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Old 11-09-2018, 09:57 AM   #1
redubbed
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Crankcase pressure, deceleration "pulsing"

Hey all,

I've recently run in to an issue that is baffling both me & my local dealer.

After hard acceleration & in higher gears (5, 6) over 3k RPM, the car "bucks" on decel, almost as though the throttle is being lightly opened, then closed & so on. The problem is intermittent, but happens regularly when the car is hot.

Accompanying this problem is what seems to be excessive crankcase pressure, pushing oil past the seals in the valve cover/girdle. This was verified with UV dye. They may be unrelated.

Boost gauge reads normal vacuum at idle & it makes great peak boost (22+ lbs).

I pulled my GFB DV+ thinking that may have been the issue & it did have a worn seal & I didn't reinstall it, but with the stock rev. D valve, the problem persists.

I've replaced the PCV valve (latest rev.) & the PCV hoses.

I was running an ECS catch can, but bypasses it for the colder weather (it tends to fill & freeze). The problem seemed to appear after this, but that may be a coincidence.

It's a 2012 CBFA, K04, AWE boost hoses, Golf R intercooler, Fluidamper, Cobb Turbo-back, modified Volant intake, red top coils, Stratified ProTune via Cobb Access Port. Carbon cleaning was done with intake manifold replacement at 50k miles. It currently has 73,xxx miles.

The RSR clutch slips at torque peak, but that's being replaced in the spring.

Any insight would be appreciated.

Last edited by redubbed; 11-09-2018 at 03:56 PM.
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Old 11-09-2018, 02:24 PM   #2
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Any codes? Could be throttle body or throttle body wiring issue. There is a bulletin for replacement of throttle body wiring (TSB 01-09-04).

I had same symptoms plus EPC light and code P0121. Dealer replaced throttle body and re-pinned the wires but symptoms are coming back once engine gets hot. Just replaced coilpacks to see if that makes a difference.
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Old 11-09-2018, 02:48 PM   #3
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No codes (yet), I do have VAG-COM. I pulled the TB yesterday & cleaned it, though it was hardly even dirty. Ran a TB alignment afterwards. I'll ask my dealer about the TSB.

Edit: looks like that TSB is for '08-'09 vehicles. Mine's a 2012 (edited my OP)

I'm having compression & leakdown tests done next week just to rule out rings.

Last edited by redubbed; 11-09-2018 at 02:53 PM.
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Old 11-09-2018, 03:14 PM   #4
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Old 11-09-2018, 04:13 PM   #5
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out of curiosity, what type of oil are you running? My symptoms started after I used 0W oil for the 1st time (always used 5W since car was new). Probably a coincidence but who knows.
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Old 11-09-2018, 04:32 PM   #6
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5w-30, dealer oil changes & OEM filters every 5k miles
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Old 11-12-2018, 04:47 PM   #7
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Rings are good. Compression & leak down tests passed at my local dealer. Going to check the throttle body wiring next.
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Old 11-14-2018, 03:59 PM   #8
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I was able to capture the phenomenon on my Access Port & I've sent it to Alex to have a look. I'll update once he replies. Looks like the ECU is both requesting & applying throttle in very small amounts randomly during decel.
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Old Yesterday, 12:13 AM   #9
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I’m not having the bucking problem but there are sometimes some weird noises around 3k on decel. I am having the excessive cc pressure problems. My mechanic called me today of another car having the same problem as me. The only thing the three of us have in common is the Ecs cc kit. Don’t know if it’s weird coincidence or not but they’re suggesting I either go back to factory or get a cc that uses an Africa plate
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Old Yesterday, 02:07 PM   #10
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Quote:
Originally Posted by redubbed View Post
I was able to capture the phenomenon on my Access Port & I've sent it to Alex to have a look. I'll update once he replies. Looks like the ECU is both requesting & applying throttle in very small amounts randomly during decel.
hmmm... odd that the tune would start acting this way all of a sudden. Keep us posted.

I'm going to clean my MAP, MAF, and AIT sensors this weekend. Not sure if things will improve.
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