random misfire
Thread Starter
Teching In
Joined: Jan 2014
Posts: 1
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From: Toronto, Canada
random misfire I have a 2006 GMC 2500 Series Savana with a 6.0L Engine.
I've had a mechanic replace the ignition coils without properly diagnosing the problem and also replaced and returned the original Camshaft Sensor. Although I found out after the fact that this was a total waist of time, I am now left with the same dilemma as previous.
Since then I have replaced two ignition coils as they showed up in a scan as faulty and the problem has now cleared.
However I am left with a random misfire code and unable to determine what the problem is. Nothing comes up on the code reader, the only thing that I can think of is that I may need to re-learn the PCM as the Camshaft Sensor was removed and reinstalled days later. If anyone can advice me on this issue I would greatly appreciated, any suggestions?
Thank you,
Sparky
I've had a mechanic replace the ignition coils without properly diagnosing the problem and also replaced and returned the original Camshaft Sensor. Although I found out after the fact that this was a total waist of time, I am now left with the same dilemma as previous.
Since then I have replaced two ignition coils as they showed up in a scan as faulty and the problem has now cleared.
However I am left with a random misfire code and unable to determine what the problem is. Nothing comes up on the code reader, the only thing that I can think of is that I may need to re-learn the PCM as the Camshaft Sensor was removed and reinstalled days later. If anyone can advice me on this issue I would greatly appreciated, any suggestions?
Thank you,
Sparky
You need a scanner that will give you misfire data. You will see in the history counters which cylinder. Most common is intake gasket leaks on high milage motors. Fuel trim data will help find that.
Random misfire is rarely ignition related. It's usually fuel/air or mechanical issue.
Crank relearn can be performed without scan tool:
1) Start engine, run till normanl temp.
2) Turn off A/C.
3) Set park brake.
4) Turn off engine.
5) Start engine.
6) In park, press gas pedal quickly to WOT until it hits rev limiter.
7) Turn off ignition.
Crank relearn can be performed without scan tool:
1) Start engine, run till normanl temp.
2) Turn off A/C.
3) Set park brake.
4) Turn off engine.
5) Start engine.
6) In park, press gas pedal quickly to WOT until it hits rev limiter.
7) Turn off ignition.
I have never seen a coil go bad on one of these engine unless it has physical damage ... Cracked / water intrusion etc......intake gaskets were semi common on earlier engines but only acted up cold ....once the gaskets warmed up and the fuel trim was back to normal the misfires would go away...this was not he type of misfire you would really feel but it would register on the scan tool ..... Did not really see the problem in 2006...
crank relearn is a great possibility ..but I'm calling b.s on being able to perform a ckp relearn with out a scan tool .. I would like to hear others opinion on ckp relean with out a scan tool........
So the problem is a misfire code .... Can you actually feal the miss fire .......
You need a scan tool with misfire and fuel trim data or your waiting your time ......
Spark plug?? Maf.... Cat conv. .. Ckp relearn ?.? Broken valve spring ...
crank relearn is a great possibility ..but I'm calling b.s on being able to perform a ckp relearn with out a scan tool .. I would like to hear others opinion on ckp relean with out a scan tool........
So the problem is a misfire code .... Can you actually feal the miss fire .......
You need a scan tool with misfire and fuel trim data or your waiting your time ......
Spark plug?? Maf.... Cat conv. .. Ckp relearn ?.? Broken valve spring ...
Thread Starter
Teching In
Joined: Jan 2014
Posts: 1
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From: Toronto, Canada
Hi there thanks for all the inputs, The vehicle is running fine the only thing is at about 100+KM/H it brings up the flashing engine light and a random P0300 misfire. There is nothing else in the system that is present. There where some old codes for some cylinders but it has now all been cleared.
The only thing that I have found is that when the engine is cold it runs not too bad and also the MAF registered fluctuating KHZ readings on the Signal wire and drops down to 344 - 375 HZ I'm not sure if this is due to the cold weather affecting the Multimeter. However, it's not reading 3.2KHZ as I read in another article.
Other than that I don't seem to find anything else wrong and no other codes come up.
The only thing that I have found is that when the engine is cold it runs not too bad and also the MAF registered fluctuating KHZ readings on the Signal wire and drops down to 344 - 375 HZ I'm not sure if this is due to the cold weather affecting the Multimeter. However, it's not reading 3.2KHZ as I read in another article.
Other than that I don't seem to find anything else wrong and no other codes come up.
Last edited by Sparkys; Jan 23, 2014 at 01:09 PM. Reason: correction on posting
Thread Starter
Teching In
Joined: Jan 2014
Posts: 1
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From: Toronto, Canada
Thanks for the reply but it looks like the Cam Sensor is not the culperet it appears to be something else but I can't pin point it. I spoke to some mechanics and they all say that it is a selflearner and does not need to be relearned. The vehicle runs fine but I'm having a little bit of a low idel and the KPA on the Oil pressure are also low, otherwise the vehicle runs pretty fine. I am only looking to resolve the problem as I am tired of looking at a flashing light letting me know that it is a random misfire. Plus I hate driving a vehicle that is not running to it's spect performace, just the way I am.
If you have any other suggestions I would appreciate hearing them.
Thanks,
If you have any other suggestions I would appreciate hearing them.
Thanks,
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Thread Starter
Teching In
Joined: Jan 2014
Posts: 1
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From: Toronto, Canada
As for the MAF Sensor it looks like I got it working fine now and I am reading for now 3.2KHZ as it should be on the Signal wire. One good thing so far!
I'm wondering if I may just need to do an Injector Flush?
If anyone has any suggestions I would appreciate it.
Please keep in mind that it is only a random misfire and no other codes come up!
Thanks,
I'm wondering if I may just need to do an Injector Flush?
If anyone has any suggestions I would appreciate it.
Please keep in mind that it is only a random misfire and no other codes come up!
Thanks,
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TECH Apprentice
Joined: Dec 2010
Posts: 325
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From: canada
you need to find a scanner that will tell you what cylinder is missfireing. the next step is to check compression on the cylinder or clinders that are missfireing. if it passes over 100 psi at least. next step is to do leakdown test. if it passes that.you have verified the mechanical part. next is to pull the valve covers and check for broken or cracked valve springs. it will probably be bad cam and lifters. have seen it many times. as for low oil pressure you could have a bad oil pressure sensor. or if that's okay it probably has exesive main bearing cleances causing low oil pressure. take it step by step to diagnose it properly.
Sorry to beat a dead horse man but
You gotta find a scan tool that will let you do a ckp relearn.....
Would not spend any more time until you do that
You say cam sensor is not the culprit ........do you mean crank sensor ??
Where is it located ........
Crank relearn needs to be done and reevaluated ....
I work on these truck everyday .....only job I have ever had is working at the gm dealer ...... ...it not published any where that I have found but .. You have the symptoms of numerous. Trucks I have had in the past and fixed with a simple relearn ....
I have see guys at the dealer replace plugs wires Replace cats flush injectors clean carbon ....and still have the same issue ......
Crank relearn fixes it ever time symptoms are ......p0300 code flashing mil at hiwaynspeeds misfires stored all cylinders . And it runs well
You gotta find a scan tool that will let you do a ckp relearn.....
Would not spend any more time until you do that
You say cam sensor is not the culprit ........do you mean crank sensor ??
Where is it located ........
Crank relearn needs to be done and reevaluated ....
I work on these truck everyday .....only job I have ever had is working at the gm dealer ...... ...it not published any where that I have found but .. You have the symptoms of numerous. Trucks I have had in the past and fixed with a simple relearn ....
I have see guys at the dealer replace plugs wires Replace cats flush injectors clean carbon ....and still have the same issue ......
Crank relearn fixes it ever time symptoms are ......p0300 code flashing mil at hiwaynspeeds misfires stored all cylinders . And it runs well
Last edited by im-not-guilty; Jan 24, 2014 at 09:14 PM. Reason: Addition to post
Listen to Im-not-guilty... you're just wasting money if you dont start with the crank relearn. If the only code stored is the P0300, then the crank relearn will more then likely fix it. I just fixed a 6.0 that had the exact same problem.
Thread Starter
Teching In
Joined: Jan 2014
Posts: 1
Likes: 0
From: Toronto, Canada
Hi there,
Sorry for not replying sooner but busy with things and also trying to fix this particular issue.
However, I just thought to let you know the end result for the Random Misfire that I was having.
It appears that it was the Cam Sensor or Crank Relearn as you put it that was causing this issue.
Unfortunately I am not an expert and could not get this information regardless of the Scanner that I had. However, it was a trying moment to find an honest guy that would actually find and fix this problem for me. Once this was done my issue is since been resolved.
Thank you,
for all of your input and recommendations, please note that I was not ignoring you but it was a trying moment getting this issue resolved.
Sorry for not replying sooner but busy with things and also trying to fix this particular issue.
However, I just thought to let you know the end result for the Random Misfire that I was having.
It appears that it was the Cam Sensor or Crank Relearn as you put it that was causing this issue.
Unfortunately I am not an expert and could not get this information regardless of the Scanner that I had. However, it was a trying moment to find an honest guy that would actually find and fix this problem for me. Once this was done my issue is since been resolved.
Thank you,
for all of your input and recommendations, please note that I was not ignoring you but it was a trying moment getting this issue resolved.