Newbie with P0300 Code issues
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Newbie with P0300 Code issues
Got woke up by my wife yesterday with truck didn't want to start and when it did, made funny noise then started missing/shaking. I went out and sure enough it's missing bad. Pulled code P0300, last time this happened got a code for specific coil being bad. Replaced coil and all was golden. This time I haven't got a clue what to check first. It's an 05 2wd 1500 5.7 Hemi QC SLT w/97k miles. It ran perfectly the night before. I'm thinking it's a valve spring, but want to know what you guys think before I go tearing into it. Also, when I try to start it now, I have to give it quarter to half throttle before it will start up and it dies when you put it in gear or turn on A/C.
Thanks for your time and input.
Sam
Thanks for your time and input.
Sam
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Joined: May 2005
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From: Central Oklahoma
Before you tear into anything, be certain to understand the trouble code:
P0300 Random/Multiple Cylinder Misfire
P0300 Random/Multiple Cylinder Misfire
Possible causes
- Faulty spark plug (s)
- Faulty ignition coil (s)
- Clogged or faulty fuel injector (s)
- Intake air leak
- Fuel injectors harness is open or shorted
- Fuel Injectors circuit poor electrical connection
- Ignition coils harness is open or shorted
- Ignition coils circuit poor electrical connection
- Insufficient cylinders compression
- Incorrect fuel pressure
Tech notes
The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see "Possible Causes"
When is the code detected?
The control module monitors the crankshaft speed and has detected a misfire condition
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/loss of power
- Hard start
- Engine hesitation
P0300 Description
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.
- Faulty spark plug (s)
- Faulty ignition coil (s)
- Clogged or faulty fuel injector (s)
- Intake air leak
- Fuel injectors harness is open or shorted
- Fuel Injectors circuit poor electrical connection
- Ignition coils harness is open or shorted
- Ignition coils circuit poor electrical connection
- Insufficient cylinders compression
- Incorrect fuel pressure
Tech notes
The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see "Possible Causes"
When is the code detected?
The control module monitors the crankshaft speed and has detected a misfire condition
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/loss of power
- Hard start
- Engine hesitation
P0300 Description
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring.
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I've already looked it over for loose connections and vacuum leaks. Couldn't find anything loose or cracked. It acts more like a bent valve misfire (had a firebird with a bent valve once and it ran the same way).
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I'm going to try plugs and a can of fuel injector cleaner. Pulled #1 plug and it was pretty black and tip was worn (rounded corners). Another thing that probably lead to this issue is that I drained the tanks on my boat and dumped the fuel into my truck's tank. It was 91 premium fuel mixed with about 30% 100 octane race gas. About 6 gallons was very fresh, but about 8 gallons was from April (only used pass side tank once during whole season and only about 2 gallons worth). So I'm thinking that maybe had some condensation in the gas from that side not to mention 6 months old sitting in old dirty tank. I did run it through a filter when draining tanks so I'm not worried about sediment.
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4.7 Troubles
I recently had a round of trouble. Got the same Engine Misfire Code on my 2007 Dodge Dakota 4.7. I took it to Local Dodge Service ,,They cleaned the Throttle Body and did a Tune Up, Problem Solved they said. Drove 2 miles after that it started misfiring again. Took it back to the shop they said some trash may have got in during cleaning. about 2 weeks later,,same problem. Decided to take it to a Different Shop. (Not Dodge) #2 Injector was bad. No problem with it since then. Dodge Not Fixing the Problem was around 300.00 including parts,,,Actual Repair at another shop 150.00 including parts
Last edited by jcintennessee; Nov 15, 2013 at 01:39 PM.
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Okay changed plugs (first time, 97k miles on original plugs) and added bottle of Gumout fuel system cleaner. Plugs were very black and worn. It ran smoother for about 60 seconds but got P0172 and P0113 codes immediately. I remembered I forgot plug in connector on the front of the air box. Connected that and reset codes. The light didn't come back on. Still running rough. Smells super rich. No smoke, but shut it down after about 5 minutes because I'm worried about plugging up cats with it running so fat. Noticed throttle body is nasty, but the symptoms started up overnight so I don't think it is the root cause. Should I try new O2 sensor next?
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Try some Seafoam thru the brake booster vaccum line. About a half a can is what most use. When you have almost half a can in pour a little extra in tomake it stall and let sit for 20 minutes and reconnect the vaccum line and go for a drive. Any carbon buildup should be burned away including any on the O2 sensors and the cats.