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1999 996 Surge At Around 2,000 Rpms


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I have a 1999 996 carrera tiptronic and it has a surge in engine speed between 1500 and 2200 rpms. The tac and engine speed goes up and down, in a steady rhytm. It does not do this while in park at the same rpms. Also, when I am in that range and I mash the pedal there is a stutter, almost like a miss. I know this is hard to explain, but there are no check engine lights. It does this in all gears in the same range. It is smooth below and above the range I have listed. I need help!

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You might not have a check engine light but there might be codes in the system. I would have the DME and transmission checked for codes first.

I have it scheduled in the morning. I'll post the results. Thank you for the suggestions. It's my first Porsche!

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Does the car have an electronic throttle? - if so, problem may be linked to carbon build up in the throttle body - not difficult to clean yourself...

I don't know about electronic throttle. I took it to a garage today and he said it was most likely the transmission. He referred to it as the car looking for a gear while in the 2,000 rpm range. He noted that if it was climbing a grade it became worse. He received no error codes so he felt it was mechanical. He recommended going to the Porsche dealership to rule out a software problem. Any thoughts?

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I would also recommend a dealer visit. Can you feel it dropping out of gear?

No it doesn't drop out of the gear, it just surges while in the gear. It does it in all gears as long as it is in that RPM range. It also gets worse when it is climbing a grade.

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Here is what the Porsche mechanic said. He said the main line pressure for transmission fluid control loses pressure on and off which is a sign of a weak solenoid. He suggests to replace transmission ( I can't afford!) also, he says I can replace valve body or individual solenoids. Does this sound right?

1. He did a 89757 internal malfunction test with piwis tester - none registered.

2. fluid level - good.

3. tested MAF - good

4. tested for power and ground on TCM module - good

5. removed torque converter lock up wire and test drove- good

6. checked fuel pressure - good

7. no codes in vehicle

8. solenoid circuits are intact and complete

Diagnoses: He said the main line pressure was checked with a piwis tester and it it showed the main line for transmission fluid control loses pressure on and off which is a sign of a weak solenoid.

Is this possible and what is the cost of a repair?

Edited by valley996
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  • Admin

Here is what the Porsche mechanic said. He said the main line pressure for transmission fluid control loses pressure on and off which is a sign of a weak solenoid. He suggests to replace transmission ( I can't afford!) also, he says I can replace valve body or individual solenoids. Does this sound right?

1. He did a 89757 internal malfunction test with piwis tester - none registered.

2. fluid level - good.

3. tested MAF - good

4. tested for power and ground on TCM module - good

5. removed torque converter lock up wire and test drove- good

6. checked fuel pressure - good

7. no codes in vehicle

8. solenoid circuits are intact and complete

Diagnoses: He said the main line pressure was checked with a piwis tester and it it showed the main line for transmission fluid control loses pressure on and off which is a sign of a weak solenoid.

Is this possible and what is the cost of a repair?

If he suspects a bad solenoid (in the Tiptronic) why did he not run the Tiptronic tests on PIWIS?

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Loren,

I found out today the Porsche mechanic did not run the Tiptronic computer test. Could we be missing something by not running the test or would it show up anyway on the main computer check?

Thanks

Yes, that is why the test is there.

Run the Tiptronic tests and you might be lucky and it tells you exactly what is wrong.

  • Upvote 1
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Loren,

I found out today the Porsche mechanic did not run the Tiptronic computer test. Could we be missing something by not running the test or would it show up anyway on the main computer check?

Thanks

Yes, that is why the test is there.

Run the Tiptronic tests and you might be lucky and it tells you exactly what is wrong.

I really appreciate the advice.

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Loren,

I found out today the Porsche mechanic did not run the Tiptronic computer test. Could we be missing something by not running the test or would it show up anyway on the main computer check?

Thanks

Yes, that is why the test is there.

Run the Tiptronic tests and you might be lucky and it tells you exactly what is wrong.

Loren,

Nothing on the Tiptronic test. Could this not be a transmission problem? It is smooth while in park revving the engine, but it surges while in gear and moving. Could it be an ignition issue, coil pack, etc?

Thanks,

Aaron

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I assume they checked the Tiptronic fluid level?

Any difference going uphill or downhill?

They did and the fluid was good. It does get much worse going uphill and almost nonexistent going downhill mainly because I'm not using the throttle or no load on the transmission. It does it in all gears.

Edited by valley996
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I assume they checked the Tiptronic fluid level?

Any difference going uphill or downhill?

Fluid level was good. It is much worse going uphill, almost nonexistent going downhill. It does it in all gears if it is in the 1500 to 2500 rpm range. It is smooth above 2500 or below 1500rpms. It does not miss while in park and revving the engine.

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Does the whole transmission have to come off to replace. I want to rule out as much as possible, before I spend $5,000 on transmission. I really don't want to lose that money and it turns out to not be the problem. Thank you so much for the suggestions, I'm just really lost and don't know what to do at this point.

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Loren or anyone who may be familiar,

Can I ask you to watch this video of an Audi A4 with the EXACT same problem as mine? Especially at 1:08 into the video. I just don't want to replace a transmission if I don't need to, and It may turn out to not be a transmission at all. I appreciate any help or suggestions at this point. I just don't want to sink a fortune in a rebuilt transmission and not need it.

Thank you

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