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Lambda sensor not fitted, does this cause other sensor issues?

Lambda sensor not fitted, does this cause other sensor issues?

  #1  
Old 04-23-2019, 11:54 AM
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Default '93 940 B200 engine, Lambda sensor not fitted, does this cause other sensor issues?

Essentially, th title says it all. 1993 940 B200 engine, 300,000 on th clock, owned for three weeks. Previous owner, of 23 yrs had th guy she bought it off, he was 1st owner, do all th maintenance, there's no history with it, and I surmise that only necessary work was done and every unnecessary expense was spared.
When bought, th lambda light was on, she said her mechanic said not to worry about that... It drives reasonably, tho I can feel a hesitancy thru th seat of my pants as you move off, it just doesn't feel quite right, tho it starts well, goes OK, and th only sign of anything is a varying tickover at idle, once it's warmed up a bit, between 500-900rpm.
I've had a go with th OBD box and th codes indicate lambda signal faulty or missing, MAF sensor faulty or missing, engine coolant sensor signal faulty or missing.
I've had a crawl underneath, there is no lambda sensor in th exhaust, only a blank hex plug just before th joint with th cat, midway down th front door, roughly. There's also no discernable wiring in th area, or up nearer th engine, so I'm assuming it's all been removed in some cost cutting exercise.
Will th lack of a lambda throw th other sensors out or at least baffle th ECU or am I grasping at straws a little, and where would th lambda plug into, once I've obtained and fitted one, I've found a spare connector, below th intake manifold, below th engine coolant sensors, which both appear to be wired up, I'll attach a photo of this. Any views, tips or inspirational moments welcome, as I'm beginning to wonder if I've finally bought a lemon, despite th engine having very healthy compression figures, and it's first wash in 8 years revealed it to be a quite attractive metallic maroon and not a dirty faded red as I first thought... Cheers folks, John.

 

Last edited by Grumbling big ends; 04-23-2019 at 01:34 PM.
  #2  
Old 04-23-2019, 12:17 PM
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Th irony of my situation is not lost on me, I decided to buy another 940 as I had one, almost by accident, several years ago, and fell for it, and spurning sensible suggestions of either a more modern Volvo or some lesser estate, I insisted I wanted a 940 as I'd avoid many of th curses of modern vehicles, all this fancy pants electrickery, I built engines for classic alfas for a while, and was amazed at how many new ones were appearing with sensor issues and ecu problems, so I kinda assumed an old volvo prob wouldn't have anything too fancy, I've kinda learned my lesson now.... I've actually had to go and buy a multimeter as every other vehicle I own or work on, I restore properly old cars and bikes, has a really simple electrical system. Th mickey taking at home and work is becoming almost unbearable, so please, before I have to start wielding a chainsaw at innocent passers by.....
 
  #3  
Old 04-24-2019, 08:18 AM
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with all older cars, part of the "fun" is understanding and undoing shoddy work from prior owners. The lamda sensor is your O2 sensor so it should plug into the exhaust upstream from the cat and into the wire harness under the hood. Not sure why anybody would think removing that is a good idea as that manages your fuel trim. When you start unplugging stuff or have a failed part, you can often get a happy meal of codes so you will need to inspect and test each, clear codes, see what resets etc.
 
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Old 04-24-2019, 08:47 AM
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just as an aside, how on earth did it pass a MOT test like that?
 
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Old 04-24-2019, 11:30 AM
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I'm guessing it's either a relatively recent bodge or possibly as it's a 93 model, less stringent emmisions regs apply.
I've had a good burrow around, and can see no trace of any spare wiring where th 02 sensor would plug in, bar that connector I've shown, under th intake manifold, it also has th wiring to th coolant sensors in th same bit of loom, so I'm guessing/hoping/praying that this is where it goes, as I assume they're all off to th ECU. Of course in all my fiddling and watching YouTube videos on checking maf sensors and all that stuff, I left th doors open all day, so now th battery is flat, my charger is 94 miles away, as I'm tending to my dear old dads needs after he had his hip replaced a while back, so I'm going to have to smile at th neighbour when he returns home, whilst brandishing jump leads....
I usually enjoy unpicking other folks bodges, it's kinda what I do for a living, but I've decided it's far less fun when it's your own vehicle and you're on a budget so limited that Bolivian shepherds are having collections for you... Its th maf sensor that worries me, having seen th price of replacements, th lambda isn't exactly pennies but if I can fathom that out, then maybe th others may settle down, he says with an unfeasible degree of optimism....

I fear my assertions of 'no, I don't want a mondeo of something tinny, I want another good solid reliable volvo 940 estate!' may be about to bite me on th backside.

Previous owner has no real idea of what's been done, bar th recent stuff, new radiator, new starter motor, replacement exhaust Inc cat, which is when I presume th lambda was omitted, so I'm hoping that once I've dealt with all this, there may be a fairly unmolested vehicle lurking beneath it all.
Oh, and obviously, th odometer, speedometer and fuel gauge don't work, but that just adds a certain frisson of excitement to every journey...
 
  #6  
Old 04-24-2019, 01:11 PM
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O2 plug is along the firewall passenger side underneath the coil.


O2 sensor plug location on my 1989 740 with Bosch. Same location on my '91 740 and '92 940 with Regina.
 

Last edited by dytha99; 04-24-2019 at 01:15 PM.
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Old 04-24-2019, 02:10 PM
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Aha, well, I'll finish me cuppa, then pop out to make sure hamfist Harry, th previous spanner wielder, hasn't utterly ruined my week... Tho having seen th amount of hard carbonised deposits totally blocking th flame trap, I'm not holding my breath...
 
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Old 04-24-2019, 02:12 PM
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H, and thank you very much for th reply and info, I could have poked around for ages looking for that...
 
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Old 04-24-2019, 05:52 PM
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i'm surpriised it even has an 02/lamda sensor...
 
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Old 04-24-2019, 05:56 PM
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Originally Posted by Grumbling big ends View Post
Aha, well, I'll finish me cuppa, then pop out to make sure hamfist Harry, th previous spanner wielder, hasn't utterly ruined my week... Tho having seen th amount of hard carbonised deposits totally blocking th flame trap, I'm not holding my breath...
lol to that mate!
 
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Old 04-25-2019, 02:16 AM
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Well, I have no idea if it did or not, I'm just going by th light being on and th ECU saying th signal is missing, and as it decided to throw a mini monsoon at me last night, I've put off th investigation until I can work on th car without th need for gills and flippers...
My first 940 is to blame for this, same scenario when buying, ebay, unseen, but I was desperate, I was visiting my girlfriend, and she lived miles away and I blew th engine totally in my car on th way, but had 3 of my dogs with me and I had to be at work at 0400 Monday morning, so I just found a car that ended on th Sunday that was under 500 quid, as that's all I had in th bank. I got a lovely 91 model 940, I just loaded th dogs in, drove home and barely had anything to do to it up until some git stole it several years later. I was hoping for a repeat performance.... Ah well.... I'll have a dig around once I've consumed another pint of tea and a similar amount of coffee, and being as I'm not doing anything today, a healthy squirt of rum, then I'll wander out and report back my findings... Its quite chilly so maybe a double squirt of rum, just to keep my spirits up...
 
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Old 04-25-2019, 07:02 AM
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Sustained by pints of proper deep orange coloured tea, motivated by a pint of teeth chatteringly string coffee and calmed by a few swigs of rum, I've braved th seasonal monsoon, had a look and found an unconnected plug. Looks nothing like yours, but that doesn't mean it's not it... I'll attach a pic.
Anyway, using a pdf of a factory manual, and referencing my chassis plate for engine and build specifics, and referencing that to another page, I've obtained th OEM bosch part number, located one, and have just ordered it. Let's just hope it is th right one, and that this is th plug, guess I'll find out tomorrow.... Once more, thank you for all your efforts and replies so far, tho I'm sure this is just th first chapter of quite a long book.... J
 
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Old 04-25-2019, 07:03 AM
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Th connector in question......
 
  #14  
Old 04-25-2019, 11:37 PM
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every 80s and newer volvo I've seen, the O2 sensor has two connectors, a 2-pin square one for the heater circuit, and a 1 pin round one for the signal. and even on the venerable 240, its near the top of the firewall, on the right side of the car, where its shown near the coil in that one pic. Note that the coil itself can move around on different cars.
 
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Old 04-26-2019, 04:10 AM
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Aye, that's my concern too, but that's all I could see or feel in there. Well, I've ordered th sensor, oem part number, let's see what falls out of th box.... Tho, to get from where th sensor isn't plugged into th exhaust, to go up into th engine bay there, that's quite a distance, tsk, if only I had a vehicle lift,life is so much easier when you're not scrabbling about on your back like a Friday night drunk...
 
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Old 04-26-2019, 08:48 AM
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Well, slap my thighs and call me Cuthbert, further scrabbling around in th grit, th grease and th grime has revealed not only wiring, but also a lambda, only this is mounted at th front of th cat, on th inboard side, and th wiring takes a quite circuitous route, to th aforementioned style of connector. Well, that's something at least, I'll replace th front section of exhaust as I don't like th look of what I've got too much, I'm not convinced th plug sealing th lambda hole is going to come out, but I'll still chuck my new lambda in and just leave th other in situ but without wiring. Darn it, I'll clear these codes off and see what happens, we'll, as I've got to charge th battery I'll do it that way, see if things settle down a bit. I thought it bad practice to mount an 02 sensor in th cat, that far away from th engine. Hmmm, blimey, I think I mignt get someone who knows their Volvos to have a butchers at this, see what they reckon... Its at times like this that th vagaries of JAP V twin powered Morgans seem inconsequential....
 
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Old 04-26-2019, 01:52 PM
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that plug was there from the factory, its for inserting an exhaust gas analyzer before the cat.
 
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Old 04-26-2019, 03:07 PM
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Ah, well, that makes sense, after charging th old tubs battery, she's started perfectly, and, so far her tickover is nice and steady, no wandering up and down between 5-900, even th lambda light stayed of for 10 mins and after a quick squirt up and down th road, she seems far smoother than she did. Tho, as its dark and raining again, I think I'll call it a night and resume play in th morning, with fresh road tax and a hopeful spring in my step. Tho I have detected a slight oil weep from th front, poss crank seal, ah well, fix one thing, find another, I was expecting to have to do all that, so thinking it'd healed itself was a bonus, onwards and upwards and pass me th rum...

Cheers folks, I'm sure this isn't over, I know when a car is planning something...

For a few moments,well ,10 mins,I was a very happy pixie !
 
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Old 04-26-2019, 05:37 PM
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some models also have an EGR tube which quite often over the years somebody probably snipped off and plugged the port rather than replacing a rusted out tube.
 
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Old 04-26-2019, 09:49 PM
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you mentioned a few posts ago about a clogged flame trap. if you could clean that out it may lessen/stop
any oil seals leaking. oh and unless that gauge isn't working you are outa gas bro!!
 

Last edited by silvermine; 04-26-2019 at 09:51 PM.

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