Is Higher Idle a Solution?

My 996.2 has had a check engine light for low-lift cam faults, misfires, and the occasional limp mode ever since I bought it. The long-term plan is still to rebuild it, but as long as I drive it hard and stay out of the low-lift cam range, it’s manageable. And with the constant flow of customer projects, there never seems to be time to work on my own cars. Last week, a friend was in town for Porsche Parade and asked if his wife could borrow my car for a drive tour while he was autocrossing. Wanting to minimize the chance of any issues while she had it, I made a quick change—raised the idle to 1200 RPM via the tune, hoping it would keep it out of limp mode. I’d already bumped a few other cars to 1000 RPM because we’ve found it solves the Bank 2 hot idle tick—a sound that's consistently misdiagnosed as bore scoring. (I spend about as much time convincing people that their engine is fine, as I do helping people that need/want a rebuild). Fast forward 500 miles later: - No fault codes or misfires - The car purrs at idle - No ticking at hot idle At this point, I’m really starting to think Porsche set these cars to idle too low—probably for emissions compliance. But from what I’m seeing, these engines seem much happier around 1000–1200 RPM. I think this could be one of those simple, overlooked changes that actually clears up a whole bunch of mysterious issues.

Yes, thats how Jake set up my 4.0.

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That is very insightful...

How are you adjusting the tune? With a handheld flasher through the OBD2 port?

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Handheld OBDII or ecu bench mode. Handhelds are the most convenient. But if I have the ecu then there is no handheld cost and I can get all of the files required to make a clone if ever needed.

Heard that from an M96-experienced engine builder too just this weekend. Raises idle to just below 1000 rpm at operating temp.

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And what rpm is commanded when we turn off a/c? About 1000-1100, correct? My oil pressure is > .3 bar higher at idle when it�s hot.

I will have to ask the guy who works on my car about this, it makes sense, great info.

I have to look at this question from a Porsche Dealer Technicians perspective ( of course) as if it were a CPO car or still in Warranty. And the answer is no, it would not be a solution...Sorry, but without a root cause of the problem, it cannot be an acceptable solution and be considered as "normal" .. These type issues have not been seen as "normal" for 25 years, why start now ?? If the root cause of the tick/tap is identified and understood, then "maybe" ....

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Seems like a better solution than telling people it�s bore scoring and then raising the idle after rebuild and telling them the rebuild fixed it. 🤷‍♂️ Happens 20 degrees into the cylinder 3 power stroke on every engine we�ve tested. Both before and after rebuild. Intensity does not change when forcing high cam lobe at idle, but the where it happens in the cycle moves equivalent to the difference in lobe centerlines. Advancing the cams at idle changes moves where it happens an equivalent amount (ecu adjustment is in crank degrees but movement of tick in the cycle is in cam degrees). Tick is in the 3-4khz frequency which is equivalent to tapping a chain guide against a case half. Tapping piston against cylinder is sub 1khz frequency. Always sounds like it�s coming from cylinder 5. Replacing lifters, tensioners, variocam solenoids, cams and lifter carriers have not solved it. Manual chain tensioners tightened to the point of nearly breaking the chain does not solve it either. Unplugging the variable lift solenoid doesn�t make a difference. Simply turning on AC significantly reduces it. That�s when I tried raising the idle and it went away at 1000. And that�s as far as I�ve made it to date. Thoughts?

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I most certainly agree that that would not be acceptable... I appreciate all the collection of relevant data about the tick/tap noise ....it really helps and I like that about you .. My thoughts.. 20 degrees into the #3 power stroke means the #5 cylinder is just starting to open the intake valves....( possible clue since the noise seems to emanate from #5 Cyl, and changes if Cam timing is advanced/changed) I assume this particular tick'/tap is only occurring on 3 chain engines ?? One bank of Cylinders/Cams with only 3 sets means at low RPM the chain drive/Cam Drive is really being jerked hard advanced/retarded by the Cam Lobes.... On the back-side ( closing-side)of the Lobe the Cam will try to run faster than the Crank, then on the front-side ( opening-side), the Cam will try to run Slower than the Crank.....this is all due to Spring Pressures pushing the Cams forward, and pushing them backwards.. On the 3 chain engines the Intake Cams are not "mechanically connected" to the chains or crankshaft , The Intake Cams are connected to the Vane Adjusters inner drive and is a Hydraulic Drive except when at the "rest stop"...At the "rest stop" there is also a steel pin that can lock the Cam position when at rest or to set the Cam Timing...... Have you changed the Spring Pressure Specs or are they still Factory Spec ?? With engine running and oil pressure applied to the Vane Adjuster the steel pin is moved and the drive is "unlocked" but it can still hit on the rest stop if pushed backwards by the valve springs, in the other direction it has plenty of space to move as thats where it advances to when forced to do so by the oil pressure/solenoids... So ,after short deliberation my hypothesis is the source of the tick/tap is the Vane Adjuster Put a new Vane Adjuster on one of the effected engines and gather some more Data !!!

@Porschetech3 My thoughts keep heading in this direction as well. But then why only B2? My next test is to bring an engine up to temp and then shut it down, depin the variocam solenoids (easier than unplugging on a hot Cayman engine) and then restart it. I tested once with 0w-40 and it didn�t seem to make a difference. Except when the engine oil temp got to 102C, then it stopped. I shut it down just long enough for it to come below 100C, restarted and it ticked again until 102C, then stopped again. I tried the same test with 15W50 and was unable to reproduce the result, though I also didn�t push oil temps beyond 103C to see if the 15W50 just had a higher point. But it doesn�t make sense to me that the tick would have a viscosity range. ie that it doesn�t happen when the oil is too thick or too thin. Another test I would like to try in the near future is see if switch to a standalone ecu makes any difference. I believe the issue is isolated to the 3 chain engines. Which is another vote for variocam actuator. Lastly, it�s anecdotal because I didn�t get measure it, but I know of another car that had the entire engine with ancillaries swapped out with a rebuilt core engine and the tick seemed to be nearly the same.

@SlakkerRacingDev Working off the Hypothesis that the Vane Adjuster is the source of the Tick/Tap :: And to answer your Questions: 1Q.My thoughts keep heading in this direction as well. But then why only B2? 1A. The Bank 2 head/Cam will have a higher oil pressure by ~1 bar...( this is due to the oil channeling in the block...Bank 2 comes off the main channel on the block whereas Bank 1 has to feed through the Crank Carrier first ) 2Q. . But it doesn’t make sense to me that the tick would have a viscosity range. ie that it doesn’t happen when the oil is too thick or too thin. 2A . The Vane Adjuster is a Hydraulic Drive to the Cams..."IF" the Vane Adjuster is banging on the stops ( either rest stop for full stop) then absolutely, oil pressure and/or Viscosity will determine how hard and/or if it bangs the stops.. 3Q. Another test I would like to try in the near future is see if switch to a standalone ecu makes any difference .. 3A ..The ECU isn't "causing" the tick/tap, but having a more user-friendly one may make it easier to manipulate the control of the Vane Adjuster for verification.. then once verified the appropriate remedial action can be carried out.. Could be as simple as just worn Vario-Cam Vane Adjusters....Those things are very very "tight" when new... The ones used by FoMoCo are very similar and those things fail all the time a rattle like crazy...

What are the cam deviation readings? Chances are they are way out of wack and need the pads replaced.

This ticking at idle happens on a freshly rebuilt engine where new chain guides are used so highly unlikely that they need to be replaced.

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Where in the original post did it say it was "freshly rebuilt"?

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Maybe try locking out the hydraulic cam gear vane adjuster just to isolate the problem and confirm its the hydra cam gear. V8's of all various types have aftermarket devices to lock out the cam gears advance function when installing performance cams. A couple of sharp guys like yous 2 could easily figure out some simple device....Some of these devices are as simple as a small wedge installed in gear that stops all internal movement. Hell, while you're at it might as well ditch those button lifters and install some fat big ol SCHRICK camshafts , and manually set/advance it as needed, call it day and have a much more dependable/simple valve train with no hydraulic noise makers....

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Fair point, however, I was pointing out that the ticking noise *also* happens on freshly rebuilt engines, as is the case in my car.

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I wonder what the difference is. I was talking to Lee the other day and he told me that 99% of the engines that come in to Hartech for bore scoring do in fact have bore scoring on strip down.