Losing Spark
Thread Starter
Racer
Joined: Mar 2009
Posts: 394
Likes: 1
From: Everywhere US
Losing Spark
After spending a good amount of hours reading threads on this and other forums, I'm at a loss ....
Picked up our 2002 Roadster at the end of last year .... it had a slight flutter with medium amount to throttle increase ... started the investigation almost immediately ..... starting with cleaning the sensor at the intake ..... then checking all of the grounding points ..... including the coil grounds on the head ..... changed the fuel filter .... plugs and wires ..... including a couple of bottles of Injector cleaner (Techron) ..... all with no gain or change of any kind ....
Seems to be getting more apparent with time .... and get worse with the increase in engine temp.
Currently at idle .. in gear (auto) the drop out is quite noticeable ... again more so as the engine warms up.
We had our local LS tuning guru plug in ... and reported seeing spark drop out .... and all over the map ..... can happen on either bank ... and cylinder .... one time it will be in #1 ... then #7 ... then #4. Not consistent in time .... nor any particular pattern ....
There is no noise ... other then a bit of popping at WOT .... again inconsistent .... oh yeah .... and no codes !!
So now where to go from here ..... thoughts ?????
Picked up our 2002 Roadster at the end of last year .... it had a slight flutter with medium amount to throttle increase ... started the investigation almost immediately ..... starting with cleaning the sensor at the intake ..... then checking all of the grounding points ..... including the coil grounds on the head ..... changed the fuel filter .... plugs and wires ..... including a couple of bottles of Injector cleaner (Techron) ..... all with no gain or change of any kind ....
Seems to be getting more apparent with time .... and get worse with the increase in engine temp.
Currently at idle .. in gear (auto) the drop out is quite noticeable ... again more so as the engine warms up.
We had our local LS tuning guru plug in ... and reported seeing spark drop out .... and all over the map ..... can happen on either bank ... and cylinder .... one time it will be in #1 ... then #7 ... then #4. Not consistent in time .... nor any particular pattern ....
There is no noise ... other then a bit of popping at WOT .... again inconsistent .... oh yeah .... and no codes !!
So now where to go from here ..... thoughts ?????
Last edited by LastC3AZ; Mar 22, 2012 at 01:52 PM.
Racer
Joined: Dec 2005
Posts: 287
Likes: 2
From: Bay Area California
Losing Spark
Your description is almost exactly the same symptoms my 1999 is experiencing. I too changed out and checked the items you listed to no avail. And, my symptoms also become prevalent once the vehicle gets to operating temperature and into closed-loop mode. FYI, the vehicle has a manual six-speed. I have not had any past issues similar to this with the exception of a loose plug wire. I even replaced the plugs and wires although they had few miles and months of use.
I will be substituting all of my fuel injectors next week to see if perhaps they were affected by the vehicle having very little use for 5 months. It was at the shop and moved routinely, but on reserve fuel the entire time. I did find a very restricted fuel filter upon replacement and perhaps this contributed to the problem. If the problem persists after this I will be looking to catalytic converters as possible issues related to the O2 sensors. Real-time analytical scope indicates miss among the cylinders, no other codes come up. The cats are stock and will remain so.
I will inform you if I have success with the above or am fortunate enough to find another cause. Best of luck...
A1
I will be substituting all of my fuel injectors next week to see if perhaps they were affected by the vehicle having very little use for 5 months. It was at the shop and moved routinely, but on reserve fuel the entire time. I did find a very restricted fuel filter upon replacement and perhaps this contributed to the problem. If the problem persists after this I will be looking to catalytic converters as possible issues related to the O2 sensors. Real-time analytical scope indicates miss among the cylinders, no other codes come up. The cats are stock and will remain so.
I will inform you if I have success with the above or am fortunate enough to find another cause. Best of luck...
A1
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
There have been several car with simular issues. If you truely have NO CODES (checking the DTCs immediately upon seing the issue without turning the ignition OFF, I would suspect the Crank Sensor.
I highly doubt that ALL eight fuel injectors could fail all at once and cause the car to die. If you measure the injector COIL RESISTANCE and there all with in spec, ther most likely NOT the issue.
Here are the secondary ignition schematics just for reference:
I highly doubt that ALL eight fuel injectors could fail all at once and cause the car to die. If you measure the injector COIL RESISTANCE and there all with in spec, ther most likely NOT the issue.
Here are the secondary ignition schematics just for reference:
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
There have been several car with simular issues. If you truely have NO CODES (checking the DTCs immediately upon seing the issue without turning the ignition OFF, I would suspect the Crank Sensor.
I highly doubt that ALL eight fuel injectors could fail all at once and cause the car to die. If you measure the injector COIL RESISTANCE and there all with in spec, ther most likely NOT the issue.
Here are the secondary ignition schematics just for reference:
I highly doubt that ALL eight fuel injectors could fail all at once and cause the car to die. If you measure the injector COIL RESISTANCE and there all with in spec, ther most likely NOT the issue.
Here are the secondary ignition schematics just for reference:
If you examine the schematics above, look at everything that is COMMON to all the of the coils. You will see that it is Power and Ground.
Always check and make sure that the grounds are in good condition and properly connected to the ground source.
The power HOT in ON and Start, comes from the IGNITION SWITCH. That have a very common problem and should be checked and cleaned if its found to not be proving power to the car when the key is ON. When the car fails, thats the time to have the meter to check the voltage on the coil fuses. (Mini fuse 16 PCM)
Heres a post for you to examine:
-C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html
BC
Racer
Joined: Dec 2005
Posts: 287
Likes: 2
From: Bay Area California
Losing Spark
Thanks Bill. Although not the OP on this topic appreciate your schematic and recommendations. Will follow up on these components. Also, never had the engine stop running, just had the mis-fire and real-time scope indicates any one of the cylinders and especially #2 and #7. Your advice and expertise is much appreciated...
A1
A1
Thread Starter
Racer
Joined: Mar 2009
Posts: 394
Likes: 1
From: Everywhere US
Thanks Bill. Although not the OP on this topic appreciate your schematic and recommendations. Will follow up on these components. Also, never had the engine stop running, just had the mis-fire and real-time scope indicates any one of the cylinders and especially #2 and #7. Your advice and expertise is much appreciated...
A1
A1
Thanks a bunch for posting up ......Will continue to update with results .....
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Racer
Joined: Dec 2005
Posts: 287
Likes: 2
From: Bay Area California
Losing Spark
This is a follow-up to hal1phx OP regarding a loss of ignition spark. My response simply was to indicate similar symptoms that were occuring in my 1999 M6 vehicle.
Real-time scanning was done on the car since no ECU codes were being displayed. Considerable under-load misfires were present along with random backfire and an apparent enrichening of fuel delivery.
The vehicle had the following repairs/replacements completed:
With no codes present testing for grounds was completed per recommendations from Bill C. None were found a problem. The vehicle has around 112K miles so changing out the sensors was probably timely. Their service life had been extensive and these changes will only benefit future reliability.
In researching this LS1 problem, many owners have had this similar running condition and difficulty in finding a culprit. One guy in Australia simply fixed the problem by trading in the vehicle! Regardless, this post is too long yet I trust it may prove useful for others if this perplexing problem rears it's head...
A1
Real-time scanning was done on the car since no ECU codes were being displayed. Considerable under-load misfires were present along with random backfire and an apparent enrichening of fuel delivery.
The vehicle had the following repairs/replacements completed:
- MAF sensors thoroughly cleaned
- Alternator output/diodes tested and found acceptable
- Crankshaft Position Sensor replaced
- Camshaft Position Sensor replaced
- Replaced one downstream O2 sensor that read low
- Replaced both upstream O2 sensors
- Switched coilpacks from another properly functioning vehicle
- Replaced previously replaced sparkplugs
With no codes present testing for grounds was completed per recommendations from Bill C. None were found a problem. The vehicle has around 112K miles so changing out the sensors was probably timely. Their service life had been extensive and these changes will only benefit future reliability.
In researching this LS1 problem, many owners have had this similar running condition and difficulty in finding a culprit. One guy in Australia simply fixed the problem by trading in the vehicle! Regardless, this post is too long yet I trust it may prove useful for others if this perplexing problem rears it's head...
A1
