And... Code light back on...
Gonna read it tonight, but I'm assuming it's the same misfire back again.
Gonna read it tonight, but I'm assuming it's the same misfire back again.
Misfire on Cylinder 7
- Thread starter Inferno333
- Start date
C-ya
Member
- Aug 24, 2012
- 1,098
You said the mechanic checked and changed the injectors. Did he swap the trouble cylinder injector with another? I would try that if it hasn't already been done. What about the compression check on that cylinder? How did it compare to other cylinders?
ETA: If you haven't gotten Torque yet, get it. I'm not sure if the free one will monitor misfires, but the pay version is only $5 I think. You can watch all 8 cylinders for misfires and history. It was nice when I was chasing a misfire.
ETA: If you haven't gotten Torque yet, get it. I'm not sure if the free one will monitor misfires, but the pay version is only $5 I think. You can watch all 8 cylinders for misfires and history. It was nice when I was chasing a misfire.
I'll verify what exactly he did, but I'm pretty sure he swapped them.
Do you just search the App Store for Torque? EngineLink and OBD Fusion are the only ones that come up.
EngineLink was $5 and it's decent. I'm hoping Torque will provide more info if I can find it.
Do you just search the App Store for Torque? EngineLink and OBD Fusion are the only ones that come up.
EngineLink was $5 and it's decent. I'm hoping Torque will provide more info if I can find it.
C-ya
Member
- Aug 24, 2012
- 1,098
Do you have an Iphone? If so, no Torque for you! (In my best soup nazi voice.)
https://play.google.com/store/apps/details?id=org.prowl.torquefree&hl=en
https://play.google.com/store/apps/details?id=org.prowl.torque&hl=en
https://play.google.com/store/apps/details?id=org.prowl.torquefree&hl=en
https://play.google.com/store/apps/details?id=org.prowl.torque&hl=en
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I checked the invoice. He swapped plugs, plug wires, coils, and injectors. He pulled the valve cover, checked the rockers, and blew out the fuel rail. Compression was 135 psi on that cylinder.
What else is possible? A valve not seating?
I just don't know.
What else is possible? A valve not seating?
I just don't know.
Mooseman
Moderator
Maybe just buy a cheap Android tablet or an old phone and get Torque.
Now I'm starting to think it's a wiring issue or the PCM. Not much left.
Now I'm starting to think it's a wiring issue or the PCM. Not much left.
I'll ask around about an and rio phone.
I did have a non-DOD 5.3L cam installed which PCMofNC suggested since the 6.0L cam was on back order. Could that have anything to do with it?
I wonder if they would be able provide any insight as to what's going on.
I did have a non-DOD 5.3L cam installed which PCMofNC suggested since the 6.0L cam was on back order. Could that have anything to do with it?
I wonder if they would be able provide any insight as to what's going on.
Mooseman
Moderator
I doubt very much the cam is responsible for an issue on just one cylinder, and an intermittent one at that. What about a flaky lifter? Wouldn't be the first time a new part has failed.
RedRocketZ28
Member
- May 16, 2014
- 114
Need to verify the current compression on all cylinders to see if they jive with each other. A leak down test should be done as well.
If that checks out I would look into checking the intake gaskets and/or intake. I have seen and heard of some funny things happening if the intake doesn't seal right.
If that checks out I would look into checking the intake gaskets and/or intake. I have seen and heard of some funny things happening if the intake doesn't seal right.
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Think I should get my mechanic to start discounting some of this work since it's still not running correctly?
He did mention on the last invoice it could possibly be a valve not seating properly. It sucks bad being down a vehicle when it goes in there to get tore down.
He did mention on the last invoice it could possibly be a valve not seating properly. It sucks bad being down a vehicle when it goes in there to get tore down.
Mooseman
Moderator
Could be a weak of failing valve spring or damper, making it bounce at speed. Definitely also check for a leak at the intake manifold.
Is there a way to check for a weak spring other than pulling it apart?
I have some leftover throttlebody cleaner. I'll check for leaks around the intake in the morning.
AWD V8
Member
- Jan 12, 2015
- 463
I had a Dodge V8 that had an intermittent misfire on one cylinder. I did all the things, swap coils, plugs, injectors, checked compression, etc. At times it would go for days with no misfire. Finally, I found out that the oil pressure would intermittently drop low, lots of oiling problems with these engines. When the oil pressure dropped the lifter failed to open the exhaust valve on this one cylinder. Dodge had revised lifters to address this, not the oiling problem! It did fix the misfire.
It could very well be a bad/weak lifter.
It could very well be a bad/weak lifter.
Well shit. I'll do the leak check for the intake manifold and see if I find anything.
I'll pull the plug and read it before it warms up too much.
I want this truck totaled if it's a bad lifter. I don't want to pay my mechanic to rip the whole thing apart again. I'm easily $4k into it since November.
Hopefully the wind dies down by morning. I'll use the throttle body cleaner to check for intake manifold leaks.
If nothing then I guess it goes back to my mechanic so he can tear bank 1 apart again.
If nothing then I guess it goes back to my mechanic so he can tear bank 1 apart again.
I sprayed throttlebody cleaner all around the injectors and intake manifold. There was no change in rpms at all and no fizzing sounds.
I pulled the 3, 5, and 7 plugs. All of them were a light tan with nothing abnormal that I could find. I did notice that the 7 plug looked like it was dropped on the plug wire end. It was flattened in a little on the tip at an angle.
I swapped the 5 and 7 plug to see if it ran any differently. No change. The pending misfire came back after revving the engine up to around 3k.
Main question:
Are the injectors supposed to be able to be turned side to side by hand while installed? All of bank 2 were tight. Injector 1 and 3 were tight. Injector 5 was mostly tight and injector 7 could easily be pushed side to side.
I pulled the 3, 5, and 7 plugs. All of them were a light tan with nothing abnormal that I could find. I did notice that the 7 plug looked like it was dropped on the plug wire end. It was flattened in a little on the tip at an angle.
I swapped the 5 and 7 plug to see if it ran any differently. No change. The pending misfire came back after revving the engine up to around 3k.
Main question:
Are the injectors supposed to be able to be turned side to side by hand while installed? All of bank 2 were tight. Injector 1 and 3 were tight. Injector 5 was mostly tight and injector 7 could easily be pushed side to side.
AWD V8
Member
- Jan 12, 2015
- 463
Most times you will find the injector will rotate. However, if it is "loose" as in wiggles at the base, it will let false air in and cause that cylinder to run leaner at idle, won't affect higher RPM though. Your Fuel Trims for that bank would be slightly higher. If idling you sprayed some WD40 at the base, if leaking enough to cause a lean code, it should alter the idle noticeably.
I'll check it a bit closer in the morning.
Would I be able to replace an injector myself? Does it entail taking a lot of stuff apart or special tools?
Would I be able to replace an injector myself? Does it entail taking a lot of stuff apart or special tools?
RedRocketZ28
Member
- May 16, 2014
- 114
The injectors will move around some and that isn't an issue. They are extremely easy to change and require no special tools. I find it very hard to believe an injector would be bad though.
Well after changing the plugs around yesterday there aren't any codes. The idle is still rough though.
Would you guys recommend changing out the O2 sensors since I've had so many misfire issues? Especially since I had a broken lifter that left a valve open. Could that resolve the idle issues?
Recommendations on O2 sensor brand?
Ordering brakes tonight. They're grinding a bit so it's well past time.
Would you guys recommend changing out the O2 sensors since I've had so many misfire issues? Especially since I had a broken lifter that left a valve open. Could that resolve the idle issues?
Recommendations on O2 sensor brand?
Ordering brakes tonight. They're grinding a bit so it's well past time.
I haven't poked my head in the engine bay yet, but I'm guessing there's one upstream sensor for each bank. Think I should replace the downstream one at the same time? Do these just require the fuse pull relearn like the throttle-body?
And do I want to even attempt this one at home? 130k on the truck. I probably should've had them replaced back when the engine was torn apart.
Sounds like a plan then. The drivers side has way more room to work anyways.
Now to pick out brake parts... I'll get over to that section and see what people have had good experience with.
I took a couple pictures showing fuel trim percentages. I can only guess what I'm looking at, but it looks fairly simple.
First one is at idle. Second is at 1500 rpm in park.
First one is at idle. Second is at 1500 rpm in park.
AWD V8
Member
- Jan 12, 2015
- 463
The Fuel Trims look good.
Fuel Trims are how far from "ideal" is it running. The computer (PCM) is programmed with what the factory considered should be the correct "on time" for the injectors for any given condition. The Oxygen sensors report back to the PCM what the actual oxygen content is in the exhaust, the PCM makes an adjustment based on this feedback. "How much" of an adjustment is shown in the fuel trim. If the PCM had to add fuel, longer on time for the injectors, this is shown as a positive number, if the PCM had to remove fuel, less on time, then this shows as a negative number. In a perfect world the fuel trim would be zero, 0.00%
Generally any single digit number is good. So -2.34% is quite acceptable, as is 0.78%
If you had a number or 10.0 % at idle only it could be a manifold leak as the PCM is trying to compensate by adding more fuel. Generally I monitor the shirt term fuel trim as it shows what is happening right at this time. Long term fuel trim shows a trend over time.
If you can find a condition that brings out the misfire, that is when you want to be watching the fuel trim. If it only misfires at idle, cruise or WOT, you need to watch closely at that time. Fuel trim is shown for a bank of cylinders and not just one cylinder. If the O2 sensor on the bank with your misfiring cylinder shows lean, or fuel trims of more than 10%, the PCM will up the injector time on all the cylinders on that back.
The easiest way to monitor the fuel supply to the engine is monitor short term fuel trim & O2 voltage at the same time. Beyond about 75% throttle the PCM will disregard the O2 sensors and run solely on the programmed map. Under this operating condition the fuel trims will show zero, BUT, the O2 sensors are still sending info. At WOT the engine requires a richer mixture than the O2 sensors can report, so you will see a steady maxed out reading of about .9 volts as long as the engine is receiving sufficient fuel supply. In the case of a weak fuel pump or a clogged fuel filter the voltage will drop down showing a lean condition. If the voltage remains steady and maxed out, you for sure have enough fuel and can look at other areas.
You can see where I went WOT, the voltage jumped up and stayed there.
A misfire caused by a lean condition should show up as a positive fuel trim but exceed 10%. Your long term fuel trim looks good, so I would conclude that the misfire is not caused by a lean condition. However, I would still perform a WOT run to confirm the fuel delivery is consistently good. I had a fuel pump that would perform well 95% of the time. Sometimes after about an hour of driving the CEL would come on for a lean condition, and at times I could feel the misfire. I did a WOT run at that time and found a fuel trim exceeding 25%. That led me to check fuel pressures again, but this time on the road. I determined the pump was bad and replaced it.
Fuel Trims are how far from "ideal" is it running. The computer (PCM) is programmed with what the factory considered should be the correct "on time" for the injectors for any given condition. The Oxygen sensors report back to the PCM what the actual oxygen content is in the exhaust, the PCM makes an adjustment based on this feedback. "How much" of an adjustment is shown in the fuel trim. If the PCM had to add fuel, longer on time for the injectors, this is shown as a positive number, if the PCM had to remove fuel, less on time, then this shows as a negative number. In a perfect world the fuel trim would be zero, 0.00%
Generally any single digit number is good. So -2.34% is quite acceptable, as is 0.78%
If you had a number or 10.0 % at idle only it could be a manifold leak as the PCM is trying to compensate by adding more fuel. Generally I monitor the shirt term fuel trim as it shows what is happening right at this time. Long term fuel trim shows a trend over time.
If you can find a condition that brings out the misfire, that is when you want to be watching the fuel trim. If it only misfires at idle, cruise or WOT, you need to watch closely at that time. Fuel trim is shown for a bank of cylinders and not just one cylinder. If the O2 sensor on the bank with your misfiring cylinder shows lean, or fuel trims of more than 10%, the PCM will up the injector time on all the cylinders on that back.
The easiest way to monitor the fuel supply to the engine is monitor short term fuel trim & O2 voltage at the same time. Beyond about 75% throttle the PCM will disregard the O2 sensors and run solely on the programmed map. Under this operating condition the fuel trims will show zero, BUT, the O2 sensors are still sending info. At WOT the engine requires a richer mixture than the O2 sensors can report, so you will see a steady maxed out reading of about .9 volts as long as the engine is receiving sufficient fuel supply. In the case of a weak fuel pump or a clogged fuel filter the voltage will drop down showing a lean condition. If the voltage remains steady and maxed out, you for sure have enough fuel and can look at other areas.
You can see where I went WOT, the voltage jumped up and stayed there.
A misfire caused by a lean condition should show up as a positive fuel trim but exceed 10%. Your long term fuel trim looks good, so I would conclude that the misfire is not caused by a lean condition. However, I would still perform a WOT run to confirm the fuel delivery is consistently good. I had a fuel pump that would perform well 95% of the time. Sometimes after about an hour of driving the CEL would come on for a lean condition, and at times I could feel the misfire. I did a WOT run at that time and found a fuel trim exceeding 25%. That led me to check fuel pressures again, but this time on the road. I determined the pump was bad and replaced it.
Thank you for the in depth explanation! It seemed to follow what logic was telling me.
I don't have the ability to monitor O2 voltage with EngineLink. Is there another way?
The misfire has not returned as current or pending since I switched the plugs around. It's quite perplexing actually. I don't see a reason why that would've fixed it.
The idle is still around 530-570 rpm and rough. No cause found yet. It feels normal above 1000 rpm.
I don't have the ability to monitor O2 voltage with EngineLink. Is there another way?
The misfire has not returned as current or pending since I switched the plugs around. It's quite perplexing actually. I don't see a reason why that would've fixed it.
The idle is still around 530-570 rpm and rough. No cause found yet. It feels normal above 1000 rpm.
Mooseman
Moderator
Maybe my wife will let me get it on her phone. Is there a significant difference between the regular and pro app?
I haven't gone out and checked it after the O2 sensor was replaced on Wednesday. The new brakes work awesome according to my wife though.
gmcman
Member
- Dec 12, 2011
- 4,666
Correct me if I'm wrong, but 135 is pretty low. From what I have come up with, 149 is the lowest spec and 165-180 is normal...again, I could be wrong.
So you found plugs 7 & 8 finger tight? What do the plug seats look like in the head?
Mooseman
Moderator
Looks like I might be buying a compression tester so I can check them all myself. Any recommendations on which brand/model? Same for a fuel pressure gauge. I like buying tools anyways.
Torque Pro it is. I'll snag the wife's phone when she gets home from work.
If this thing does actually have low compression in one or more cylinders after the $$$ we've put into it then I'll be pissed and trading it in asap. That will make the wife happy since she wants to get rid of the TB and I still get to drive her shitty Saturn Ion...
Torque Pro it is. I'll snag the wife's phone when she gets home from work.
If this thing does actually have low compression in one or more cylinders after the $$$ we've put into it then I'll be pissed and trading it in asap. That will make the wife happy since she wants to get rid of the TB and I still get to drive her shitty Saturn Ion...
gmcman
Member
- Dec 12, 2011
- 4,666
Ok, I wasn't sure to the authenticity of my findings in regards to the normal compression, I was thinking low 200's myself.
That being said, 135 is kinda low, even if it's within 70%. I wonder if the compression was comprised after the heads were reinstalled? Did you perform a compression test before you had the heads off?
If your misfires started after the head was off for the lifter repair, I would start to look at a head gasket.
Are the 5.3 head bolts TTY? If so, we're they reused? If they were reused then that would be the fault of the mechanic.
So yes, a compression test is in order, I use the Innova 3612, has worked well..just make sure the rubber o ring is seated and you snug the tester down real good but not terribly tight. Do a dry test then wet.
You could also run some seafoam through it or gm top engine cleaner in hopes there's some carbon build up under a valve.
Maybe the head wasn't torqued to spec.
I wouldn't throw in the towel, could be something minor just needing a few beers and pizza to get it right.
That being said, 135 is kinda low, even if it's within 70%. I wonder if the compression was comprised after the heads were reinstalled? Did you perform a compression test before you had the heads off?
If your misfires started after the head was off for the lifter repair, I would start to look at a head gasket.
Are the 5.3 head bolts TTY? If so, we're they reused? If they were reused then that would be the fault of the mechanic.
So yes, a compression test is in order, I use the Innova 3612, has worked well..just make sure the rubber o ring is seated and you snug the tester down real good but not terribly tight. Do a dry test then wet.
You could also run some seafoam through it or gm top engine cleaner in hopes there's some carbon build up under a valve.
Maybe the head wasn't torqued to spec.
I wouldn't throw in the towel, could be something minor just needing a few beers and pizza to get it right.
Mooseman
Moderator
Ignore that spec I posted. That's for the 4.2. I'll have to look at it when I get home for proper compression spec for the 5.3.
All the work has been done by my mechanic. I trust him to do good work. He's build some awesome show/pro-street cars.
The first post in this thread gives a full history since last November when a DOD lifter broke. I know that new head bolts were used.
Right now it is not showing any pending or current codes. The idle is just rough. More than it should be. It's running well otherwise.
The first post in this thread gives a full history since last November when a DOD lifter broke. I know that new head bolts were used.
Right now it is not showing any pending or current codes. The idle is just rough. More than it should be. It's running well otherwise.
Mooseman
Moderator
gmcman
Member
- Dec 12, 2011
- 4,666
Is that the spec from the GM service manual? I'm just curious because it uses 150 as an example.
100 psi an any motor pretty much is the low limit and even that's barely running.
Not trying to doubt you Moose, just going by the language in your post on the compression.
Another thing, is it a pita to pull the valve cover? I wonder what the cam lift is on that cylinder, makes a difference with compression.