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Discussion Starter · #1 ·
Hello, I replaced my computer last night with a remanufactured computer. I followed their instructions to turn the key on with the engine off and let it sit for about 120 seconds. After that started the engine, however, the engine ran worse than the old computer. The old computer has an issue with the ignition firing cylinder number 4. This replacement reman computer will not idle the vehicle or run in drive. I contacted the company who sold me the reman, and they recommended doing a hard reset which consists of disconnecting the battery and then connecting the two cables with a tie strap for about 10 hours.

My question is, has anyone else experienced this type of issue with your nitro? Has anyone replaced the computer and had a similar issue, and how did you address it?
 

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WHAT engine code error is shown using a OBD II scan tool?
 

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I guess you must have a PO304-code error that is common with the Nitro on both engines of the Nitro.
Dodge Nitro: Engine Problems / Code Errors

I guess you have checked out our above Thread, if not it should be helpful.


You may have already cheeked out the many causes and eliminated most but everything from cam ware issues to head valve seat are also sometime the reason for this code. Hopefully not! Good Luck! Let us know what you finally find is the issue to help others.

Fixing P0304 should be considered a high priority. Unlike a lot of the OBDII codes, this code has to do directly with engine combustion. It also can cost money to ignore it, since driving with a misfire can damage the vehicle’s catalytic converter. The engine is also not firing all of the fuel, so raw fuel is also passing through Cylinder 4 into the exhaust. Mileage may suffer as well when your Nitro has P0304 as well.


P0304 Trouble Code Diagnosis- Dodge Nitro

There are quite a few things that can cause the P0304 trouble code to trigger the Dodge Nitro. Here are the most common problems that will throw the code. They are presented somewhat in order from most to least likely to be causing the code:



Bad Spark Plugs– Spark plugs are one of the most common causes of P0304. Take a look at the electrodes and see if they are in good shape. Most vehicles now come with iridium plugs that need changed very infrequently. That being said, the plugs are a great place to start. Here’s a great video on how to see if a spark plug is bad.

Spark Plug Wires– On most modern engines, the plug wires are not nearly as long as they once were, but they can still go bad. Here’s how to tell if your plug wires are bad (video).
Coil Packs– Coil packs rarely go bad, but when they do, they can certainly cause P0304 in your Dodge Nitro. Replacing a set can be very expensive. Here’s how to test them.

Bad Fuel Injector–
If you have a fuel injector that has gone bad, it won’t be able to properly atomize the fuel and you’ll get the P0304. Here’s a good video on how to diagnose an injector, it can be a little tricky. This is definitely not the place to start.
Vacuum leak– If your Nitro has a vacuum leak, it can be very difficult for it to get the right air/fuel mixture. This will cause the cylinders to misfire and it’ll throw the P0304 if the leak is around that specific cylinder on the intake manifold. It’s easy (and kind of fun) to chase one down. Popular Mechanics: How to find a vacuum leak.

Cam or Crank Sensors– This one is very unlikely, but it does happen. If the ECU is not getting the right signal from these sensors, the vehicles timing is not going to sync up and it’ll misfire.

Low Compression– If you have a leaking head gasket, bent valve, cracked head, etc.. that would cause compression to not be as high as it should, you’re going to get P0304. You should also feel the vehicle is down on power as well.
 

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Discussion Starter · #6 ·
I guess you must have a PO304-code error that is common with the Nitro on both engines of the Nitro.
Dodge Nitro: Engine Problems / Code Errors

I guess you have checked out our above Thread, if not it should be helpful.


You may have already cheeked out the many causes and eliminated most but everything from cam ware issues to head valve seat are also sometime the reason for this code. Hopefully not! Good Luck! Let us know what you finally find is the issue to help others.

Fixing P0304 should be considered a high priority. Unlike a lot of the OBDII codes, this code has to do directly with engine combustion. It also can cost money to ignore it, since driving with a misfire can damage the vehicle’s catalytic converter. The engine is also not firing all of the fuel, so raw fuel is also passing through Cylinder 4 into the exhaust. Mileage may suffer as well when your Nitro has P0304 as well.


P0304 Trouble Code Diagnosis- Dodge Nitro

There are quite a few things that can cause the P0304 trouble code to trigger the Dodge Nitro. Here are the most common problems that will throw the code. They are presented somewhat in order from most to least likely to be causing the code:



Bad Spark Plugs– Spark plugs are one of the most common causes of P0304. Take a look at the electrodes and see if they are in good shape. Most vehicles now come with iridium plugs that need changed very infrequently. That being said, the plugs are a great place to start. Here’s a great video on how to see if a spark plug is bad.

Spark Plug Wires– On most modern engines, the plug wires are not nearly as long as they once were, but they can still go bad. Here’s how to tell if your plug wires are bad (video).
Coil Packs– Coil packs rarely go bad, but when they do, they can certainly cause P0304 in your Dodge Nitro. Replacing a set can be very expensive. Here’s how to test them.

Bad Fuel Injector– If you have a fuel injector that has gone bad, it won’t be able to properly atomize the fuel and you’ll get the P0304. Here’s a good video on how to diagnose an injector, it can be a little tricky. This is definitely not the place to start.
Vacuum leak– If your Nitro has a vacuum leak, it can be very difficult for it to get the right air/fuel mixture. This will cause the cylinders to misfire and it’ll throw the P0304 if the leak is around that specific cylinder on the intake manifold. It’s easy (and kind of fun) to chase one down. Popular Mechanics: How to find a vacuum leak.

Cam or Crank Sensors– This one is very unlikely, but it does happen. If the ECU is not getting the right signal from these sensors, the vehicles timing is not going to sync up and it’ll misfire.

Low Compression– If you have a leaking head gasket, bent valve, cracked head, etc.. that would cause compression to not be as high as it should, you’re going to get P0304. You should also feel the vehicle is down on power as well.
Hey Rick I appreciate your response but my Nitro's issue is not common. I have a unique situation with the fact that this vehicle has misfired for quite some time. It wasn't a hard failure until recently so it is easier to diagnose however since I have narrowed it down to a computer now the issue is finding a replacement unit. I have reached out to MAK which sells remanufactured computers. They shipped me one but that reman is defective because the truck ran worse even after soft and hard resets of the computer. I am working with their lead engineer to figure things out but thus far no progress. I will keep this forum up to date because if I can help someone else who has a similar issue I am good with that accomplishment.
 

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Discussion Starter · #7 ·
My Dodge Nitro's historical issue after three or four years of an engine misfire, I finally found the cause. The engine had an intermittent misfire for three years, so diagnosing it wasn't easy. The fault became a hard misfire about six months ago. I ran several tests using lab scope and other diagnostic tools. The coil's ignition patterns in the scope appeared to be firing correctly. Injectors, too, show strong inductive kicks in the electrical waveform. My diagnosis was hard to see until it became a hard failure. After much testing, I determined it was a fault transistor in the computer not firing the cylinder number 4 coil. I ordered a remanufactured computer from MAK TIPM Rebuilders HOME. I installed it last night, and the engine ran like a new vehicle again. Keep in mind this misfire has been an issue for several years although intermittent the last six months, it became a hard failure.
 

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Thanks for your UPDATE!
 

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Discussion Starter · #9 ·
I may have spoken too soon. I fixed the cylinder number four issue, but then I had an EGR and catalytic converter code. I replaced both components after diagnosing them using a Snap-on Scanner. The codes went away, but now I have cylinder 2,4,6 misfiring. I ordered two oxygen sensors, one upstream of even cylinders and one downstream of the catalytic converter. I plan to install them this afternoon and conduct further testing. I will post an update as soon as I install these components.
 

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Thanks for the update again and GOOD LUCK!!!
 

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Discussion Starter · #11 ·
Thanks for the update again and GOOD LUCK!!!
So I tested the system with the oxygen sensors, and no change in performance. I am meeting with a national automotive technical trainer this afternoon to do so further testing. I plan to narrow down this issue; however, it is puzzling and bizarre simultaneously. I am one not to go through components to keep one's sanity, but I am close. In my lifetime, I have troubleshot many vehicles and been able to diagnose them without throwing components. Further, my automotive technical skills are dated after several years (approx. 12 years) of not tinkering with fuel-injected systems. It will be interesting if I can pinpoint the issue and one for the books. Stay tuned for more to come.
 
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