Multiple cylinders misfiring
#31
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I'll answer generally as specifics would take me forever.
1) The misfires are random - ie: sometimes on the same cylinders, but sometimes not
2) The only real constant is that I don't get the misfires until the car is driven close to 10 miles (a little less if it's hot out side) - it seems to be temperature dependent.
* Bad ground is a real possibility and I have so far checked the engine ground by the rear passenger side wheel. Cleaned both ends and both sides (engine and chassis) lugs and studs and re-tightened. No love...
3) Fuel? Mmmmm, I don't think so (although anything is possible) - I always use Shell V nitro plus 93 and mostly from the same station (I'm almost positive that at least the last 5 fills have been from the same station).
How's about have you checked,cleaned,retightened ground points #10 and 11?
If that doesn't work ring out ignition coil sockets between X59/1 connector and coils. If that checks then pin side of connector to DME plug. Looking for faulty or broken down wires.
Possibly a fault of some sort will show up.
^^^This is what I'm working on now...
1) The misfires are random - ie: sometimes on the same cylinders, but sometimes not
2) The only real constant is that I don't get the misfires until the car is driven close to 10 miles (a little less if it's hot out side) - it seems to be temperature dependent.
* Bad ground is a real possibility and I have so far checked the engine ground by the rear passenger side wheel. Cleaned both ends and both sides (engine and chassis) lugs and studs and re-tightened. No love...
3) Fuel? Mmmmm, I don't think so (although anything is possible) - I always use Shell V nitro plus 93 and mostly from the same station (I'm almost positive that at least the last 5 fills have been from the same station).
How's about have you checked,cleaned,retightened ground points #10 and 11?
If that doesn't work ring out ignition coil sockets between X59/1 connector and coils. If that checks then pin side of connector to DME plug. Looking for faulty or broken down wires.
Possibly a fault of some sort will show up.
^^^This is what I'm working on now...
#32
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^^^ Interestingly, after cleaning and tightening the passenger side engine ground point #11 (no change in misfires) I moved over to the drivers side to check #10... ... ... Hmmm, no ground point #10! There is clearly a lug on the engine block and a point on the frame near the bottom of the motor mount. The point on the frame was pretty rusted and the stud was missing - it looked like someone had put some kind of sealer/goop on it. I cleaned it out and tapped it the best I could with a M8 1.25 tap. It was super difficult to get the tap wrench up the the spot... I finally went to Lowe's and got a tap wrench that allows the tap to be driven by a socket or standard ratchet handle with a long extension on it. Unfortunately, they didn't have a flat bottom/flush cut 8mm 1.25 tap. I'll probably get one a NAPA tomorrow (Advance didn't have it either - only a 8mm 1.0
). In any case, I'm not expecting this to cure my problem as I'm sure there's never been a ground at this point (I had the engine out a few years ago before the full rebuild). According to the Bentley manual there are at least two more ground points in the engine bay - I don't remember seeing these either when I dropped the engine... I'm also planning on going back and checking the grounds at the ECU relay are as well...
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#33
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Not true, read my response below.
A few years ago (you can search) I was having symptoms similar to the OP. I replaced my plugs, wires, MAF, and did every other piece of troubleshooting I could imagine.
I would get a misfire every time I would try to rev over 4500 RPM. It was never consistent (in terms of the cylinder affected) either so it was really frustrating as I couldn't figure out why it was happening.
Finally I gave up and took my car to the dealer. They tried quite a few things as well and finally decided to drive the car with the cats unhooked. Problem was gone!
I ordered the cat x-pipe from Fabspeed and haven't had any issues since. So for the OP, do yourself a favor and check the cats!
A few years ago (you can search) I was having symptoms similar to the OP. I replaced my plugs, wires, MAF, and did every other piece of troubleshooting I could imagine.
I would get a misfire every time I would try to rev over 4500 RPM. It was never consistent (in terms of the cylinder affected) either so it was really frustrating as I couldn't figure out why it was happening.
Finally I gave up and took my car to the dealer. They tried quite a few things as well and finally decided to drive the car with the cats unhooked. Problem was gone!
I ordered the cat x-pipe from Fabspeed and haven't had any issues since. So for the OP, do yourself a favor and check the cats!
#34
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#35
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Also bizarre is that I opened up X59 plug 1 and found that I’m missing the connection on pin/socket 11 (valve lift control cyl 4-6)
strange no?
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#36
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#37
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^^^ Not the case - I was reading the wrong page (The EWD pages are many, and slightly confusing) - I was looking at Motronic 7.8 when I should have been looking at 7.2... In any case, I won't be able to get back to it until tomorrow. Will post back then. Not sure if I want to drive around without cat's - how loud is it? Please compare to stock with cats (as opposed to "it's not loud at all")...
#38
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^^^ Not the case - I was reading the wrong page (The EWD pages are many, and slightly confusing) - I was looking at Motronic 7.8 when I should have been looking at 7.2... In any case, I won't be able to get back to it until tomorrow. Will post back then. Not sure if I want to drive around without cat's - how loud is it? Please compare to stock with cats (as opposed to "it's not loud at all")...
https://www.topgear-eurosport.com/po...ll-sports-cats
You would be in at about $750 for the CATS and the O2s.
#39
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I have these these 200 cell cats on my '99 C2 with FSI 3.6 Street Performer. I also have their headers. Along with the install I replaced the O2s with the Bosch Universals from Warehouse33. Not a bit of trouble with any of it so far with over 10k miles logged.
https://www.topgear-eurosport.com/po...ll-sports-cats
You would be in at about $750 for the CATS and the O2s.
https://www.topgear-eurosport.com/po...ll-sports-cats
You would be in at about $750 for the CATS and the O2s.
I'd probably be ok with something like that^^ if I'm sure that's my problem - the difficulty is in figuring it out... I don't want to spend $800 to find out I've still got this misfire problem...
#40
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I'm just sharing this, should the CATS be your problem. It is not a terribly expensive route if you have to go down that road.
#42
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I have these these 200 cell cats on my '99 C2 with FSI 3.6 Street Performer. I also have their headers. Along with the install I replaced the O2s with the Bosch Universals from Warehouse33. Not a bit of trouble with any of it so far with over 10k miles logged.
https://www.topgear-eurosport.com/po...ll-sports-cats
You would be in at about $750 for the CATS and the O2s.
https://www.topgear-eurosport.com/po...ll-sports-cats
You would be in at about $750 for the CATS and the O2s.
Within 30 miles, and continually after that, I got Cat efficiency codes for both bank 1 and bank 2. Used Durametric to monitor voltages, and the sensors are good, the Cats just don't do enough to attenuate the oxygen level. I tried to contact TopGear asking what they generally recommended, but I could never get them to reply. I had to install O2 spacers onto my after-Cat sensors. Finally got to that a month ago, and the code is finally cleared and gone.
You can search the forums, some people haven't had an issue, but many have. If you DO have a Cat issue, my recommendation would be to either:
1) Be honest about it and just use a straight/test pipe and O2 spacers. The TopGear Cats really aren't doing much anyway.
2) Pay more for better Cats. (Would have been my choice, since I generally like having breathable air on the planet.)
Good luck!
#43
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So far I’ve : cleaned & checked all engine ground connections (gp10 & 11) cleaned & checked ECU connections, cleaned and checked coil grounds and toned out all coil green wires to X59-1 plug (black) in engine bay. Unfortunately, I’ve only been able to do this while the engine is cool And of course the engine runs great while it’s cool 😩... How about the injectors? I suppose I should check for power to them as well... once again, not sure how I can pull this off when the engine is hot??? I’d be grateful for any ideas... Thanks
#44
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So far I’ve : cleaned & checked all engine ground connections (gp10 & 11) cleaned & checked ECU connections, cleaned and checked coil grounds and toned out all coil green wires to X59-1 plug (black) in engine bay. Unfortunately, I’ve only been able to do this while the engine is cool And of course the engine runs great while it’s cool 😩... How about the injectors? I suppose I should check for power to them as well... once again, not sure how I can pull this off when the engine is hot??? I’d be grateful for any ideas... Thanks