Random misfire

Tiny
SAMGREW
  • MEMBER
  • 2009 CHEVROLET AVEO
  • 1.6L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 125,000 MILES
Car now runs but surges when idling and bogs down when accelerating, will only get to about 10 mph. Just replaced ho2 sensor.
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Wednesday, June 11th, 2014 AT 12:52 PM

18 Replies

Tiny
SATURNTECH9
  • EXPERT
Have you checked for codes in the computer yet? Also have you checked for a plugged cat yet?
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Wednesday, June 11th, 2014 AT 12:59 PM
Tiny
SAMGREW
  • MEMBER
Code P0300 Rodded cat.
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Wednesday, June 11th, 2014 AT 2:36 PM
Tiny
SATURNTECH9
  • EXPERT
Has your timing belt ever been changed?
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+3
Wednesday, June 11th, 2014 AT 5:24 PM
Tiny
SAMGREW
  • MEMBER
Has timing chain, not belt. No has never been changed.
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Thursday, June 12th, 2014 AT 9:26 AM
Tiny
SATURNTECH9
  • EXPERT
I see a belt for the vehicle you listed that's why I asked thought maybe the belt jumped.Have you checked the quality of the spark? You may have a weak coil
Read the guide below, it will help

https://www.2carpros.com/articles/how-to-test-an-ignition-system
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Thursday, June 12th, 2014 AT 9:44 AM
Tiny
DONALDDING
  • MEMBER
  • 2005 CHEVROLET AVEO
  • 1.6L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 86,000 MILES
Random missfire at idle. P0300. No cylinder missfire code. No other code. Engine compression 120psi on all 4 cylinders. Spark plugs clean. Engine vacuum low but not swing wildly. No vacuum leaks. Small intake manifold easy to check vacuum leaks. Ignition timing dance between -5 to +15 at idle. When the engine rav to 1600 rpm every thing back to normal. Smooth no missing.I changed, swaped or disconnected every sensor and computer with no luck. Could the engine has mechanical problem but still have good compression? I also put gas treatment in the tank in case there has water. I filled tank 2 times after I burn up all the gas. Thanks
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
SATURNTECH9
  • EXPERT
Have you checked to make sure you have spark at each cylinder?While it's missing at idle?
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
DONALDDING
  • MEMBER
I don't know how to check that since I don't have anything can do that at my disposal. I only have a Autel AL619 OBD live data scanner. I put a new coil pack, new wires and new spark plugs at early stage. Since this is a 2005 so OBD self diagnostic is not that sensitive as cars made in recent years.I never got a single cylinder missing code. What could cause ignition system not produce sparks at idle speed? The spark plugs very clean and not have any black color at all. Thanks for help.
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
SATURNTECH9
  • EXPERT
You could have a miss at idle and not feel that miss you still have at a higher rpms so much at higher rpms I have seen that happen Alot. So is it a Constant misfire at idle?If so let the engine idle while it's running carefully pop the wire loose from the spark plug then put it back on. Do this to all four spark plugs careful not to shock yourself. You will hear if the spark is working for each plug. Plus not if pulling one of the wires off doesn't change the way the engine runs?That will tell you which cylinder isn't working.A bad coil spark plug or spark plug wire will cause one cylinder to not spark. Let me Know what you find.
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
DONALDDING
  • MEMBER
I can tell if there has any miss by put my hand at exhaust pipe. I feel those pulse at idle but there has not even been a single one at 1600 rpm. There seems has a gap between 900rpm and 1600rpm. Even a slightly movement on throttle which I put 2 layer of printing papers on the throttle stop screw.I can't turn that screw because they put some locktight. This is a used throttle I bought from ebay but it actting same as my old one so I don't know if both of them are bad. This car use waste spark ignition coil pack so if the coil has problem would cause two cylinders miss and stall the engine but my engine never stalled. I have new NGK wires and spark plugs.
The slowest idle I can achieve is 1600rpm by sticking paper between stoper and lever. The idle will goes to 2200rpm if I stepped on the gas padal. Do you think this could be a bad throttle?
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
SATURNTECH9
  • EXPERT
Honestly I have two posts per coil and seen only one spark many times it is possible. Have you looked a vacuum leak?You could have a lean miss.
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
SATURNTECH9
  • EXPERT
Honestly I have seen two posts per coil and seen only one spark many times it is possible. Have you looked a vacuum leak?You could have a lean miss.
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
KONE
  • MEMBER
  • 2004 CHEVROLET AVEO
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 35,000 MILES
It'2004 aveo 1.6liter Throwing codes p0700 transmission control system, p0300 random misfire detected, p1781 engine torque signal circuit. Car randomly dies driving on the hiway, pull over, stop restart car goes again any answers? My local chevy dealer tells me thier is nothing wrong! Please help
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
BRIAN 1
  • MEMBER
Some customers may comment on an engine misfire on rare occasions. Typically, misfires related to this valve sealing concern will be very intermittent. The intermittent misfires may or may not be felt by the driver and they will normally occur during engine warm up, deceleration, highway driving, wide open throttle acceleration, and/or uphill driving.

Additionally, DTCs P0300, P0700, and/or P1781 (2004 models)/U0401 (2005 models) may be set. If a brief engine misfire occurs, it is possible that a P1781 or U0401 DTC may set without the presence of a DTC P0300. The engine misfire may be experienced due to a valve sealing concern. Replace all 8 exhaust valves, all 8 intake valves, and all 16 valve seals or replace all 8 exhaust valves and all 16 valve seals depending on the VIN number.
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
DONALDDING
  • MEMBER
Thank you for point out the possibility two posts per coil and only one spark. I tried before using timing gun and I did find out that one spark plug wire has stronger light than another wire even they came from same coil and both coil have similar results. How could it be? I am really baffled. I changed a new coil but no improvement from old one. I also changed a used computer and also is same. No vacuum leaks and long term fuel trim always negative around 15%. I am really appreciated your help. Can you tell me why this 2 post from same coil could have different voltage?
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
SATURNTECH9
  • EXPERT
Unless you're using something like a lab scope to measure the secondary voltage of the coil a timing light can't tell you if one coil post has a greater voltage etc then another coil post. Timing lights are for timing the engine not measuring voltage. How did you look for vacuum leaks?Smoke is the best way to look for vacuum leaks. Brake clean isn't a accurate way to tell if you have a vacuum leak or not
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
DAVIDGREE74
  • MEMBER
  • 2004 CHEVROLET AVEO
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 167,000 MILES
I have changed the plugs and wires on my aveo, and there was oil around the spark plugs. So, I put on a new valve cover gasket with the gromets, and that solved the oil problem. But, it is still random misfiring. What else could be the problem?
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Could be caused by vacuum leak or bad fuel.
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Tuesday, December 18th, 2018 AT 6:09 PM (Merged)

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