C4 newbie question

Finally bit the bullet and switched from an 03 Boxster S to a 99 C4. And boy how I wish i'd done it years ago Anyway, one thing I've noticed is that if I'm driving at low revs and put the foot down, there seems to be something slipping - the revs build up freely, but it seems like the car has to build up the power slowly to match the revs. say I go over a speed bump at 20mph in 2nd gear, it feelslike the 4wd system is slipping until the speed of the car builds up. Sorry if that sounds vague, but the best I can describe it is that its like a slipping clutch - but the clutch itself is good and strong... So is it something in the 4wd system - or is this completely normal ?

Hi, I certainly don't get that in my C4. The transfer of power from axle to axle should definitely not be noticeable. Maybe the MAF wire needs a clean. You should me abel to find instructions on how to clean it here or on Rennlist. I got the PCB cleaner from Maplins. God luck Stu

Strangely enough... the MAF was changed on the car last May - but its only done 1200 miles since then. It was changed by the Porsche Centre - so perhaps my hunt can start there.... I dont know if its transfer from Axle to axle - but its definitely a big increase in revs - with no increase in speed.. but the MAF was the last thing changed, so best to start there...

If it is the viscous coupling in the front drive unit, it can be tested. The front wheels are put on a roller brake tester (as used in MOTs) and the PST2 reads the wheel speed from the ABS sensors. The roller brake tester shows the 'slippage load' (the rear wheels are on terra firma), and this is compared to a load/speed graph to determine if it is within limits. Therefore it shouldn't be too costly to check if the coupling is slipping excessively. Are you sure it isn't clutch slip though? Far more likely, IMHO.

I'm not sure I guess... but the specialist that checked out the car before I bought it was adamant the clutch was ok... I spoke to him again this morning about it and he was sure the clutch was ok... Then again - he drove it in city traffic, and the slippage isnt noticable when pulling off in traffic - just when you put the foot down at low speed. Thats what is confusing me - there is good bite on the clutch and definitely no issue changing gear etc.. I should also say that if I do a straight line drag type of take off - its perfect through the gears - no slippage at all... its just when I'm trying to accelerate in a higher gear with low revs... Anyway, its going to the OPC to get the expansion tank replaced ( a bit dearer - but can be done before x-mas ) and I'll get them to check it out then and see what they say.... Seeing as how I came from a tiptronic box - this whole manual 4wd thing is all new to me [ ]

I agree with Richard, sounds like the classic symptoms of a clutch on the way out. I hope the dealer has given you a warranty. Terry

Sounds odd, but I've never heard of the 4wd system letting anyone down. If it's not too late, get the expansion tank yourself from Eurocarparts and get an Indy to replace it at under 2 hours labour. Should be around 1/2 price of the OPC.

Ah.. well its Ireland here - and they all need to order them from the OPC. and I want to get it done before xmas....

Sounds like the clutch to me... try this- get it up to speed in say 3rd gear, and at max torque (about 4.5k if memory serves) then floor it, ideally up hill. If the revs flare before the speed picks up, the clutch is on the way out. After it slips, is there a distinct "burning" smell coming from the car. I don't want to be alarmist, but get it seen to quickly as once clutch wears out, you can (and I am may be getting the terminology wrong here, but I was informed by Ray Northway, a well-respected specialist) damage the thrust bearing or plate or something, and need a new engine...

I'll give that a try.... I'm pretty sure the slip is only up to about 4500rpm... And there is definitely NO burning smell in the car... I'll get the OPC to check it on Wednesday.... Bought the car private - so its caveat emptor I'm afraid

Sorry to say but the symptom you describe are exactly what I saw with my C4 when clutch was on way out. It drove fine under normal conditions, but if you floor it at about 2K RPM rev counter would zoom up to about 4 or 5K and waver there while the car caught up. Normal driving it was fine. Can't see how the viscous coupling can be the cause - it's actually meant to slip. With loads of power, if the viscous coupling was not gripping (at the point it is supposed to grip) the symptom would be the rear wheels spinning without the front doing the same. As for the MAF sensor.... all this does is measure speed/volume of air entering the air intake .... it's not related to the drive train (or at least not in a 993!)

Yeah... I've kinda resigned myself to it being the clutch... Did the test at 4.5k rpm - and no revving of the engine when I put the foot down.. and no burning small at all.. I did the standard 'put the car in 3rd and let the clutch out when stopped' test and the revs slipped up and the car moved off... Redid it several times after that - and everytime the car stalled...

It was the clutch in the end.... It went in for an expansion tank on Wednesday... and 2 hours later I got a phone call telling me my clutch was gone.... anyway, got it back yesterday afternoon and despite being a lot of euro lighter, I'm glad to have it back this side of christmas Thanks for all your advise and doomsday prophecies