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I'm infuriated and at a loss, hoping someone here can help me after 4 months and over $1000 spent. Starting back in Sept, had a very rough idle on startup. Truck is shaking and not getting consistent power. Needed a new water pump anyway, so had it towed into my local mechanic. Replaced water pump and fuel sensor to address the idle issue, as it was corroded and seemed to be the problem. Drove fine home from the mechanic.

Few days later, same rough idle on startup. Towed back to same mechanic. Left it with them for 3 weeks and they spent several hours over many days troubleshooting. Said it would run fine some days, then experience the issue others. They ruled out several issues, but couldn't identify the root cause. Said it looked like possibly a PCM issue and would need to go to the dealer. Ran fine on the way home again.

Once home, I hit the forums looking for answers and found instructions on resetting the PCM (via removing PCM fuse and turning ignition to on position, etc). Did that and continued running fine...for about a month and a half, thought I'd found the issue.

Then a couple of weeks ago hit the same issue again. Had it towed to dealership...against my better judgment. They found a PCM software upgrade that was needed, which they did, and narrowed the issue to the spark plugs (?!?!?!), which needed changing. Really didn't feel like that was the issue, but went ahead with it. They kept it a couple of extra days to make sure it was running right, which it was. Charged me $700 for that...Drove fine home and 2 more days, then this morning, same rough idle on start. About blew my own gasket at that point.

I need help figuring out what this is...mechanic and dealership couldn't find it, but hoping you geniuses have some better (and hopefully cheaper!) ideas. It's 2007 1500 Thunder Road package w/5.7 Hemi. About 112,000 miles. Once I try it a few times with the issue, I get the flashing check engine light. It doesn't return any codes for me via ignition, but the dealership said it showed multiple cylinder misfire codes. I've had very intermittent cylinder misfire codes in the past, but always sporadic and corrected themselves. I've been working from home since March, so not driving everyday...usually only Thurs - Sun, so will sit a few days in between.

Sorry for the long post, but quite a bit of background. Anybody else had similar issues? Any help at all? Thank you!
 

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I’ve been chasing a similar issue on my 08 4.7. Starts up fine and every once in a while when it comes off high idle it will start missing. New plugs, multiple sensors changed, fuel injectors. Not sure where I’m going next.
 

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I'm infuriated and at a loss, hoping someone here can help me after 4 months and over $1000 spent. Starting back in Sept, had a very rough idle on startup. Truck is shaking and not getting consistent power. Needed a new water pump anyway, so had it towed into my local mechanic. Replaced water pump and fuel sensor to address the idle issue, as it was corroded and seemed to be the problem. Drove fine home from the mechanic.

Few days later, same rough idle on startup. Towed back to same mechanic. Left it with them for 3 weeks and they spent several hours over many days troubleshooting. Said it would run fine some days, then experience the issue others. They ruled out several issues, but couldn't identify the root cause. Said it looked like possibly a PCM issue and would need to go to the dealer. Ran fine on the way home again.

Once home, I hit the forums looking for answers and found instructions on resetting the PCM (via removing PCM fuse and turning ignition to on position, etc). Did that and continued running fine...for about a month and a half, thought I'd found the issue.

Then a couple of weeks ago hit the same issue again. Had it towed to dealership...against my better judgment. They found a PCM software upgrade that was needed, which they did, and narrowed the issue to the spark plugs (?!?!?!), which needed changing. Really didn't feel like that was the issue, but went ahead with it. They kept it a couple of extra days to make sure it was running right, which it was. Charged me $700 for that...Drove fine home and 2 more days, then this morning, same rough idle on start. About blew my own gasket at that point.

I need help figuring out what this is...mechanic and dealership couldn't find it, but hoping you geniuses have some better (and hopefully cheaper!) ideas. It's 2007 1500 Thunder Road package w/5.7 Hemi. About 112,000 miles. Once I try it a few times with the issue, I get the flashing check engine light. It doesn't return any codes for me via ignition, but the dealership said it showed multiple cylinder misfire codes. I've had very intermittent cylinder misfire codes in the past, but always sporadic and corrected themselves. I've been working from home since March, so not driving everyday...usually only Thurs - Sun, so will sit a few days in between.

Sorry for the long post, but quite a bit of background. Anybody else had similar issues? Any help at all? Thank you!
I'm infuriated and at a loss, hoping someone here can help me after 4 months and over $1000 spent. Starting back in Sept, had a very rough idle on startup. Truck is shaking and not getting consistent power. Needed a new water pump anyway, so had it towed into my local mechanic. Replaced water pump and fuel sensor to address the idle issue, as it was corroded and seemed to be the problem. Drove fine home from the mechanic.

Few days later, same rough idle on startup. Towed back to same mechanic. Left it with them for 3 weeks and they spent several hours over many days troubleshooting. Said it would run fine some days, then experience the issue others. They ruled out several issues, but couldn't identify the root cause. Said it looked like possibly a PCM issue and would need to go to the dealer. Ran fine on the way home again.

Once home, I hit the forums looking for answers and found instructions on resetting the PCM (via removing PCM fuse and turning ignition to on position, etc). Did that and continued running fine...for about a month and a half, thought I'd found the issue.

Then a couple of weeks ago hit the same issue again. Had it towed to dealership...against my better judgment. They found a PCM software upgrade that was needed, which they did, and narrowed the issue to the spark plugs (?!?!?!), which needed changing. Really didn't feel like that was the issue, but went ahead with it. They kept it a couple of extra days to make sure it was running right, which it was. Charged me $700 for that...Drove fine home and 2 more days, then this morning, same rough idle on start. About blew my own gasket at that point.

I need help figuring out what this is...mechanic and dealership couldn't find it, but hoping you geniuses have some better (and hopefully cheaper!) ideas. It's 2007 1500 Thunder Road package w/5.7 Hemi. About 112,000 miles. Once I try it a few times with the issue, I get the flashing check engine light. It doesn't return any codes for me via ignition, but the dealership said it showed multiple cylinder misfire codes. I've had very intermittent cylinder misfire codes in the past, but always sporadic and corrected themselves. I've been working from home since March, so not driving everyday...usually only Thurs - Sun, so will sit a few days in between.

Sorry for the long post, but quite a bit of background. Anybody else had similar issues? Any help at all? Thank you!
Could be the egr. If it is open during warm up it will run rough. Once it warms up it will run normal with the egr open. I have fixed a similar problem like this on a 5.9 magnum but not the 5.7 hemi. Just a guess.
 

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It would be interesting to check the fuel pressure both while it's running normally and while it's misfiring.
 

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Could be the egr. If it is open during warm up it will run rough. Once it warms up it will run normal with the egr open. I have fixed a similar problem like this on a 5.9 magnum but not the 5.7 hemi. Just a guess.
If the EGR was stuck it would throw a code almost immediately. EGR has very precise expected positions. If that position doesn't match the expected value you'll get a check engine very fast.
 

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I'm infuriated and at a loss, hoping someone here can help me after 4 months and over $1000 spent. Starting back in Sept, had a very rough idle on startup. Truck is shaking and not getting consistent power. Needed a new water pump anyway, so had it towed into my local mechanic. Replaced water pump and fuel sensor to address the idle issue, as it was corroded and seemed to be the problem. Drove fine home from the mechanic.

Few days later, same rough idle on startup. Towed back to same mechanic. Left it with them for 3 weeks and they spent several hours over many days troubleshooting. Said it would run fine some days, then experience the issue others. They ruled out several issues, but couldn't identify the root cause. Said it looked like possibly a PCM issue and would need to go to the dealer. Ran fine on the way home again.

Once home, I hit the forums looking for answers and found instructions on resetting the PCM (via removing PCM fuse and turning ignition to on position, etc). Did that and continued running fine...for about a month and a half, thought I'd found the issue.

Then a couple of weeks ago hit the same issue again. Had it towed to dealership...against my better judgment. They found a PCM software upgrade that was needed, which they did, and narrowed the issue to the spark plugs (?!?!?!), which needed changing. Really didn't feel like that was the issue, but went ahead with it. They kept it a couple of extra days to make sure it was running right, which it was. Charged me $700 for that...Drove fine home and 2 more days, then this morning, same rough idle on start. About blew my own gasket at that point.

I need help figuring out what this is...mechanic and dealership couldn't find it, but hoping you geniuses have some better (and hopefully cheaper!) ideas. It's 2007 1500 Thunder Road package w/5.7 Hemi. About 112,000 miles. Once I try it a few times with the issue, I get the flashing check engine light. It doesn't return any codes for me via ignition, but the dealership said it showed multiple cylinder misfire codes. I've had very intermittent cylinder misfire codes in the past, but always sporadic and corrected themselves. I've been working from home since March, so not driving everyday...usually only Thurs - Sun, so will sit a few days in between.

Sorry for the long post, but quite a bit of background. Anybody else had similar issues? Any help at all? Thank you!
Intermittent problems can be the hardest to track down. Misfiring has very specific causes...either the engine is not getting a good spark, the spark is at the wrong time, or the air/fuel mixture is incorrect, due to not enough fuel being available, or too much air being available. We'll ignore mechanical faults like low compression, cracked head, etc., since these things have obvious symptoms and are easy to diagnose.
This would indicate that something is causing your spark to fail, get very weak, or be far off time...or that something is interfering with consistent fuel delivery.
Possible causes:
Bad plugs (not likely, if it's intermittent, bad plugs are usually bad plugs, and these were replaced)
Bad coil/coils (not likely, unless multiple units are failing...bear in mind cracked coil housings can cause wildly intermittent misfiring...if it's the same cylinders always misfiring, this would be a big clue)
Plugged injectors (possible, but should be getting worse all the time)
Faulty injector wiring or corroded connectors (should just hard fail at some point)
Intermittent fuel pump performance (hard to diagnose unless you have a gauge on for an extended time)
Intermittent failure in fuel pressure regulator (same as above)
Intermittent PCM injector driver performance or similar (hard to diagnose if the PCM's internal checks don't detect an explicit problem..this is usually a hard fail at some point)
 
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