Porsche Enthusiasts Club Forum

I have just been through a lot of this very recently, I can highly advise checking the plugs and their gaps first. For one thing it's 100% free to do. In my case it took a lot of money before this was diagnosed.

If you need an ICV I have the (perfectly fine one) I removed in my hunt for a solution that I could let you have for £10 + P&P. I'm going to clean it tomorrow.

Steven

It had a new set of Bosch super 4 plugs just over a week ago and it was the same plugs that came out. As they are four pin the gap does not need setting (as far as I am aware, could be wrong but would be a suprise).

I could be interested in your ICV, did you remove the inlet to change the ICV or how did you do it?

I didn't remove the inlet, there should be enough hose to move the fuel damper out of the way, you can (a little painfully) get your hand in far enough, then work a 10mm spanner in. I used a ring spanner which has the Z type bent end. Also if it still has the original hose clips just break them in taking them off and use new ones as re assembly would be nearly impossible from what I could see if you had to compress them in again.

I think all in all it took 30mins, of which 10 was walking into town for a box of clips. The other 20 were also laced quite heavily with heavy swearing.

Steven

Did you remove the two bolts that hold the clamp to the inlet or just loosen off the bolt on the clamp to release the ICV?

Dragging up an old thread but I thought I would provide an update. I just gave the throttle body a clean and job done. Every now and then it starts to make a comeback in which case a spirit drive brings it back to normal.

You mentioned you installed a new airflow meter recently. Did you set up it's idle mixture?

I just fitted it straight out of the box. How do I check and adjust if required?

All this was done a long time ago and it hasn't given me any problems.

Adjust as follows... (you need a CO gas analyser)

For non cat equipped cars.

1. Remove bolts which locate airflow meter onto the bodywork
2. loosen the jubilee clip that secures the airflow meter to the hose leading to the throttle body.
3. Remove the connection on the other side of the airflow meter to the badge panel and air filter
4. unplug the airflow meter wiring harness
5. Rotate the airflow meter so that the side that was facing down, is now facing upwards
6. reconnect the wiring connector to the airflow meter
7. You will see a hole in the airflow meter that was facing down (now facing upwards) it had an alan key headed adjuster inside, 3 or 4mm allan key usually.
8. Run the engine and warm it up completely, this will take twice as long as the gauge has indicated... so if on the coolant gauge it shows as being up to temperature
after 15 mins, run it for 30 mins... Have the probe of the CO meter up the exhaust at the time.
9. Once the engine is fully warmed up follow the tuning sequence at the end of this message,,,,

For cat equipped cars..
1. Remove bolts which locate airflow meter onto the bodywork
2. loosen the jubilee clip that secures the airflow meter to the hose leading to the throttle body.
3. Remove the connection on the other side of the airflow meter to the badge panel and air filter
4. unplug the airflow meter wiring harness
5. Rotate the airflow meter so that the side that was facing down, is now facing upwards
6. reconnect the wiring connector to the airflow meter
7. You will see a hole in the airflow meter that was facing down (now facing upwards) it had an alan key headed adjuster inside, 3 or 4mm allan key usually.
8. Run the engine and warm it up completely, this will take twice as long as the gauge has indicated... so if on the coolant gauge it shows as being up to temperature
after 15 mins, run it for 30 mins...
8a. Your car will have a pre cat test point, which will either be a test point in the engine bay between the engine and clutch master cylinder with a rubber cap on it.. or it will be a boss welded just in front of the cat with (usually) a 10mm bolt in it... remove the rubber cap or the bolt, and connect up your co meter to it.. (in the case of the bolt, you might be wise to knock up a metal pipe of about 18 inches long, which screws in place of the bolt, to reduce the heat, which may melt your co test probe)
9. Once the engine is fully warmed up follow the tuning sequence at the end of this message,,,,

Idle mixture test process.

1. Watch the CO meter for about 60 seconds, you are aiming for a CO figure of about 2% (not porsche recommendations, but mine!)
2. if the CO level is higher than the target, turn the adjuster clockwise half a turn and go to step 1.
3. if the CO level is lower than the target, turn the adjuster anti-clockwise half a turn and go to step 1

Remember, each time on step 1, wait the 60 seconds.

Every 5 mins, bring the revs up to 2000 rpm for 60 seconds to clear any pooling fuel in the intake manifold and to clear carbon from the engine and then go to step 1

Once you reach the target co level, turn off the engine, remove your test equipment, and refit the airflow meter correctly.

if you fitted the airflowmeter in warmer weather, it could be that the engine could tolerate whatever the mixture at idle was then, but now it is unable to tolerate the rich or lean condition of the airflow meter, which with colder air temps is causing fuel icing, poor atomisation or many other factors, causing an erratic idle.

I normally follow this procedure in autopilot, so the instructions may be slightly off, but the gist is there, if you notice anything different, let us know here and I will change the instructions and then turn them into an article on the website so anyone can benefit.

The 2% CO level I aim for is different to the advisory from Porsche, which is based on californian emissions standards, which are tight and not in the best interests of the engine, whereas in the UK the MOT requirement is much more lax, so 2% is kinder to the engine, cat (or not) and better for starting and generally a smooth idle.

With a good and well calibrated airflow meter, I also find that it improves very low RPM (labouring) performance with less shuddering (not that you should let the engine labour anyway!)