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Old 07-05-2015, 12:25 PM   #1
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Default Misfire issue. Yep, I need help...

2004 MSM with 22,000 miles. A few upgrades: FM intake, FM downpipe, FM O2 signal modifier (the old kind), ebay intercooler, MBC. We rarely drive the car so it sits 3-6 months at a time (yeah, I know). We are currently getting CELs concerning misfire issues. It started as P0304 (misfire on #4) and occasionally P0301 (cylinder #1) or P0300 (multiple cylinders). I figured it was the #4/#1 coil so I replaced it. Since then I started getting misfire on other cylinders so I changed out the plug wires and CAS (crank sensor - set to around 1 credit card gap from the crank "****"). Still having the issue. Any ideas???
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Old 07-05-2015, 01:40 PM   #2
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Bad gas?
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Old 07-05-2015, 02:41 PM   #3
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Change the plugs. 50% of all miata misfires are the plugs in my experience.
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Old 07-05-2015, 02:52 PM   #4
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Does an '04 have a cam position sensor? I have seen variable/multiple misfire codes with a bad cam position sensor.
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Old 07-05-2015, 03:08 PM   #5
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Quote:
Originally Posted by rmcelwee View Post
2004 MSM with 22,000 miles. A few upgrades: FM intake, FM downpipe, FM O2 signal modifier (the old kind), ebay intercooler, MBC. We rarely drive the car so it sits 3-6 months at a time (yeah, I know). We are currently getting CELs concerning misfire issues. It started as P0304 (misfire on #4) and occasionally P0301 (cylinder #1) or P0300 (multiple cylinders). I figured it was the #4/#1 coil so I replaced it. Since then I started getting misfire on other cylinders so I changed out the plug wires and CAS (crank sensor - set to around 1 credit card gap from the crank "****"). Still having the issue. Any ideas???
Just reread this. Did you change just the 1&4 coil (not coil for 2&3)? Usually people swap the entire coilpack but I believe it's possible to swap them individually.
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Old 07-05-2015, 03:16 PM   #6
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Bad gas?
It could be BUT this problem has actually come and gone several times over the past 5 years.
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Old 07-05-2015, 03:17 PM   #7
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Originally Posted by patsmx5 View Post
Change the plugs. 50% of all miata misfires are the plugs in my experience.
I've done that in the past but it would be a cheap test. Not sure how they could have gone bad in 500 miles.
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Old 07-05-2015, 03:18 PM   #8
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Quote:
Originally Posted by Ted75zcar View Post
Does an '04 have a cam position sensor? I have seen variable/multiple misfire codes with a bad cam position sensor.
Yes, I could change that fairly easily. I haven't heard of that causing problems but apparently I just don't know what will fix this.

Edit:
WOW, found a new cam sensor on Ebay for $16 and used a $12 paypal bonus so $4 shipped. Nice (they are $90 at AutoZone).

I'll let you know how it works...

Last edited by rmcelwee; 07-05-2015 at 03:30 PM.
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Old 07-05-2015, 03:19 PM   #9
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Quote:
Originally Posted by patsmx5 View Post
Just reread this. Did you change just the 1&4 coil (not coil for 2&3)? Usually people swap the entire coilpack but I believe it's possible to swap them individually.
The '04 MSM uses a coil on plug system (two total). At $100+ for each it was cheaper just to replace the one on the cylinder that gave the initial CELs.
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Old 07-05-2015, 03:43 PM   #10
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Ok. So you changed the coils for cylinders 1&4. Did the misfire on cylinders 1&4 go away and never return after replacing that coil?
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Old 07-05-2015, 03:44 PM   #11
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Ok. So you changed the coils for cylinders 1&4. Did the misfire on cylinders 1&4 go away and never return after replacing that coil?
No
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Old 07-13-2015, 07:05 PM   #12
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Just changed the Cam Angle Sensor. Took the car for a drive. Started out slow and kept out of boost (negative pressure). Ran the car at 5000 rpm in 3rd for a while with no problems. Approached 6000 rpm and still no problems. Gave it a little gas (I'm assuming it blipped the PSI) and it threw a "cylinder #2 misfire" and "random cylinder misfire". It seems like it has something to do with the car going into boost.
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Old 07-13-2015, 07:21 PM   #13
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Hmmm, has the timing belt cover ever been off? Any chance the intake is off by a tooth?
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Old 07-13-2015, 07:26 PM   #14
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Originally Posted by Ted75zcar View Post
Hmmm, has the timing belt cover ever been off? Any chance the intake is off by a tooth?
I've never had it off (22k miles on the clock). As I said, I can drive you around all day at 5000 RPM and you would never notice a problem. I'm going to try to find an OBDII datalogger of some sort and see if I can visually see what is going on.
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Old 07-14-2015, 09:51 AM   #15
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Are the plugs gaped properly? Could be spark blow out. Also, do you know how close you are to maxing out the stock injectors? What do you have the MBC set to? Any way you can get a datalog of a pull / the event?

Edit - I see you got your comment in before mine about the datalogger, that would be extremely helpful.
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Old 07-14-2015, 12:27 PM   #16
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Quote:
Originally Posted by Voltwings View Post
Are the plugs gaped properly? Could be spark blow out. Also, do you know how close you are to maxing out the stock injectors? What do you have the MBC set to? Any way you can get a datalog of a pull / the event?

Edit - I see you got your comment in before mine about the datalogger, that would be extremely helpful.
All valid questions but the car is setup the same way it always has been. I think this is something that is broken, not a "pushed it too far" or "set it up wrong" issue. The car has been to Deals Gap, autocross and drag strip. Never an issue.


Still have not found any datalogging software. They say Torque Pro will do it but I have not seen any info about that.
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Old 07-14-2015, 10:50 PM   #17
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Quote:
Originally Posted by Voltwings View Post
Are the plugs gaped properly? Could be spark blow out.
I banged off my rev limiter for 30 seconds or so as a test and it didn't throw a code.

The second test was very interesting and will probably lead to the solution...

I backed my MBC out (to around 5-6 PSI) and could not get the car to throw a code. Maybe I need to look at the plugs again (blowing the spark at 12PSI or whatever I was running)??? Suggestions on what plug/gap to use (for those of you who have it memorized)?
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Old 07-15-2015, 10:23 AM   #18
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I was having a random miss while cruising. In my brief thread, someone suggested coils or CAS. I removed all connections, made sure they were clean, and reconnected. Not sure what actually did the trick, but it seems to be gone.

I'd check coil connections, including the wires into the igniter connector itself, and the wires going into the CAS connector. Something must have been just loose enough to be making poor contact.
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Old 07-29-2015, 03:34 PM   #19
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Ok, after a few hundred in parts (new coils, plugs, wires, Crank Angle Sensor, Cam Angle Sensor, etc) it seems like boost pressure may have been the issue the whole time. I cannot get the car to throw a code now. I'm running around 8 PSI now instead of the 11 or whatever I was running before. I'm calling this fixed...


Oh, thanks to all you guys who helped. I really appreciate it!
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Old 07-29-2015, 04:44 PM   #20
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What gap are you running on the plugs?
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