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Discussion Starter · #1 ·
I still havent sorted out my idle / misfire issues due to no one responding to my other posts, so maybe i'll get lucky third time???

Anyways so im going to try this again.....

Idle is rough, car shakes, rpm is at around 600.

This happens on cold starts when the car calms down after starting and does the same when warmed up. rough idle is still there.

When driving, at a random time when i accelerate from a stop sometimes it hesitates and then it wouldn't accelerate further at all, tries to accelerate, bogs / jerks and gives me a random misfire code P0300 and starts misfiring. I also have a Bank 2 / sensor 1 code heater circuit which i cant seem to solve, ive replaced 02 sensor, its still there, i've put in new spark plugs (OEM), coils (OEM, swapped them over also), new intake gaskets, new engine oil, new coolant, new coolant reservoir, throttle body is cleaned out, checked my intake manifold inside and there is a small pool of oil in there. New IAT also. MAF sensor looks dirty (oil) and has some small deposits on the inside of the little tube. Last mechanic who checked the computer, cyclinder 1,3,5,7 are rich and i can smell alot of fuel from driver's side exhaust and passenger side not so much.

A small trick i do is whenever this happens i disconnect the negative terminal and connect it again and it drives fine for like 15 mins to an hour and sometimes randomly. Furthest i've driven without random misfire was 2 days. It happened again to me yesterday and i did the battery trick and drove back home fine.

PLEASE, i beg you guys, PLEASE help / assist me to solve this issue and not just read and leave, as i love my car alot and would love to drive it without and headaches!

Hope someone who has experienced this before or has some experience in solving such issues can help me out!
 

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Mine does the same thing and I can’t seem to find out what it is but I have 02 sensor codes for high voltage that may be my issues or a bad catalytic converter. I have to unplug fuse 11 for 10 secs and start it up and it feels like it has full power again. Try that and see if it changes the idle for you
 

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First off......I have only been on this forum for about 2 months now and I see that it is not very active. I would have expected a lot more traffic than it gets.....so don't get too frustrated if nobody responds.

Have you checked your ground locations? Bad/dirty ground locations can make vehicles go WACKY. That is a free thing to check and perform maintenance on. If they all check out good or ok, then we move on to other possibilities.
 

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Discussion Starter · #5 ·
First off......I have only been on this forum for about 2 months now and I see that it is not very active. I would have expected a lot more traffic than it gets.....so don't get too frustrated if nobody responds.

Have you checked your ground locations? Bad/dirty ground locations can make vehicles go WACKY. That is a free thing to check and perform maintenance on. If they all check out good or ok, then we move on to other possibilities.
I did clean my grounds and applied Di-electric grease on the contacts and the surface it mounts onto, no difference. The grounds im talking about are the ones behind the fuse box in engine bay. There are 2 separate grounds which are coming from the engine harness wiring I assume.

Which other grounds should i be checking / cleaning?

I installed new PCV valve today along with a camshaft position sensor too and it seems only a little bit better, idle shake is not so bad now but still noticeable. PCV value tube is cracked as it was really hard when i remove it and it cracked tearing them basically, dealership didnt have any in stcok, coming by Saturday or Monday, so for now PCV valve tube is installed as is for now.

I've also ordered a new PCM too just in case it needs replacing. As in some cases that could be the possibility of rough idling and PCM not reading 02 sensor heater signal.

So what do you suggest the other possibilities can be?
 

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Discussion Starter · #7 ·
I think the pcm and the pcv valve hose should bring it back to life I would wait and see what happens. Lmk if it works because that’ll be my issue as well.
Sure thing i'll keep you posted

Also i ordered the PCM from Flasgship One website here if you want to order yours - https://www.fs1inc.com/
No programming needed, plug and play.
 

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I still havent sorted out my idle / misfire issues due to no one responding to my other posts, so maybe i'll get lucky third time???

Anyways so im going to try this again.....

Idle is rough, car shakes, rpm is at around 600.

This happens on cold starts when the car calms down after starting and does the same when warmed up. rough idle is still there.

When driving, at a random time when i accelerate from a stop sometimes it hesitates and then it wouldn't accelerate further at all, tries to accelerate, bogs / jerks and gives me a random misfire code P0300 and starts misfiring. I also have a Bank 2 / sensor 1 code heater circuit which i cant seem to solve, ive replaced 02 sensor, its still there, i've put in new spark plugs (OEM), coils (OEM, swapped them over also), new intake gaskets, new engine oil, new coolant, new coolant reservoir, throttle body is cleaned out, checked my intake manifold inside and there is a small pool of oil in there. New IAT also. MAF sensor looks dirty (oil) and has some small deposits on the inside of the little tube. Last mechanic who checked the computer, cyclinder 1,3,5,7 are rich and i can smell alot of fuel from driver's side exhaust and passenger side not so much.

A small trick i do is whenever this happens i disconnect the negative terminal and connect it again and it drives fine for like 15 mins to an hour and sometimes randomly. Furthest i've driven without random misfire was 2 days. It happened again to me yesterday and i did the battery trick and drove back home fine.

PLEASE, i beg you guys, PLEASE help / assist me to solve this issue and not just read and leave, as i love my car alot and would love to drive it without and headaches!

Hope someone who has experienced this before or has some experience in solving such issues can help me out!
Im a Chrysler tech I can try and help you. First off, what’s the mileage on the engine and is it a 6.4 or 5.7? Also, what’s the actual P-code list other than just P0300?
 

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Discussion Starter · #9 · (Edited)
Im a Chrysler tech I can try and help you. First off, what’s the mileage on the engine and is it a 6.4 or 5.7? Also, what’s the actual P-code list other than just P0300?
Thank you Lettercar

The mileage is 341,900 KM the code im getting is P0175 (System too rich Bank 2) P0300 (Random Misfire Detected) and P0155 (Heater Circuit, Bank 2, Sensor 1) in that order. its a 6.1

P0155 comes up before the random misfire takes place.

Ive changed 02 sensors on that one and still the fault code exists. New spark plugs put in, new camshaft position sensor, PCV valve. new coils and intake gaskets too.
 

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I think your whole problem has to do with the P0155 code.
Ok here’s some theory first: Disconnecting the power to the PCM is erasing not only codes, but also the adaptive memory that is learned from the oxygen sensors.
The oxygen sensor needs the heater to maintain a certain temperature to send a proper signal to the PCM regarding fuel mixture.
If the heater doesn’t work, the sensor will cool down and send a higher voltage signal (high voltage = rich and low voltage = lean). So basically it takes the PCM a while to adapt, and a continual high voltage reading will make the PCM try to lean out that bank. After trying to lean that bank it will reach a threshold and set a code. It will keep trying to compensate and eventually make it so lean it starts misfiring. So the P0300 and P0175 are most likely caused by the heater circuit problem.
You have replaced that sensor so you can assume the sensor is good so it’s either a wiring issue or the heater driver in the PCM is bad. You’re going to need to do some circuit checks and I think you’ll find the problem.
I have access to wiring diagrams that I can give you. What year is this car so I can look up the proper diagram?
 

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Discussion Starter · #11 · (Edited)
I think your whole problem has to do with the P0155 code.
Ok here’s some theory first: Disconnecting the power to the PCM is erasing not only codes, but also the adaptive memory that is learned from the oxygen sensors.
The oxygen sensor needs the heater to maintain a certain temperature to send a proper signal to the PCM regarding fuel mixture.
If the heater doesn’t work, the sensor will cool down and send a higher voltage signal (high voltage = rich and low voltage = lean). So basically it takes the PCM a while to adapt, and a continual high voltage reading will make the PCM try to lean out that bank. After trying to lean that bank it will reach a threshold and set a code. It will keep trying to compensate and eventually make it so lean it starts misfiring. So the P0300 and P0175 are most likely caused by the heater circuit problem.
You have replaced that sensor so you can assume the sensor is good so it’s either a wiring issue or the heater driver in the PCM is bad. You’re going to need to do some circuit checks and I think you’ll find the problem.
I have access to wiring diagrams that I can give you. What year is this car so I can look up the proper diagram?
Thanks for all the info, the car is a 2008 model, i did forget to mention that the previous owner did change the fuse box block in the trunk and had it updated to SRT programming, dont know what he meant by that and with all the codes i mentioned im getting no Check engine light by the way, which is a good thing and i dont want that to happen! lol.

I did order a programmed PCM but then cancelled the order due to another technician from chrysler telling me its to do with the alternator / battery but they are fine, no issues there, voltage is at around 14.0 to 14.3

Currently i have both battery terminals zip tied for 24hrs as advised by the other technician and put in a new battery so it has fresh juice for fresh start, dont think i'll do that as my battery isnt the issue or the alternator here.

Yes please do send me the wiring diagram so i can check it out and if the issue has not been resolved from this diagram then i guess its PCM issue?
 

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I don’t know your level of skill so here is a simplified two-step diagnosis (with diagrams) for P0155:

1. First verify the heater ground is good. I strongly suggest using the voltage drop method to test this ground because it needs to flow significant current.
The ground is referred to as G109.
G109 is located on the right valve cover and is connected to terminal 2 at the O2 sensor. (See the photos I hope you can decipher them)
.
2. Then test terminal 1 at the O2 to the terminal 17 at PCM. It should be less than 3-4 ohms or preferably pass a voltage drop test.
>> Very important…. Make sure there are no bent or spread terminals in any of the connectors.
If all the results pass, replace the PCM.
Good luck!
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Discussion Starter · #13 · (Edited)
I don’t know your level of skill so here is a simplified two-step diagnosis (with diagrams) for P0155:

1. First verify the heater ground is good. I strongly suggest using the voltage drop method to test this ground because it needs to flow significant current.
The ground is referred to as G109.
G109 is located on the right valve cover and is connected to terminal 2 at the O2 sensor. (See the photos I hope you can decipher them)
.
2. Then test terminal 1 at the O2 to the terminal 17 at PCM. It should be less than 3-4 ohms or preferably pass a voltage drop test.


If all the results pass, replace the PCM.
Good luck!
Thank you for the helpful info here!

I did check for the ground wires as you showed in the first image but i dont see anything on the passenger valve cover, could you explain a little more where its exactly mounted, i've attached an image which i think are the grounds for it, please let me know if its correct because i did clean that ground with a brush and di-electric grease. Still need to get under the car and check the connector voltage. Do i need to check the voltage with a multimeter? or with a tester light?

Also im not sure if these 3 wires in total are supposed to be connected together on one ground.
 

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I don’t think that is the ground. The heater grounds are always usually attached to the engine. That image from the service manual may not be 100% precise on the location. Check the back side near the metal coolant tube and on the front of the head as well. Don’t get so concerned as to where that ground is, just make sure terminal 2 at the O2 sensor connector is grounded to the engine. You could cut the wire and actually run a new ground if there’s not a good circuit.

Also, don’t worry about checking voltage at this point. The PCM controls the voltage and it is “pulse width modulated”. This means it will not always sending a full 12 volts depending on how warm the heater needs to be, it will vary the voltage. The main concern is a good connection… or good continuity between PCM terminal 17 (orange connector C2, less than five ohms) and terminal 1 at the O2 connector. Again, if you don’t have a good connection you can run a new wire!

Do you need a good demonstration of a voltage drop test? I could search for a good YouTube video for you.


Believe it or not, a voltage drop test with a conventional test light (not LED or a crazy expensive one) using 12 volts is the best way to test a circuit. A multimeter is good for checking for a short to ground or short to power in the circuit. When you do these tests you want the two components unplugged.

I forgot to mention, use extreme care probing terminals at to not damage or spread them apart. They are delicate, don’t force anything into them.

Let me know if you need voltage drop testing demonstrations.
 

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Discussion Starter · #15 ·
I don’t think that is the ground. The heater grounds are always usually attached to the engine. That image from the service manual may not be 100% precise on the location. Check the back side near the metal coolant tube and on the front of the head as well. Don’t get so concerned as to where that ground is, just make sure terminal 2 at the O2 sensor connector is grounded to the engine. You could cut the wire and actually run a new ground if there’s not a good circuit.

Also, don’t worry about checking voltage at this point. The PCM controls the voltage and it is “pulse width modulated”. This means it will not always sending a full 12 volts depending on how warm the heater needs to be, it will vary the voltage. The main concern is a good connection… or good continuity between PCM terminal 17 (orange connector C2, less than five ohms) and terminal 1 at the O2 connector. Again, if you don’t have a good connection you can run a new wire!

Do you need a good demonstration of a voltage drop test? I could search for a good YouTube video for you.


Believe it or not, a voltage drop test with a conventional test light (not LED or a crazy expensive one) using 12 volts is the best way to test a circuit. A multimeter is good for checking for a short to ground or short to power in the circuit. When you do these tests you want the two components unplugged.

I forgot to mention, use extreme care probing terminals at to not damage or spread them apart. They are delicate, don’t force anything into them.

Let me know if you need voltage drop testing demonstrations.

I do see a wire attached behind the coolant inlet tube at the back of the passenger valve cover area, there is a bolt then the ground wire, i dont have a multimeter at this point so i would check on what i can now.

A video would help once i can get my hands on a multimeter yes please.
 

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Ordered a pcm just in case thank you for that website! Now I do have another issue going on my 6.1 when starting it’ll start idle and chop real bad then shutoff. Try and start it it’ll start then die instantly. Pulled fuse 11 for 10 secs then started it then back to normal again like what it is going on !
 

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Discussion Starter · #18 ·
Ordered a pcm just in case thank you for that website! Now I do have another issue going on my 6.1 when starting it’ll start idle and chop real bad then shutoff. Try and start it it’ll start then die instantly. Pulled fuse 11 for 10 secs then started it then back to normal again like what it is going on !
No problem at all! Glad to help. If its starting then dying immediately i would check your starter.
 

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Starter checks out but it’ll start and run but idles from 800 then bounces back down to about 350 and idles rough then when you shut off the car start it up it’ll either keep doing that or it’ll die. Pull fuse 11 for 10 seconds and the car acts brand new again.
 

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Discussion Starter · #20 ·
Starter checks out but it’ll start and run but idles from 800 then bounces back down to about 350 and idles rough then when you shut off the car start it up it’ll either keep doing that or it’ll die. Pull fuse 11 for 10 seconds and the car acts brand new again.
Im on the same boat as you too, does the same thing but doesnt die, it just literally rocks the whole damn car, but i realized that i have a leak in mid magnaflow muffler, my tuner says that could be affecting my engine's performance, another guy says thats not the cause because its way downstream from the engine. I've attached the picture of the leak, not sure if this mid muffler / resonator leak will cause an engine to throw a P0300 code and bank 1 rich?
 

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