TrailBlazer :: Random Misfire And Code P0300 - Rough Idle
Dec 8, 2012
'02 TB w/ code P0300 / Random misfire. Started the other day when it was very damp out, FWIW. Feels like ur driving on rumble strips during acceleration. Rough idle also. It does not do this continually though as after a while (minute) it clears up and runs smooth for a while then runs rough & light will again for a while. I seafoamed it today since it been about 60k since last seafoam. I thought that might have worked until I drove about 20 mile and it went rough again. I also cleaned the oil out of the cam sensor elect connector, since that caused rough running before, although it didn't throw that code. It seems to be very intermittent. '02 TB, 185k miles, orig plugs changed at 125k. Is it actually just going in & out of a limp-mode? O2 since it's random ???
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Just started getting a p0300 random misfire code on the durango a couple days ago. pretty sure it isn't moisture related since it started on a nice sunny day. it was running pretty rough so it was obvious that it was misfiring. I changed the plugs since it was about time anyway, and they needed it and I cleared the codes. new plugs (put in the oem champion copper plugs) didn't make the problem go away. The engine still ran rough and the code came back. 2 of the plugs looked like they may have been fouling a little bit. they were a fair bit blacker than the rest of the plugs. I went ahead and changed the coils on those two cylinders and reset the codes again. Still runs rough and the p0300 came back. where do I go from here? I am not getting any specific cylinder codes so it makes sense to me that it isn't one or two cylinders not getting spark. 2003 durango 4.7 ....
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04 trailblazer, 4.2. Running rough and SES light on. Had codes pulled and showed p0340 (CMP sensor circuit malfunction) and p0300 (Multiple engine misfire detected). Replaced the CMP sensor and left negative battery cable unhooked for 20 minutes or so to clear the codes. Upon start up no more SES light and idle was slightly better. Within seconds it SES was back and it is again running poorly. Cruise control is no longer functional as well.
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Recently i started the car and it was shaking more that usual. the CEL light came stating P0300 with random misfires. It sounds and feels like misfires so i believe this is true.
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2004 GMC Sierra 2500 HD, 227,000 miles 6.0L V8.
While driving up hills or increasing load, the CEL will flash multiple times, I pull over as I know CEL flashing is not good. I turn the truck off, allow it to sit for a few minutes, whip out the code scanner, only code that was there happens to be P0300. Truck has poor MPGS, idles rough, loss of power. this happens every time I drive this vehicle as I use this truck to pull my trailer that weighs around 4000 lbs. Problems come and go. Some days I can drive the truck for an hour with no problems, come up to a red-light, BAM, CEL is flashing, truck is bouncing side to side due to the poor idle, other days this happens while sitting in the parking lot of my job with the ac on.
Truck has been to the shop several times as I'm no mechanic. Parts replaced are as follows:
- Fuel pump
- Throttle Body
- All plugs
- All wires-All Coils
- Intake Manifold Gasket-
- Battery
- Sensor 1 Bank 1 O2 Sensor
- Sensor 1 Bank 2 O2 sensor
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I have a 2004 Hyundai Santa Fe 3.5L V6 when i was driving a couple of days ago the check engine light flashed and after a while it stayed on the codes are P0300 which is a random misfire as well as a misfire in cylinder 2, 4 and 6
I replaced all 6 spark plugs and the 3 spark plug wires still the same issue. The car hesitates when accelerating when i accelerate it looks like it wants to stop the rpm goes to almost zero and then it moves and so on. the rpm goes up and down like crazy.
Sometimes it won't move past 1000 rpm I'm moving 60mph and still on 1000rpm and sometimes it works just fine like there is no issue at all. When idle the car is fine and everything seems normal it stays on 900rpm. The car has 158K miles on it.
I uploaded a video to show you what's happening to the tachometer when I accelerate [URL] ....
I'm on a limited budget I'm thinking of changing the ignition coils but i want to make sure that's what is causing the problem first because i spent 200$ to change spark plugs and wires and the mechanic didn't fix the issue.
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I have a 2000 Impala with a 3800 V6 series 2 with 165,000 miles. The only code I had was a P0300 Multiple random misfire that occured off and on at first, Worse in the city Better on Highway. It would start running on half the cylinders and bogged down, with the check engine light flashing, after getting onto the highway it would straighten itself out at first. I thought i had water in the gas so i ran some heat through it. straightened out for a day then happened again so I thought maybe a should run some premium gas in it, The car ran like total crap until the premium was gone, so i thought maybe it's running too rich, I put 87octane in it and it ran great for a day or two, then it gradually got worse to where it would not straighten up on the highway, tried to die at stoplights and i had to drive it with 2 feet to get it home and park it. I've replaced the battery, spark plugs, wires, ICM checked good, coil packs are good, replaced fuel Pressure regulator, looked for arcing on the spark plug heat shields and it will not start. It turns over but doesn't try to ignite and when I get the slightest rumble of ignition, it backfires up through the manifold and I see a puff of gas or light smoke by the exhaust manifold.
The car had a vacuum leak around the intake manifold cover gasket and a leak on the fuel rail. I pulled the fuel rail off my impala, snugged up the rest of the intake bolts then disassembled the fuel rail, flushed it out and cleaned the injectors the best i could, then reassembled it. before i re-installed the fuel rail I hooked it up to the fuel lines outside of the engine and tried to start the vehicle. all injectors had a nice spray pattern. So i installed the rail and it still didn't start but it had more combustion than before although it's still backfiring like before. Checked the fuel pressure by turning the key on and the fuel pressure went to zero very fast. I blew the rail out with air so to make sure i didn't damage the regulator I replaced it with the old one, ran the test again with same results, so i reinstalled the new regulator. I performed the fuel pressure test a few more times while moving the fuel hoses and when i moved the back supply line the vacuum loss stopped then dropped to zero when i let off of it. So I replaced the fuel line connector and O-rings on the injectors. It no longer has a vacuum leak.
I cleaned the EGR Valve out and had no luck there, then I removed the Idle Air Control Valve-pushed the pintle in, re-ionstalled it and WooHoo! it started! Although it still ran like crap with the same random misfire I was still happy to hear it start.I pulled the plugs on it to do a compression test and all 6 cylinders have between 180-190psi so the engine is in good condition mechanically. I installed new plugs before getting the car restarted and when i removed them for the test they were covered in thick black soot after running for roughly 15 minutes max.
I have (2) 2000 Chevy Impala's so I've swapped sensors from my wifes car to see if it would fix it. I've tested the following MAP, MAF, IAC, coil packs and ECM. None of these made the car change. I believe it is a timing chain because the car has never had a new timing chain and is way overdue, but I haven't had a code for a crankshaft position sensor. Can the timing chain be bad without throwing a code? It's not out of time enough to change the valve timing because I had a good compression test but its not firing right and still has the multiple random misfire. I have not checked or received a trouble code for o2 sensors, crankshaft position sensor or cam sensor. Something has the timing retarded and is dumping extra fuel into the engine because my new plugs looked like they were in the engine for a year.
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I have a 2007 Hyundai Accent GLS. I just got it from a used car dealership (local) and it runs perfectly. It had a misfire code when i first got it, for all cylinders plus the p0300. It went away when i started the engine again, and didnt come back til a month later (Now). now it wont go away.
I went to advance auto and had them use their OBD2 reader for a trouble code and i got p0300, p0301, p0303, p0304. No other codes present.
I am not feeling anything bad, and from what I am told, a misfire feels like a hard shift. This is of course after getting the plugs and wires changes as well as an oil change. Standard preventative maintenance.
The mechanic used OEM parts got from local parts shop. i think the OEM plugs are the copper ones. I would have preferred iridium as they arent that much more expensive but I don't want to pay for another plug change.
The only symptoms I can think of, is that according to google, I should get around 380 miles to a full tank (11.9 capacity, 32 mpg city). I am only getting 280 from full tank to gas light.
I have also gone through a lot of oil. I checked the dipstick and it was below the low line, so i bought a quart of high mileage oil (same exact brand and type of oil that i gave to the mechanic to use) and it went to just above the full line. This was at around 1500 miles after oil change.
After visiting multiple sites about misfires, i found a few things that caught my attention. One is a site called auto service professional, which talks about the OCV for the MC accent. A lot of sites also recommend gaping the plugs at .035.
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My 03 Chev Avalanche is giving me a P0300 code (multiple or random misfire). With no distributor or individual coil is this something I can fix myself or is it shop time?
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Have an 06 F150 5.4 3v with no power. spark knock. rough idle. wants to die while driving, and random misfire code. Have replaced fuel pump, filter, coils and plugs. What to check next? Already thought of EGR - it doesn't have one.
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Had this code show up after the warning light came on and then the light went away after two day, the car seems to be a little sluggish now. I have read that this is a random engine misfire and it could be a bad plug..
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I know it is a random cylinder misfire code however I started my car in the morning and it was fine I moved it and put it back in my driveway. I started it up later and waited for it to heat up i came back outside 10 min later and my check engine light was flashing and my car was shaking like crazy you could tell the engine was misfiring like crazy. I had under a quarter of a tank but not empty yet. I shut it off and turned it back on and it was still doing it. I drove the mile to the gas station the way it was.
Under partial throttle it was revving to 4500 and over 5, had to let of throttle to make the car shift up a gear. I filled up and started the car again performed fine after that however the check engine light was solid now and still on. I went to my local mechanic and he read that code P0300. I changed my spark plugs that day and they were crap the original spark plugs I have 65,xxx on my car now. Car is smooth now. I cleared check engine when i saw him first and it did not come back on all day even before i changed the spark plugs later that night. Why my light was flashing and why my car was acting like that till i filled up?
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New plug on right, lower bank 2 plug on left
Started getting a P0300 and various misfire codes for random cylinders. Truck has 95,000 kilometers so figured I would change the plugs. Several of the plugs on the lower bank on both sides were pretty much toast. Most of the plugs on the top looked good. All of the plugs had a small deposit where the spark hits the ground probe. Picture is typical plug from lower side. changing the plugs should make a big difference in how she runs and eliminate the codes.
Took right on 4 hours same as dealer said it would. I would have got it quicker but it was not a race.
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I have a 2000 Suburban 4wd that has a p0300 code. The misfires are coming mainly from #2 and #7 cylinders. Misfires only occur at idle. over 1500 rpm the misfires disappear. I have put new A/C Iridium plugs in, new wires, and new coil packs on both cylinders but the problem is not any better. All 8 fuel injectors all go to 55 psi when activated and drop to 28 when released. All tests were done with my Snap-On Solus.
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97 chevy k1500 with 305, engine rebuilt by shop 60k ago, last few months only drove truck 4-5 times, last time driving gave p0306, new plugs, wires, cap, rotor, cleared code, now gives p0300, took intake apart removed spider, sprayed/scrubbed each injector and poppet with cleaner, but no way of cleaning the line between the injector and poppets. No change after cleaning. Also ran injector cleaner through tank. All vacuum hoses look in good order, sprayed carb cleaner around intake to check for leaks at intake/throttle body, no leaks.
Checked TPS, IAC, MAF, Coil and fuel pressure, all good except fuel pressure was 52-54 while idle, replaced fuel pump, screen filter and main filter, cleared code, rough start and rough idle still gives p0300. Checked coil with ohmmeter, between posts A & C, Chilton says 0.1 ohms, i got 0.5 ohms, went to autozone and had them check a new coil, it have 0.5 ohms......? Can drive at higher speeds and runs smooth, but idle is poor almost dies.Checked fuel pressure after pump replacement, still ~54 psi. Stumped and don't want to throw more parts at it without a proper diagnosis. Have a OBDII pocket scan tool, but can't find manual, will try to find manual and see if I can pinpoint the misfiring cylinders.
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I have a 2000 Toyota Avalon XLS with 134k miles, engine is a v6 (3.0). It has a rough idle and a steady misfire. You can drive it sometimes and it will run perfect and you can drive it sometimes and it will misfire. I am getting codes P1150, P0300,P0302, P0304,P0306. Driving me nuts.
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I have a 100% stock 2004 Celica GT ~125,000 miles. Over the last few months I have been getting a rough idle and stumble at low rpms. The other day the car would not restart after sitting for about 20 minutes. Only recently has it actually thrown a DTC. The error codes were for misfires (P0300, P0301,P0302,P0303, P0304). I don’t get a code every time but the problem seems to be more noticeable if the car has been ran for a while, sits for 20-30 minutes while in a store and then when I try to start it when I come out of the store is when the problem most often occurs. When it restarts it will stumble at low RPM and if I hit the gas it has little response and misses badly. I have never used a scanner until now. I am using a Autel MS509 scanner and I am not sure it is giving me the correct diagnostic numbers for the live data. I think the DTC are correct but the live data is questionable.
Here is what I have done so far.
- Cleaned IAC valve (completely removed and cleaned)
- Searched for vacuum leaks using carb cleaner
- Cleaned MAF sensor
- Replaced all 4 injectors
- Replaced upstream and downstream O2 sensors
- Replaced Coolant Temp Sensor
- Ensured cam tensioner is providing adequate pressure to the cam chain
- Tried 2 sets of new Iridium NGK plugs and a new set of Bosch Copper plugs
- Moved coil packs around
- New air filter
- New fuel filter
- SeaFoam through intake and gas tank. I have not mixed in the oil.
- Compression Test (1=190,2=190,3=160,4=178)
Things I have not done.
- Taken it to the stealership
- Fuel pressure test
- Valve Clearance
I am concerned about the compression test because according to the service manual it should be around 218. I was using a Harbor Freight compression tester and I am not 100% sure I had a good seal with the tester.
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Just did the timing chain, phasers, oil pump and lash adjusters on my 05 5.4 s-crew. Always had a bit of a rough idle but now it's worse. If the truck idles for an extended period it sets a p0300. Just off idle the misfire is gone. It does seem a touch down on power but otherwise runs great. I did have the plugs out during the work. I cleaned them, applied anti seize and re installed. The previous owner had the plugs and COPs changed 10k miles ago. Plugs are motorcraft and coils are aftermarket.
I monitored with oreillys crappy scan tool and the miss only happens at idle. It is not a dead miss; unplugging COP on each cylinder still makes it worse.
Truck idles warm at like 570 rpm and if I hold my foot on the pedal to raise rpm a bit miss goes away.
Each cylinder is logging misfire counts with no rhyme or reason. The only thing odd during the timing job was 4 spark plugs were partially loose.
I'm sure the timing is correct; I used the OTC crank tool and for timing kit. Truck has 150k, front 02s are fairly new...
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I have a 02 Trailblazer that on Monday it gave me a code of P0300 (Random misfire), then two days later P0301 (Number one misfire); (I replaced plugs, boots and cam sensor) ran fine for 1 day now its a P0758 code (Shift solenoid B Electrical).
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My brother-in-law brought me his 2004 Trailblazer that had an extremely rough idle and would die if ya thought about the air conditioner and all! So he had replaced the cam sensor, didn't work. He replaced the spark plugs didn't work. He replaced the fuel filter didn't work. So he asked me about it and ran across a fella talking about the CAM ACTUATOR SOLENOID and explained all about what to look for and such and low and behold new solenoid later purrs like a new one!!! It is look right above the power steering pump there is a plug in the side of the engine there with electric wires running to it.
One of the signs of being bad is oil inside that 2 wire plug just pull it off and look in it. Now to remove it you will have to take the power steering pump loose so it will move back out of the way so you can pull the solenoid out of the engine if ya get it out look on the end there are grooves running around it with little screens on them see if any are gone or coming apart, this usually sets a P0016 code which is stuff interfering with the sensors inside. If there is any oil in the plug or any screens missing then it will have to be replaced.
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I hookup an OBD2 tester on my Prius 2014 Plugin and saw the OBD2 P0300 - Random Misfire. I did a reset and the error still came on. I also tested my friend Prius 2014 Plugin which is factory stock and had the same error. Wonder if that is by design or not. Going to take my ride into the dealer on Friday for my 25K maintenance and have them look into that error. P0300 can be anything. Hopefully doesn't cause more problems down the run..
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