1999 996 Surge At Around 2,000 Rpms

[CabC2]

Consider the following: If the transmission is going, you might as well drive it until it breaks. It could be years. Not using it will not prevent it from getting worse, so you might as well use it while it lasts.

[valley996]

I am asking for help again. I am thinking this may not be a transmission issue. What is happening is the car rpm's are jumping up and down as if I am pressing the gas pedal and letting off, but it is doing it on it's own. I does get worse on a grade. It does it while crusing between 1500 and 2500 rpms, when the car has no need to shift, which leads me to believe it may not be a transmission issue as was though early on. I can use the manual mode of the tiptronic in all gears and it does it in that range. Note: If the car is in Park, there is no problem in that same range when I rev the engine, it's only when moving. Also, as a reminder I have no codes with the PIWIS or Durametric tester.

What I have done so far with no changes:

1. Cleaned the TCV ( very dirty, also looking inside of it the flap that opens and closes is not fully opened or closed. Is

this normal?)

2. Unplugged the MAF and drove, no changes

3. Cleaned the throttle body.

I am sorry for being a pest, but this is driving me crazy. Thanks

[Loren]

1. Yes, but it should move freely. Usually they get sticky.

[valley996]

1. Yes, but it should move freely. Usually they get sticky.

Loren,

I cleaned it and it moves better, but not what is causing my problem. Any more thoughts or suggestions I can work on?

[Loren]

1. Check the throttle potentiometer using Durametric, PST2, or PIWIS tester.

2. Likewise check the operation of the VarioCam actuation.

VarioCam

To increase the torque and to improve cylinder charging, the engine has two VarioCam actuators which are installed in the chain tensioners of the camshafts. The two actuators are operated by electromagnetic valves activated by the DME control unit.

Functioning

When the ignition is switched on, the electromagnetic valves of the camshaft adjusters are supplied with positive potential. If the engine is started, the control unit applies ground to terminal 25 (camshaft adjuster for cylinder line 4 - 6) and to terminal 52 (camshaft adjuster for cylinder line 1 - 3) if the following conditions are fulfilled (VarioCam activated);

1 - Engine oil temperature between -3°C and 133°C

2 - Engine speed > 1,300 rpm

3 - Throttle opening > 5%

-or-

1 - Engine oil temperature > 133°C

2 - Engine speed > 1,480 rpm

3 - Throttle opening > 3.9%

The ground potential is deactivated by the DME control unit (VarioCam deactivated) if:

Engine speed > 5,120 rpm

[valley996]

1. Check the throttle potentiometer using Durametric, PST2, or PIWIS tester.

2. Likewise check the operation of the VarioCam actuation.

VarioCam

To increase the torque and to improve cylinder charging, the engine has two VarioCam actuators which are installed in the chain tensioners of the camshafts. The two actuators are operated by electromagnetic valves activated by the DME control unit.

Functioning

When the ignition is switched on, the electromagnetic valves of the camshaft adjusters are supplied with positive potential. If the engine is started, the control unit applies ground to terminal 25 (camshaft adjuster for cylinder line 4 - 6) and to terminal 52 (camshaft adjuster for cylinder line 1 - 3) if the following conditions are fulfilled (VarioCam activated);

1 - Engine oil temperature between -3°C and 133°C

2 - Engine speed > 1,300 rpm

3 - Throttle opening > 5%

-or-

1 - Engine oil temperature > 133°C

2 - Engine speed > 1,480 rpm

3 - Throttle opening > 3.9%

The ground potential is deactivated by the DME control unit (VarioCam deactivated) if:

Engine speed > 5,120 rpm

I'll do that. I ordered a Durametric yesterday. It will be here Wednesday. I really do appreciate the help. Based on your experience does it sound like it could possibly be the torque converter? I am hoping it is not, because that is an expensive fix!

[valley996]

I should say the car appears and feels like it is shifting okay. I would note that when I pull out fast and floor the gas it shifts smoothly and there is no missing or rpm fluctuations. It's only if I am cruising in that rpm range (1500-2500) or especially when pulling a grade. Also, if I am in the manual tiptronic mode it does it in all the gears in the same rpm range.

[Loren]

I am not convinced it is a Tip problem...

[valley996]

I am not convinced it is a Tip problem...

Do you think I should replace the throttle position sensor? Also, I will have some numbers from the Durametric this week. Again, thank you.

[Loren]

I would not replace anything until you get the diagnostic data from the Durametric.

[bluejoker01]

Your Car is doing exactly what mine was doing. Its the Torque Converter!

I went mad trying to work it out. The Porsche Mechanic was stumped trying to work it out.

We pressure tested the engine and fixed leaks, but the problem remained.

Did all the code tests but not faults came up.

Had the transmission removed and tested - All good.

Like your car, putting my foot down and driving hard - the car would feel fine. It changes gears well. Its just cruising that was the issue.

Ended up replacing the torque converter and the problem was solved.

My car was at the mechanic for 6 weeks. Very frustrating!

[valley996]

Your Car is doing exactly what mine was doing. Its the Torque Converter!

I went mad trying to work it out. The Porsche Mechanic was stumped trying to work it out.

We pressure tested the engine and fixed leaks, but the problem remained.

Did all the code tests but not faults came up.

Had the transmission removed and tested - All good.

Like your car, putting my foot down and driving hard - the car would feel fine. It changes gears well. Its just cruising that was the issue.

Ended up replacing the torque converter and the problem was solved.

My car was at the mechanic for 6 weeks. Very frustrating!

I know, the more people I talk to, the more say it is a torque converter. I was just in hopes that it would be a little cheaper fix. Does anyone know if it is the torque converter, does the transmission usually stay in decent condition? Can I mostly likely get by with a torque converter only or do I need the rebuilt tranny with it.

[valley996]

Loren,

I got my Durametric today. I hooked it up and had no codes. Can you give me an idea how to capture the reading that you suggested.

Thanks

1. Check the throttle potentiometer using Durametric, PST2, or PIWIS tester.

2. Likewise check the operation of the VarioCam actuation.

VarioCam

To increase the torque and to improve cylinder charging, the engine has two VarioCam actuators which are installed in the chain tensioners of the camshafts. The two actuators are operated by electromagnetic valves activated by the DME control unit.

Functioning

When the ignition is switched on, the electromagnetic valves of the camshaft adjusters are supplied with positive potential. If the engine is started, the control unit applies ground to terminal 25 (camshaft adjuster for cylinder line 4 - 6) and to terminal 52 (camshaft adjuster for cylinder line 1 - 3) if the following conditions are fulfilled (VarioCam activated);

1 - Engine oil temperature between -3°C and 133°C

2 - Engine speed > 1,300 rpm

3 - Throttle opening > 5%

-or-

1 - Engine oil temperature > 133°C

2 - Engine speed > 1,480 rpm

3 - Throttle opening > 3.9%

The ground potential is deactivated by the DME control unit (VarioCam deactivated) if:

Engine speed > 5,120 rpm

[valley996]

Loren,

I got my Durametric today. I hooked it up and had no codes. Can you give me an idea how to capture the reading that you suggested.

Thanks

Is there an option for both of these on the Durametric?

1. Check the throttle potentiometer using Durametric, PST2, or PIWIS tester.

2. Likewise check the operation of the VarioCam actuation.

[Loren]

On Durametric I think the category is called "Actual Values".

Choose from the list what you want to monitor (both throttle and Tiptronic).

[valley996]

On Durametric I think the category is called "Actual Values".

Choose from the list what you want to monitor (both throttle and Tiptronic).

Thank you. I'll check it.

[valley996]

Okay, I did my final flush of the transmission, changed the oil and replaced the fuel filter. I drove the car afterwards and the surge is still there but it is only half as bad as it was. There were numerous bubbles in the fuel that came out of the filter. I assume that was water. I am still lost on the total solution. I do have to replace my motor mounts, the right spilled out the fluid yesterday while I had it up.

Loren,

I will post my values today, so if you don't mind looking them over, I'd really appreciate that.

[valley996]

Loren,

Will you look over the Durametric readings and see if anything looks bad. Do the O2 sensor voltage look right?

Thanks

996.txt

Edited July 19, 2010 by valley996

[valley996]

Loren,

Alright, I got my car back from the mechanic today. He changed the plugs and it 'may" have helped a little. He says what is causing my problem is the car is running too lean. He says most likely it is the coolant temperature sensor. He says the sensor is too sensitive and he can adjust the sensor by changing the resister in it. He said he has fixed this same problem on BMW, Mercedes and Porsche. He says the problem gets worse as the car gets warmer. I have not paid attention to this enough to know. He added Techroline to the gas to clean carbon out. He also said the combustion chamber can get allot of carbon build-up in it thus causing the car to run lean. I did clean the throttle body and there was no change. Does this sound like anything you have heard before? Also, will my Durametric tell me anything about this?

Thanks

[dammad]

Did you find out any more about this? I have a similar surge around 2700RPM that I'm trying to determine is the Tiptronic, Variocam or something else.

[valley996]

Did you find out any more about this? I have a similar surge around 2700RPM that I'm trying to determine is the Tiptronic, Variocam or something else.

I can't find an answer at all. I have about 20 different opinions so far. I bought the Durametric and it is nice, but there is nothing to tell you what the readings and values should normally be. What is normal voltage? What is the correct reading for the O2 sensors? What is the correct timing? I can't find anything from Durametric to help out on this. It's like having a brand new book written in Chinese and I can't read Chinese! I have had everything suggested (and I appreciate them all) from torque converter, spark plugs (replaced), MAF (cleaned and checked), TPS (replaced), fuel filter change (may have helped some), serviced the transmission ( may have helped some), checked for vacuum leaks (none found). I am afraid to go ahead and replace the torque converter, because that is going to cost me at least $2,000. This was my dream car and I was so excited to have a Porsche and I have yet to enjoy it. I am thinking I have made a mistake at this point. So far I have spent around $1500 and no fix!

Anymore ideas out there. I can't even sell it at this point!

[JeTexas]

I agree that this sounds like a torque converter problem. When they are failing, the transmission will still make its shift, but the torque converter will make your RPMs wander up and down causing the car surge under normal acceleration.

[valley996]

I agree that this sounds like a torque converter problem. When they are failing, the transmission will still make its shift, but the torque converter will make your RPMs wander up and down causing the car surge under normal acceleration.

What is strange is that it does the surging while just cruising, not when the car is in need of a shift. I can go to manuel tiptronic and force it to stay in a gear at that rpm and it still surges. Would this still possibly be the torque converter? It also does it in all the gears as long as it is that particular rpm range. It does get worse as it is pulling a hill.

[JeTexas]

I agree that this sounds like a torque converter problem. When they are failing, the transmission will still make its shift, but the torque converter will make your RPMs wander up and down causing the car surge under normal acceleration.

What is strange is that it does the surging while just cruising, not when the car is in need of a shift. I can go to manuel tiptronic and force it to stay in a gear at that rpm and it still surges. Would this still possibly be the torque converter? It also does it in all the gears as long as it is that particular rpm range. It does get worse as it is pulling a hill.

Yes, that is the torque converter.

[Jtown1973]

I know this is an old thread, but I'm having the same problem with my '99 tiptronic. Was the problem ever fixed and what was the cause? I'm also thinking it's the torque converter but wanted to know if it fixed anyone else's issues before spending that kind of money.