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Engine misfiring

Tiny
JACK DAVIDSON
  • MEMBER
  • 41 POSTS
The Bosch 4428s are the "NO-Gap" style plugs and I haven't messed w/ that. I was going to test the coils if I kept getting specific misfires (P0301-P0306), but those DTC(s) went away. Now it just the P1399. Is there a specific procedure to test the coil itself, other than faul isolating thru the wiring between the plug-connector and the ECM? I can do that, but didn't want to as there's no specific misfire to id which cylinder I should testing?
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
JACK DAVIDSON
  • MEMBER
  • 41 POSTS
Additionally, someone told me to replace the Bosch w/ the NGK(s). I thought the Bosch were pretty good plugs. But if they're part of the problem, I'ss certainly replace them.
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
The gapping might not be as specified. I would try replacing them first to see if it solves the problem.

Have the compression tested if changing the plugs does not help.

Coils can be tested for resistance but if it is misfiring on all cylinders, the likelyood of all coils failing at the same time is almost zero.

Apart from compression, check the fuel pressure and exhaust system.
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
JACK DAVIDSON
  • MEMBER
  • 41 POSTS
Thnx-a-million. I'll put new NGK(s) in and see.
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
You're welcome.

Good luck and have a nice day.
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
JACK DAVIDSON
  • MEMBER
  • 41 POSTS
Put in new NGK Platinum plugs gapped to.44, but still getting multiple misfires. Can't do compression check myself and not getting any codes for fuel delivery system errors. So I gotta go to my pro I guess. Thnx for all the help guys!
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
NEAL 0101
  • MEMBER
  • 1 POST
  • 1999 ACURA TL
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 70,000 MILES
The car has no power and idles rough. What would cause this misfire problem on all cylinders?
Thanks
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
P0300 Random misfire/P0306 no. 6 cyl

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Did you check the fuel pressure?
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
JACK DAVIDSON
  • MEMBER
  • 41 POSTS
No. But a mech friend said if one Coil/boot causes a misfire it sometimes confuses the computer & reports multiple cylinders. He suggested unplugging coils 1-@-a-time while idling to see if I can isolate the skip to a single cylinder. Duh! I should've thought of that istead of relying on the DTC to try and isolate. Thnx.
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
JACK DAVIDSON
  • MEMBER
  • 41 POSTS
That was it! Unplugged #2 cyl w/ eng idling and got no chnge. All others RPM(s) dropped. Swapped coil w/ #5. Now no change in RPM when #5 unplugged. Replaced coil. Skip gone! So. EGR fixed, intk mnifld cleaned. EGR prt cleaned out. Good NGK plugs. Skip GONE! Runs like a new Singer Sewing Machine! Thnx for all the help!
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
You're welcome.

Glad to know you have fixed the problem.

Have a nice day.
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
BRADLEY_E_THOMAS
  • MEMBER
  • 1 POST
  • 1999 ACURA TL
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 148,000 MILES
I replaced my O2 (bank 1) sensor and a week later my vehicle began misfiring on all cylinders. I ran the codes and it said P0301, P0302, P0303, P0304, P0305, and P0306 - all cylinders misfiring - as well as the Multiple Misifre code of course. It also registered P1399 - Manufacturer Control Ignition System or Misfire - which is not an acura trouble code. I therefore replaced all my spark plugs, my EGR Valve, and one Coil Pack that had a hairline fracture. I cleaned my EGR Valve Ports using Sea Foam twice and used MAF Sensor cleaner to clean the MAP Sensor. The vehicle still registered P1399. Shortly after, P0305 registered followed by the remaining P030's. The vehicle feels like it's misfiring. My catalytic converter needs replaced soon. What can be the cause of the misfire? And what would cause the P1399 trouble code?
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)
Tiny
DAVE H
  • MECHANIC
  • 13,383 POSTS
Check/clean/replace also check the wiring

CKP Sensor. Behind crankshaft pulley, attached to oil pump.
Crankshaft Position (CKP) Sensor
Sensor detects speed and position of crankshaft. Used for fuel injection timing and ignition timing.

Check freeze frame data. Perform PCM reset procedure and clear freeze frame data (if present) and DTC(s). See PCM RESET PROCEDURE/CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. Exchange spark plug from suspect cylinder with one from another cylinder. Connect SCS service connector. See Fig. 1. Test drive vehicle several times in freeze frame data range. If there is no freeze frame data of misfiring, test drive vehicle under various conditions and try to duplicate malfunction. If DTCs P0301, P0302, P0303, P0304, P0305, P0306 or temporary DTC P1399 are set, go to next step. If DTCs P0301, P0302, P0303, P0304, P0305, P0306 or temporary DTC P1399 are not set, problem is intermittent, possibly due to fouling spark plug. Misfire is not detected at this time. If misfire follows spark plug to different cylinder, replace spark plug. If misfire remains in same cylinder, go to next step.
Exchange fuel injector from suspect cylinder with one from another cylinder. Let engine idle for 2 minutes. Test drive vehicle several times in freeze frame data range. If there is no freeze frame data of misfiring, test drive vehicle under various conditions and try to duplicate malfunction.
If DTC P0301, P0302, P0303, P0304, P0305 or P0306 is not indicated, misfire condition is not detected at this time. Possible intermittent fuel injector poor connection. If misfire follows injector to another cylinder, replace faulty fuel injector. If misfire remains in same cylinder check valve adjustment, cylinder leak down, engine compression and Crankshaft Position (CKP) sensor. Repair as necessary.
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Tuesday, April 7th, 2020 AT 1:21 PM (Merged)

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