Is this a new O2 sensor?

[John_B]

Been out for a little sunny evening bimble and got the EML & TC lights and limp-home come on again. (This ruins my theory that so far it only happened after long periods of motorway cruising).

Anyone familiar with these codes? (On a 1998 2.8 if that's relevant)

I'm happy to throw a new O2 sensor at it, but I just wanted to check with you knowledgeable folk first in case there was another likely cause

thanks in advance!

 

[ChrisD]

Been out for a little sunny evening bimble and got the EML & TC lights and limp-home come on again. (This ruins my theory that so far it only happened after long periods of motorway cruising).

Anyone familiar with these codes? (On a 1998 2.8 if that's relevant)

I'm happy to throw a new O2 sensor at it, but I just wanted to check with you knowledgeable folk first in case there was another likely cause

thanks in advance!


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The post-cat sensor is primarily used for diagnosing a degraded catalytic converter.
Since the diagnostic is tripped for both the sensing element and the heater, it would be worth visually inspecting for major damage to the sensor (e.g. impact damage) or to the wiring.

 

[John_B]

The post-cat sensor is primarily used for diagnosing a degraded catalytic converter.
Since the diagnostic is tripped for both the sensing element and the heater, it would be worth visually inspecting for major damage to the sensor (e.g. impact damage) or to the wiring.

Thanks Chris, I'll get under and have a look!

Possibly a dumb question - but when you say impact damage do you mean like debris on the road, or bits of cat breaking apart and hitting the sensor on the way through the exhaust? (Or both! )

cheers

 

[ChrisD]

I meant road debris - something that would give you a visual clue as to what has happened. Its somewhat unusual but not unheard of to have all elements of the sensor fail at once. You’d be replacing the sensor anyway for anything other than a wiring issue but that is at least one feasible cause. My initial comment about the purpose of this sensor was to give you an idea of the severity of this fault. i.e. not critical. Good luck with the investigation.

 

[John_B]

I meant road debris - something that would give you a visual clue as to what has happened. Its somewhat unusual but not unheard of to have all elements of the sensor fail at once. You’d be replacing the sensor anyway for anything other than a wiring issue but that is at least one feasible cause. My initial comment about the purpose of this sensor was to give you an idea of the severity of this fault. i.e. not critical. Good luck with the investigation.

Thanks mate, I wasn't too worried about severity, it only started happening a couple of weeks ago, but in that time I have done more than 2k miles. It's probably happened about 6 times in total and each time a quick restart clears it. It's more of an annoyance at this stage, however I would prefer to fix it!

I'll have a visual check of the sensor and attempt to chuck a new one in and see how we get on

 

[John_B]

I finally got to have a good look at the sensor this weekend, no obvious signs of damage - with its position it is pretty well protected from road debris. The outer cable shielding looked like it had a couple of nicks but nothing too deep or drastic looking. When I removed the sensor it didn't look too dissimilar from the replacement either. So I think this one goes down as a mystery.

I have kept the old sensor (mainly because I could totally see myself replacing the wrong one and needing to put it back ) but if anyone is curious I can get some close-up photos.

thanks for the advice and suggestions

 

[John_B]

I drove down to Luton and back today, partly to test the new lambda sensor fixing the EML fault, but partly because the weather was beautiful and I fancied the return journey with the roof down.

Sadly when I got off the M1 in Luton I got the same EML & limp mode come on. This time with a new symptom which is that it cut out as I approached a mini roundabout! A quick restart got me going again but within 30secs I got the EML & limp mode again.

Parked up for a few hours and then on the return journey it behaved perfectly.

Checked the codes and the ICV & MAF codes have returned (P0505 and P0101 respectively). So at least the lambda sensor looks to be sorted, but I am going to have to do something with the ICV and MAF. I wonder if the ICV is behind the cut-out as I noticed a few times today the revs dropped super low at idle.

Psyching myself up to strip the intake manifold far enough to get at the ICV and give that a clean this weekend. Not really sure what to do with the MAF. I'm finding conflicting information about squirting some carb cleaner through it but also absolutely not to squirt anything through it

 

[colb]

Only specific Maf cleaner spray should be used on it, nothing else otherwise you will kill it.
My experience of Maf's are they either work or they don't. whatever you do do not cheap out on a replacement they don't work or rarely last long always use oem either Bosch or Siemens, expensive but they work out of the box,

 

[John_B]

Only specific Maf cleaner spray should be used on it, nothing else otherwise you will kill it.
My experience of Maf's are they either work or they don't. whatever you do do not cheap out on a replacement they don't work or rarely last long always use oem either Bosch or Siemens, expensive but they work out of the box,

Thanks Colb!

I managed to extract the ICV, and sure enough it felt pretty gunked up. Liberal application of carb cleaner got it clicking and clacking freely. Hopefully that solves the P1510 - "idle-speed control valve, mechanical fault" code.

I also discovered that the intake boot was cracked so I have ordered a replacement that should arrive tomorrow. I wonder whether this could account for the MAF code (P0101 - "Signal, air-mass flow sensor") if the engine is getting more air than the MAF is saying? I could be talking rubbish though At least the MAF is easy to get to if the code remains and I decide to give it a clean or replacement.

unfortunately I had a mishap with the DISA valve when I inadvertently removed the wrong lower bolt (that turned out to be for the ICV bracket). And then prying the DISA away from the manifold broke the plastic around the lower bolt bole. I thought it felt like something was still attached, but after removing two bolts I just assumed it was suction in the manifold and a really good seal!! The valve housing itself is intact, it's just the bolt hole. I think there is enough plastic to attempt a repair (I'm thinking of using a soldering iron to try and melt the broken piece back into place, and/or installing it with a big washer before I fork out for a replacement. I'm interested in doing the M54B30 manifold upgrade later this year which will mean replacing the DISA anyway

 

[colb]

Good find on the idle control valve, cleaning that may well sort the idle issue. If the intake boot had a hole or split that would have a big effect on what the exhaust sensor was seeing, it would have seen the unmetered air that had entered and not measured by the maf sensor. When that happens the exhaust sensor sees a lean mixture and the dme will compensate by adding more fuel at the injectors to richen the mixture. A look at live data fuel trims on a scanner would see high fuel trims, the dme will keep adding fuel until its sending 20% more fuel until it realises its not curing it and then sets the EML to draw attention to the fault. New intake boot and a clean ICV should get you back to normal. These engines require a sealed vacuum system to run correctly any air leaks however small can cause mayhem with fuelling. Bad luck with the DISA if you cant repair @spurs fan in a coupe probably can come up with one if you ask him./

 

[Andyboy]

I have a DISA valve if you need one.

Some very good intake boots as well but no MAF's. As above, only Siemens make the M52 MAF and Bosch make the 1.8/1.9's.

Aftermarket MAF's are largely crap although febi ones are generally Siemens with the logo ground off. Delphi and Bremi ones don't work.

 

[John_B]

Thanks Andy!

I'm not going to worry too much about the MAF (yet). With it being an intermittent issue, but people such as Colb saying MAFs either work or they don't, I'm working on the assumption that the MAF is fine, but something else is interfering.

Such as this split intake boot!

My current working theory is that the MAF code has always been there due to this split meaning the engine is getting unmetered air, but the EML (and new cutting-out symptom) were being triggered by the ICV misbehaving.

Having cleaned out the ICV, I am currently in the process of replacing the intake boot, however I am struggling since the new rubber is much less flexible and I'm finding that once I have fitted the spur for the ICV, it's very difficult to get the main opening on the throttle body. I've managed it a couple of times but then when I fit the airbox it pops off the throttle body.

I fashioned a repair to the broken bolt-hole on the DISA valve and I'm reasonably confident that it should do the trick for a few months while I muster the parts and courage to do an M54B30 manifold swap:

 

[Synclare]

I had exactly the same issue going for an mot on my 2.8TU. Started holding back then cut out, limp home mode then died.
Disconnect/reconnect battery and was fine, for a while.

On @colb suggestion I checked the intake boot which was not that old in mileage, exactly the same as yours and in the same place. Mine looked as though it had been nibbled away.

New boot and cleared the codes and problem solved. The codes were similar to yours including fuel supply shutting off.

Sometimes it's easy to 'over think' things

 

[colb]

Split boot is almost certainly the major cause of your issue it's imperative that the whole intake and. Vacuum system is sealed on these engines to run correctly.

 

[John_B]

Thanks both, sounds very promising! I will have another go with fitting the new intake boot soon. It was too hot under that black bonnet yesterday, with the sun directly on it it was like a radiator. And I was getting majorly p***** off with it popping off the throttle body after I'd refit the other part of the boot, the DISA and the airbox - two or three times!!

I think next time I'm going to try fitting it to the throttle body first and get it nice and tight before trying to bend the spur onto the ICV. I think it was holding it against the stiffness of that spur that was stopping me from getting it seated securely on the TB.

 

[colb]

Make sure the main boot to throttle body is in right orientation there is a shaped cut out the boot flap fits into on the throttle body so it sits at the right angle so the idle tune is in the right place to connect up

 

[colb]

Tube not tune

 

[John_B]

I finally got it fitted. I took it off the ICV port and fitted it to the TB first, and then did the ICV again. Kicking myself that I didn't think to try that yesterday, but hey ho!

Fingers crossed that is the end of this chapter!