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P0303 cylinder misfire after camshaft replacement

Tiny
TOMTHEMINIMECHANIC
  • MEMBER
  • 2011 CHEVROLET EQUINOX
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 79,000 MILES
Car overheated due to a broken timing chain and was repaired by dealer under special warranty but they would not fix P0016 and P0017 which were set at the event.
After replacing all sensors, determined that the camshafts had rotated since they were pressed on. Followed TSB and also a very thorough path to replace them. Triple checked the timing marks and they are perfect.
Started car and all codes went away but after about a minute, it shuts off with a P0303.
The car runs rough during the period but gets a little smoother at higher rpm.

No codes are set except for the P0303. The previous codes did not set again.
Changed all spark plugs and swapped coil but the P0303 remains. Firing order is 1-3-4-2, so I made sure to swap cylinder 4 and cylinder 3 coil to make cover all bases.
I was unable to do a compression test because of a bad tester but the car ran fine for 10,000 miles.

There is no apparent head damage, coolant and oil are clean for 10,000 miles after the original timing chain replacement.

Any ideas?
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Monday, December 17th, 2018 AT 10:50 AM

5 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

I would start by doing a compression test on number three cylinder. there may have been valve damage from the timing chain failure.

https://www.2carpros.com/articles/how-to-test-engine-compression

Did they do any checks for the misfire?

Did the 16 and 17 codes return after the camshaft replacement?

Roy
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Monday, December 17th, 2018 AT 11:38 AM
Tiny
TOMTHEMINIMECHANIC
  • MEMBER
  • 3 POSTS
Hi Roy,

I attempted to do a compression test but I believe that the tester was defective. It did not build pressure on any of the cylinders, but it tried to jump to 30 on each cylinder. The car ran for 10,000 miles after the timing chain replacement.

Recapping checks above, moved all coils and replaced all plugs. Problem remains with cylinder #3. No coded returned (P0016 and P0017) after the camshafts were replaced. The camshaft replacement fixed that issue.

Could you please clarify if a P0303 is actually a problem with physical cylinder number four because of the firing order of 1-3-4-2 or is a P0303 really on the physical cylinder three?

Briefly the graph on the OBD2 scanner showed fuel pressure between 48 to 58 and varied with speed. Any thoughts on fuel pump or injector? The car does start and run for about one minute, but stoops with a P0303.
Thanks for the help!
Tom
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Monday, December 17th, 2018 AT 12:39 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Got it.

First, get your compression tester fixed or rent one. We need that reading first.

Yes, it could be an injector but need to verify there is no internal damage.

303 is for cylinder number three misfire. It is not the third cylinder in the firing order but a very good question.

Roy
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Monday, December 17th, 2018 AT 12:50 PM
Tiny
TOMTHEMINIMECHANIC
  • MEMBER
  • 3 POSTS
Hi Roy,

After they pulled the valve cover, they found that cylinder #3 had a sheared valve. The shaft is not visible in the hole. There could be damage to the cylinder wall. We haven't scoped it to be certain. The shop is recommending an engine swap.

Can you give me your thoughts on repair or replacement. If I were doing the work I would pull the head and see what's there, but I'm out of time for being without a car. I have a couple of questions:

1. If a shop is doing it and and I can get a low mileage (68K) complete motor delivered to them for about $2K would you lean toward replacement?
2. The GM book says about 11.8 hours for replacement including the add-ons. I think the hourly rate is about $85 for this shop which brings it to about $1000 for installation.
Excluding anything unforseen, what extras should I plan on besides Oil & Filter.
3. Would you consider any of the seals/gaskets to be in of changing? Cost is a factor and do I want to disturb them?

Thank you for taking a look. Your knowledge and opinion is greatly appreciated.

Tom
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Thursday, December 20th, 2018 AT 11:06 AM
Tiny
ASEMASTER6371
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Hi Tom.

Okay, did they agree to the 11.8? If they have to swap over external parts, plan on adding about 3 to 4 hours on top of the 11.8

85 is very reasonable for hourly rate. Remember one thing, you will have no warranty from the shop for the work since you provided the part. They will not be responsible for anything wrong with the motor once they turn the key.

Besides fluids, change the water pump, rear main oil seal, front transmission seal, and plugs and coils from your engine.

Check this site for your motor. Www. Car-part. Com Good site. I used them many times with great success.

Roy
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Thursday, December 20th, 2018 AT 12:12 PM

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