Low RPM Misfire/Hesitation Issue
01-13-2012, 06:00 PM
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Low RPM Misfire/Hesitation Issue Okay guys, this issue isn't really affecting the cars over all performance. It is just a little annoying.
I started a thread about spark plug replacement because I had a misfire at idle and got a misfire code. So I replaced all 8 spark plugs and changed out the wires for MSD wires. I thought the issue was resolved. But then again my V sits in the garage most of the time. But I have been driving it all this week and noticed the issue is still there.
From idle from a complete stop, when I feather the gas, it seems to either misfire or hesitate. As soon as I get past 2500 rpms, the hesitation goes away. If I go WOT from a stop, I don't get any misfire or hesitation at all. And if I am driving at any speed and stab the gas, I get no issues at all.
Gas tank is full. 91 octane. Car is taken care of. Clean air filter.
2005 CTS-V. LS6. 55,000 miles.
Does anyone have any suggestions? Please post up. Thanks.
I started a thread about spark plug replacement because I had a misfire at idle and got a misfire code. So I replaced all 8 spark plugs and changed out the wires for MSD wires. I thought the issue was resolved. But then again my V sits in the garage most of the time. But I have been driving it all this week and noticed the issue is still there.
From idle from a complete stop, when I feather the gas, it seems to either misfire or hesitate. As soon as I get past 2500 rpms, the hesitation goes away. If I go WOT from a stop, I don't get any misfire or hesitation at all. And if I am driving at any speed and stab the gas, I get no issues at all.
Gas tank is full. 91 octane. Car is taken care of. Clean air filter.
2005 CTS-V. LS6. 55,000 miles.
Does anyone have any suggestions? Please post up. Thanks.
01-13-2012, 06:26 PM
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307 would be cylinder 7 missfire. ive had similar problems with my MSD wires cracking and arching to my headers. could also be the wire is not connected all the way. easy checks. could possibly be a coil but i dont see that as easily with on 55k on the clock, it could be tho
01-13-2012, 06:34 PM
#6
I worked at a parts store and those coils don't go bad often, but they are like anything else they do go bad sometimes for no reason. That spark plug/ coil tester is cheap and works good to show you the spark power....an old school trick is to switch that coil to a different cylinder and see if you get a misfire on that clyinder then you will kno it's the coil.
Everything i listed was for an ignition misfire...the only other possibilities are compression (more than likely good with 55k) or the fuel side being pressure/injector...but I would bet its an ignition misfire....
Everything i listed was for an ignition misfire...the only other possibilities are compression (more than likely good with 55k) or the fuel side being pressure/injector...but I would bet its an ignition misfire....
01-13-2012, 06:52 PM
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I worked at a parts store and those coils don't go bad often, but they are like anything else they do go bad sometimes for no reason. That spark plug/ coil tester is cheap and works good to show you the spark power....an old school trick is to switch that coil to a different cylinder and see if you get a misfire on that clyinder then you will kno it's the coil.
but I would bet its an ignition misfire....
but I would bet its an ignition misfire....
Also, car is bone stock except for a Magnaflow cat back exhaust.
Also, I had a clutch replaced last year, but I don't think having a clutch slipping would cause the same issue. Just a thought.
Last edited by Kurlee Daddee; 01-13-2012 at 07:14 PM.
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01-13-2012, 07:54 PM
#8
Yea that tool is on http://www.jcwhitney.com/spark-indicator/p2004215.jcwx
I also dont think that clutch should have any bearing on the issue...if you get that tool make sure you compare the weak cylinder to a healthy one so you can see the difference
I also dont think that clutch should have any bearing on the issue...if you get that tool make sure you compare the weak cylinder to a healthy one so you can see the difference
01-14-2012, 01:22 AM
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Yea that tool is on http://www.jcwhitney.com/spark-indicator/p2004215.jcwx
I also dont think that clutch should have any bearing on the issue...if you get that tool make sure you compare the weak cylinder to a healthy one so you can see the difference
I also dont think that clutch should have any bearing on the issue...if you get that tool make sure you compare the weak cylinder to a healthy one so you can see the difference
I got a CEL tonight on my way home. I will pull the code tomorrow. Hopefully its form the same cylinder so I can swap coils and see if the code changes.
01-14-2012, 11:04 AM
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Pulled the code and it was:
P0300 Random/Multiple Cylinder Misfire Detected
I am certain I gapped all the plugs properly and all plug wires are secure. Now what?
P0300 Random/Multiple Cylinder Misfire Detected
I am certain I gapped all the plugs properly and all plug wires are secure. Now what?
01-14-2012, 11:09 AM
#12
random multiple misfire usually has something to do with something other than ignition, bc all the cylinders have their own coil...i would lean more towards fuel pressure or crank sensor if its a multiple misfire...a p300 code usually deals with something that is affecting all cylinders thats why i say fuel pressure or crank sensor...i have also seen MAF sensors that are pad cause the same codes...i would check fuel pressure just to get that out of the way and go from there...def dont just start throwing the parts gun at it...do some diagnostics and save yourself some money...you can also test the crank sensor for resistance if you can get to it...keep trying and you will fix it!
01-14-2012, 11:14 AM
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random multiple misfire usually has something to do with something other than ignition, bc all the cylinders have their own coil...i would lean more towards fuel pressure or crank sensor if its a multiple misfire...a p300 code usually deals with something that is affecting all cylinders thats why i say fuel pressure or crank sensor...i have also seen MAF sensors that are pad cause the same codes...i would check fuel pressure just to get that out of the way and go from there...def dont just start throwing the parts gun at it...do some diagnostics and save yourself some money...you can also test the crank sensor for resistance if you can get to it...keep trying and you will fix it!
Good thing I have another vehicle. Ole Miss V may go back in the garage for the rest of the winter.
01-14-2012, 11:27 AM
#14
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A cylinder misfire can be caused by a number of things:
Ignition Breakdown: By far the most common problem, this type of problem gets worse under load (going up a hill) and usually gets better with higher RPM's. You can test coil output with a spark tester (cheap tool) but I usually use a spare plug wire and run the spark tester in series...ie. plug wire from coil to spark tester, spark tester grounded to additional plug wire connected to the spark plug (spark tester has to be hung by bungee cord to not ground out). You should see a strong BLUE spark jumping...if you have a ORANGE/YELLOW spark you have weak spark, poor compression, or incorrect air/fuel mixture. This will test the entire spark system. You can swap coils if you have a single point failure (cylinder 7 misfire, swap with cyl #3, etc). This is THE FIRST STEP...a plug will not fire under poor compression, etc., so this will give a better overall idea as to what is happening inside the cylinder.
Vacuum Leak: Gaskets don't last forever...GM has had issue's with intake gaskets and fuel injector O-rings. Usually causes a miss at idle that cannot be traced to any one cylinder, unless only one cylinder is leaking. Fuel trims will be way out at idle and low speed operations if you have a scan tool. If you get lucky, you can sometimes find a vacuum leak using carb cleaner, but this is not a sure fire approach. I have had vacuum leaks that were not found this way even though that's where they were.
Fuel Injector: An injector with poor flow will have a hard miss at idle and under load, but will smooth out everywhere else...somewhat like a mix between an ignition break down and a vacuum leak. If you believe you have a fuel injector problem, you can test the injector signal (from the PCM) with a "NOID LIGHT". You can swap injectors with an adjacent one pretty easily.
Valve timing/lift: If the Valve timing or lift changes due to worn cam, bent or broken push rod or rocker arm, or broken valve spring will change the amount of air/fuel in the cylinder. Pop the valve cover off and take a look...crank the motor over and check in relation to the neighboring components.
Cam Timing: Incorrect cam timing can cause a miss at idle that is not attributable to any one cylinder, and usually makes poor power. Incorrect cam timing can cause poor compression (usually in DOHC motor though, not very common in OHV motors unless newly built).
Poor Compression: The air/fuel mixture cannot combust unless compressed, causing a misfire. Compression can be compromised by worn parts (piston rings or valve) or parts breakage (piston, valve, or gasket damage). If you have low compression, you can squirt a small amount of engine oil in the cylinder to fill the scores in the cylinder walls, if it increases you have identified worn piston rings.
Crank Position Sensor: CKP sensors have had and issue causing rough running, usually at idle and low speeds and the higher RPM's. Not very common however.
The hardest part of diagnosing an engine miss on a feedback fuel injection system is that the O2 sensor's see that 14.7 parts of O2, not the one part of fuel...so every other cylinder is commanded to compensate for this. I have sometimes found it easier to disconnect the O2 sensors to prevent this cause/effect/cause situation that leads one to chasing things endlessly when diagnosing.
Overall, I generally prefer a systematic method of diagnosis that checks every one of the points above. Now, its not often that a cam is worn
on a low mileage motor for example, so I look towards what last happened. If someone was racing, it is possible that they broke a valve spring, etc.
Lots of variables involved here and I cannot tell you what is wrong specifically, but I hope this helped.
Ignition Breakdown: By far the most common problem, this type of problem gets worse under load (going up a hill) and usually gets better with higher RPM's. You can test coil output with a spark tester (cheap tool) but I usually use a spare plug wire and run the spark tester in series...ie. plug wire from coil to spark tester, spark tester grounded to additional plug wire connected to the spark plug (spark tester has to be hung by bungee cord to not ground out). You should see a strong BLUE spark jumping...if you have a ORANGE/YELLOW spark you have weak spark, poor compression, or incorrect air/fuel mixture. This will test the entire spark system. You can swap coils if you have a single point failure (cylinder 7 misfire, swap with cyl #3, etc). This is THE FIRST STEP...a plug will not fire under poor compression, etc., so this will give a better overall idea as to what is happening inside the cylinder.
Vacuum Leak: Gaskets don't last forever...GM has had issue's with intake gaskets and fuel injector O-rings. Usually causes a miss at idle that cannot be traced to any one cylinder, unless only one cylinder is leaking. Fuel trims will be way out at idle and low speed operations if you have a scan tool. If you get lucky, you can sometimes find a vacuum leak using carb cleaner, but this is not a sure fire approach. I have had vacuum leaks that were not found this way even though that's where they were.
Fuel Injector: An injector with poor flow will have a hard miss at idle and under load, but will smooth out everywhere else...somewhat like a mix between an ignition break down and a vacuum leak. If you believe you have a fuel injector problem, you can test the injector signal (from the PCM) with a "NOID LIGHT". You can swap injectors with an adjacent one pretty easily.
Valve timing/lift: If the Valve timing or lift changes due to worn cam, bent or broken push rod or rocker arm, or broken valve spring will change the amount of air/fuel in the cylinder. Pop the valve cover off and take a look...crank the motor over and check in relation to the neighboring components.
Cam Timing: Incorrect cam timing can cause a miss at idle that is not attributable to any one cylinder, and usually makes poor power. Incorrect cam timing can cause poor compression (usually in DOHC motor though, not very common in OHV motors unless newly built).
Poor Compression: The air/fuel mixture cannot combust unless compressed, causing a misfire. Compression can be compromised by worn parts (piston rings or valve) or parts breakage (piston, valve, or gasket damage). If you have low compression, you can squirt a small amount of engine oil in the cylinder to fill the scores in the cylinder walls, if it increases you have identified worn piston rings.
Crank Position Sensor: CKP sensors have had and issue causing rough running, usually at idle and low speeds and the higher RPM's. Not very common however.
The hardest part of diagnosing an engine miss on a feedback fuel injection system is that the O2 sensor's see that 14.7 parts of O2, not the one part of fuel...so every other cylinder is commanded to compensate for this. I have sometimes found it easier to disconnect the O2 sensors to prevent this cause/effect/cause situation that leads one to chasing things endlessly when diagnosing.
Overall, I generally prefer a systematic method of diagnosis that checks every one of the points above. Now, its not often that a cam is worn
on a low mileage motor for example, so I look towards what last happened. If someone was racing, it is possible that they broke a valve spring, etc.
Lots of variables involved here and I cannot tell you what is wrong specifically, but I hope this helped.
01-14-2012, 11:30 AM
#15
Sometimes the MAF can go bad, even if you clean it or not...the important part is the fine wire that reads the incoming air...it could be bad and you would literally never be able to tell by eye...i know at autozone you can buy a part and try it, and if it isnt that you can return it...not saying for sure its the MAF, just breaking it down lol...
a misfire is always caused by one of three things, spark, fuel, compression...stay with it...unless you got the big bucks to get it fixed (which isnt a bad thing)
If you know any garages that have the GM tech 2 they can monitor all of the sensors in real time to see if your problem is in open loop (pcm uses preloaded parameters) or closed loop (when pcm reading sensors)...also supringingly some of the new scan tools can do this...you can rent one from autozone (called code connect) and it will read your codes and then give you all the top rated fixes for it, which is nice since it is reading from a national database
a misfire is always caused by one of three things, spark, fuel, compression...stay with it...unless you got the big bucks to get it fixed (which isnt a bad thing)
If you know any garages that have the GM tech 2 they can monitor all of the sensors in real time to see if your problem is in open loop (pcm uses preloaded parameters) or closed loop (when pcm reading sensors)...also supringingly some of the new scan tools can do this...you can rent one from autozone (called code connect) and it will read your codes and then give you all the top rated fixes for it, which is nice since it is reading from a national database
01-14-2012, 11:39 AM
#16
TECH Fanatic
Sometimes the MAF can go bad, even if you clean it or not...the important part is the fine wire that reads the incoming air...it could be bad and you would literally never be able to tell by eye...i know at autozone you can buy a part and try it, and if it isnt that you can return it...not saying for sure its the MAF, just breaking it down lol...
EDIT: Also, a Tech II cannot be compared in any way to anything that Autozone has...their purpose is to justify selling **** to people they do not need, a Tech II is a diagnostic tool.
01-14-2012, 11:43 AM
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You guys are awesome. I may have a friend with a Tech 2. Not sure if he still has it. Honestly I don't have the money to take it to a shop right now. I may just wait a while and fix it later. But thanks guys for the suggestions. That's why I came here to ask. You guys are on point.
01-14-2012, 03:15 PM
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A cylinder misfire can be caused by a number of things:
Ignition Breakdown: By far the most common problem, this type of problem gets worse under load (going up a hill) and usually gets better with higher RPM's. You can test coil output with a spark tester (cheap tool) but I usually use a spare plug wire and run the spark tester in series...ie. plug wire from coil to spark tester, spark tester grounded to additional plug wire connected to the spark plug (spark tester has to be hung by bungee cord to not ground out). You should see a strong BLUE spark jumping...if you have a ORANGE/YELLOW spark you have weak spark, poor compression, or incorrect air/fuel mixture. This will test the entire spark system. You can swap coils if you have a single point failure (cylinder 7 misfire, swap with cyl #3, etc). This is THE FIRST STEP...a plug will not fire under poor compression, etc., so this will give a better overall idea as to what is happening inside the cylinder.
Vacuum Leak: Gaskets don't last forever...GM has had issue's with intake gaskets and fuel injector O-rings. Usually causes a miss at idle that cannot be traced to any one cylinder, unless only one cylinder is leaking. Fuel trims will be way out at idle and low speed operations if you have a scan tool. If you get lucky, you can sometimes find a vacuum leak using carb cleaner, but this is not a sure fire approach. I have had vacuum leaks that were not found this way even though that's where they were.
Fuel Injector: An injector with poor flow will have a hard miss at idle and under load, but will smooth out everywhere else...somewhat like a mix between an ignition break down and a vacuum leak. If you believe you have a fuel injector problem, you can test the injector signal (from the PCM) with a "NOID LIGHT". You can swap injectors with an adjacent one pretty easily.
Valve timing/lift: If the Valve timing or lift changes due to worn cam, bent or broken push rod or rocker arm, or broken valve spring will change the amount of air/fuel in the cylinder. Pop the valve cover off and take a look...crank the motor over and check in relation to the neighboring components.
Cam Timing: Incorrect cam timing can cause a miss at idle that is not attributable to any one cylinder, and usually makes poor power. Incorrect cam timing can cause poor compression (usually in DOHC motor though, not very common in OHV motors unless newly built).
Poor Compression: The air/fuel mixture cannot combust unless compressed, causing a misfire. Compression can be compromised by worn parts (piston rings or valve) or parts breakage (piston, valve, or gasket damage). If you have low compression, you can squirt a small amount of engine oil in the cylinder to fill the scores in the cylinder walls, if it increases you have identified worn piston rings.
Crank Position Sensor: CKP sensors have had and issue causing rough running, usually at idle and low speeds and the higher RPM's. Not very common however.
The hardest part of diagnosing an engine miss on a feedback fuel injection system is that the O2 sensor's see that 14.7 parts of O2, not the one part of fuel...so every other cylinder is commanded to compensate for this. I have sometimes found it easier to disconnect the O2 sensors to prevent this cause/effect/cause situation that leads one to chasing things endlessly when diagnosing.
Overall, I generally prefer a systematic method of diagnosis that checks every one of the points above. Now, its not often that a cam is worn
on a low mileage motor for example, so I look towards what last happened. If someone was racing, it is possible that they broke a valve spring, etc.
Lots of variables involved here and I cannot tell you what is wrong specifically, but I hope this helped.
Ignition Breakdown: By far the most common problem, this type of problem gets worse under load (going up a hill) and usually gets better with higher RPM's. You can test coil output with a spark tester (cheap tool) but I usually use a spare plug wire and run the spark tester in series...ie. plug wire from coil to spark tester, spark tester grounded to additional plug wire connected to the spark plug (spark tester has to be hung by bungee cord to not ground out). You should see a strong BLUE spark jumping...if you have a ORANGE/YELLOW spark you have weak spark, poor compression, or incorrect air/fuel mixture. This will test the entire spark system. You can swap coils if you have a single point failure (cylinder 7 misfire, swap with cyl #3, etc). This is THE FIRST STEP...a plug will not fire under poor compression, etc., so this will give a better overall idea as to what is happening inside the cylinder.
Vacuum Leak: Gaskets don't last forever...GM has had issue's with intake gaskets and fuel injector O-rings. Usually causes a miss at idle that cannot be traced to any one cylinder, unless only one cylinder is leaking. Fuel trims will be way out at idle and low speed operations if you have a scan tool. If you get lucky, you can sometimes find a vacuum leak using carb cleaner, but this is not a sure fire approach. I have had vacuum leaks that were not found this way even though that's where they were.
Fuel Injector: An injector with poor flow will have a hard miss at idle and under load, but will smooth out everywhere else...somewhat like a mix between an ignition break down and a vacuum leak. If you believe you have a fuel injector problem, you can test the injector signal (from the PCM) with a "NOID LIGHT". You can swap injectors with an adjacent one pretty easily.
Valve timing/lift: If the Valve timing or lift changes due to worn cam, bent or broken push rod or rocker arm, or broken valve spring will change the amount of air/fuel in the cylinder. Pop the valve cover off and take a look...crank the motor over and check in relation to the neighboring components.
Cam Timing: Incorrect cam timing can cause a miss at idle that is not attributable to any one cylinder, and usually makes poor power. Incorrect cam timing can cause poor compression (usually in DOHC motor though, not very common in OHV motors unless newly built).
Poor Compression: The air/fuel mixture cannot combust unless compressed, causing a misfire. Compression can be compromised by worn parts (piston rings or valve) or parts breakage (piston, valve, or gasket damage). If you have low compression, you can squirt a small amount of engine oil in the cylinder to fill the scores in the cylinder walls, if it increases you have identified worn piston rings.
Crank Position Sensor: CKP sensors have had and issue causing rough running, usually at idle and low speeds and the higher RPM's. Not very common however.
The hardest part of diagnosing an engine miss on a feedback fuel injection system is that the O2 sensor's see that 14.7 parts of O2, not the one part of fuel...so every other cylinder is commanded to compensate for this. I have sometimes found it easier to disconnect the O2 sensors to prevent this cause/effect/cause situation that leads one to chasing things endlessly when diagnosing.
Overall, I generally prefer a systematic method of diagnosis that checks every one of the points above. Now, its not often that a cam is worn
on a low mileage motor for example, so I look towards what last happened. If someone was racing, it is possible that they broke a valve spring, etc.
Lots of variables involved here and I cannot tell you what is wrong specifically, but I hope this helped.
The spark plug will fire in a cylinder with low compression ,actually it will more easily fire in that set of conditions but the fuel/air mixture will sometimes not ignite .(missfire)
02-01-2012, 12:03 PM
#20
I was constantly tripping a P0300 code and it turns out that running dual springs for the valves can cause symptoms like a large cam.
The solution is to "open up" the miss fire tables.
In your case, I think you have a throttle body problem as you can get the problem to appear if you throttle it slowly.
You don't say whether your motor is modded or not.
The solution is to "open up" the miss fire tables.
In your case, I think you have a throttle body problem as you can get the problem to appear if you throttle it slowly.
You don't say whether your motor is modded or not.