, so you can replace them if they are cracked or crunchy.

and, the CPS is on the back of the engine, stuck through the transmission bell housing, on the intake manifold side of things... its wire can deteriorate with age, and if it was disturbed, it could fail. without the CPS you would not get any spark OR fuel injection as its the source of all timing.

 

Update on issue:
1. I had taken a few days away from the car to deal with some other things. When I came back to it, I started to try to diagnose the firing problem. Got in the car to try it again, just in case. It fired right up with no problem.
2. I still have the idling problem.
3. I just found I can check my own codes on the car! I had no idea. (I am new at this.) Checked this morning. Code is 1-1-3. The list I saw says Lambda control--engine running too rich/lean.

I'm thinking that the starting issue was caused simply from the engine being flooded? The few days off helped the car to start up?
I found the IAC and visually inspected the hoses in and out. I didn't see any obvious holes or cracking. The exit hose was pretty dirty, but they both looked to be in pretty good condition.

Since I have the car running now, should I go back to the MAF and reinstall the new unit? Could that be the culprit? Also, about the MAF, I have no idea how this thing works or what it does. But I when looked at the insides of in comparison with the old unit, they looked very different. Perhaps I should post a picture. But could that be due the new part not being the right match, or is that due to damage on the old part? I might have some time this morning. I'll take the old one off again and try starting it up. While I am doing that I will get some pictures of them and post here.