Misfire under load
#1
Misfire under load
Hi everybody,thank for taking the time to read this.
I have a bog standard 2000 on a x imprezza turbo classic with a misfire under load,it has been code read and came up with the lamda sensor,this has been repalced with a know working 2nd hand one,all the leads,plugs,air filter,fuel filter etc have been changed.
I have also changed the wastegate actuator,checked all vac pipes etc,any ideas please?
I have a bog standard 2000 on a x imprezza turbo classic with a misfire under load,it has been code read and came up with the lamda sensor,this has been repalced with a know working 2nd hand one,all the leads,plugs,air filter,fuel filter etc have been changed.
I have also changed the wastegate actuator,checked all vac pipes etc,any ideas please?
#4
Scooby Regular
iTrader: (78)
NPS maybe?
newage cars have this problem under big torque or when a nps is on its way out. hth
Rob
newage cars have this problem under big torque or when a nps is on its way out. hth
Rob
Hi everybody,thank for taking the time to read this.
I have a bog standard 2000 on a x imprezza turbo classic with a misfire under load,it has been code read and came up with the lamda sensor,this has been repalced with a know working 2nd hand one,all the leads,plugs,air filter,fuel filter etc have been changed.
I have also changed the wastegate actuator,checked all vac pipes etc,any ideas please?
I have a bog standard 2000 on a x imprezza turbo classic with a misfire under load,it has been code read and came up with the lamda sensor,this has been repalced with a know working 2nd hand one,all the leads,plugs,air filter,fuel filter etc have been changed.
I have also changed the wastegate actuator,checked all vac pipes etc,any ideas please?
#6
I have had a boost gauge on it today,under load in 2nd and 3 rd the psi drops when it does it,it is more like a boost cut now you mention it.
#7
Scooby Regular
iTrader: (78)
ah right.... thought the Neutral Position Switch might be faulty. The ecu on the newage flashes up with a misfire code when the car is reving high with a faulty NPS as the ecu think the car is in neutral so it gives off the OBD2 misfire code.......HOWEVER Im under the i impression this doesnt alter the performance, but i can not vouch for the classic... just a thought.
ie: my car running a brand newly built engine on a standard TD04 was fine, no ECU issues. Now engine running in with a complete overall inc 3" decat, STI pinks and VF30 etc has now started offering up the misfire code frequently due to the torque pushing the NPS out of sync on the gearbox. The gearbox litteraly twists slightly under load. Im getting a new NPS fitted next week (£50)
HTH
Rob
ie: my car running a brand newly built engine on a standard TD04 was fine, no ECU issues. Now engine running in with a complete overall inc 3" decat, STI pinks and VF30 etc has now started offering up the misfire code frequently due to the torque pushing the NPS out of sync on the gearbox. The gearbox litteraly twists slightly under load. Im getting a new NPS fitted next week (£50)
HTH
Rob
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#8
ah right.... thought the Neutral Position Switch might be faulty. The ecu on the newage flashes up with a misfire code when the car is reving high with a faulty NPS as the ecu think the car is in neutral so it gives off the OBD2 misfire code.......HOWEVER Im under the i impression this doesnt alter the performance, but i can not vouch for the classic... just a thought.
ie: my car running a brand newly built engine on a standard TD04 was fine, no ECU issues. Now engine running in with a complete overall inc 3" decat, STI pinks and VF30 etc has now started offering up the misfire code frequently due to the torque pushing the NPS out of sync on the gearbox. The gearbox litteraly twists slightly under load. Im getting a new NPS fitted next week (£50)
HTH
Rob
ie: my car running a brand newly built engine on a standard TD04 was fine, no ECU issues. Now engine running in with a complete overall inc 3" decat, STI pinks and VF30 etc has now started offering up the misfire code frequently due to the torque pushing the NPS out of sync on the gearbox. The gearbox litteraly twists slightly under load. Im getting a new NPS fitted next week (£50)
HTH
Rob
#11
What was wrong with the inspiration that Tidgy gave you? On the basis of what you've told us, getting your car looked at by a specialist would be a perfectly legitimate way forward.
You can forget about the neutral position switch btw. If this was a factor you'd get an error code when you checked the memory.
What's your boost gauge reading when you get the "misfire"? How, if at all, is the car modified?
You can forget about the neutral position switch btw. If this was a factor you'd get an error code when you checked the memory.
What's your boost gauge reading when you get the "misfire"? How, if at all, is the car modified?
Last edited by Splitpin; 15 January 2010 at 07:17 PM.
#12
What was wrong with the inspiration that Tidgy gave you? On the basis of what you've told us, the most worthwhile way forward would be to get your car looked at by a specialist.
You can forget about the neutral position switch btw. If this was a factor you'd get an error code when you checked the memory.
You can forget about the neutral position switch btw. If this was a factor you'd get an error code when you checked the memory.
#15
The boost is peaking at 15 psi,the car is totaly standard
sorry,should of said it wasnt on
sorry,should of said it wasnt on
Last edited by spannerboy; 15 January 2010 at 07:35 PM.
#17
Thank you for your help.
#21
Any idea what the the fuel pressure should be?
Last edited by spannerboy; 15 January 2010 at 09:14 PM.
#22
Just been out in it again,it hunts on idle,it is almost as if it has an air leak,I have changed the pipes that operate the actuator for ones off another one,I made sure the restricted one was in the right place.
#23
Hunting idle points to, among other things an airflow sensor issue. If your reading of c.15psi is accurate, that suggests you are not experiencing overboost and fuel cut. While there are still any number of possible explanations, one of them may be a failing airflow sensor and corresponding very lean on-boost mixtures (and probably very serious detonation).
You would therefore be well advised to take Tidgy's advice and get it looked at by someone able to diagnose the car properly. You need to know what's wrong with it ASAP, as it sounds like there's enough of a fault to be doing your engine long-term damage.
Incidentally - someone who doesn't know better might be along in a bit to tell you about a test which involves unplugging the airflow sensor with the engine running and seeing if the engine stalls, with a stall meaning that the "sensor is good", and a lack of stall meaning the sensor is "bad". This "test" is a myth based on complete bullsh*t and, as described above, can give dangerously misleading results, don't bother doing it.
What might be worth trying is unplugging the airflow sensor with the engine off and then starting it up. If the idle magically stabilises, that adds further weight to the theory of a damaged sensor, but is not, in itself, conclusive.
Oh - if you've changed the boost control pipework, one presumes that the "new" pipes have the correct size restrictor in them?
#24
The pipework came off another car,so all pipes are genuine,so therfore pressuming the restrictor is the right size.
Now this is the thing,when you do a cat test,the co and hc's are fine.
The plugs are a nice browny colour,so that would suggest all is ok on the mixture,could it be wrong plugs? what should it have in there?
The maf sensor was changed,I bought a 2nd hand one of grade a,we also tried this on my friends classic.
I am in Guildford or down on the south coast,anyone recommend someone I can go to please?
Now this is the thing,when you do a cat test,the co and hc's are fine.
The plugs are a nice browny colour,so that would suggest all is ok on the mixture,could it be wrong plugs? what should it have in there?
The maf sensor was changed,I bought a 2nd hand one of grade a,we also tried this on my friends classic.
I am in Guildford or down on the south coast,anyone recommend someone I can go to please?
Last edited by spannerboy; 15 January 2010 at 10:17 PM.
#25
The plugs are a nice browny colour,so that would suggest all is ok on the mixture,
Aside from anything else the 99-00 MAF has a failure mode in which its output momentarily disappears due to fractures in its internal wiring causing bad connections - with the duration of the drop-out getting longer and longer as the sensor degrades. In practice this under-read on the airflow input causes the ECU to under-calculate the fuel mix for the duration of the drop-out. Depending on how bad and how long the drop-out lasts, the symptoms can either be undetectable (and undamaging) to undetectable (but cumulatively damaging) to detectable and seriously damaging. You need to know which, if any, of the above apply.
could it be wrong plugs? what should it have in there?
#27
Scooby Regular
iTrader: (78)
"Reputable garage required near southampton or portsmouth"
That ought to work mate.
Cheers
Rob
Edit- And put it in the Southern section https://www.scoobynet.com/southern-england-22/ ;-)
Last edited by Rob Day; 16 January 2010 at 10:26 AM. Reason: Area search
#29
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sorry if im hijacking the thread here,
i have a newage wrx and keeps throwing faults when i boot it in 4th gear mainly. the cel comes on and when i get the codes read its showing missfires on all cylinders so im asuming after changing all the plugs etc etc its the nps switch am i right???
thanks phil
i have a newage wrx and keeps throwing faults when i boot it in 4th gear mainly. the cel comes on and when i get the codes read its showing missfires on all cylinders so im asuming after changing all the plugs etc etc its the nps switch am i right???
thanks phil
#30
Scooby Regular
iTrader: (78)
sorry if im hijacking the thread here,
i have a newage wrx and keeps throwing faults when i boot it in 4th gear mainly. the cel comes on and when i get the codes read its showing missfires on all cylinders so im asuming after changing all the plugs etc etc its the nps switch am i right???
thanks phil
i have a newage wrx and keeps throwing faults when i boot it in 4th gear mainly. the cel comes on and when i get the codes read its showing missfires on all cylinders so im asuming after changing all the plugs etc etc its the nps switch am i right???
thanks phil
There are two switches on top of the gearbox, 1)reverse swtich and 2)NPS, so if doing it yourself get the right one. Personaly im taking mine to Scoobyteknx in fleetwood.