Richard Hamilton

This is a UK specification 3.4 litre pre-facelift 2001 model C4S cabriolet. Does it have fly-by-wire throttle, and hence is cruise control retro-fittable?

There must be some region-specific coding in the instrument display, to account for the difference between UK/US gallons. Even my '98 996 is user-switchable between Metric/Imperial - not just on the OBC, but the digital speedo as well. However, you have to connect the PST2 to change the temperature display on the aircon.

The most likely difference between the 996 and GT3 gearboxes would be the ratios used. It might be that the synchro rings and hubs could be the same.

I know that Porsche have a similar policy on the tiptronic boxes - replace the whole box - but you can get the parts from ZF suppliers.

Perhaps when the box ends its production run (I assume that the 997 uses the same box) the parts will miraculously become available.

Is the GT3 gearbox the same basic unit as the 996? If you look at the PET you will see that all the gearbox parts are listed separately, and most have 996 part numbers. It might be worth looking in to.

I wonder if it could be a differential problem. Do you feel or hear any rear tyre scrub in slow speed tight turns?

Mine is definitely 10mm hex, which is the ISO standard for M6 thread. 13mm is the standard hex head on M8 screws. Either mine is unusual (maybe it has been replaced with an ISO standard screw) or Mr Porsche, in his infinite wisdom, chose a special screw for this application.

Just to get really picky, the DIY shows the M6 screw as needing a 13mm wrench - in fact, it should be a 10mm wrench.

Sad, aren't I?

Thanks Jeff

I guess I should stop worrying until it starts to run rough.

Can you tell me what the EVAP canister purge valve is?

I had this on mine, and it was the anti-roll bar drop links. (Maybe you call it the stabiliser bar). The joints on one end had worn, causing the clonking sound. "Cheap" and easy to fix - less than $100 for the parts.

Maybe I should try this as a new post. My DME fault register shows P1123 and P1125 fault codes, but I DO NOT get the CEL coming on at all. The car runs fine, but I would like to find out what is wrong sooner, rather than later. The DME actual values I am reading are:

Idle Speed - 680rpm

Load Signal - 1.3ms

Mass Air Flow - 19 kg/hr

Hot film mass air flow meter - 1.31 volts

Engine Temperature - 90°C

Throttle Plate Angle - 0°

Ignition Timing - 5.3° crank

Specific Air Mass - 17.0 kg/hr

Specific Air Adaption - 3.0kg/hr

Injection Time - 2.8ms

Oil Temperature - 90°C

IATS - 27°C

ECTS - 92.3°C

Oxygen Sensing Cyls 1-3 - 0.9 to 1.0 (varying)

Oxygen Sensing Cyls 4-6 - 1.0 to 1.15 (varying)

Range cylinder 1-3 (FRA) - 1.02

Range cylinder 4-6 (FRA2) - 1.01

Range cylinder 1-3 (TRA) - -0.36

Range cylinder 4-6 (TRA2) - -0.33

O2 sensor ahead of cat conv (1-3) - 0.1 to 0.7 volts (varying)

O2 sensor ahead of cat conv (4-6) - 0.1 to 0.7 volts (varying)

Camshaft Position deviation - -3.0° crank

Rough running threshold - 8.4

Rough running - 0.0

Segment (A) - 1.0

Segment (B) - 1.0 This should be Segment B - I can't get rid of the smiley!

Learning progress, sensor wheel adaption - 0.000

Misfire detection - 0.000

Engine compartment temperature - 60.0°C

Oxygen sensor heat resistance ahead of cat conv - 3.2ohms

I have checked the fuel pressure, and it is spot on - 3.8 bar engine off, and 3.3 bar at idle. I think all the readings are within the range of nominal values in the manual, except the TRA values that are way out.

"TRA - Time Relative Adaptation; a fuel injection adaptation method used to compensate for engine/sensor changes at idle, which are short term & small affecting the AFR, e.g. intake air leaks, and which generally varies equally with +/-values under normal conditions (taken from www.systemsc.com/glossary.htm)". I don't think it is an air leak, because the idle speed and mass air flow are within limits. The MAF sensor readings also seem to be correct, and I think the FRA values being correct bear this out.

Any ideas anyone?, and BTW what is the EVAP canister purge valve mentioned in other similar posts? Sorry for the amount of data, but I thought that too much was better than too little. I'm not sure what all these readings mean - I just took them straight off the PST2.

Berny

By taking the oil filler cap off you will have introduced an air leak and the ECU will richen the mixture accordingly, hence the rough running. Small leaks, like a leaking cap, can cause the idle speed to raise 3-400 rpm, and again it adversly affects the mixture control. If you have a scanner, plug it in and check the idle speed (should be 680 rpm), and also see if you have error codes.

Richard

Sorry to butt in here, but I have a similar problem on my 1998 C2 tiptronic. My fault register shows P1123 and P1125 fault codes, but I DO NOT get the CEL coming on at all.

Ignore this - I started a new thread.

I agree with Loren that the third party manuals aren't very good, and the bootleg Porsche manuals are pretty poor quality usually. However, this week I bought one on eBay made by LexCom Informationssysteme GmbH in Germany, which seems to have been made for Porsche, or with their approval, perhaps. It is a properly indexed and bookmarked pdf copy of the factory manuals, and covers 1998-2001 models. If you see one of these, go for it - it's the real deal.

Yes - thanks for that Loren - extremely useful!

1qt/1000 miles seems like a lot to me. I change my oil every 6000 miles, and don't need any top-ups between changes. Mine is a 60,000 miler.

Piston ring wear could be one cause, but it could also be valve guide wear. If you get a cylinder leakage test done, it would determine if it is one or the other (or both).

Thank you for all the information Jeff. I ordered the wires from my local VW dealer and they should be in today. They were readily available from VAG UK. Maybe all us Porsche guys buying these leads are causing the factory to remanufacture them!

ps. I should be able to email you the pictures we discussed on Thursday.

Jeff

What is described on "whiteson.org/boxster/mods/obc/" seems very straightforward, and the fact that Paul Marsh's garage shows that he did the mod recently using the switch, inspired me to have a go. Are you saying that it can't be done with the switch? Are the wiring instructions wrong?

Those instructions basically show a toggled earth connection to pin 21 for the mode-up signal or to pin 25 for the reset. (Mine is a 98 car). PLEASE let me know as soon as you can if this is wrong.

Sorry Chaps, panic over, I just found Yoseif's DIY page. If anyone else wants the info it is at:

http://www.whiteson.org/boxster/mods/obc/

Brilliant! - thank you very much.

Guys

TP - Is there a DIY for this?

Paul Marsh - Could you give details of the button and wiring connections you used?

Thanks

Loren.

Do you have a list of Porsche DME fault codes? I don't mean the OBD2 codes, but the ones that are referred to in the workshop manual. The only manual I have access to is an early one, and I wondered if they have issued an appendix with a decent list of codes.

I have DME error codes 27 and 35, which correspond to OBD2 codes P1123 and P1125. Thing is, the CEL doesn't come on and the car runs perfectly at all times. I think the fault must be intermittent and doesn't exist for long enough for the CEL to come on. I was hoping the Porsche codes might give me a bit more of a clue.

Porsche Integrated Workshop Information System.

It is the Porsche version of the Bosch KTS650.

You can read the radio code with a PST2, so it would mean a trip to the dealer.

Try www.mytyres.co.uk - select the tyre size and speed rating to search, select the tyre you are interested in, and click on the reifentest.com link. They give grip and wear ratings for most of the N-rated tyres. (Note: 1=best 6=worst). You can get to the site via www.tyretest.com but doesn't seem to include info for some tyres (P-Zero Rossos, for example)

I doubt if you would get 30k miles from the fronts of a C4, as they tend to wear more than the C2 and Boxster. 8500 from the rears is pretty poor. I got 12000 from a set of rear Conti's on my 993, with some spirited driving on our winding English roads.

Is the wear perfectly even? - they might have scrubbed out early if the alignment wasn't correct. You should get this checked at least once every couple of years, although lots of people have it done annually.

If you look in the 996 TSB's, there is one for dashboard noises - it's 9 pages long!! There are others for all sorts of internal squeaks and rattles!!