Oil inside intake manifold - JeepForum.com
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post #1 of 16 Old 07-08-2020, 09:51 AM Thread Starter
batman137
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Oil inside intake manifold

I’m replacing the intake/exhaust manifold gasket on my 2005 Rubicon, and I noticed a lot of oil inside the intake. I’m going to replace the valve cover gasket as well, but just wanting to know what the culprit could be and how to fix it.
180,000 miles on the engine.

I’m basically doing all of this in an attempt to cure a p0306 that doesn’t seem to be fixed by anything else I’ve thrown at it. Intake/exhaust manifold gasket looked good, but I guess a new one will be better? Lol. Ugh.

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post #2 of 16 Old 07-08-2020, 01:22 PM
mukluk
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It's from fumes and oil mist ported into the intake manifold via the CCV line from the valve cover, I'd consider what is visible to be somewhat normal given the mileage on the engine. Clean it out with solvent and make sure both CCV lines are clear. If you're concerned about the amount of oil mist making it into the intake, check for worn piston rings.

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post #3 of 16 Old 07-08-2020, 01:31 PM
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did you do a compression test?

I would CLEAN then reassembly new gaskets and seals (injector), might want to check the PCV/CCV system.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 16 Old 07-08-2020, 02:30 PM Thread Starter
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I’ve had 2 mechanics do a compression and leak down test and they said everything was fine. Didn’t give me any numbers of course (mechanics suck).

Would a leaking valve cover gasket cause an engine misfire on cylinder 6?
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post #5 of 16 Old 07-08-2020, 03:29 PM
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I would say NO.

As far as a misfire it could be Ignition, fuel, mechanical. Ideally a scanner to check codes and live data, Checking or changing Plugs, injectors, and then compression test,

I think a compression test would be advised.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #6 of 16 Old 07-08-2020, 05:10 PM Thread Starter
batman137
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I have done compression tests and both mechanics said the compression was good.
I did find a crack on the exhaust header for cylinder six. Would something like that cause a misfire?
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post #7 of 16 Old 07-08-2020, 05:11 PM Thread Starter
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Injectors and plugs have been changed. Fuel pressure test was good. Coil rail changed twice.
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post #8 of 16 Old 07-08-2020, 07:35 PM
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I still suggest a compression test. So we can see the #s.

you could swap #6 injector with #1 to see if code moves to #1.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #9 of 16 Old 07-08-2020, 09:23 PM
Jerry Bransford
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Normal as described above. Start the engine once it's back together and help it ingest an aerosol can or two of throttle body cleaner that'll help clean that gunk out. Spray 1/3 of the can in at idle rpms so the cleaner will pass through the IAC (idle air controller). At rpms above idle it will bypass the IAC.

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post #10 of 16 Old 07-08-2020, 10:04 PM Thread Starter
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Thanks Jerry. I noticed a small crack around the cylinder 6 exhaust manifold. Would you suggest I patch it with fireplace cement, or would you recommend something else?
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post #11 of 16 Old 07-10-2020, 07:35 PM Thread Starter
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Everything is back together and looks cleaner than it’s ever been. She runs. Feels strong. I’m going to use a can of throttle body cleaner tomorrow. My friend said it might destroy the O2 sensors!? Never heard of that. Can anyone comment on that?
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post #12 of 16 Old 07-10-2020, 07:44 PM
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Read the can: if it says it's sensor-safe throttle body cleaner then you'll be fine. Be sure to follow the instructions.
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post #13 of 16 Old 07-10-2020, 11:08 PM
Jerry Bransford
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Quote:
Originally Posted by mukluk View Post
Read the can: if it says it's sensor-safe throttle body cleaner then you'll be fine. Be sure to follow the instructions.
X2. Modern throttle body cleaners I've seen were all sensor safe since pretty much all modern engines have O2 sensors. Carb cleaners would probably wipe out an O2 sensor pretty quickly.

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post #14 of 16 Old 07-11-2020, 06:57 AM
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To let you know we are following along - might want to do at night sometimes a wee bit O smoke. Let us know -

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #15 of 16 Old 07-11-2020, 03:56 PM Thread Starter
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I put about 2/3 of a can through it. It was the first warm up since putting everything back together. There was a wee bit O smoke while doing it from the exhaust/intake manifold area. That stuff really wants to big the engine down.
I’ll put a wrench on everything in the morning again to make sure it’s all tight, then run the rest through it and take it to the car wash for a good engine bay cleaning with degreaser.
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