The Black Flash
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| posted on 29/1/14 at 09:09 AM |
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v6 Emissions problems
Following an IVA fail on emissions, I've had a mobile chap come out have a look. I was expecting just to have to tweak a couple of points on the
ECU map, but it's all turned out a bit more complicated.
The engine is a 3.0 v6, with a separate exhaust per bank with cats integrated into the silencer cans, Emerald ECU, all mapped on Emerald's
rollers back in October. Emissions then were fine, well inside the 0.02 CO / 200 HC limits I need. It uses a single throttle and plenum chamber.
I've done nothing to the engine, other than take the exhausts off, and drive it 70 miles. It's been run a number of times on the drive to
check various things.
So yesterday, we did the warm up (2-5000 rpm until the fan cut in at 97 degrees - about 10 minutes). I noticed the "eggy" smell during
this time which I've since read indicates the cats starting to work?
We did both slow and fast (2500-3000rpm) tests, a number of times each, each time leaving the probe in for several minutes.
C0 was very high, HC about right. I reduced the fueling to about half around those positions, which reduced it somewhat, but still way too high.
At fast idle, on bank 2 (nearside), it came down but only to about 0.5. On bank 1 it was about 4.0
Slow idle, bank 1 was in, just, at 0.03; bank 2 was still up at 3.5-4!
Unfortunately his lambda sensor wasn't working; however the narrowband on the car suggests that it's rich. I think I'm going to
need a full day on a proper test rig somewhere, but does anyone have any ideas of things to check?
Perhaps the cat on bank 1 did not get hot enough? Though the exhaust tip was so hot that it melted his probe!
Maybe the fuel pressure regulator has gone, leading to higher pressure in the fuel rail and rich running?
The injectors are all brand new after a failure in the old set; but I guess one could be not working correctly and causing the whole bank to be rich?
(Could test this by swapping all the ones from one bank to the other)
Presumably not air leaks as that would make things lean.?
erm...?
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Slimy38
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| posted on 29/1/14 at 10:51 AM |
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Air leaks into the exhaust from when you removed them, leading to the lambda sensor getting confused and overfuelling?
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The Black Flash
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| posted on 29/1/14 at 11:28 AM |
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Alas no, as it was running open loop.
Though I should probably check for air leaks anyway I guess.
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davidimurray
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| posted on 29/1/14 at 01:03 PM |
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Is there any compensation in the map for inlet air or coolant temp? Do they show sensible values and are they changing? If these play up the map can
get stuck in starting compensation.
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
Gallery 2 http://www.facebook.com/media/set/?set=a.245243755324.181913.601005324&l=a9831a9319
Gallery 3 http://www.facebook.com/media/set/?set=a.440671625324.232627.601005324&l=3f0d42c523
Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
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The Black Flash
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| posted on 29/1/14 at 01:58 PM |
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It does have a starting enrichment map and one to compensate for coolant temps. I'm pretty sure it wasn't remaining the starting
enrichment when running, but it's worth checking. I'll be able to see on the live screen what it's doing. Cheers!
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perksy
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| posted on 29/1/14 at 05:10 PM |
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Have you checked fuel pressure ?
Worth double checking the injectors aswell
[Edited on 29/1/14 by perksy]
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The Black Flash
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| posted on 29/1/14 at 11:13 PM |
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Not yet but I think I will, just in case.
I had a bit of a play with it tonight and think I have found the reason for the difference between banks. It's always sounded a bit lumpy at
idle, not massively so, and I'd put it down to the more lairy cams. But a close listen to both pipes tonight (using a bit of card in front of
the pipe to accentuate the noise of each cylinder) showed that actually I've got a missfire, or possibly 2:
Nearside bank (OK)
Offside Bank (misfiring like a biatch)
It becomes much less obvious when it's revved. But it seems to pick up an occasional miss on the other bank then...only every second or so, and
just misses one beat, but it's there.
Nearside - slight miss at 2000 rpm
Can't say I noticed when driving it, but it was only the once, and I was taking things very easy as it was wet. I imagine that'll be the
cause of the high readings, although I'd expect the HC to be up as well.
It seems very electrical, so I'm going to guess at plugs or a coilpack. I'll change the plugs first 'cos it's cheaper.
Once I cure the misfire I'll drop by the local MOT place I think and get it analysed properly.
[Edited on 29/1/14 by The Black Flash]
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davidimurray
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| posted on 30/1/14 at 11:47 AM |
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A few thoughts -
Can you swap injectors around to see if the fault moves.
Have you got a good earth on both heads.
Can you swap coilpacks / leads around between cyls ?
Have you tried pulling a lead at a time to see which cyls are problematic?
Have you got equal fuel flow to both heads?
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
Gallery 2 http://www.facebook.com/media/set/?set=a.245243755324.181913.601005324&l=a9831a9319
Gallery 3 http://www.facebook.com/media/set/?set=a.440671625324.232627.601005324&l=3f0d42c523
Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
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The Black Flash
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| posted on 30/1/14 at 10:39 PM |
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Thanks for the reply 
"Can you swap injectors around to see if the fault moves. "
Yes, but I'm going to try the electrics first, I'm pretty sure it's not fuel; but I will try that afterwards if I get no joy
"Have you got a good earth on both heads. "
Hmmm. I think I have, and I have checked, but thinking about it, the loom earths to the head without the misfire, and I did remove an earth lead from
the other side. (it was on the plenum and stuck out too much). I've checked continuity but not resistance, so that might be something to look
into. Might be a coincidence, might not. Good thought, and easy to check.
"Can you swap coilpacks / leads around between cyls ? "
Coilpacks, yes, and that's my next move. Unfortunately it'll be a week before I can do anything, but I've ordered new plugs so
I'm going to change them and swap the packs over. If the misfire moves to the other bank, I'll know what the problem is.
"Have you tried pulling a lead at a time to see which cyls are problematic? "
I don't think that's practical unfortunately; all of the inlet runners and plenum bolt down on top of the coilpacks, so it'd take
about an hour to do each one.
"Have you got equal fuel flow to both heads?"
Yes, common fuel rail for both. That and the new injectors is one reason I think it's unlikely to be fuel; 20 year old coilpacks are a much
more likely culprit I reckon!
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The Black Flash
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| posted on 10/2/14 at 11:32 PM |
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Bump.
Well this is doing my noggin in. 
I replaced the plugs with new ones. In doing so, found that one of the plug wells was full of oil, another was partly full. Hurrah, I thought, I
found the problem. But no, that wasn't it. Though the very faint miss on the good bank at a couple of thousand rpm has gone, so I guess that
new plugs have helped a little.
Swapped the coilpacks from one bank to the other. Nope, still misfiring on the same bank!
Earthed various places on the head and plenum directly to the battery, no difference.
I also pulled injector leads so that only one cylinder at a time on the bad bank is getting fuel, to see if they are all misfiring or just one. It
seems like they all are to a greater or lesser degree.
Erm...at a bit of a loss now. All I can think of to check is the cam timing on that bank, though it doesn't seem like that would cause it to
miss ever other beat or so.
What can cause a seemingly random misfire at low rpm, under no load, that only affects half the engine?
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Oddified
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| posted on 11/2/14 at 09:01 AM |
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How's the ecu set-up, are the injectors sequential, banked or batch fired?.
Ian
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jimmyjoebob
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| posted on 11/2/14 at 09:22 AM |
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Long shot but how old is the fuel?
Shelf life is not what it used to be and this could be enough to up the emissions readings but not to make engine run noticeably different.
Maybe add some fresh fuel - just a thought. Hope you get it sorted
If at first you don't succeed, hide all evidence you ever tried!
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The Black Flash
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| posted on 11/2/14 at 11:22 AM |
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quote:
Originally posted by Oddified
How's the ecu set-up, are the injectors sequential, banked or batch fired?.
Ian
Sequential. The thought has occurred to me that they could be in the wrong order, but I'm sure that would give more than a slight misfire at
idle.
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Andy S
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| posted on 11/2/14 at 11:36 AM |
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Was the cam timing all present and correct on that bank?
Can you compression test ?
Did the fuel pressure all come up to specification?
What do the plugs look like comparing one side to the other?
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The Black Flash
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| posted on 11/2/14 at 11:51 AM |
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"Was the cam timing all present and correct on that bank? "
Going to check that tonight! Though I'm convinced it's not that, it doesn't seem as if a couple of degrees out would cause a
misfire?
"Can you compression test ? "
No, but I can take it to a garage and get it done if I come up blank on everything else.
"Did the fuel pressure all come up to specification? "
Not checked yet but it's a single rail, so if it's right for one side it must surely be right for the other? Worth taking it off and
checking for blockages though I suppose, I can do that when the cam cover is off.
"What do the plugs look like comparing one side to the other? "
horrible and sooty on the misfiring side, nice and light brown on the other, as you'd expect.
Cheers for the help, it's really useful to talk this through...
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Andy S
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| posted on 11/2/14 at 02:01 PM |
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Just trying to drift through it logically
If we assume that fuel and sparks are good as they should be side to side then we are left with mechanical items.
As the inlet is shared we can also risk and assumption that it is ok.
So what is not shared - Cams - Exhaust
Compression test ensures all is healthy with both banks
Timing confirms that mechanically its symetrical
If the silencers are external I would also swap them over just in case one has blocked - just removing them to run it may not be an option for you. 
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The Black Flash
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| posted on 12/2/14 at 10:21 PM |
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Well...
I stripped it all down, again, again. Took out the coilpacks and tested for sparks, all ok.
Striped the fuel rail, blew it through, swapped the injectors over from one bank to the other. Cranked it with the coils and inlet disconnected so
that I could see the injectors firing...all ok.
Checked the timing...the exhaust cam on the misfiring bank was retarded a fair bit. It's not unheard of for these early 24v engines to skip a
tooth or two on this bank, because of a poor belt path (they changed it a year or two later for exactly this reason). So I guess that's what
has happened at some point.
Put it all back together, and that seems to have solved it, well almost. The constant misfire on that bank is now gone, and the engine sounds quite
different at idle. So that's a result.
What I do still have is an occasional stutter, if I hold it at say 3000 rpm, every couple of seconds it'll just miss one. So I think I will
change the coilpacks anyway.
Cheers to all for the suggestions.
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Oddified
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| posted on 13/2/14 at 09:02 AM |
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Good news that the problem seems to have been found. The next question regarding the current slight missfire/stutter...is it possible that it was
mapped on the rolling road with the cam retarded?.
Ian
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mcerd1
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| posted on 13/2/14 at 10:13 AM |
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quote:
Originally posted by The Black Flash
It's not unheard of for these early 24v engines to skip a tooth or two on this bank, because of a poor belt path (they changed it a year or two
later for exactly this reason)
is there any permanent fix for that issue ?
[Edited on 13/2/2014 by mcerd1]
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The Black Flash
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| posted on 13/2/14 at 05:54 PM |
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quote:
Originally posted by Oddified
Good news that the problem seems to have been found. The next question regarding the current slight missfire/stutter...is it possible that it was
mapped on the rolling road with the cam retarded?.
Ian
I'm rather thinking that it might have been. The o2 sensor was in the "bad" bank, so that's what he would have mapped
against, but he did the emissions test from the other side (just because of where the machines were).
Though I'm not sure what difference it would make. I will have to speak to them and see what they reckon.
Big arse.
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The Black Flash
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| posted on 13/2/14 at 05:56 PM |
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quote:
Originally posted by mcerd1
quote:
Originally posted by The Black Flash
It's not unheard of for these early 24v engines to skip a tooth or two on this bank, because of a poor belt path (they changed it a year or two
later for exactly this reason)
is there any permanent fix for that issue ?
[Edited on 13/2/2014 by mcerd1]
Yeah, get a newer block 
They changed the oil pump and tensioner, and it can't be retrofitted to an older block, alas.
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