Which Lambda Sensor?

[Paul240480]

My 91' 480 Turbo Auto (144k miles) has had a rough running, rough idle syndrome that returns every 500 or miles caused by the plugs fouling up.

I have worked through most causes, air-leaks, air mass sensor & am pretty sure these are now okay.

Thoughts are now with a duff Lambda. I have tested it following an excellent 'how'to' on the 480europe site. My sensor appears to be switching but is not giving the readings it should. Thoughts were that it should be okay......

Bosch website reckons lifespan to be 100k for these things. My full service history does'nt show that mine has ever been changed - hence my suspicions.

Anyway, to the point! I can get a universal one from GSF for about £25, or a Bosch one for about £52.

Is the Bosch one going to be that much better or make any difference compared to the universal one?

[Baffler]

Pesonally I'd go with the Bosch sensor but it's really down to what you can afford I suppose. This may sound silly but did you get a price from the main dealer?

[Paul240480]

Ta for that. Since posting I've heard that universal ones can cause all sorts of snags if the wires are'nt crimped together exactly right etc.

The Bosch ones come fitted with a plug that'll connect straight into the one that's on the car already.

Pretty sure that Bosch was the original fitment on 400 series.

The mainstealer over here wants around 100€, about £80 these days.

Thanks.

[Paul240480]

I've decided to go for a Bosch direct-fit (LS02 I think).

£52 + VAT + P&P from GSF

Will update once its fitted & has run a few miles.

[Paul240480]

Just fitted the new sensor, 'christening' a mates second hand four-poster lift that we fitted in his hanger in the process:thumbs_up:.

Been for one quick test run, say 10 miles max. Fuel consumption according to the onboard computer says 26.9, recently has been sitting at 25.2. So a step in the right direction. Although early days yet.

The old sensor was completley black & sooty over the whole of the tip & was blocking the two 'splits' in it.

[Paul240480]

Been 4 days with the new Lambda now. SWMBO has been running it to work each day as norm. She works in various schools in our area & covers from as little as 15 miles on her 'short-day' & around 50 on her 'long day.

General concensus is that little has changed with the new sensor :angry:
Performance is erratic, one minute going like a rocket smooth as you like, pull up at, say a junction, idle rubbish & struggles to pull away, then all of a sudden off it goes again.

When she got home today, it was purring smoothly. Mileage on teh computer still a measly 25.2 :cryhard:

I'm very near to giving up with this one.

[Baffler]

Did you disconnect the battery, to reset the ECU, when you replaced the sensor?

How's the condition of your dizzy cap, rotary arm and leads?

Have you cleaned the IAC and throttle housing recently? Maybe they still have some gunk in them?

Just some suggestions...

Oh...and I believe you should be getting an average 32-35 mpg.

[Paul240480]

Did you disconnect the battery, to reset the ECU, when you replaced the sensor? Yes, but only for the time it took to replace it, say 15 mins or so. Was that long enough, or should I disconnect it overnight?

How's the condition of your dizzy cap, rotary arm and leads? HT Leads spanking new. Dizzy cap & Rotor Oct 07 & 8k miles ago - changed in order to solve this very snag, made no change then. Maybe worth changing again, as I fitted BERU bits, perhaps I should get Volvo originals?

Have you cleaned the IAC and throttle housing recently? Maybe they still have some gunk in them? Erm' if IAC = idle valve, yes I've soaked it in petrol for an hour or so, dried & replaced. Throttle housing, no, I need to look that one up! Would I use carb' cleaner spray for that?

Just some suggestions... Thanks I need them, as I'm flumaxed!

Oh...and I believe you should be getting an average 32-35 mpg. Yeh thats what I would expect too.
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Baffler...

[Paul240480]

Been having yet another look this morning: Typically the 'fault has not reared its ugly head & tickover has been spot on for the two hours that I've been out there!

This is what I've looked at/done at today.

1) Check for air leaks with carb cleaner in every location I could think of. Nothing found.

2) Clean throttle body & Throttle valve position switch teminal.

3) Cleaned Idle valve (again) Great 'how to' on 480 europe!

4) Rechecked Flywheel Sensor resistance (251Ohms). So okay.

5) Cleaned connections to coolant temp sensor.

6) Checked Dizzy cap & rotor. Rotor fine, no cracks, cleaned it up for good measure. Cap, no cracks. Terminals did look a bit manky, so cleaned them up. I got these from GSF & IIRC they are MANN make. Been on for about 1 year now & something like 7.5k miles. Should I change it again, and if so would I be better off with a Volvo one?

7) I found the diagnostic box (did'nt know it had one!) Now this was odd. I've got instructions on how to read the codes, but nothing seemed to work. Tried in socket 2 (fuel codes) & it gave no reading at all?
Tried in socket 6 (ignition codes) & it gave no reading at all? Tried in socket 5 (turbo codes) & it gave 2:1:2. According to my list this = Oxygen sensor signal (front sensor on 94 & later models) Seeing as my Lambda is brand new (Bosch direct fit), this seems odd.
When I tried clear the codes it did not light up in the sequence described in the instructions. So 'chocolate tea pot' springs to mind! Or I'm just not doing it right, dunno?

As ever, any advice gratefully received.
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[Baffler]

Paul240480 says; Yes, but only for the time it took to replace it, say 15 mins or so. Was that long enough, or should I disconnect it overnight?
The ECU will need an hour or more to reset. I used to leave mine off over night. This may be your problem....fingers crossed ;)

HT Leads spanking new. Dizzy cap & Rotor Oct 07 & 8k miles ago - changed in order to solve this very snag, made no change then. Maybe worth changing again, as I fitted BERU bits, perhaps I should get Volvo originals?
Should be fine. Apart from cost, I don't imagine there's a huge difference between OEM parts and non OEM for this engine.

Erm' if IAC = idle valve, yes I've soaked it in petrol for an hour or so, dried & replaced. Throttle housing, no, I need to look that one up! Would I use carb' cleaner spray for that?
Yep...IAC = Idle Air Control valve. Carb cleaner will be fine on the throttle housing. I believe there are some airways near the butterfly valve that can clog up with carbon so it's a good idea to remove the housing for a thorough cleaning. NB You will need a new gasket if you do take it off!

Sorry I can't be of more help Paul. I'll be picking my brain in the meantime...

[Paul240480]

Ta Baffler, batteries disconnected, leavin' that way overnight:thumbs_up:

[Paul240480]

Having had the thing dis-connected overnight, I've just got in from a 20 or so mile run. Did a mix of country lanes, main roads, a smidge of motorway & a couple of stops.

Everything ran smoothly & mileage (according to the computer) was 28.5mpg. Not seen it that high for a long time, so maybe, just maybe.........

Not relaxed fully yet, been in a similar position quite a few times chasing this one.

Will update again next weekend once its had a bit of 'normal use' (or before if it plays up).

Thanks to all for putting up with me so-far.:thumbs_up:

[Paul240480]

Well that did'nt take long! Mileage is back at 25mpg. Tick-over this morning as SWMBO left was like 'a bag of bricks', followed by her 'kangeroo-ing' off down the lane.

I'm like this now:
http://uk.youtube.com/watch?v=L8vUFRkxie0&feature=related

[Paul240480]

Been over all the electrical connectors I could find to day. Checked, cleaned with contact cleaner & applied a smidge of vaseline before re-fitting. Included ecu multi-plug.

Tried 'upping' the maf resistance to 450Ohms & went for a 20 mile dual-carriageway run at a steady 70. MPG 23.7:realmad:

So that's going back down to factory setting of 386 after lunch.

I did check the plugs again & 'no sootiness' so I suppose that's a step forward!

Tickover seems to have settled again, but it always does for a short time after I try something................ infuriating this one!!

[Baffler]

I'm like this now:
http://uk.youtube.com/watch?v=L8vUFRkxie0&feature=related

Brilliant...that really cheered me up...thanks :D I know how you feel though!

Having read your last post it crossed my mind that it may be your MAF? This can be expensive to replace so would it be possible for you to borrow one to test?

[Paul240480]

Brilliant...that really cheered me up...thanks :D I know how you feel though!

Having read your last post it crossed my mind that it may be your MAF? This can be expensive to replace so would it be possible for you to borrow one to test?


Ta, I don't THINK it's the MAF, as this was replaced under warranty in 2002. At least I'm hoping it's not! Borrowing one, at present I don't know of anyone with a 4 series over here...... so a tad difficult.

I've got a list of things to try from the 480 site forum. They've suggested I test the coolant temp sensor & throttle position sensor next. I have cleaned up all the contacts on all sensors I can find, but have not 'tested' them yet.

I've also found the diagnostic box, that I did'nt know it had! It's a bit 'crusty' though.

[jlgrosvenor]

Try testing the lambda sensor with a voltmeter as follows.

1) Locate connectors to the lambda sensor (on my car they are with a bunch of connectors just to the drivers side of the battery). If unsure trace the cable back from the sensor, located on in the manifold downpipe or in the CAT.
2) The connectors are a black 2 pin conector (white wires and for heating the lambda during operation) and a spade connector with a rubber sleeve (signal).
3) Slide back the rubber sleeve on the spade connector so the metal is exposed.
4) Set the volt/multimeter to a suitable range to detect up to 1volt.
5) Connect between spade connector and the battery negative.
6) Start and warm up engine.
7) Once fully warm note the voltage range on the meter.

Kindly borrowed from 480 forum (http://volvo480.dragons.org.uk/forum/viewtopic.php?t=14683)

With the engine idling, a correctly functioning sensor should be switching from 0.8v to 0.2v and back, at a rate of about 1 per second.

A fixed 0.8 volt reading
- Car running rich, probably due to some other reason on the car, such as the MAF being set incorrectly. Dan had this problem. BTW, 0.8v equates to a lambda reading of 0.97 on an MOT.

A fixed 0.2v reading
- Sensor is probably dead, but also an air leak in the exahaust, upstream of the sensor is possible.

If the reading fluctuates, but goes beyond, or nowhere near 0.8v or 0.2v, the sensor is dead or dieing. For example, a sensor that goes from 0.7 to 0.3v and back has become sluggish. A sensor which goes from 0.1v to 0.7v and back is proably inpinged with contaminants.

If the sensor gives a constant voltage which doesn't or hardly fluctuates, between 0.2 and 0.8v - its dead.


I have had the lambda light come on my dash a coupe of times in the past few months after a long run, so I am going to change my sensor. I don't want to risk the CAT. I opted for an NTK (lambda department of NGK) sensor because it was £28 delivered off ebay rather than £41 for the bosch (search part number on ebay for 16444). I have just checked my sensor and it starts at 0.375V with the ignition ready to start a cold car, then when warm fluctuates between 0.048V and 0.869V. This lower reading may be causing the problem, and I can check this against the readings with the new sensor.

B18U engine by the way.

[B20F]

Go for the Bosch lambda, other brands cause problems.

[Paul240480]

Go for the Bosch lambda, other brands cause problems.

Thanks, it was a Bosch one that I've fitted. I've sort of given up on this I'm afraid. The car is running brilliantly & has not faltered really since my last update - which is a BIG improvement as I had to clean the plugs each week to keep it running before.

The only downfall is that its averaging 23mpg:loser:

Have decided that its going later this year.

Cheers.