Misfire
08-19-2018, 10:57 AM
#1
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Misfire
porsche 996 turbo 2002 with 135,000 miles, the car had both turbos replaced, engine out to drill out manifold bolts and finally a stage 1 tune carried out 2years ago, the car has done 2000 miles and was laid up for 8 months due to illness.
Took car out for drive, after 120 miles or so it started to jerk about a further 10 miles of this CEL came on stopped car checked fault cylinder 1,2,and three misfires, this has repeated every attempt to drive.
Car in shop, replaced plugs and coils, no change, replaced varicam and the other cam no change. Unplugged Maf all ok no misfire, replaced with new Maf misfire on bank 1 is back. Checked for air leaks fuel pressure, etc all seems ok. Where to next?
Took car out for drive, after 120 miles or so it started to jerk about a further 10 miles of this CEL came on stopped car checked fault cylinder 1,2,and three misfires, this has repeated every attempt to drive.
Car in shop, replaced plugs and coils, no change, replaced varicam and the other cam no change. Unplugged Maf all ok no misfire, replaced with new Maf misfire on bank 1 is back. Checked for air leaks fuel pressure, etc all seems ok. Where to next?
08-19-2018, 11:35 AM
#2
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Try the Turbo section of the forum...You'll get more experienced "Turbo members" there.
Out of curiosity, how old is the fuel in it?
Out of curiosity, how old is the fuel in it?
08-19-2018, 12:31 PM
#3
08-19-2018, 01:05 PM
#5
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at this age and mileage combined with "sitting time" after coils and plugs pull and clean fuel injectors or simply swap two throwing code
simple and easy to rule in or out
simple and easy to rule in or out
08-19-2018, 01:11 PM
#6
I agree with the others and from personal experience with letting cars sit. The ethanol based gas sitting in the tank for this long could be the culprit. To my surprise, some of the "experts" on the forums recommend adding two cans of Seafoam and then top tier gasoline from Shell or Chevron. In my opinion, I would fist change the oil and filter, then add Seafoam, drive it for an hour or so, then put a full tank of top tier gas in it. Drive it for a long time and let the car adapt. It's been in hibernation.
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08-19-2018, 07:31 PM
#8
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yes and no
fuel spray on each individual injector can be affected differently
some gum up while other dont or at least not enough to throw a code
seafoam is good stuff and cheaper than swapping injectors if not a DIY guy
fuel spray on each individual injector can be affected differently
some gum up while other dont or at least not enough to throw a code
seafoam is good stuff and cheaper than swapping injectors if not a DIY guy
08-20-2018, 09:22 PM
#9
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before seafoam.. i'd simply try adding some quality octane booster. sounds like bad fuel to me also. if you do go the seafoam route? make sure to change oil afterwards. GL. sounds like old gas.
08-20-2018, 09:48 PM
#10
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The first thing that I would do is measure your fuel pressure, the second is to re-visit your spark plugs and coil pack connectors>>while in there check for a failed low lift high lift solenoid bracket will cause a misfire issue. Next is fouled fuel injectors.
I would also measure your camshaft deviation. It might not be enough to trigger a CEL but close..
Broken hydraulic tappets will induce misfires.
I would also measure your camshaft deviation. It might not be enough to trigger a CEL but close..
Broken hydraulic tappets will induce misfires.
08-21-2018, 05:00 AM
#11
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Now in workshop:
Replaced plugs and coils
Replaced both cam on bank1
No change!!
Unplugged Maf
Runs fine!!
Fit new Maf
Back to misfire on bank1!!
Check for air leaks, fuel pressure, seems ok (fuel pressure steady while engine running, but did keep rising a little while after engine switched off)
Where to next, fuel injectors, cats ??
Car has done 2000 miles over 2 years, since tune.
Prep work before tune:
Engine out to drill out manifold seized studs and replaced both turbos and other work.
Parts used for tune: gt2 intercoolers,intake plenum,diverted valves and F pipe,free flowing panel filter and tune carried out.
Any suggestions??
Could any of the parts repalced for tune be the cause??
Replaced plugs and coils
Replaced both cam on bank1
No change!!
Unplugged Maf
Runs fine!!
Fit new Maf
Back to misfire on bank1!!
Check for air leaks, fuel pressure, seems ok (fuel pressure steady while engine running, but did keep rising a little while after engine switched off)
Where to next, fuel injectors, cats ??
Car has done 2000 miles over 2 years, since tune.
Prep work before tune:
Engine out to drill out manifold seized studs and replaced both turbos and other work.
Parts used for tune: gt2 intercoolers,intake plenum,diverted valves and F pipe,free flowing panel filter and tune carried out.
Any suggestions??
Could any of the parts repalced for tune be the cause??
Last edited by 996turbo39; 08-21-2018 at 01:19 PM.
08-21-2018, 03:56 PM
#12
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Did you install a oiled BMC or KN? That will screw up a new working MAF.
Did you see 15psi on a gauge when they tested for leaks. This varies between shops. Is your plenum secure and not leaking? Do you have a blown plenum check valve? If you have a intake leak coming from XYZ you will get a misfire.
What were the fuel pressure values at startup?
Does the shop have a PIWIS 2 to check fuel trim?
Did you see 15psi on a gauge when they tested for leaks. This varies between shops. Is your plenum secure and not leaking? Do you have a blown plenum check valve? If you have a intake leak coming from XYZ you will get a misfire.
What were the fuel pressure values at startup?
Does the shop have a PIWIS 2 to check fuel trim?
08-22-2018, 08:48 AM
#13
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Did you install a oiled BMC or KN? That will screw up a new working MAF.
Did you see 15psi on a gauge when they tested for leaks. This varies between shops. Is your plenum secure and not leaking? Do you have a blown plenum check valve? If you have a intake leak coming from XYZ you will get a misfire.
What were the fuel pressure values at startup?
Does the shop have a PIWIS 2 to check fuel trim?
Did you see 15psi on a gauge when they tested for leaks. This varies between shops. Is your plenum secure and not leaking? Do you have a blown plenum check valve? If you have a intake leak coming from XYZ you will get a misfire.
What were the fuel pressure values at startup?
Does the shop have a PIWIS 2 to check fuel trim?
They swapped the varicam from left to right no change.
Removed fuel fuse and fired up the engine
put everything back together and started up all ok no misfires. Warmed up the engine all ok.
took it for a short run all fine boosting to 1.3
returned for the night.
fired up next morning took it for all ok slowed down in traffic and into 2 nd gear the misfire started up.
back I shop with the same fault misfire cylinder 1,2, and 3.
Thinking back this was how the fault started, on the motorway all fine at speed for 70 or so miles slowed down to 1st and second and the misfire started for a while ending wit CEL.
Last edited by 996turbo39; 08-22-2018 at 08:59 AM. Reason: Spelling
08-23-2018, 03:17 AM
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Did you install a oiled BMC or KN? That will screw up a new working MAF.
Did you see 15psi on a gauge when they tested for leaks. This varies between shops. Is your plenum secure and not leaking? Do you have a blown plenum check valve? If you have a intake leak coming from XYZ you will get a misfire.
What were the fuel pressure values at startup?
Does the shop have a PIWIS 2 to check fuel trim?
Did you see 15psi on a gauge when they tested for leaks. This varies between shops. Is your plenum secure and not leaking? Do you have a blown plenum check valve? If you have a intake leak coming from XYZ you will get a misfire.
What were the fuel pressure values at startup?
Does the shop have a PIWIS 2 to check fuel trim?
I have asked them to check out the above.
08-23-2018, 03:50 AM
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Get injectors checked. I had mainly "Misfire Cylinder #5", but randomly also Bank 2 and 4-5-6 misfiires. Mostly with hot engine and with boost. Found out that injecor(s) were bad, #5 the worst.
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Pete
Power. Lots is good, more is better, too much is just right...
'87 951, RIP
'00 996 C2 L92U AQ / IXAA IXRB IX54 M96/7.xx G96/7.88 M030 M375 M376 M436 M476 M601 M983 ... + 991 GT3 brakes, 997 GT3 sway bars, fully monoball'd suspension, Bilstein Cup Car coilovers, do88 Big Pack ICs. 10 & 12 x 19" BBS CH-R wheels with 265/30 & 325 /30 -19 MPSC2s.
Pete
Power. Lots is good, more is better, too much is just right...
'87 951, RIP
'00 996 C2 L92U AQ / IXAA IXRB IX54 M96/7.xx G96/7.88 M030 M375 M376 M436 M476 M601 M983 ... + 991 GT3 brakes, 997 GT3 sway bars, fully monoball'd suspension, Bilstein Cup Car coilovers, do88 Big Pack ICs. 10 & 12 x 19" BBS CH-R wheels with 265/30 & 325 /30 -19 MPSC2s.
