Multiple cylinders misfiring
02-08-2016, 12:54 PM
#16
Race Director
A bad cat should not cause a misfire. A persistent misfire might cause a bad cat, though.
*edit* In my experience, I have never been able to attribute a misfire to a bad cat...
*edit* In my experience, I have never been able to attribute a misfire to a bad cat...
Last edited by 5CHN3LL; 02-08-2016 at 03:38 PM.
02-08-2016, 12:57 PM
#17
Former Vendor
Flat 6, an MAF failing should cause most if not all cylinders to misfire if this was what was failing, correct? I'll check the MAF tonight on the durametric.
The MAF can effect all cylinders, because issues were the MAF has a range with an issue will lean out, or enrich all cylinders to an extreme level, across the board. When this happens, the result is often multiple misfires, a flashing CEL, and random occurrences where the engine runs perfectly, then acts up, and quickly clears up.
I have literally seen a bad MAF lead to an engine with 36 random codes.
02-08-2016, 01:09 PM
#18
Rennlist Member
If the cats internals have deteriorated they can become plugged, which can lead to misfire at higher revs. One bad cat will cause a misfire on one bank, but there is the possibility of both going bad. One of mine was plugged and causing misfires on bank 2 (mostly just one cylinder, sometimes two). When they were taken off we found that the other cat was falling apart inside as well. This was on my 2004 with 24K miles just after I got the car about 3 years ago. I don't know of any test, other than removing them to check for rattles or loose internals.
02-08-2016, 01:41 PM
#19
Addict
Rennlist Member
Rennlist Member
If the cats internals have deteriorated they can become plugged, which can lead to misfire at higher revs. One bad cat will cause a misfire on one bank, but there is the possibility of both going bad. One of mine was plugged and causing misfires on bank 2 (mostly just one cylinder, sometimes two). When they were taken off we found that the other cat was falling apart inside as well. This was on my 2004 with 24K miles just after I got the car about 3 years ago. I don't know of any test, other than removing them to check for rattles or loose internals.
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!
03-05-2020, 09:45 PM
#21
AutoX
Join Date: Feb 2016
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
How do you "check the cats"?
Another cause from what I've read might be the cam timing being off from the chain pads wearing down. I have not checked mine yet - I am having these same issues with misfire on 1 bank after 5k RPM. Coil packs are good.
Another cause from what I've read might be the cam timing being off from the chain pads wearing down. I have not checked mine yet - I am having these same issues with misfire on 1 bank after 5k RPM. Coil packs are good.
03-06-2020, 09:36 AM
#23
Rennlist Member
Based on what I read above, the dealer took the cats off and ran it without.
07-17-2020, 12:07 PM
#24
Rennlist Member
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!
07-17-2020, 12:48 PM
#25
Rennlist Member
I've been trying to track down similar misfires for about 6 weeks now... Getting pretty frustrating, seeing as I only get a couple hours at a time and I'm trying to troubleshoot in a systematic way. What does "cats unhooked" mean ? The O2 sensors unplugged? The cats themselves removed? That must have been crazy loud - where did they test it? I'm wondering if I can pull this off in my garage on a lift...
07-17-2020, 01:44 PM
#26
Rennlist Member
Unfortunately yes. I've been working through this with Jake via email, so as not to create some big uproar/flame fest here (while quietly searching through misfire threads), but I just found this thread and it seemed interesting. Jake has been super responsive and helpful as I pick his brain relentlessly! The car was running absolutely perfect at the time I did about a 50 mile drive when I suddenly had some misfires (it sounded and felt like a VW power wise). I was close to home at the time, so I limped in shut it down and checked it with the Durametric - misfires on 1, 2, 5 & 6, with post Cat O2 sensor codes as well. Per Jake's suggestion, I ordered new O2 sensors (genuine Bosch) and cleared the codes. Upon clearing the codes, the car ran fine for another 2 weeks or so (without cleaning/replacing anything). Then it happened again - more misfires. In the mean time I had received the new O2 sensors and MAF - ok time to replace them...that should take care of things... Well, needless to say the O2 sensors were a real pita - they took about a week due to my work schedule. In the end, I removed the rear bumper and the CAT pipes so I could bring them to my shop, put them in a vise and get some air tools on them. Easy peasy - finished removing and replacing the sensors in about an hour including chasing the threads with an 18mm tap. The right tools are EVERYTHING when it comes to getting things done!
Upon getting everything back together and starting her up, everything was great for about 10 miles - then it was back to the same old misfires again (this seems to be a pattern - the car runs fine when cool and starts to misfire when up to temp - anywhere between 6 - 10 miles). That was about 2 or 3 weeks ago. So far I've
1) Replaced upstream and downstream O2 sensors (no more codes for them so that was productive)
2) Cleaned original MAF and replaced original MAF with a new genuine Bosch unit (same part # - old '99 style)
3) Checked and cleaned male/female sides of X59 connectors (though I haven't pulled the pins on the female side to check there yet - that's next on my list)
4) Pulled/checked/cleaned plugs on the ECU for corrosion/bad connections - nothing obvious. I may go back in and open it up to look at the board itself - last time I did that, it cleared a CEL that "wouldn't go away"... (Also prior to doing this I disconnected the battery and did the "full reset" - touched positive and negative cable ends together)...
5) **So far, I've found no rodent damage which has been gnawing at the back of my mind (see what I did there?
) - but it's definitely still on my radar.
This is where I am, and I'm heading back to the garage to work on it now - If anyone has any ideas, I'm open to 'em! Thanks in advance, and please no flaming/blame games...
Upon getting everything back together and starting her up, everything was great for about 10 miles - then it was back to the same old misfires again (this seems to be a pattern - the car runs fine when cool and starts to misfire when up to temp - anywhere between 6 - 10 miles). That was about 2 or 3 weeks ago. So far I've
1) Replaced upstream and downstream O2 sensors (no more codes for them so that was productive)
2) Cleaned original MAF and replaced original MAF with a new genuine Bosch unit (same part # - old '99 style)
3) Checked and cleaned male/female sides of X59 connectors (though I haven't pulled the pins on the female side to check there yet - that's next on my list)
4) Pulled/checked/cleaned plugs on the ECU for corrosion/bad connections - nothing obvious. I may go back in and open it up to look at the board itself - last time I did that, it cleared a CEL that "wouldn't go away"... (Also prior to doing this I disconnected the battery and did the "full reset" - touched positive and negative cable ends together)...
5) **So far, I've found no rodent damage which has been gnawing at the back of my mind (see what I did there?
) - but it's definitely still on my radar.This is where I am, and I'm heading back to the garage to work on it now - If anyone has any ideas, I'm open to 'em! Thanks in advance, and please no flaming/blame games...
Last edited by dporto; 07-17-2020 at 02:04 PM.
07-17-2020, 03:06 PM
#27
I am sure most if not all of these have been thought of by Jake, I am just sit balling through some of the things I would check.
I will keep thinking on this and post up I have anything else I can think of for you to check.
- When it misfires, is it always the same cylinders, 1,2,5&6 or is it different each time?
- Have you hooked up your scan tool, looking at misfire monitoring on each cylinder, than started the car and watch each cylinder misfire in real time? (Can durametric do this?)
- If so, what changed(if anything) when the misfires started?
- Did the secondary air shut off? Did you touch the throttle? A/C?
- you said it will only happen when the engine gets hot.. Does it seem to be when the oil or coolant get to a certain temp? Is it the same every time?
- Does it happen at the same time if the car is started and idling vs started & driven?
- If so, what changed(if anything) when the misfires started?
- Have you cleaned the grounds on both cylinder heads and the engine to body ground?
- Try looking at the battery voltage at the engine disconnect post while this is happening, any change in voltage?
- I don't know how long you have had the car, but have you confirmed that the MAF PN you got is actually for your car? I know there used to be numerous versions, I dk if that is still the case.
- How are your RKAT values? Any change before misfires?
- As crazy as this sounds.. have you tried a hard battery reset? Disconnect BOTH leads of your battery and touch & hold them together (you can use a jumper wire) for 30 seconds?
I will keep thinking on this and post up I have anything else I can think of for you to check.
Last edited by kwright997; 07-17-2020 at 04:05 PM.
07-17-2020, 06:02 PM
#29
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.
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.
07-17-2020, 07:10 PM
#30
Rennlist Member
Unfortunately yes. I've been working through this with Jake via email, so as not to create some big uproar/flame fest here (while quietly searching through misfire threads), but I just found this thread and it seemed interesting. Jake has been super responsive and helpful as I pick his brain relentlessly! The car was running absolutely perfect at the time I did about a 50 mile drive when I suddenly had some misfires (it sounded and felt like a VW power wise). I was close to home at the time, so I limped in shut it down and checked it with the Durametric - misfires on 1, 2, 5 & 6, with post Cat O2 sensor codes as well. Per Jake's suggestion, I ordered new O2 sensors (genuine Bosch) and cleared the codes. Upon clearing the codes, the car ran fine for another 2 weeks or so (without cleaning/replacing anything). Then it happened again - more misfires. In the mean time I had received the new O2 sensors and MAF - ok time to replace them...that should take care of things... Well, needless to say the O2 sensors were a real pita - they took about a week due to my work schedule. In the end, I removed the rear bumper and the CAT pipes so I could bring them to my shop, put them in a vise and get some air tools on them. Easy peasy - finished removing and replacing the sensors in about an hour including chasing the threads with an 18mm tap. The right tools are EVERYTHING when it comes to getting things done!
Upon getting everything back together and starting her up, everything was great for about 10 miles - then it was back to the same old misfires again (this seems to be a pattern - the car runs fine when cool and starts to misfire when up to temp - anywhere between 6 - 10 miles). That was about 2 or 3 weeks ago. So far I've
1) Replaced upstream and downstream O2 sensors (no more codes for them so that was productive)
2) Cleaned original MAF and replaced original MAF with a new genuine Bosch unit (same part # - old '99 style)
3) Checked and cleaned male/female sides of X59 connectors (though I haven't pulled the pins on the female side to check there yet - that's next on my list)
4) Pulled/checked/cleaned plugs on the ECU for corrosion/bad connections - nothing obvious. I may go back in and open it up to look at the board itself - last time I did that, it cleared a CEL that "wouldn't go away"... (Also prior to doing this I disconnected the battery and did the "full reset" - touched positive and negative cable ends together)...
5) **So far, I've found no rodent damage which has been gnawing at the back of my mind (see what I did there?) - but it's definitely still on my radar.
This is where I am, and I'm heading back to the garage to work on it now - If anyone has any ideas, I'm open to 'em! Thanks in advance, and please no flaming/blame games...
Upon getting everything back together and starting her up, everything was great for about 10 miles - then it was back to the same old misfires again (this seems to be a pattern - the car runs fine when cool and starts to misfire when up to temp - anywhere between 6 - 10 miles). That was about 2 or 3 weeks ago. So far I've
1) Replaced upstream and downstream O2 sensors (no more codes for them so that was productive)
2) Cleaned original MAF and replaced original MAF with a new genuine Bosch unit (same part # - old '99 style)
3) Checked and cleaned male/female sides of X59 connectors (though I haven't pulled the pins on the female side to check there yet - that's next on my list)
4) Pulled/checked/cleaned plugs on the ECU for corrosion/bad connections - nothing obvious. I may go back in and open it up to look at the board itself - last time I did that, it cleared a CEL that "wouldn't go away"... (Also prior to doing this I disconnected the battery and did the "full reset" - touched positive and negative cable ends together)...
5) **So far, I've found no rodent damage which has been gnawing at the back of my mind (see what I did there?
) - but it's definitely still on my radar.This is where I am, and I'm heading back to the garage to work on it now - If anyone has any ideas, I'm open to 'em! Thanks in advance, and please no flaming/blame games...