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SOLVED - 996TT Missfire bank 1 only


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Hey Everyone,

Another 996TT Question on another 996TT

2001 996TT

Missfire only on cyl 1,2 & 3

Recent repairs...

- Plugs & Coils

- Repaired Pressure/vacuum Leak + Re-Checked with smoke machine afterwards

- Replaced MAF Sensor

- Compression Test Done, All Cyl Equal\

Things I have Noticed.

Plugs are slighty dark/sooty on cyl's 1,2 & 3 - Bank 2 look normal

Just looking for some suggestions since it takes forever and a day to do anything on these turbos.

Cheers and Thanks.

D.

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Apart from ignition and injector problems, this combination of fault codes (one whole bank) can sometimes be caused by the Variocam solenoid. This also (usually) causes a rough idle. If you have access to a Porsche tester, you could try activating the bank 1 solenoid while the engine is idling, which will give you a clue if it is working or not. You can also monitor the inlet camshaft angles, and see if they read the same both sides.

Edit: Extracted from the diagnostic sheet for P0301/2/3:

VarioCam does not switch over completely

The VarioCam does not switch over completely from power to torque valve timing.

An indication of this problem is misfiring detected by the DME control module in the range of 1200 - 1500 rpm occurring in an entire bank.

So you should also check to see the speed range when the misfires occurred, which a P-tester will do.

Edited by Richard Hamilton
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  • 2 weeks later...

Update

According to PIWIS

Fault Info........

Vehicle Speed 31 km/hr

RPM 3600

According to durametric,,,

Actual camshaft angles for bank 1 & 2 seem even...

One thing I noticed.... When activating the camshaft adjustment,,, bank 1 blips then continues to idle normally whereas bank 2 continues to chug untill the activation is shut off.. Making me believe I might have a cam adjuster / solenoid issue with bank 1....

As always, any input is greatly appreciated..

Cheers

Edited by EleCTriCT
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SOLVED!!!!

Bank 1 Cam adjuster solenoid hold bracket had a hairline crack through it... Thus when the solenoid would activate, it would push itself out of the head thus not pushing the cam adjuster plunger all the way... the bore is deep enough that the solenoid actually forces out of the head but not enough to leak oil or anything like that.

Made a large washer to temporarely hold down the broken side of the bracket, and test drive to verify..

Now when the cam adjuster activation is done in durametric, it stumbles the same from bank 1 to bank 2.

Cleared faults and test drove, no more missfires and vehicle runs as it should.........

Loren can you edit the thread title to solved?

Thanks everyone.

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Congrates. Are you sure you were using the drive link for cam adjustment and not the lift? The solenoid with the crack bracket is for lift, not timing. That's why your values were good.

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You might be right and I might have my terms mixed up. As I have to admit I not that fluent with the turbo engines yet...

The actuator that was backing out of the side of the cyl head is 996 105 301 71

The failed hold down bracket that requires replacement is 996 105 310 72

It would appear that you are correct and that is the solenoid for the valve lift control....

Although, I made the discovery with the durametric activation labled camshaft adjustment and I noticed major differences in the way the vehicle ran from bank1 to bank 2. Which led me to investigating that area.

Either way, I am happy the problem is delt with and I pleased to be able to document it on renntech.org :thumbup:

Cheers...

Edited by EleCTriCT
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