Misfire problems...
09 June 2003, 02:38 PM
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MY99, full decat, ITG filter, Forge re-circ DV and tek2.5 ecu.
Right, had a MAF fail last month due to a poor idle and occasional 'judder' whilst cruising at around 70 in fifth gear.
Replaced MAF, idle fine.
Engine still 'Judders' at constant throttle, especially around 2500rpm. There is an audible misfire there as well which can clearly be heard as I have a Blitz bb.
I thought spark plugs, was told it could be an air leak. Took it to Keith Price in Abergavenny who inform me that the Lambda sensor is not switching at all, so that may be the problem. So I changed it today and guess what.. there is no difference.
I have now spent almost 300 in labour and parts and it is still misfiring... What I want to know is.. What could be causing it? I am still suspecting a plug, but not sure as when I put my foot down there doesn't seem to be a problem as it pulls like a train and doesn't appear to have lost any performance! Help!!!
Oh and for the record there is no engine light, or any fault codes on the select monitor. Just no movement from the lambda sensor.
[Edited by Twigster Home - 9/6/2003 3:03:17 PM]
Right, had a MAF fail last month due to a poor idle and occasional 'judder' whilst cruising at around 70 in fifth gear.
Replaced MAF, idle fine.
Engine still 'Judders' at constant throttle, especially around 2500rpm. There is an audible misfire there as well which can clearly be heard as I have a Blitz bb.
I thought spark plugs, was told it could be an air leak. Took it to Keith Price in Abergavenny who inform me that the Lambda sensor is not switching at all, so that may be the problem. So I changed it today and guess what.. there is no difference.
I have now spent almost 300 in labour and parts and it is still misfiring... What I want to know is.. What could be causing it? I am still suspecting a plug, but not sure as when I put my foot down there doesn't seem to be a problem as it pulls like a train and doesn't appear to have lost any performance! Help!!!
Oh and for the record there is no engine light, or any fault codes on the select monitor. Just no movement from the lambda sensor.
[Edited by Twigster Home - 9/6/2003 3:03:17 PM]
09 July 2003, 11:45 PM
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There are a number of potential causes of this, so I'd be reluctant to say with certainty that the lack of lambda input is the cause, but this scenario certainly fits the facts as you've related them.
Without input from the lambda sensor, your ECU can't control the mixture via closed loop, and will tend to overfuel, thus causing bogging (is your "normal driving" fuel economy really crap?). When the ECU goes open loop under boost/higher rpm, fuelling is controlled by the MAF sensor alone, which would explain why the car still feels fine when you're giving it some.
It's always possible that something else is causing the misfire, but there's no way you can get it sorted until the lambda is inputting to the ECU properly.
The thing that's confusing me about all this is that you seem to be saying there are no CEL codes at all. If the Select Monitor literally reads nothing, 0.0 volts from the lambda input, the implication is that there's no connection to the sensor at all. Under these circumstances, the ECU should throw error 32.
If it doesn't, the only thing I can think is that somewhere along the way, the lambda sensor signal lead has been shorted to ground, leading the ECU to think there's still a connection. If you can get hold of a digital multimeter, there's another simple test you could do to verify this, so if you're still having problems, beg borrow or steal a meter!
BTW, on a not entirely related note, if you've already gone through one MAF sensor, swapping the ITG for a Green, K&N or STi panel might be a good bet for the future!
[Edited by greasemonkey - 9/7/2003 11:45:46 PM]
Without input from the lambda sensor, your ECU can't control the mixture via closed loop, and will tend to overfuel, thus causing bogging (is your "normal driving" fuel economy really crap?). When the ECU goes open loop under boost/higher rpm, fuelling is controlled by the MAF sensor alone, which would explain why the car still feels fine when you're giving it some.
It's always possible that something else is causing the misfire, but there's no way you can get it sorted until the lambda is inputting to the ECU properly.
The thing that's confusing me about all this is that you seem to be saying there are no CEL codes at all. If the Select Monitor literally reads nothing, 0.0 volts from the lambda input, the implication is that there's no connection to the sensor at all. Under these circumstances, the ECU should throw error 32.
If it doesn't, the only thing I can think is that somewhere along the way, the lambda sensor signal lead has been shorted to ground, leading the ECU to think there's still a connection. If you can get hold of a digital multimeter, there's another simple test you could do to verify this, so if you're still having problems, beg borrow or steal a meter!
BTW, on a not entirely related note, if you've already gone through one MAF sensor, swapping the ITG for a Green, K&N or STi panel might be a good bet for the future!
[Edited by greasemonkey - 9/7/2003 11:45:46 PM]
06 September 2003, 06:15 PM
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Twig,
As a matter course I`d change the plugs m8. Last 2 times i`ve had missfires thats solved it. The other thing thats a regular for misfires is hairline cracks in coils, but as you have a coil pack instead of individual coils thats out Lambda not switching 
the lambda sensor generates a voltage m8 (from memory between 0v and 1v) to the ecu, it doesn`t "switch"
L8r bud
Pete
As a matter course I`d change the plugs m8. Last 2 times i`ve had missfires thats solved it. The other thing thats a regular for misfires is hairline cracks in coils, but as you have a coil pack instead of individual coils thats out
Lambda not switching the lambda sensor generates a voltage m8 (from memory between 0v and 1v) to the ecu, it doesn`t "switch" L8r bud
Pete
06 September 2003, 06:24 PM
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Sorry, by the term 'switching' I mean it wasn't registering any voltage at all on the select monitor.
Was simply locked on 0.0 and that was it. Have just changed the ecu to an 802 with a John Banks 2.5 though, so will that affect the lambda at all?
If so then plug change is my next bet.
For the record, Keith Price Subaru in Abergavenny have said that if the lambda doesn't sort the problem out they will refund me the money and I can send the new one back. Many thanks to them for that!!
Was simply locked on 0.0 and that was it. Have just changed the ecu to an 802 with a John Banks 2.5 though, so will that affect the lambda at all?
If so then plug change is my next bet.
For the record, Keith Price Subaru in Abergavenny have said that if the lambda doesn't sort the problem out they will refund me the money and I can send the new one back. Many thanks to them for that!!
07 September 2003, 08:20 AM
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I've had misfire but only when hot. Tried everything and think i've found the cause. Heat coming up from my de-cat exhaust so i've ordered exhaust wrap to keep the heat away from the engine bay and sop heat soak????????????
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07 September 2003, 03:43 PM
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Interesting. If the Select Monitor says the lambda isn't registering anything, are you getting a CEL code? With an open circuit lambda you should get illuminated CEL when you start the engine, with error 32 showing on read memory. If not, it sounds as if the problem's in the ECU somewhere. Anyway, let's try and find out...
By "switching" the garage is likely to be referring to the lambda sensor output's behaviour of bouncing around the stoichiometric point. If the select monitor isn't registering any reading from the lambda sensor at all, sounds like there's a break in the signal path between the sensor head and the ECU's brain. All you have to do is find out where this break is. Could be that the second sensor you bought is also dodgy, could be a fault in the wiring loom between ECU and sensor, could be a fault in the ECU itself. How to find out?
Do you have (or can you borrow) a digital multimeter? If so, you can do some simple diagnosis that should hopefully clue you in to the source of this problem.
Run the engine up to temperature, stop it, then, being careful not to burn yourself, disconnect the lambda sensor plug from its loom.
Put the positive meter electrode on the signal pin of the lambda sensor's plug (ask if you don't know which one is which!), and the negative on any good earth point, like a connection point for an extended earth system (if you have one), or a clean bit of the inlet manifold.
Restart the engine and let it run for a minute or three, maybe giving it the odd gentle blip on the throttle. Check the reading on the meter during this time. Do you see anything on it?
Set the DVM to the 2 volt range and see what it reads. It likely won't act fast enough to keep up with a properly functioning sensor's output, but you should, if the sensor is okay, see a constantly fluctuating voltage, anything up to 0.8 or so. Don't worry if you see it go a tad higher than that though, or indeed if you only see 0.4-0.5, what you're looking for is an output (seeing as the Select Monitor says there's nothing!).
If you don't see any worthwhile reading, the new sensor is 99% certain to be buggered. If you do see a reading, the sensor's 99% certain to be okay and the problem is further down the line. In this case stop engine, reconnect the lambda to the loom and move inside the car.
Uncover the ECU in the passenger footwell by unclipping and withdrawing the carpet, and removing the kickplate. Locate pin 21 of the blue connector going into it. Looking at the wiring side, it's the third row down, third pin in from the right (White with black stripe IIRC), and get your positive voltmeter probe on it. Make certain you're getting a connection to the metal of the pin.
Put the negative DVM probe on a good earth (the ECU case should do), and run the engine for a few minutes as earlier. After allowing a minute or two for the sensor to warm back up, look again at the DVM reading. Do you see a similar pattern of fluctuating voltages as you observed when reading direct off the sensor output?
If you don't see any reading of note, your problem is 99% certain to be a fracture in the wire or fault in the connectors between the sensor socket and the ECU plug, so you can proceed on either identifying where the break is, or else get another wire installed straight from lambda sensor plug to ECU connector.
If you do see the same pattern of fluctuating voltage, the fault is almost certain to be a bad joint or other failure on the ECU PCB itself, so deal on that basis.
[Edited by greasemonkey - 9/7/2003 3:53:29 PM]
By "switching" the garage is likely to be referring to the lambda sensor output's behaviour of bouncing around the stoichiometric point. If the select monitor isn't registering any reading from the lambda sensor at all, sounds like there's a break in the signal path between the sensor head and the ECU's brain. All you have to do is find out where this break is. Could be that the second sensor you bought is also dodgy, could be a fault in the wiring loom between ECU and sensor, could be a fault in the ECU itself. How to find out?
Do you have (or can you borrow) a digital multimeter? If so, you can do some simple diagnosis that should hopefully clue you in to the source of this problem.
Run the engine up to temperature, stop it, then, being careful not to burn yourself, disconnect the lambda sensor plug from its loom.
Put the positive meter electrode on the signal pin of the lambda sensor's plug (ask if you don't know which one is which!), and the negative on any good earth point, like a connection point for an extended earth system (if you have one), or a clean bit of the inlet manifold.
Restart the engine and let it run for a minute or three, maybe giving it the odd gentle blip on the throttle. Check the reading on the meter during this time. Do you see anything on it?
Set the DVM to the 2 volt range and see what it reads. It likely won't act fast enough to keep up with a properly functioning sensor's output, but you should, if the sensor is okay, see a constantly fluctuating voltage, anything up to 0.8 or so. Don't worry if you see it go a tad higher than that though, or indeed if you only see 0.4-0.5, what you're looking for is an output (seeing as the Select Monitor says there's nothing!).
If you don't see any worthwhile reading, the new sensor is 99% certain to be buggered. If you do see a reading, the sensor's 99% certain to be okay and the problem is further down the line. In this case stop engine, reconnect the lambda to the loom and move inside the car.
Uncover the ECU in the passenger footwell by unclipping and withdrawing the carpet, and removing the kickplate. Locate pin 21 of the blue connector going into it. Looking at the wiring side, it's the third row down, third pin in from the right (White with black stripe IIRC), and get your positive voltmeter probe on it. Make certain you're getting a connection to the metal of the pin.
Put the negative DVM probe on a good earth (the ECU case should do), and run the engine for a few minutes as earlier. After allowing a minute or two for the sensor to warm back up, look again at the DVM reading. Do you see a similar pattern of fluctuating voltages as you observed when reading direct off the sensor output?
If you don't see any reading of note, your problem is 99% certain to be a fracture in the wire or fault in the connectors between the sensor socket and the ECU plug, so you can proceed on either identifying where the break is, or else get another wire installed straight from lambda sensor plug to ECU connector.
If you do see the same pattern of fluctuating voltage, the fault is almost certain to be a bad joint or other failure on the ECU PCB itself, so deal on that basis.
[Edited by greasemonkey - 9/7/2003 3:53:29 PM]
07 September 2003, 03:55 PM
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Doubt it will be in the ECU as I have recently changed this and the problem has been continuous even with the old ECU. I dn't have a voltmeter or anything to check with so perhaps I can get this checked at the garage??
There are definitely no alarm codes coming from the ECU at all, but that is what I meant when I was saying 'swithching'. There was no voltage at all simply locked on 0.00 all the time. They did say that this may be caused by an air leak, but that the sensor was the first thing to rule out.
Anyone near me got a digital multimeter so we can have a look?
Thanks for the advice though mate...
There are definitely no alarm codes coming from the ECU at all, but that is what I meant when I was saying 'swithching'. There was no voltage at all simply locked on 0.00 all the time. They did say that this may be caused by an air leak, but that the sensor was the first thing to rule out.
Anyone near me got a digital multimeter so we can have a look?
Thanks for the advice though mate...
07 September 2003, 05:48 PM
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Garage certainly could check this, but of course they'll charge you for the privilege. If the Select Monitor is genuinely reading nada, all you've got to do is, as mentioned earlier, check there's a signal coming out the sensor, and once you know there is, find the point at which it stops reading.
If you've tried another ECU that tends to point to a break in the wiring loom, so again this is something the garage could test, but it's also something you could do with some extra wire and a DVM's continuity/resistance function.
If you can't borrow a multimeter, getting hold of a cheap one from somewhere like Maplins would be well worth your while, both in diagnosing this problem and in the toolbox for the future.
If you've tried another ECU that tends to point to a break in the wiring loom, so again this is something the garage could test, but it's also something you could do with some extra wire and a DVM's continuity/resistance function.
If you can't borrow a multimeter, getting hold of a cheap one from somewhere like Maplins would be well worth your while, both in diagnosing this problem and in the toolbox for the future.
08 September 2003, 09:09 AM
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I checked the ECU for errors with delta dash and there were any!! When I was in the car, I couldn't really hear / feel the misfire. Tried my ECU in his car, and it still did it apparently!
I have posted 3 logs on my webspace :-
http://www.babber.pwp.blueyonder.co.uk/DeltaLog1.csv
http://www.babber.pwp.blueyonder.co.uk/DeltaLog2.csv
http://www.babber.pwp.blueyonder.co.uk/DeltaLog3.csv
It does ask for a passcode, but just enter through that
Thanks Phill
I have posted 3 logs on my webspace :-
http://www.babber.pwp.blueyonder.co.uk/DeltaLog1.csv
http://www.babber.pwp.blueyonder.co.uk/DeltaLog2.csv
http://www.babber.pwp.blueyonder.co.uk/DeltaLog3.csv
It does ask for a passcode, but just enter through that
Thanks Phill
09 September 2003, 05:43 PM
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Piece of string. If you went about it the "proper" way it'd involve replacing all or part of the loom bundle, so could be ££££, especially if you got garage to do it.
Slightly less neat - although just as effective, would be to run some wire through the bulkhead and crimp/solder it onto the loom side of the sensor connector. Cut the original wire an inch or two before it goes into the ECU plug, then solder the new one on instead. Total cost, probably less than £2, plus your time.
Haven't looked at those DD logs yet, BTW, will have a squizz now.
Slightly less neat - although just as effective, would be to run some wire through the bulkhead and crimp/solder it onto the loom side of the sensor connector. Cut the original wire an inch or two before it goes into the ECU plug, then solder the new one on instead. Total cost, probably less than £2, plus your time.
Haven't looked at those DD logs yet, BTW, will have a squizz now.
10 September 2003, 01:31 PM
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Broken/shorted wire does seem to be the common diagnosis. Is in a garage at the moment beibng checked out (again) but has reported no faults on any of the diagnostic equipment and apparantely the lambda sensor is now switching!?
Which leads me back to my suspicion.. Leaky wastgate possibly??
Which leads me back to my suspicion.. Leaky wastgate possibly??
10 September 2003, 04:59 PM
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Well, it's been at the best garage I know of all day and they can find nothing that can be causing it at all. So I have just about given up on the bloody thing now!! Any other ideas?
10 September 2003, 05:34 PM
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Just looking at your DD logs now. Unfortunately, I'm not too familiar with DeltaDash, or indeed the way your car is supposed to fuel post-remap, so might be misinterpreting the results.
Before saying too much, can you check with Phil to see whether the O2 sensor values shown in the logs are direct reads off the sensor input, or whether it's some sort of interpreted wideband?
If the lambda voltage shown in the logs is a direct read, it's reading far too low. The run through the gears in file 1 (on your private test track of course!) shows a maximum O2 sensor read of 0.635 volts, and the average read during acceleration is 0.268 volts.
In gear and under WOT, it should be nearer the 0.8-0.9 volt area all the way through to you lifting off the throttle, so something (either the sensor or my interpretation of what I'm seeing!) is wrong here.[/b]
[Edited by greasemonkey - 9/10/2003 5:37:35 PM]
Before saying too much, can you check with Phil to see whether the O2 sensor values shown in the logs are direct reads off the sensor input, or whether it's some sort of interpreted wideband?
If the lambda voltage shown in the logs is a direct read, it's reading far too low. The run through the gears in file 1 (on your private test track of course!) shows a maximum O2 sensor read of 0.635 volts, and the average read during acceleration is 0.268 volts.
In gear and under WOT, it should be nearer the 0.8-0.9 volt area all the way through to you lifting off the throttle, so something (either the sensor or my interpretation of what I'm seeing!) is wrong here.[/b]
[Edited by greasemonkey - 9/10/2003 5:37:35 PM]
10 September 2003, 06:03 PM
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Well it just cost me £75 for the garage to tell me there was no misfire, (which I then performed for him on the spot) and to tell me that there is nothing wrong.
I told them to check wiring etc, but they said nothing wrong there so to be honest I don't think they even checked.
The only thing of use to me is that one of the bolts on the front pipe has been cross-threaded and stripped, so perhaps that has come loose allowing air to come through??
I told them to check wiring etc, but they said nothing wrong there so to be honest I don't think they even checked.
The only thing of use to me is that one of the bolts on the front pipe has been cross-threaded and stripped, so perhaps that has come loose allowing air to come through??
11 September 2003, 09:37 AM
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Exactly.
That is what I asked! I think he means the downpipe, but will have to get someone else to check. I'm not convinced they even looked at it to be honest.
I am starting to get a little upset about it all to be honest!
That is what I asked! I think he means the downpipe, but will have to get someone else to check. I'm not convinced they even looked at it to be honest.
I am starting to get a little upset about it all to be honest!
11 September 2003, 09:59 AM
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Just seen this thread and looked at the logs. The obvious thing is the lambda sensor voltages - leak or duff sensor would explain. It could also be duff fuel pressure/fuel pump but I would expect more knock correction if it was that lean.
In the third log the ECU goes to +25 on air fuel correction to try and get the lambda voltage up to go closed loop, tries a few times and gives up. If the lambda is knackered, 25% extra fuel than you require may make it feel strange, although it shouldn't do it for long.
You could try unplugging the lambda sensor to see if that improves things.
CEL 32 takes a while with a duff lambda to come on, sometimes a few weeks. I think it should be quicker - if it can't run closed loop it would ideally CEL straight away.
Sorry if I missed it and you changed the lambda already.
In the third log the ECU goes to +25 on air fuel correction to try and get the lambda voltage up to go closed loop, tries a few times and gives up. If the lambda is knackered, 25% extra fuel than you require may make it feel strange, although it shouldn't do it for long.
You could try unplugging the lambda sensor to see if that improves things.
CEL 32 takes a while with a duff lambda to come on, sometimes a few weeks. I think it should be quicker - if it can't run closed loop it would ideally CEL straight away.
Sorry if I missed it and you changed the lambda already.
09 November 2003, 10:15 AM
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Well it goes in for the cambelt change soon so if that is all it is then no problem. Truth be told though I don't think that is the problem as I am told that it would affect the top-end performance more than it currently is.
I have narrowed it down to around 2600rpm, at 3k it seems ok and at 2k I definitely don't notice it, and I can't hear it if I rev the car whilst at a standstill. Whereas, if i am in neutral and on the drive it will happily splutter away!
* Edited to say, sorry John, I already changed the Lambda with no results. Although I am wondering about this bolt, if it is oose/stripped that may have, over time, developed into a leak, and it is certainly in a position where it would cause a problem.. Will get it looked at I think.
[Edited by Twigster - 9/11/2003 10:19:14 AM]
I have narrowed it down to around 2600rpm, at 3k it seems ok and at 2k I definitely don't notice it, and I can't hear it if I rev the car whilst at a standstill. Whereas, if i am in neutral and on the drive it will happily splutter away!
* Edited to say, sorry John, I already changed the Lambda with no results. Although I am wondering about this bolt, if it is oose/stripped that may have, over time, developed into a leak, and it is certainly in a position where it would cause a problem.. Will get it looked at I think.
[Edited by Twigster - 9/11/2003 10:19:14 AM]
09 November 2003, 04:24 PM
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up we go...
It is booked in with Keith Price Subaru again for tomorrow day so I would ideally like to get an idea of what may be happening to take to them as a starting point.
Am trying to keep the labour costs down to a reasonable amount rather than having to pay for something like 8 hours labour on it!!
Let me know if you have any more ideas guys.
[Edited by Twigster - 9/11/2003 4:30:36 PM]
It is booked in with Keith Price Subaru again for tomorrow day so I would ideally like to get an idea of what may be happening to take to them as a starting point.
Am trying to keep the labour costs down to a reasonable amount rather than having to pay for something like 8 hours labour on it!!
Let me know if you have any more ideas guys.
[Edited by Twigster - 9/11/2003 4:30:36 PM]
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