Lumpy Idle When Warm – Variocam?

[ickle_monster_au]

I have been hit by the PCar vampire again & its determined to make me a poor man. My 99 C4 Cab developed a lumpy idle resting at about 600 rpm when warm. Until it’s warm it runs like a dream, full power and full enjoyment. Once it’s warm however I have to watch it preparing to stall when idle. Once I nurse it off the mark it runs ok but I can hear the exhaust not running to it’s usual note.

When I dropped it into my only OPC within 50 miles and got them to stick a tester on it, there were no codes or faults present. They scratched their head and asked me to leave it with them.

Net result, I got the quote back today stating:

Camshaft Vario Unit Bank 1-3 is faulty

Parts £ 409.37

Labour - 7 hours - £ 553.00

Camshaft Vario Unit Bank 4-6 is faulty & leaking Oil

Parts £ 409.37

Labour - 7 hours - £ 553.00

Rear Main Oil Seal

Parts £ 400.93

Labour - 6-8 hours - £ 537.20

Prices do not include VAT

1. Can both banks go at once?

2. What are the alternate diagnostics and cheap fixes I can use before I empty my account in the search for happy motoring?

3. They only diagnosed the RMS during the last service 2 months ago. What are the chances they saw oil and assumed that it was RMS?

4. What the chance this could all be caused by the variocam solenoid on bank 4-6 alone?

Cheers

Peter

[1999Porsche911]

It is extremely unlikely that any of the problems mentioned above would effect your warrm idle. A bad variocam solenoid would give a error code anyway. If both variocams were inoperatable, you would know it due to the dramatic loss of power. Your idel is too low.

Possible things to look at and maybe just replace yourself would be the engine temperature sensor located on the back right bottom side of the engine. These are known to go bad and cause idle problems when warm. The idle control valve may be faulty. MAF might be dirty. Vacuum leak?

First thing I would do is hook up your scanner and take a look at the sensor reading after you go closed loop. When compared to expected readings, you can sometimes get a direction to look in. Also, reboot the computer by disconnecting the begative battery cable for a few minutes. Your idle will wander for a few driving cycles, but when the computer stabilizes, your idle problem may disappear too.

I would find a new dealer too. They obviously want to rip you off.

Edited August 10, 2005 by 1999Porsche911

[ickle_monster_au]

Sigh... I am with you on your rip-off statement.

I am not sure how they felt they could invent what they did and not get questioned.

When I stated lumpy I mean to say that it kind of hunts between 600-800 and the exhaust note is kind of blippy for a lack of better term to describe it.

Even if what they diagnosed is right, what's the chance of long term damage if I drive it off their lot?

[1999Porsche911]

Sigh... I am with you on your rip-off statement.

I am not sure how they felt they could invent what they did and not get questioned.

When I stated lumpy I mean to say that it kind of hunts between 600-800 and the exhaust note is kind of blippy for a lack of better term to describe it.

Even if what they diagnosed is right, what's the chance of long term damage if I drive it off their lot?

<{POST_SNAPBACK}>

Reboot the computer and see if it improves the idle. Clean the MAF and run a bottle of injector cleaner in you tank. No problem driving as is. Without you hooking up a scanner and providing us with sensor readings, we are pretty much blind.

Edited August 10, 2005 by 1999Porsche911

[Izzy]

I had similar problems. In the end, replacing the MAF did the trick. But before:

Remove battery power for a few minutes to reset computers back to factory standard (make sure you got the radio code).

Check the engine air filter and replace if needed.

How old are the plugs, how many miles? Replace (see DYI in this site) since they are easy and inexpensive to do.

The last one would be the idle potentiometer, rarely they fail.

Most likely sounds like Mass Air Flow Sensor, easy to replace. Same symptons in most cars just like you described. The lack of code is puzzling, but no system is perfect

Good luck

[ickle_monster_au]

Ok.. Todays News.

The P code they based my GBP 3K quote was a not present P1341 only.

It never actualy came up with a CEL.

Since I have taken my car back I have:

1. Drained / replaced the existing fuel with some nice new Optimax

2. Cleaned / inspected my MAF.

3. Re-set my computer.

So far on it's last run it did not start hunting but it is still idling down at about the 600 RPM mark but it seems quite happy.

[1999Porsche911]

Ok.. Todays News.

The P code they based my GBP 3K quote was a not present P1341 only.

It never actualy came up with a CEL.

Since I have taken my car back I have:

1. Drained / replaced the existing fuel with some nice new Optimax

2. Cleaned / inspected my MAF.

3. Re-set my computer.

So far on it's last run it did not start hunting but it is still idling down at about the 600 RPM mark but it seems quite happy.

<{POST_SNAPBACK}>

Glad it worked out for you. Enjoy driving.