Like it says in the title...

A little background; about 3 weeks ago, my car was running well, then all of a sudden after turning at a traffic light, the engine went from purring contentedly to this FLUBFLUBFLUBFLUB noise and I can't accelerate. It would surge and go back to running normal, then FLUBFLUBFLUBFLUB again a little further down the road. I barely made it up the hill to my house, let it sit and took a look at the plugs and wires because it sounded (to my inexperienced ears) like a cylinder missing. Plugs looked fine, and I un-plugged and re-plugged the wires just to give them a fresh seat. The car worked fine after that, but did it again three days later. This time I looked in the distributor cap and it looked like the rotor was awful worn, so I went down to O'Reilly's and bought new cap/rotor/plugs/wires (though I could have stopped at the plugs, but it's my money, I'll waste it how I see fit ). The original rotor was worn down by 1/16" or so, and I thought that was the problem. All was well for another 3 days or so, but ow the same thing is happening, and I'm digging deeper. The MAF is fine and there are no holes in the downstream hose. Internet wisdom and a "2-3-2" code from the diagnostic all point to the oxygen sensor, but by golly I cannot find the cussed thing. I've seen many different pictures of where it's supposed to be in everything from the Bentley manual, Haynes Repair Manual, random pictures and drawings on the internet, but it's just not in any of those places on my car.
Anybody got any clear pictures of it's location on a 1990 240DL non-turbo?

 

So it wasn't in the catalytic converter or behind it.

 

By catalytic converter, you mean this shell thing wrapped around the exhaust header?



Because that's the only thing that resembles what I've seen pictured.

 

That looks like the heat shield on the exhaust pipe. The cat would be in front of that coming off of the exhaust header and should be a round muffler type pipe.

 

http://www.autozone.com/emission-con...rter/volvo/240

The O2 sensor screws into the threaded hole .

 

Nope, nothing like that. I got two straight pipes that come down off the exhaust headers that merge into one just before the heat shield in my photo, and there's no gadget screwed into that anywhere.

 

Wellllll... maybe this?



That one's downstream from the heat shield thingy, just before the first muffler stage. But I can't see nor feel any where that a gadget screws into it. Maybe I'll have to jack up the car a little higher tomorrow and actually scoot under and have a look-see. I thought this was gonna be relatively easy...

 

IIRC, its on the right side of the end of the downpipe, just before the cat. and yes, the cat is the fat thing behind that heat shielded section, but forward of the first muffler.

 

the Ox sensor is plugged in on the top of the firewall near the wiper motor, on our 87, there were two plugs, a square 2-wire one, and a round 1-wire one, but on a 1990 it might be a single 4 pin plug. follow the wire that goes down the firewall, that should lead to the sensor. it can either be in the side of the downpipe before the cat, or directly into the front 'cone' section of the cat.

 

Aha, I saw that plug assembly and suspected as much (I also have the 2-wire plug and a single-plug green wire) because it matched the descriptions I had seen, but couldn't trace where it goes. I had other things to do today, so I didn't get around to jacking up the car, but I'll do that tomorrow and see what I can find. Thanks!

 

Found it:



After further reading though, it sounds like the code I was given indicates that there isn't an actual fault with the O2 sensor, it is doing its job and there is a problem upstream. I'm going to check vacuum hoses and whatnot to see if I can figure this out.
Any suggestions?

 

there's a simple test to see if your engine is running in proper lambda balance, using a multimeter in DC Volts mode...

get a thin strand of bare copper wire a couple inches long, like one strand from a piece of zip cord (lamp wire). unplug the single pin connector, wrap this wire around that pin and snap it back together so the wire is hanging out. connect the + lead of a volt meter to this bare wire, and the - lead to a handy ground.

start the engine, let it warm up a few minutes. once it goes into lambda cycle, you should see a DC voltage that swings from around 0.6-0.9 volts to around 0.1-0.4 volts and back. the exact value isn't important, it just needs to be swinging back and forth between a lower and higher voltage... at idle those swings should take maybe 4-5 seconds, but no longer than about 10 seconds. if you raise the RPM they should happen faster. if the voltage stays pegged at the higher or lower value, then the engine is not running in lambda balance. if the swings are too slow, the o2 sensor is old and tired.

 

OK, I hooked up my multi-meter to the O2 sensor wire as described. After a minute or two, the voltage started swinging wildly, then climbed steadily to 0.75, then wandered back down to 0 and stayed there. I turned off the car and let it sit for a few minutes, then started up again and hooked up the meter. Stuck at 0. Waited another few minutes and it was still pegged at 0. I can smell gas, so I assume it's running rich.
Just by way of experimentation, I pulled the vacuum hose off the flame trap and got vacuum. I pulled the connector off the MAF and it immediately almost quit, but sputtered to stay alive, so that tells me the MAF is working. Through all this, I still don't have a check engine light on. I know it works because all the lights come on when I start the car.


EDIT: I just read in the Bentley manual that a voltage of 0 means the Oxy sensor is dead. I attempted to run the car with the O2 sensor unplugged, and there was no change in how it ran. I'll be ordering a new one and picking it up tomorrow.

 

Curiouser and curiouser...

Since this is my only car, I limped to work this morning, then limped into town after work to get the O2 sensor I ordered. Then I saw that I was getting a little low on fuel. "No time like the present", I said to myself and went for a fill-up at the Shell station around the corner from O'Reilly. After filling up, the car didn't sputter, limp, or hiccup ONCE from the gas station all the way home. "Could it be more troubles with the fuel pumps?" I asked myself. I checked the codes as I now had a Check Engine light (didn't before), and came up with two new ones: 1-1-3 and 2-3-1. Faulty Injector and another vague warning about the fuel mixture being too lean or rich.

Could all these be inter-related? Or do I really have more than one problem? As soon as the car cools down I'm going to do more diagnostics and replace the O2 sensor, then look into how the injectors are doing and check the fuel pumps ONE. MORE. TIME.

Jeez Looeez, cars give me a headache sometimes...

 

sputtering when below 1/3rd tank is often a sign that the in-tank pump isn't working correctly.

 

I jumpered fuse #6 to both sides of #4. Both pumps are working. When I was on the freeway coming back from work, the sputtering was going in cycles; smooth for one second, sputter for one second, repeat. Which tells me the Lambda-Sond was TRYING to work, but something's not kosher. Low fuel pressure would be a convenient culprit, but when this all started, I had at least a half tank if not more. I'll try testing the fuel pressure when I can make it down to the store again. As for the O2 sensor, that baby is STUCK. I've got some PB Blaster working on it right now. Hopefully that'll help it to come loose in a few...

 

Those codes 113, 231 are O2 related, ignore the 'leaky injector' diagnosis, that was superseded by a later tech bulletin. I'm having the same situation now with a 1993 240. Changing the O2 this week...

 

Your best bet is to go get a O2 sensor socket before you round off the sensor hex. If you do that then you'll have to remove the cat to get it off.

 

I heeded the advice I heard on the internet, which was to get a 22mm Crow's Foot wrench. They didn't have individual Crow's Foot wrenches in 22mm, but they did have a set of heads that go on your socket wrench for about the same price as the wrenches individually. It's a pretty tight fit actually, it's kind of hard to get it down on the hex and once it is on there's no wiggle at all, so I'm pretty sure as long as I don't slip, it's not gonna round it. What sucks is trying to muster up enough leverage when your underneath a car and the part you're trying to wrench is 6 inches from your face. And you have weenie arms like me.

...And don't worry, I got it up solid on jack stands, so I won't be flattened before I get it off. Sprayed some more PBB on there after getting home from work and letting it cool down a bit. We'll see how it goes in a few...

 

Oxygen sensor wrench. note it grabs the sensor on 5 sides


Crowsfoot wrench, note it only grabs on two sides, not really any better than using an open end.