Random Misfires, Thoughts?

[bjtheman1]

First off....car is a 2007 Roush 427R with supercharger @50,000 miles

Having random cylinders misfire, rough idle, and loss of power. Been data logging a lot as well to try and figure this out. Car is throwing no codes just FYI!

What I've done or had done so far:

Compression Test -good
Cleaned MAF
Cleaned TB
Cleaned Air Filter
Leak down Test - good
New Fuel Filter
New spark Plugs -Brisk Silver Racing gapped to 0.32
New FRPS
Oil Change
Coils checked - good
New front 02 Sensors

Shop that replaced the 02's for me think it could be the tune, I just never knew a tune could go bad over time?

I'm still datalogging and even today had multiple misfires pop up while driving.

Anyone have or know of a site where I can find out details about datalogging parameters? I'd like to learn a bit more what the correct numbers are for certain pids. For example: short term or long term banks....what ranges should I be in when driving, etc?

Any thoughts or ideas would be appreciated for this has been ongoing for a bit now

 

[stkjock]

New spark Plugs -Brisk Silver Racing gapped to 0.32

if that is accurate, there's your issue.

-tune's do not go bad


--have you checked your alternator and battery?

 

[skwerl]

Once you open up the gap a little you can reload the tune (or just disconnect the battery for 3 minutes) so the computer will clear all the adaptive learning it has recorded and start over.

 

[ArtQ]

I had a tune get compromised during an upload. I believe I had a battery voltage problem. Had random misfires P0300 and engine idled rough. Checked everything, during datalogging my short term fuel trims were all over the place and high. Should be approx. +3 to
-3. I returned the car to stock, deleted the suspect tune from the tuner, then reloaded a saved tune from my laptop. Reloaded the tune and all was well. If you have your tunes saved to your computer give it a try.

 

[bjtheman1]

if that is accurate, there's your issue.

-tune's do not go bad


--have you checked your alternator and battery?

How's that the issue with the plugs?

Yes, checked battery and alternator. Load test, voltage checks, etc all fine. Plus, both are less than a 1 yr old.

I forgot to add an important thing, my car is 2007 Roush 427R

 

[scramblr]

Initially you didn't mention you had F/I and for N/A plugs are supposed to be at 0.045". Since you do have F/I, then you should see if you have blowout and adjust from there. What plugs were you using before and what were they gaped to?

 

[stkjock]

How's that the issue with the plugs?

because they should be .032. A third of a inch is too damn big

 

[bjtheman1]

Initially you didn't mention you had F/I and for N/A plugs are supposed to be at 0.045". Since you do have F/I, then you should see if you have blowout and adjust from there. What plugs were you using before and what were they gaped to?

Yep, that was my bad forgot to include that needed info. Prior plugs were Autolite HT0's and I'm not sure what the prior gap was.

 

[stkjock]

how much boost?

 

[bjtheman1]

how much boost?

About 6-7 psi

 

[stkjock]

.032 should be fine for that boost level and not see blow out IMO

 

[Eel Mit]

because they should be .032. A third of a inch is too damn big

0.032 inches is not 0.33 (1/3) inch, lol. Remind your friends to never ever let you use a caliper or feeler gauge.

You can't gap a plug to 1/3in without having the ground electrode stab the piston.

BOT, double check fuel pressure or volume. If either is low, it will cause misfires. But first, I would try a new, different brand plug.

 

[bjtheman1]

BOT, double check fuel pressure or volume. If either is low, it will cause misfires. But first, I would try a new, different brand plug.

What's the normal ranges for fuel pressure, flow, voltage, etc? I've been trying to find a reference with this type of info for our cars so I know what to look for while data logging.

Also, I had these symptoms before I replaced the spark plugs so I don't believe they are the issue.

 

[stkjock]

First off....car is a 2007 Roush 427R with supercharger @50,000 miles

Having random cylinders misfire, rough idle, and loss of power. Been data logging a lot as well to try and figure this out. Car is throwing no codes just FYI!

What I've done or had done so far:

Compression Test -good
Cleaned MAF
Cleaned TB
Cleaned Air Filter
Leak down Test - good
New Fuel Filter
New spark Plugs -Brisk Silver Racing gapped to 0.32
New FRPS
Oil Change
Coils checked - good
New front 02 Sensors

Shop that replaced the 02's for me think it could be the tune, I just never knew a tune could go bad over time?

I'm still datalogging and even today had multiple misfires pop up while driving.

Anyone have or know of a site where I can find out details about datalogging parameters? I'd like to learn a bit more what the correct numbers are for certain pids. For example: short term or long term banks....what ranges should I be in when driving, etc?

Any thoughts or ideas would be appreciated for this has been ongoing for a bit now

0.032 inches is not 0.33 (1/3) inch, lol. Remind your friends to never ever let you use a caliper or feeler gauge.

You can't gap a plug to 1/3in without having the ground electrode stab the piston.

BOT, double check fuel pressure or volume. If either is low, it will cause misfires. But first, I would try a new, different brand plug.

LOOK AT HIS FIRST POST - emphasis added.



and my first response

http://s197forum.com/forum/showpost.php?p=1950407&postcount=2


Reading is fundamental!

 

[bjtheman1]

This was a first today, upon starting my datalog before I actually started the car it showed misfires on multiple cylinders...is that possible even though the car wasn't started yet?

I use the SCT Xcal 3 with my laptop

 

[bcb06gt]

Were the plugs changed after the issue or before? So car was running fine and then the symptoms arose and all the items in the first post were done?

I only ask because I have changed my plugs only to have 1 bad one in the group (all were new). PITA to find the bad one since the car doesn't really throw a code for random misfire. Mine didn't throw the code but the poor idle, acceleration was there.

 

[bjtheman1]

Were the plugs changed after the issue or before? So car was running fine and then the symptoms arose and all the items in the first post were done?

I only ask because I have changed my plugs only to have 1 bad one in the group (all were new). PITA to find the bad one since the car doesn't really throw a code for random misfire. Mine didn't throw the code but the poor idle, acceleration was there.

No, I had had the rough idle and misfires before which is why I changed the plugs while troubleshooting.

 

[Eel Mit]

LOOK AT HIS FIRST POST - emphasis added.



and my first response

http://s197forum.com/forum/showpost.php?p=1950407&postcount=2


Reading is fundamental!

Lol, should have been clearer, I was agreeing with you about the gap (sure it was a typo).

 

[TexasBlownV8]

A couple things come to mind:
- your mentioned checking alternator and battery; during datalogging, log voltage as well. You could be experiencing drops in voltage when running.
- tell us about your choice of fuel: have you changed where you get it from? I mention fuel because I've seen a change in fuel or even a bad batch cause issues, even from the same place I buy from normally.

You'll get codes on key-on if the codes were 'pending' and the pcm was waiting for the next drive cycle to see if the issues remain.

And FYI, I had issues like that with Brisk plugs. Hence the note about that being your problem.