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Code P0303

Tiny
CHRIS CALAMARI
  • MEMBER
  • 2005 HYUNDAI SONATA
  • 2.7L
  • V6
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
I have been checking out this code and I have swapped out plugs, moved injectors and coils. Ohmed out wiring under plenum, still get code. Trying to tell if it is the ECM. I do not know where to go next.
Tuesday, October 17th, 2017 AT 1:17 PM

8 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
Have you looked at compression or done a leak down test? Could be the result of low compression or a sticky/burnt valve. Toss a scope on the ignition and injector and see which one is dropping out and causing the misfire.
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Tuesday, October 17th, 2017 AT 3:56 PM
Tiny
CHRIS CALAMARI
  • MEMBER
  • 4 POSTS
Did compressed test and it is twenty pounds lower.
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Tuesday, October 17th, 2017 AT 5:20 PM
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Do a wet test this will show if rings or valves are the main problem. If compression does not come up you have a valve issue to look at. Also, just make sure that you do not have a vacuum leak as well. Check these first.
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Tuesday, October 17th, 2017 AT 5:23 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
Yep, as MHP says, do a wet test. 20 psi is enough to cause a misfire monitor to trip. Hopefully the wet test shows the same number. Easier to pull just the head and deal with valves than pulling the bottom end apart to play with the rings.
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Tuesday, October 17th, 2017 AT 8:45 PM
Tiny
CHRIS CALAMARI
  • MEMBER
  • 4 POSTS
Complete dry and wet compression test #1-193/235 #3-183/245 #5-190/255 #2-195/195 #4-195/210 #6-195/195. So I guess I can say the rings are gone?
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Wednesday, October 18th, 2017 AT 8:01 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
Nope, you have a valve issue on #2 and #6. With the firing order on that engine and the slightly lower compression in three the ECM is tossing out the P0303 because the crank is slowed by #2 and #3 then speeds up when #4 fires and it thinks #3 is the issue.

Do a leak down test and see where the leak is.
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Wednesday, October 18th, 2017 AT 9:13 AM
Tiny
CHRIS CALAMARI
  • MEMBER
  • 4 POSTS
I am retired and do not have the equipment any longer at my disposal to preform a leak down test. Is there another way to check?
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Wednesday, October 18th, 2017 AT 9:48 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
Not as easily. If you have a compressor the tool itself can be borrowed from many parts stores.
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Wednesday, October 18th, 2017 AT 1:52 PM

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