I do not recall the numbers for the battery. I visited the dealer parts department and the parts..

(Tried to post this a couple minutes ago and it didn't seem to stick... hope I didn't do something wrong! Trying again... )

Nope, I didn't misspell taco...

I have a bouncy tachometer.

Car has a smooth idle, but at resting idle (it's hard to watch it when I'm driving) the needle does its little dance.

It's not crazy bouncy, but rather a little up a little down a little up a little down... you get the point. I have wanted to (and will tomorrow ) post a video showing said tacho bouncing. I think a visual will be useful.

So, what are we thinking?

-Voltage regulator?
-Battery?
-Alternator?
-CDI Box?
-other?

Some interesting factoids (thanks for your interest so far!!!):

-When the engine is idling, if I turn the "dome" cabin light (by the release latch) on, the light lumen output ("candelas" for us physics peoples) is not continuous... it has a bit of "luminous resonance", as I like to call it. I remember my dad's old '84 Carrera doing that too when idling.
-Similar to above, as expected, the dash lights, especially in the dials also has this sort of light resonance.
-Power changes and upgrades currently in car include and are not limited to: XM full integration to OEM 220 radio (external, but powered and aux'd in), electronic audio auxiliary bypass (super cool device that cuts the XM signal when my phone rings or plays pandora etc), HID headlights, rear spoiler switch (Porsche OEM part)... that's all I can think of for now.
-About a year ago, the dealership said my battery was still healthy (despite being about or over 6 years old). However, a week later, at another shop (independent), the guy there told me the batter was registering below accepted output (AKA replace it now!). Same battery sits in my car now

Kinda strange!

I find it somewhat concerning in that I don't like the idea of engine, or electrical for that matter, malfunction. Like I said, the engine seems to idle normally... nothing out of the ordinary.

The needle should be solid at idle... not bouncing, we can all agree to that. It's not violently bouncing, as I have read in other forums, nor have I noticed it when accelerating.

It starts when the car starts and stays consistent till the car is turned off.

I mentioned the battery before, obviously I don't need to get the Porsche one, I have an Interstate or some other brand in there right now... need to check. What numbers do we like for batteries? Crank etc. I just thought of this now and I haven't yet jumped into the search pool, figured I'd ask anyway. (I'll delete this particular question if I feel it's redundant to other posts, going to investigate now)

For those of you keeping score, I'm still waiting on my clutch kit, RMS, (holding off on IMS $$$ for now), top cable and other replacement parts etc to arrive.When I do my DIYs, I'm going to document it (with color images!) and make it all nice and "pretty" for future reference! It's my way of saying thank you for all the help!!!!

I may add more info to this thread if I see fit... you guys will see that I've edited it if I do.

Looking forward to your $.02!

and other electrics like the HID headlights when what appears to be electrical problems appear.

The electrical signal that ultimately feeds the tach comes from the crankshaft position sensor which appears to be working just fine. That the radio has been messed with causes me to believe the problem is in the dash area. You can try to clean the electrical contact of the tach though this might be hard to get at. Sometimes if the radio installer doesn't know what he is doing the radio is wired into to a CAN line (which in some Porsches is used for the comfort bus) and is powered from not a real power line but from one of the CAN lines cause the tech checks it and finds it 'high' and assumes the line is power which it is not.

Another consideration is the battery's condition. I believe it would be a good shot in the dark to replace the battery due to its age and the fact the tech told you the battery's registering below accepted output.

Check with your Porsche dealer parts department. When my Boxster's OEM battery finally required replacement I checked and found Porsche had issued a TSB that bumped the AH and CCA of the OEM battery to something higher. The replacement battery not only has more AH and CCA but is physically larger, longer, and required that I move the holddown from its original position to next position to the left (passenger side) to accomodate the larger battery.

Sincerely,

MarcW.

I probably still have cable lube somewhere for when I get a 246 Dino or something like that.

Minus 40 degrees... Is that Fahrenheit or Celsius?

All very good points, and thank you for the reply!

Do you know those numbers for the new battery you got? The AH and CCA #s. I may be wrong, but I can't imagine them being unique to Porsche's battery.

I don't know a thing about the throttle bodies condition. I was planning on cleaning it when I replaced my AOS (I have leaking on the crank case and I suspect the AOS which I believe is original from 2000).

As far as I can tell, the engine sounds fine, but then again, I have a GHL on the back that is pretty loud over the engine noise so it's kinda hard to be certain.

I have done 100% of the electrical work on my car.

The radio is stock, I simply added the 220 OEM AUX (phone) kit and utilized the switched power function from that as well. I never messed with the dash elsewhere.

I don't think it's the HIDs or the radio add-ons. The reason I don't is that when I have the radio, XM, audio-bypass, and HIDs turned off, the bouncing of the RPMs at idle is the same.

Sometimes (well, I've noticed it a lot lately) when I start my car, the RPMs at idle will be around or over 1k, max I think I've seen is maybe 1,200. After the car is warmed up and I stop at a red light, for example, the RPMs will be around maybe 650-800. The bouncing is very minimal, not like a lot of the drastic bouncing other people talk about where it moves around or over 1000 RPM. It will maybe oscillate between 75 RPM down from center 75 RPM up from center (visually).

Since you bring up the radio, I would like to find a way to ground things a bit better. I really don't think this is the issue, but I'll mention it as fodder if you guys think it might be a cause. When I have the radio volume up and my RPMs are up, I can hear the whirling of the RPMs interfering with the audio signal. I currently have 2 ground loop isolators (radio shack): one for the XM and one for the secondary AUX which the bypass auto-detects when audio is played.

Thanks again for the input, MarcW!

Quote
Dwass
All very good points, and thank you for the reply!

Do you know those numbers for the new battery you got? The AH and CCA #s. I may be wrong, but I can't imagine them being unique to Porsche's battery.

I don't know a thing about the throttle bodies condition. I was planning on cleaning it when I replaced my AOS (I have leaking on the crank case and I suspect the AOS which I believe is original from 2000).

As far as I can tell, the engine sounds fine, but then again, I have a GHL on the back that is pretty loud over the engine noise so it's kinda hard to be certain.

I have done 100% of the electrical work on my car.

The radio is stock, I simply added the 220 OEM AUX (phone) kit and utilized the switched power function from that as well. I never messed with the dash elsewhere.

I don't think it's the HIDs or the radio add-ons. The reason I don't is that when I have the radio, XM, audio-bypass, and HIDs turned off, the bouncing of the RPMs at idle is the same.

Sometimes (well, I've noticed it a lot lately) when I start my car, the RPMs at idle will be around or over 1k, max I think I've seen is maybe 1,200. After the car is warmed up and I stop at a red light, for example, the RPMs will be around maybe 650-800. The bouncing is very minimal, not like a lot of the drastic bouncing other people talk about where it moves around or over 1000 RPM. It will maybe oscillate between 75 RPM down from center 75 RPM up from center (visually).

Since you bring up the radio, I would like to find a way to ground things a bit better. I really don't think this is the issue, but I'll mention it as fodder if you guys think it might be a cause. When I have the radio volume up and my RPMs are up, I can hear the whirling of the RPMs interfering with the audio signal. I currently have 2 ground loop isolators (radio shack): one for the XM and one for the secondary AUX which the bypass auto-detects when audio is played.

Thanks again for the input, MarcW!

managed looked up the battery based on my car's VIN and found the part # had changed and he looked at a battery and noted the CCA and AH numbers were higher than the original equipment battery.

Based on my info:
2.5l - Manual - 60AH, 280CCA
2.5l - Tip - 70AH, 320CCA

2.7l - Manual - 60AH, 280CCA
2.7l - Tip - 70AH, 340CCA

3.2l - Manual - 60AH, 280CCA
3.2l - Tip - 70AH, 340CCA

I can't be sure but the new battery had 80AH and maybe more CCA.

You don't have to buy a battery from your dealer but you should I believe at least replace the battery with the proper capacity and if this has been bumped up a bit then I think you ought to use that as your guide. I would not advise buying a battery either substantially under the CCA or AH of what Porsche has specified for your car but I would not go overboard the other way either.

Rpms jumping to over 1K after cold engine start is normal. In fact the rpms will -- at least what I see from the tach -- initially go much higher (2K) than that, but only for an instant. As the engine idles and gains heat the rpms drop and get smoother.

Hot engine idle speed varies depending upon MY and engine size. The 2.5l idles at around 790 IIRC), with the 2.7l around 700 and the 3.2l engine idle speed is 700 too. I do not recall the allowable variation but it is 'small' around +/- 20 rpms.

Now if the tach is moving about and the engine rpms staying the same, that's one thing. I misread your post cause this is what I thought was going on.

If the rpms are actually moving up and down this is something else entirely.

If the tach is moving about because the engine rpms are varying this is one symptom of a failing AOS.

Often times there'll be no CEL and no error codes associated with this.

Now another source of a varying idle can be the VarioCam system. Once when my 02 Boxster developed a pretty big variation in hot idle speed from over 1K to low enough I thought the engine would die. It did not. But simultaneous with the idle variation the CEL came on and the error code pointed to a VarioCam solenoid.

Now the engine ran good above idle to nearly 4K rpms which is about as high as I dared run the engine for fear something more serious could happen at higher rpms.

Also, while the CEL stayed on after I turned the engine off and left it off a while then upon restart the varying idle symptom was gone. The misbehaving solenoid/actuator (both were eventually replaced) behaved themselves upon the next engine start.

Regardless, if the rpms are actually varying you need to diagnose what's wrong and fix it pronto, or take the car someplace and have it diagnosed and fixed.

Sincerely,

MarcW.

My Porsche mechanic thought I was nuts and never heard about this in Porsches. For the first, oh 7 years of my 2000 S's life, The tach would bounce between say... 1500 and 2500 RPMs and I would hear a scratch-schratch-chzzts sound. Only on cold winter days did it do this. It seemed to have simply stopped...... Hmmmm.. The mechanic said there are no rotating parts.

Now I have had a bouncy tach at idle that got progressively worse, but the engine would bob also. It was nothing more than a dirty throttle body - this is a well known issue.

Yeah, that sounds way more intense than what I am experiencing.

Sounds like the first time you had the issue, it was the CDI box or VR... which is weird if it suddenly corrected on its own.

The throttle body is a good idea. I'm going to look into that. Out of curiosity, did you have AOS issues?

Minus 40 degrees... Is that Fahrenheit or Celsius?

Well, I'm no expert, but I was thinking that the VR could go haywire... I had a 5V VR that must have been defective and failed in a portable power device. It was just a thought.

Please see this youtube link where I have uploaded a video of the strange tachometer behavior. I had the engine cover off and the top in service position so you can hear the engine better from inside the car.

[video]http://www.youtube.com/v/jMSJ9_ivFhE[/video]

Any thoughts?

I fixed my top cables! I made the video above while I was doing the repair. I will be making a DIY video that goes through the entire process from pictures and raw video I recorded while doing the repair.

Ok, so here are some big concerns that may be linked to this:

-When I had the engine exposed, I noticed a good amount of black oil/sludge on the top of the engine intake tubes and on what appears to be a coolent(?) hose below the intake...

-I have another video I will upload shortly of something I noticed with the engine exposed. While sitting in the drivers seat with the cover off, I gave the car a little gas and took it to 1,500-2,000 RPMs. When I did this, I could hear a whisp of air from behind me. I turned my head and looked to see if I could see where the sound was coming from. It appears that when I give the engine some throttle, the top of the intake has these joints and it burps air creating a whisp! noise. I don't think this is normal so correct me if I'm wrong. I wonder if this could be linked to the issue.

Again, I will upload a video of this very soon and some pictures of the engine.

Also, when I play that video of the tachometer, I can hear the engine noise slightly changing with the RPM fluctuations. I don't know if there is a correlation, but it seems very possible that this could be a serious engine/electrical issue.

I appreciate your thoughts on this.

-Dwass

by something over and under the normal range of variation (approx. +/- 20 rpms) this is likely due to an intake air leak and my experience is in most cases (2 out of 3) the cause is a failing AOS.

In the 3rd case it was a failed VarioCam solenoid/actuator. But in this case the engine rpms varied by a greater amount and the error codes clearly pointed to the VarioCam system.

The oily/black sludge is probably oil vapor that had gotten on the intake manifold and surrounding hoses/hardware and this has attracted a goodly amount of dust or the dust was there to begin with and it absorbed the oil vapor to make the oily sludge.

The AOS has a hose the runs from the AOS and connects to the intake manifold directly after the throttle body (T.

This hose can have developed a crack or come loose. The AOS has a rubber bellows hose that connects the AOS to the engine crankcase and this can split/tear or otherwise fail. In either case oil vapor that would otherwise be routed to the intake system can instead be leaked out and end up on external engine surfaces.

One check for a possible AOS problem is to remove the TB and check it for cleanliness. If the TB is oily/dirty or if there is some oil puddled/collected behind the TB where the hose from the AOS connects the AOS is almost certainly bad.

Another check is with the engine idling unscrew the oil filler tube cap and remove it. If you can't remove the cap or it is very difficult to remove, the AOS is bad. Now the AOS might be bad anyhow and yet you can remove the cap, so just because you can remove the cap doesn't mean the AOS is in the clear.

If the bouncy tach is just the needle moving about a bit and the engine rpms are stable, that's something else.

Sincerely,

MarcW.

Thank you for all the info! Wow!

Shucks that the link doesn't work... maybe try this now? [www.youtube.com]

I think you're right about the leak... I'll try and post a video of what I described earlier.

Thanks again!

[www.youtube.com]

Video shot at night from inside cabin looking through to the back.

Any clues?

Pictures of the oil on the way too...

I uploaded a few pictures to show the oil. I used the flash for a couple to take advantage of the reflectivity of the oil. It just looks dirty in natural light, however the gradient change of color is a good indicator that "stuff" is caked on there....

[theultimateimage.smugmug.com]

Hopefully these additional items add a few missing pieces to the puzzle.

-Dwass

wettest.

I'm guessing AOS, or perhaps just its hose or the connector.

Oh, the video links still show up just as white boxes in your posts.

Sincerely,

MarcW.

Why do you think that is??? I have them "unlisted" on youtube, but I'm pretty sure you can still view a direct link.

Very strange.

Can anyone else not see the videos?

Thanks for the AOS tip. I wonder if this and a dirty throttle body could be contributing to my RPM/tacho issues.

I'll likely order and AOS this week. Confirm for me, please, it's been a while since I reviewed the DIY on Pedro's site and I'm exhausted..., can I access and do this from above, or do I need to get under or remove the rear right wheel. I'm looking to avoid lifting the car at this time...

Thanks again!

Quote
Dwass
Why do you think that is??? I have them "unlisted" on youtube, but I'm pretty sure you can still view a direct link.

Very strange.

Can anyone else not see the videos?

Thanks for the AOS tip. I wonder if this and a dirty throttle body could be contributing to my RPM/tacho issues.

I'll likely order and AOS this week. Confirm for me, please, it's been a while since I reviewed the DIY on Pedro's site and I'm exhausted..., can I access and do this from above, or do I need to get under or remove the rear right wheel. I'm looking to avoid lifting the car at this time...

Thanks again!

either to good magic or black magic.

It may have something to do with my PC here at work. Adobe wants to load another flash player upgrade but whenever I do that the PC loses the ability to play other videos. Seems there's a battle between Windows Media Player and Adobe's Flash Player, or something like that. A pox on both their houses.

If the AOS is acting up the TB will almost certainly be dirty, oily mainly, is what I observed when I removed the TB from my car when the 1st AOS was going bad. The TB throttle bore and butterfly valve were wet with oil and the valve had a drop of very black/dirty oil hanging down in its lower edge. There was some oil behind the TB at the AOS hose connection, but at the time I didn't realize the significance. I took the car to a dealer and the AOS was diagnosed there.

What I found was after I cleaned the TB and got the engine running again the varying idle and other symptoms (mainly a bit of hesitation off idle) went away but came back within just a few miles of driving.

Be sure you are convinced the AOS is the culprit though.

As for the DIY I've never done this -- both times I've had a dealer (the same one in fact) do the AOS R&R job -- so I can't help you with any direct experience.

I'd not try to cut corners, for instance not lifting the car if that is a necessary step. Generally when I worked on my cars and tried to cut corners that's when I ran into difficulty and problems and almost always the job took longer to do and cost me more in parts/supplies.

To do the job right requires specific steps and there's no short cut. But check out the various DIY articles on the AOS. More than a few owners have done their own work and have posted here and elsewhere their experiences and maybe not raising the car is ok.

Sincerely,

MarcW.

Thanks for everything. I really appreciate your honest advice.

I think you're right about the videos at work, I've had that happen. The videos seem to be getting hits so I figure some people must be able to see them.

I've never put the car on stands, I am reluctant because I know it's kinda tricky. I've seen many methods here and there so I at least have some good options. The biggest holdup now is not having the stands

I do, however, have ramps. I think Pedro said in one of my earlier posts that ramps would be ok. Need to double check that.

I agree with not cutting corners, I've been there myself and know it can open up a can of worms when you do.

I've grown to resent my local dealer. They used to have some really nice guys working there, but the current service reps are rude and snobby. I'd like to try and diagnose the AOS myself. It's not too* expensive so I figure if I do it, it couldn't hurt. There is quite a bit of oil on the TB... eh... I'm going to have to do some more research.

So many things to diagnose... check... and fix...

Thanks again for all your thoughtful input!

-Dwass