Hemi Continues to quit at Speed.

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Tincup

Tincup

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Hey guy's I could use some help, My engine continues to shut down on the highway at speed. It' like shutting off the key, it just quits. Needless to say it's a little dangerous, plus not to mention, I don't trust it. It doesn't do it till after 1 hour of continuous driving at highway speeds (But can go as long as 2 hours). At first I thought it was fuel, but I already replace the pump, filter/reg unit, and insulated the fuel line.

I really think it is electrical, I have replaced the crank position sensor, added more insulation around the ECU, and put in a new set of plugs. I found a thread on the Charger forum where guy's are complaining that it is happening to their Chargers, but nobody has a fix. I'm contemplating a new ECU, but hate to drop the cash if it's not gonna fix the problem.

Any suggestions would be appreciated.:banghead:
 
Sorry, I'm not that familiar with these. Do you have it set up to "pull trouble codes?" That seems to me the first thing.

Anyway to "rig" some lights to monitor, IE power to the ECU, power to the fuel pump, or do you have a pump pressure gauge?

I know you've put one HILL of a lotta work into that, too bad you can't have some fun, now
 
When it quits does it lose spark or fuel? Cam/crank sensors can cause this, I would make sure the fuel pump is not getting hot and popping the relay.
 
Couple of questions.

Does it quit and stay dead for a few minutes or does it restart and run fine immediately?

From what I understand regarding the Hot-Wire harness, it only requires 4 wires to hook up. I'd assume at least one of them is a ground. Where is it grounded? How close is it to the battery? How well is the engine grounded? How well is the ECU grounded? (Does it even require grounding?)

If you have to sit by the side of the road for while, that would suggest to me that you've got one or more questionable grounds that slowly builds up resistance as the under-hood temperature rises.

If it resets almost immediately, that would suggest to me that it is a computer glitch.

As others have said check for thrown error codes.

Electrical gremlins can be a pain to diagnose.

If you know someone with an oscilloscope you can check the output of various sensors like the crank and cam sensor to see how clean the signal is, perhaps when the motor heats up it introduces just enough resistance to dirty up the signal.

Hope this helps.

No one wants a car they can't drive.

Regards,

Joe Dokes
 
Good advice here. I agree with what everyone is saying, just wanted to add that there is lots of reports of new aftermarket crank sensors failing, mopars like oem sensors.Wasn't sure what you are using.
Also I have heard of coil packs shorting out on secondary side and if there is no ground straps on valve covers can cause problems with stalling out from 5 volt side of pcm shutting down from high voltage spikes .
Lots of problems with egr valves on the hemi engines with them causing a stall , but that's on a stopping situation.
Also you can use a heat gun on the suspected sensor,pcm etc. to get hot and get the problem to show up.
 
Both my 2004 Hemi Durango and my 2006 RT charger did this exact same thing. Not always but whenever they had been driven for a while. No prior warning, they just died while driving. I then turn the key and they start right back up. Never did find the problem. The dealer said he sees it all the time and it's just a computer glitch that corrects itself.

Probably a lie just to get me to leave but it sure seems like something a computer would do.
 
Joe Dokes said:
Couple of questions.

Does it quit and stay dead for a few minutes or does it restart and run fine immediately?

From what I understand regarding the Hot-Wire harness, it only requires 4 wires to hook up. I'd assume at least one of them is a ground. Where is it grounded? How close is it to the battery? How well is the engine grounded? How well is the ECU grounded? (Does it even require grounding?)

If you have to sit by the side of the road for while, that would suggest to me that you've got one or more questionable grounds that slowly builds up resistance as the under-hood temperature rises.

If it resets almost immediately, that would suggest to me that it is a computer glitch.

As others have said check for thrown error codes.

Electrical gremlins can be a pain to diagnose.

If you know someone with an oscilloscope you can check the output of various sensors like the crank and cam sensor to see how clean the signal is, perhaps when the motor heats up it introduces just enough resistance to dirty up the signal.

Hope this helps.

No one wants a car they can't drive.

Regards,
Joe Dokes
Click to expand...

The car starts right back up immediately, and will go for another hour or more. I think shutting off the key and restarting is resetting the computer. I'm leaning towards a cold solder joint in the ECU, or possibly a bad component that heats up over time an "Opens" causing it to shut down.
 
blown71duster said:
Good advice here. I agree with what everyone is saying, just wanted to add that there is lots of reports of new aftermarket crank sensors failing, mopars like oem sensors.Wasn't sure what you are using.
Also I have heard of coil packs shorting out on secondary side and if there is no ground straps on valve covers can cause problems with stalling out from 5 volt side of pcm shutting down from high voltage spikes .
Lots of problems with egr valves on the hemi engines with them causing a stall , but that's on a stopping situation.
Also you can use a heat gun on the suspected sensor,pcm etc. to get hot and get the problem to show up.
Click to expand...

I had an OEM crank sensor, that I just replaced with an aftermarket, maybe I'll get another Mopar sensor. I like the heat gun idea, I think I'll try that.
 
momoparman said:
Both my 2004 Hemi Durango and my 2006 RT charger did this exact same thing. Not always but whenever they had been driven for a while. No prior warning, they just died while driving. I then turn the key and they start right back up. Never did find the problem. The dealer said he sees it all the time and it's just a computer glitch that corrects itself.

Probably a lie just to get me to leave but it sure seems like something a computer would do.
Click to expand...

I have read that happens a lot with Chargers ( haven't heard about Magnums or 300's ) but nobody seams to have a fix, or even the cause.
 
Don't know if your running egr or not. My 04 Ram would shut down. No codes etc. I replaced the egr valve and it's been good for over 6 months.
 
Tin,
If I was looking at sensors, Id look at crank and cam sensors, but in my head I see a heat related failure taking longer to "reset", (heat would raise before it fell right?) so Im thinking voltage or ECU. It may be worth keeping a volt meter in the car and checking 12v + at your ign and ecu relays before you touch the key when it dies. Id also talk to hotwire about a reflash before you popped for a new ECU. You may even be able to see if one of these factory ECU guys would loan you theirs as a "known good" before you drop the cash...

Another thought may be what Tstat are you running? The factory 203* stat was hell on my underhood temps. I switched to a 185 and t has really helped my XFI system. You gotta reprogram the fans, but dropping 20* under the hood may solve the problem if it's heat related...

JOE
 
Tincup I was working at a Dodge dealer for the last 22 years. There's an issue with some of the Hemi engines where an interaction between sparkplugs and coils takes the pcm offline for a second and shuts it down. There was never a complete explanation from Chrysler on this but the diagnosis starts with making sure that you have a set of Oem plugs. I quess there's some counterfeit ones out there. Then try swapping out 1 coil at a time with a new to see if it is one of the coils the takes it out. If you find that the issue is not one of the coils then you replace the pcm. This seemed to usually happen on 06 to 08 engines. We would replace all the coils and plugs and then finally the pcm if needed.
 
The can bus cars would set a loss of comm with the PCM when this happens.
 
Tech857 said:
Tincup I was working at a Dodge dealer for the last 22 years. There's an issue with some of the Hemi engines where an interaction between sparkplugs and coils takes the pcm offline for a second and shuts it down. There was never a complete explanation from Chrysler on this but the diagnosis starts with making sure that you have a set of Oem plugs. I quess there's some counterfeit ones out there. Then try swapping out 1 coil at a time with a new to see if it is one of the coils the takes it out. If you find that the issue is not one of the coils then you replace the pcm. This seemed to usually happen on 06 to 08 engines. We would replace all the coils and plugs and then finally the pcm if needed.
Click to expand...

Tin if you wanna give this a shot I have a complete set of 05 coil packs I swapped off my motor before I ever fired it, they are all brand new and I'd happily ship them to ya to try a road test with at least... If you wanted them to keep, I'd make ya a pretty good deal...

Joe
 
Just to clarify on the coils shorting out.

The hemi engine valve covers have rubber isolated bolts and if the coil secondary of any coil shorts out against the valve cover it goes to the path of least resistance which can be a nearby harness and spikes into the pcm and will cause a symptom like you explained.
It shuts down the pcm and stalls the engine and then is fine on a restart.
I have heard of guys just start replacing components , sensors ,pcm, etc , and still have same problem because the ground straps are broke, or in the case of an engine swap missing.

I looked at a 04 ram in the shop and it had a ground strap on the valve cover bolt that loops from the top of the bolt back around the rubber to the base of the bolt so if it the coils short out it will shoot the secondary voltage back into the head/block ground.

Might be worth a shot to run a ground for a test. One on each valve cover.
 
This is one of my biggest hurdles for NOT going HEMI (instead of FI 408)
When it comes to that lil black box
I don't want to put too much trust in it

I'm still accumulating necessary parts that will assist in either case (got the 46RH, getting 4.10 gears, setting tank and fuel system up for EFI...)

Tincup said:
Hey guy's I could use some help, My engine continues to shut down on the highway at speed. It' like shutting off the key, it just quits. Needless to say it's a little dangerous, plus not to mention, I don't trust it. It doesn't do it till after 1 hour of continuous driving at highway speeds (But can go as long as 2 hours). At first I thought it was fuel, but I already replace the pump, filter/reg unit, and insulated the fuel line.

I really think it is electrical, I have replaced the crank position sensor, added more insulation around the ECU, and put in a new set of plugs. I found a thread on the Charger forum where guy's are complaining that it is happening to their Chargers, but nobody has a fix. I'm contemplating a new ECU, but hate to drop the cash if it's not gonna fix the problem.

Any suggestions would be appreciated.:banghead:
Click to expand...
 
Dubob said:
Don't know if your running egr or not. My 04 Ram would shut down. No codes etc. I replaced the egr valve and it's been good for over 6 months.
Click to expand...

I am running an EGR valve.

joeboy said:
Tin,
If I was looking at sensors, Id look at crank and cam sensors, but in my head I see a heat related failure taking longer to "reset", (heat would raise before it fell right?) so Im thinking voltage or ECU. It may be worth keeping a volt meter in the car and checking 12v + at your ign and ecu relays before you touch the key when it dies. Id also talk to hotwire about a reflash before you popped for a new ECU. You may even be able to see if one of these factory ECU guys would loan you theirs as a "known good" before you drop the cash...

Another thought may be what Tstat are you running? The factory 203* stat was hell on my underhood temps. I switched to a 185 and t has really helped my XFI system. You gotta reprogram the fans, but dropping 20* under the hood may solve the problem if it's heat related...

JOE
Click to expand...

Thanks Joe, I am running a 180 t-stat, as for voltage, I have not checked with a meter, but my gauge is rock steady at 14+V.

Tech857 said:
Tincup I was working at a Dodge dealer for the last 22 years. There's an issue with some of the Hemi engines where an interaction between sparkplugs and coils takes the pcm offline for a second and shuts it down. There was never a complete explanation from Chrysler on this but the diagnosis starts with making sure that you have a set of Oem plugs. I quess there's some counterfeit ones out there. Then try swapping out 1 coil at a time with a new to see if it is one of the coils the takes it out. If you find that the issue is not one of the coils then you replace the pcm. This seemed to usually happen on 06 to 08 engines. We would replace all the coils and plugs and then finally the pcm if needed.
Click to expand...

I just installed a new set of Champion plugs ( OEM ), and I have thought about the coils because one other problem I have been having is my tach will bounce ( drop to zero ) occasionally. I thought the two were connected, but now I'm not so sure.

joeboy said:
Tin if you wanna give this a shot I have a complete set of 05 coil packs I swapped off my motor before I ever fired it, they are all brand new and I'd happily ship them to ya to try a road test with at least... If you wanted them to keep, I'd make ya a pretty good deal...

Joe
Click to expand...

blown71duster said:
Just to clarify on the coils shorting out.

The hemi engine valve covers have rubber isolated bolts and if the coil secondary of any coil shorts out against the valve cover it goes to the path of least resistance which can be a nearby harness and spikes into the pcm and will cause a symptom like you explained.
It shuts down the pcm and stalls the engine and then is fine on a restart.
I have heard of guys just start replacing components , sensors ,pcm, etc , and still have same problem because the ground straps are broke, or in the case of an engine swap missing.

I looked at a 04 ram in the shop and it had a ground strap on the valve cover bolt that loops from the top of the bolt back around the rubber to the base of the bolt so if it the coils short out it will shoot the secondary voltage back into the head/block ground.

Might be worth a shot to run a ground for a test. One on each valve cover.
Click to expand...

I do have the alum valve covers, I will check to see if the ground wires are there. I did ground both heads when I wired the car.
 
Hey Guy's, I can't thank you enough for all the great ideas, definitely some good stuff. Some more background, my engine was brand new when I bought it, I only has 8K miles on it right now. So all these things we are talking about changing are basically new parts. I know that doesn't really mean much, but just thought I would throw that out there.
 
I had a hemi ram that wanted to stall out when coming to a stop or even making turns at slow speeds.

It was an intermittent problem , no codes. I unplugged the EGR valve , of course it did set a code and light , but is a good test because it will never open unplugged .

It never acted up with it unplugged and a new EGR valve took care of that problem. And was good because it was a dangerous situation on a turn and loosing power assist when it stalled.

It doesn't sound like the symptom you explained , but I would unplug it anyway just to rule it out.
 
blown71duster said:
I had a hemi ram that wanted to stall out when coming to a stop or even making turns at slow speeds.

It was an intermittent problem , no codes. I unplugged the EGR valve , of course it did set a code and light , but is a good test because it will never open unplugged .

It never acted up with it unplugged and a new EGR valve took care of that problem. And was good because it was a dangerous situation on a turn and loosing power assist when it stalled.

It doesn't sound like the symptom you explained , but I would unplug it anyway just to rule it out.
Click to expand...

I'll try it...
 
if it is a factory ecu problem, or factory efi control, i'd switch to fast efi or something similar

people report good results with the fast setup.
expensive.

or

cheaper alternative: get a setup from a wrecked vehicle from a newer year if possible
 
Tincup one other thing to try is driving with a scan tool that is capable of graphing and recording the sensors as you drive. See if cam or crank drops out. See if everything goes away as in Pcm is off line. What year engine and computer are you using? Is it from a car or truck
 
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