Codes PO302 and PO302, cylinder two misfire?

Tiny
JEFF HERMAN
  • MEMBER
  • 2003 BUICK CENTURY
  • 3.1L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 181,000 MILES
PO302 code and PO302 code pending, cylinder two misfire. Keeps wet fouling #2 plug with gas. Switched plug, wire, and coil pack and it remains with #2. Suspecting stuck injector but wanted to try checking pulse with Noid light first. It looks like I have to remove the plenum to get at the rail, connectors, and injectors? Any options?
Friday, July 29th, 2022 AT 11:46 AM

19 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

On this vehicle, the upper intake needs to be removed, as you already know. It certainly sounds like a stuck injector.

Rather than taking everything apart, you could get a fuel pressure gauge. Pressurize the system and see if the pressure drops quickly when the pump is off. It should stabilize and remain pressurized for one minute and not drop more than 5 PSI. If it does, you likely have a leaking injector.

Let me know if that helps or if you have other questions.

Take care,

Joe

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Friday, July 29th, 2022 AT 9:49 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
I will try that before removing the intake. Thank you.
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Saturday, July 30th, 2022 AT 12:07 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

No problem whatsoever. Believe me, I would want to find the quickest and easiest way to find it too. LOL

Let me know what you find.

Take care,

Joe
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Saturday, July 30th, 2022 AT 7:33 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
I tested the fuel pressure and got 48 PSI and holding. Running 45 PSI. No fuel in regulator. I did a snap test with the throttle, and it rose to 50 PSI and then back to 40 PSI and restabilized at 45 PSI. Disconnecting the line to the regulator caused a rise to 50 psi. All appears to be functioning properly, no failed injector. The only thing I see out of place is a line near the driver's side fender that has a quick connect that isn't attached. There is a Schrader valve with a green cap on it. It appears to drop down and head toward the rear of the car. Might have to do with the ABS though I haven't chased it yet? I also checked for vacuum leaks at the intake and found none. Thanks for your assistance, so with it still wet fouling number two where do we go now?
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Monday, August 1st, 2022 AT 12:44 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

The line with the green cap is likely a test port for the EVAP system. That is where at a low pressure, smoke would be injected into the system to locate leaks.

So, if the plug is wet, have you confirmed there is spark to the plug? If not, do so. Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

Let me know.

Joe
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Tuesday, August 2nd, 2022 AT 12:44 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
Cylinder 2 has spark. I put a spark tester inline between the coil pack and the plug wire.
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Tuesday, August 2nd, 2022 AT 7:41 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

If you have spark and fuel, then we must have a compression issue. I need you to check that next. Here is a link that explains in general how it's done:

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

I attached the directions below specific to your vehicle. It includes the manufacturer's pressure specifications.

Let me know what you find or if you have other questions.

Take care,

Joe

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Tuesday, August 2nd, 2022 AT 10:51 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
Unfortunately, I ran the test cold but here is what I found:
#1 130
#3 135
#5 130
#6 125
#4 105 w/oil 125
#2 75 w/oil 100
Not great looks like a ring issue, what about something like Restore that is supposed to fill the voids? I'm not a fan of additives
You can see I ran #2 last hoping against the odds, but we all knew what was up, lol.
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Wednesday, August 3rd, 2022 AT 8:58 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

That is a good indicator that the rings are worn. It could be a combination of valves or even a gasket, but the idea that it increased 25% with the oil, the rings are an issue.

As far as the restore, I've never used it, but it can't hurt. I'm a lot like you as far as additives are concerned, but considering the circumstances, why not?

Let me know if you try it and how it works.

Joe
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Wednesday, August 3rd, 2022 AT 7:04 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
I would actually rather have it be a head gasket because it wouldn't require an engine tear it down to do it especially since it's the front bank of cylinders. I'm going to either try restore or Lucas product or something I got to find the right stuff to try.
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Wednesday, August 3rd, 2022 AT 7:34 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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I understand and agree. Regardless, let me know if any of the additives work or at least help. Check for blue devil products. I was told they work well.

Take care,

Joe
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Thursday, August 4th, 2022 AT 4:18 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
I put in a bottle of 4 6 8 Rislone high mileage engine treatment with ring sealer. Drove to operating temperature. Sometimes service engine light flashes Sometimes on solid. Still has PO302 and PO302 pending. Rough idle, definitely not full acceleration but reaches freeway speed and drives fine.
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Thursday, August 4th, 2022 AT 7:29 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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So, is there an improvement? If there is, that's great. Have you tried clearing the codes to see if they come back?

Let me know.

Take care,

Joe
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Thursday, August 4th, 2022 AT 10:17 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
I cleared the codes and I'll check it tomorrow. New info I went out in the garage tonight and sprayed the wires with water and saw arcing on number 6 from the plug wire to the oil dipstick tube. Also, when it's in park, and you rev the engine, it only revs so high and then surges and falls off and surges and falls off almost indicative of a plugged cat. No coolant in oil or vice versa. Some sludge near the radiator cap. Someone told me there's wax in Dexron. Is that true?
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Thursday, August 4th, 2022 AT 10:41 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Time for a new plug wire. When you say it only revs so high and then surges, how high does it rev?

Also, I never heard of Dexron having wax in it. Are you referring to transmission fluid?

Let me know.

Joe
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Friday, August 5th, 2022 AT 4:38 PM
Tiny
JEFF HERMAN
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My mistake. No Dex cool. Have to check tomorrow on the rev, Replacing brake lines and fuel line. No pressure for now, bled out.
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Friday, August 5th, 2022 AT 9:02 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
LOL no problem whatsoever. There are too many things to remember.

As far as wax, no it isn't in DexCool. I attached the ingredients below.

Let me know if you have other questions.

Take care,

Joe

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Friday, August 5th, 2022 AT 11:18 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 468 POSTS
The vehicle doesn't have a tach so I'm guessing the falloff happens around 3000rpm. Then it revs back to that point and falls again. It doesn't do this when driving, but the acceleration from a stop is not V6 acceleration. I know this is another topic but I can't pursue the misfire without brakes. I put two lines in. At least one was from the ABS block. The bleeders are froze and I don't want to break them off so I opened the banjo on the drivers front. It had fluid. Couldn't open the line on the rear wheel cylinder or the bleeder. Is there a way to bleed the ABS block? Will try to open others tomorrow.
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Saturday, August 6th, 2022 AT 7:36 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Jeff,

You can bleed the ABS, but that isn't going to remove air beyond that point. How bad are the rear bleeders? If they are really bad, I would first wire brush them to remove as much of the rust as you can. Spray a good penetrating fluid on them and allow them to sit. Actually, I would let them sit overnight. Hopefully, they will open then.

Let me know.

Joe
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Saturday, August 6th, 2022 AT 8:02 PM

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