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Bad idle with fuel cap buzzing


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Hello,

I am a new owner of 2000 996 C2. It seems to run perfectly, except idle.

Idle is rough sometimes, hunting between 650 rpm and 950 rpm.

In one day, I found funny buzzing sound from the right side of the fender.

It comes every few seconds almost periodically, and lasts 1 or 2 seconds.

When I opened the feul cap, it diminished immediately and completely.

Then, idle seemed to be stable.

After re-cap, the buzzing come again after several seconds.

Drametric diagnostic tool reads fault code P1128 and P1130.

Air Mass was already replaced.

Actual values:

FRA 0.91 both bank

RKAT -3.61 both bank

Is this RKAT value is normal range??

Thank you all in advance for your help.

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Hello,

I am a new owner of 2000 996 C2. It seems to run perfectly, except idle.

Idle is rough sometimes, hunting between 650 rpm and 950 rpm.

In one day, I found funny buzzing sound from the right side of the fender.

It comes every few seconds almost periodically, and lasts 1 or 2 seconds.

When I opened the feul cap, it diminished immediately and completely.

Then, idle seemed to be stable.

After re-cap, the buzzing come again after several seconds.

Drametric diagnostic tool reads fault code P1128 and P1130.

Air Mass was already replaced.

Actual values:

FRA 0.91 both bank

RKAT -3.61 both bank

Is this RKAT value is normal range??

Thank you all in advance for your help.

My 2001 had a recall to replace the gas cap.

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Thank you for helpful advices, RFM and WWEST.

At first, I replaced the EVAP purge vulve at last weekend.

It seems idle is stable for this week and the fault codes never come on again until now.

But I heard the buzzing again.

Next I will try to check feul cap.

Is the cap recalled in US?

What is new parts number?

Do you know normal range of KRAT?

After replacing, KRAT is shift to about -2.50.

Thanks in advance.

Edited by NewYorkBach
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After replaced the EVAP purge vulve,

Idling is still unstable and fuel cap still bussing sometimes.

RKAT goes down, about -3.6 in both banks at now.

Then, the fault code P1128 and P1130 is on.

According to some information,

RKAT is normally within from -0.1 to 0.1.

So my RKAT is extremely low.

MAF and EVAP vulve has already repleaced.

What should I do next?

Thanks in advace.

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  • 4 weeks later...

Hello.

I am still in the trouble P1128+P1130 with a RKAT of -3.6 with buzzing.

(RKAT is now -2.1, relatively improving due to colder air, probably)

I observed the buzzing sound closely and found the sound came from not gas cap, but right front fender.

Next week, the mechanic will bring my car to the nearset dealer

and check the vaccum leak, etc.

But on the last day, the Durametric diagnostic tool pick up a new fault code!!! :eek:

That is P1341(Camshaft adjustment bank 1, below limt)

According to the actual values, the actual angle for camshaft1 is

fluctuate between 0.2 to 1.2, where as that for camshaft2 is zero.

Also the camshaft deviation1 gose up from 0.65 to 1.2.

Do you have any information or a troubleshooting about this code?

I wonder there is two different problem in my car,

or one problem leads to these fault code. :help:

My car seems to drive well except a rough idling

with sometime the strage buzzing from the right side of front fender.

Thanks in advance for all of your help,

Yutaka

Edited by NewYorkBach
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P1128 or P1130 (oxygen sensing at rich threshold) is stored in the memory, this means that the fuel/air mixture is too lean.

Look for vacuum leaks, bad injector, fuel pump delivery, leaks in the exhaust etc.. Not sure about the 996, but I have seen this problem when the vacuum canister is rusted out. Is the vacuum canister in the right fender of the 996? The buzzing may be that!

Edited by KevinMac
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Thanks KevinMac :lol:

I will inspect the emission control system including the vacuum canister and valves.

Do you know whether there is a relationship EVAP system and the crankcase ventilation or not?

Does anyone have the photo or figure of the emission control system of poreche 996? :help: :lightbulb:

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Sorry,

I have been searching the perspective and connection of the EVAP system from fuel tank to intake via the canister.

I did my best, but it seems to have been inadequacy.

I will do my best a little more.

Thanks for all helps.

Edited by NewYorkBach
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Hello.

I am still in the trouble P1128+P1130 with a RKAT of -3.6 with buzzing.

(RKAT is now -2.1, relatively improving due to colder air, probably)

I observed the buzzing sound closely and found the sound came from not gas cap, but right front fender.

Next week, the mechanic will bring my car to the nearset dealer

and check the vaccum leak, etc.

But on the last day, the Durametric diagnostic tool pick up a new fault code!!! :eek:

That is P1341(Camshaft adjustment bank 1, below limt)

According to the actual values, the actual angle for camshaft1 is

fluctuate between 0.2 to 1.2, where as that for camshaft2 is zero.

Also the camshaft deviation1 gose up from 0.65 to 1.2.

Do you have any information or a troubleshooting about this code?

I wonder there is two different problem in my car,

or one problem leads to these fault code. :help:

My car seems to drive well except a rough idling

with sometime the strage buzzing from the right side of front fender.

Thanks in advance for all of your help,

Yutaka

Dear friend,

Your Rkat readings indicate that you have a extreme rich condition. So the engine management is trying to lean out the mix. Note if you have a vacuum leak then the Rkat reading will be positive. At this point I believe you should take your baby to a certified Porsche trained Tech. You will not be able to properly diagnose this engine management system with a basic scanner, you will need Bi-directional controls to activate certain engine management components to really pin point your problem.

Sincerely,

Porsche Master Technician

VIZCARRA44 B)

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Thanks Loren for your kindness.

Your Rkat readings indicate that you have a extreme rich condition. So the engine management is trying to lean out the mix. Note if you have a vacuum leak then the Rkat reading will be positive.

:lightbulb: I understand meaning of negative RKAT. Thanks vizcarra44, Porsche Master Technician.

As your advice, it is better to search a certified Porsche trained Techs who will be in Tokyo, and consult them.

Edited by NewYorkBach
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Does the noise sound like when you blow across the top of a beer bottle? If so, it sounds like a car that I saw a while back. It ended up being one of the ORVR valves was stuck open but I cant remember for the life of me which one (a lot of help, huh). This was on a US car so I don't know if the emissions set up is similar to Japanese cars but the faulty valve was located in the passenger fender well in the vicinity of the head light.

I should note that this car didn't have a check engine light or any DME faults, just the odd noise, so you likely have two separate problems. Judging by your RKATs though, the most common cause for that would be a MAF on the way out.

Edited by PTEC
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