981 misfire and useless OPC
Discussion
My local OPC changed the spark plugs in my 981 at the correct age/mileage and the car had a new coil pack under warranty some time ago after going into limp home mode, it’s now since developed a misfire which is present from idle all the way up to 4500rpm.
As the car is under warranty I took it to an OPC who agreed they could feel it but said it was normal and that it was the car “coming on cam” which I think is absolute rubbish, unless these cars come on cam 10 times from idle and 4500rpm…
I’ve then took it to another OPC who agrees they can feel it but they can’t replace anything under warranty because the computer doesn’t report any error codes, so as far as they are concerned there is no fault.
I’m really getting frustrated now, the car isn’t nice to drive and I really want it fixing. If it were any normal car I’d just buy some new spark plugs and ignition packs and do it myself but I begrudge going through the expense and effort when I’ve paid a lot of money for a 2-year warranty that has evaporated the moment I tried to claim on it.
I can’t sell the car privately with a misfire, and my OPC won’t give me market value in a part ex until its fixed yet their own service desk are shrugging their shoulders.
Any advice would be appreciated.
As the car is under warranty I took it to an OPC who agreed they could feel it but said it was normal and that it was the car “coming on cam” which I think is absolute rubbish, unless these cars come on cam 10 times from idle and 4500rpm…
I’ve then took it to another OPC who agrees they can feel it but they can’t replace anything under warranty because the computer doesn’t report any error codes, so as far as they are concerned there is no fault.
I’m really getting frustrated now, the car isn’t nice to drive and I really want it fixing. If it were any normal car I’d just buy some new spark plugs and ignition packs and do it myself but I begrudge going through the expense and effort when I’ve paid a lot of money for a 2-year warranty that has evaporated the moment I tried to claim on it.
I can’t sell the car privately with a misfire, and my OPC won’t give me market value in a part ex until its fixed yet their own service desk are shrugging their shoulders.
Any advice would be appreciated.
Edited by SkinnyPete on Saturday 3rd November 21:54
If it was a normal ignition misfire I would expect this to put a light on the dash (probably flashing) and store a code for the cylinder that was affected.
A miss that clears above 4500 is very unlikely to be a coil and not all that likely to be a plug.
That leaves either a fueling issue on one cylinder (also unlikely), a compression fault (should flag a misfire code same as the other stuff) or it may be some form of vibration rather than an actual misfire.
Tricky to diagnose some of these problems but I'd suggest the next thing to do would be get it on an emissions tester. If it does have a misfire you'd have excessive hydrocarbons and oxygen coming out of the engine, the catalyst might scrub most of the HCs but the O2 would usually still be noticeable. If you were able to get it tested from stone cold you might be able to catch the HCs before the cat warms up. If no excessive HCs or O2 are present it's not likely to be a misfire and more likely to be a vibration.
A miss that clears above 4500 is very unlikely to be a coil and not all that likely to be a plug.
That leaves either a fueling issue on one cylinder (also unlikely), a compression fault (should flag a misfire code same as the other stuff) or it may be some form of vibration rather than an actual misfire.
Tricky to diagnose some of these problems but I'd suggest the next thing to do would be get it on an emissions tester. If it does have a misfire you'd have excessive hydrocarbons and oxygen coming out of the engine, the catalyst might scrub most of the HCs but the O2 would usually still be noticeable. If you were able to get it tested from stone cold you might be able to catch the HCs before the cat warms up. If no excessive HCs or O2 are present it's not likely to be a misfire and more likely to be a vibration.
Thanks for that Steve.
I'm pretty sure they said they checked the fuelling but I will ask them to see if they can check the emissions. In terms of vibration, what would you have in mind?
Having said all that, the fact you can hear the exhaust note missing slightly at idle and based on past experiences it still seems like a classic case of spark plugs/ignition coils. The Porsche technicians are adamant that if it were a misfire it would show on the diagnostics but I don't see how this is possible, unless there was a catastrophic breakdown somewhere.
If I don't get anywhere with Porsche then the alternative is I spend £400 on ignition packs and spark plugs, but I really want to avoid going down this route as I've read the 2 cylinders nearest the bulkhead are a pain to change. In fact the cynical side of me would suggest Porsche probably didn't even change the spark plugs...
Edited just to add, your comments about compression...if this were the case would oil consumption not be high? The car uses none.
I'm pretty sure they said they checked the fuelling but I will ask them to see if they can check the emissions. In terms of vibration, what would you have in mind?
Having said all that, the fact you can hear the exhaust note missing slightly at idle and based on past experiences it still seems like a classic case of spark plugs/ignition coils. The Porsche technicians are adamant that if it were a misfire it would show on the diagnostics but I don't see how this is possible, unless there was a catastrophic breakdown somewhere.
If I don't get anywhere with Porsche then the alternative is I spend £400 on ignition packs and spark plugs, but I really want to avoid going down this route as I've read the 2 cylinders nearest the bulkhead are a pain to change. In fact the cynical side of me would suggest Porsche probably didn't even change the spark plugs...
Edited just to add, your comments about compression...if this were the case would oil consumption not be high? The car uses none.
The ECU diagnoses a misfire in a very specific way. It looks at the data from the crank sensor and sees the acceleration of the crank on each power stroke. If it sees uneven power strokes it flags a misfire code and if it can identify it to a particular cylinder it does so. This should mean that an actual misfire, whether caused by fuel, spark or compression, should flag a fault in the ecu. This would put a light on and in most cases the light would be flashing when the fault is active.
Given that there is no light or code, I'm wondering about a vibration as that might cause a similar feeling without flagging a fault code although I agree that it wouldn't generally mean you could hear anything through the exhaust.
A compression fault could be in the valvetrain in which case oil usage might not be a consequence, I am guessing that your engine is direct injection though in which case issues with inlet valves and coking etc can cause symptoms that are more obvious at low revs and low load (this is a general comment about direct inj engines, not sure if Porsche suffer particularly).
There are some old-school tests that can be done, measure the temperature of the exhaust manifold branches form cold start and see if one cylinder warms up slower than the others, disconnect one coil at a time at idle and see how it affects the engine note etc.
Given that there is no light or code, I'm wondering about a vibration as that might cause a similar feeling without flagging a fault code although I agree that it wouldn't generally mean you could hear anything through the exhaust.
A compression fault could be in the valvetrain in which case oil usage might not be a consequence, I am guessing that your engine is direct injection though in which case issues with inlet valves and coking etc can cause symptoms that are more obvious at low revs and low load (this is a general comment about direct inj engines, not sure if Porsche suffer particularly).
There are some old-school tests that can be done, measure the temperature of the exhaust manifold branches form cold start and see if one cylinder warms up slower than the others, disconnect one coil at a time at idle and see how it affects the engine note etc.
From what you say the ECU certainly seems smart enough, but is it infallible?
If it were a vibration then why would it disappear above 4500rpm and why would it be so random? If I keep a light throttle at low revs I can get away with it but anything more than that then it rears its head, some days are worse than others.
I had a long journey last week and my passenger had their head in their hands thinking the car is going to break down, yet later on it was hardly noticeable. I've yet to find a trend or pattern.
If it were a vibration then why would it disappear above 4500rpm and why would it be so random? If I keep a light throttle at low revs I can get away with it but anything more than that then it rears its head, some days are worse than others.
I had a long journey last week and my passenger had their head in their hands thinking the car is going to break down, yet later on it was hardly noticeable. I've yet to find a trend or pattern.
If I were you, I'd take it to RPM technik as I find their attitude and helpfulness refreshing.
Do you have a good indy like them near-ish to you?
My heater fan stopped working in March, under warranty, and my OPC wouldn't look at it even though it was a known issue (i.e. to them, "normal").
Prior to this another OPC who serviced the car couldn't work out an oil gauge issue, and their technician explained that the boot has to be opened to read the oil... via its electronic gauge!?
What do they know?
Having said that, before going to a caring and well regarded indy I'd be phoning my OPC dealer principal and informing him I want Porsche to pay should an indy find a problem his OPC couldn't work out. I'd also explain that for the good of all 981 owners I'd ensure that the solution, and who found it (and who didn't) was spread across the forums.
Do you have a good indy like them near-ish to you?
My heater fan stopped working in March, under warranty, and my OPC wouldn't look at it even though it was a known issue (i.e. to them, "normal").
Prior to this another OPC who serviced the car couldn't work out an oil gauge issue, and their technician explained that the boot has to be opened to read the oil... via its electronic gauge!?
What do they know?
Having said that, before going to a caring and well regarded indy I'd be phoning my OPC dealer principal and informing him I want Porsche to pay should an indy find a problem his OPC couldn't work out. I'd also explain that for the good of all 981 owners I'd ensure that the solution, and who found it (and who didn't) was spread across the forums.
I had this following a service and plug change to my 987.2 at an independent, I returned the car and all coil packs were changed but fault still persisted so I took the car to an OPC where it was found the plugs as fitted were of shorter reach from 987.1. Correct plugs fitted and OPC billed the independent.
JensonBGTS said:
I had this following a service and plug change to my 987.2 at an independent, I returned the car and all coil packs were changed but fault still persisted so I took the car to an OPC where it was found the plugs as fitted were of shorter reach from 987.1. Correct plugs fitted and OPC billed the independent.
That's an interesting one. OP, did your symptoms start immediately after the service at the OPC? I have seen symptoms like this from a plug being fitted with the gap closed up but again if it was only on one cylinder I would have expected it to flag a light - if they were all incorrect or gapped wrong it's possible the ecu would have a harder time picking up on it??
88racing said:
Stick it on a dyno? If it’s behaviour is consistent, surely you’d see it on the trace?
A dyno measures the end result, not the cause; I'm not sure how that helps diagnose this fault especially as it happens at lower rpm and even at idle.nw942 said:
If the actuator in the exhaust was stuck in a partially open state, would that cause these symptoms?
I wouldn't have thought so but my car does not have PSE so does it even have an actuator? pete.g said:
Have you ruled out a faulty hydraulic lifter?
No, how would one diagnose/test that? Steve H said:
JensonBGTS said:
I had this following a service and plug change to my 987.2 at an independent, I returned the car and all coil packs were changed but fault still persisted so I took the car to an OPC where it was found the plugs as fitted were of shorter reach from 987.1. Correct plugs fitted and OPC billed the independent.
That's an interesting one. OP, did your symptoms start immediately after the service at the OPC? I have seen symptoms like this from a plug being fitted with the gap closed up but again if it was only on one cylinder I would have expected it to flag a light - if they were all incorrect or gapped wrong it's possible the ecu would have a harder time picking up on it??
I'm going to have another crack at my OPC but failing that I'll change plugs and coils myself and I'll bet a months salary it fixes the issue.
AW10 said:
Worth a read? http://www.boxa.net/forum/topic/73120-read-this-if...
Very interesting thanks for that. I wonder how difficult one is to fit.Why the hell were only 4 replaced?
Reading your first post the spark plug length sprung to mind, I've seen this a few times before, it's been mentioned a few times above but I can personally vouch for it causing rough running without the DME throwing a misfire code, it does however show a difference in the cylinder roughness AV's. Still, no codes show up.
Try that first. If you know the spark plug part numbers from your invoice, message them across and I'll check them.
Reading your first post the spark plug length sprung to mind, I've seen this a few times before, it's been mentioned a few times above but I can personally vouch for it causing rough running without the DME throwing a misfire code, it does however show a difference in the cylinder roughness AV's. Still, no codes show up.
Try that first. If you know the spark plug part numbers from your invoice, message them across and I'll check them.
TrackNutz said:
Why the hell were only 4 replaced?
Reading your first post the spark plug length sprung to mind, I've seen this a few times before, it's been mentioned a few times above but I can personally vouch for it causing rough running without the DME throwing a misfire code, it does however show a difference in the cylinder roughness AV's. Still, no codes show up.
Try that first. If you know the spark plug part numbers from your invoice, message them across and I'll check them.
999.170.151.90 is what is on my invoice but you never know they could have fitted different ones.Reading your first post the spark plug length sprung to mind, I've seen this a few times before, it's been mentioned a few times above but I can personally vouch for it causing rough running without the DME throwing a misfire code, it does however show a difference in the cylinder roughness AV's. Still, no codes show up.
Try that first. If you know the spark plug part numbers from your invoice, message them across and I'll check them.
I can't prove only 4 were replaced but my point was, mechanics sometimes get lazy when they think they can get away (especially when they get a bonus for completing jobs early, which they do at Porsche) with it and 2 out of the 6 plugs are difficult to change. So maybe they didn't bother and hence said plugs are now worn out.
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