My 996 doesn't like slopes - but only when its warm!

Hi, New to the forum, so thanks for taking a look. I have a March 1998 996 (so one of the early ones), 86K, good nick, full history, had it a couple of months and all seems as well as can be expected. However, one niggle which is driving me nuts. My driveway slopes down towards the road, not massively, perhaps 1:25. I park the car nose up the slope (usually). From cold the car starts no problem. Drive it around (okay go for a burn..!) park it up level on the street - no problem, restarts every time. (In fact when its hot it will start on the slope OK for a few minutes....). BUT let it cool down for about an hour, so not fully back to cold, it is the devils own job to start with much swearing and teasing the throttle until it fires - once started its good as gold again. Now this is where it gets really cookie - reverse it onto the drive so its pointing nose down the slope, the problem doesn't occur. So to recap, warm (or hot) engine, parked on the level or nose down the slope, no problem. Warm engine, nose up the slope, poor starting. Diagnostics shows nothing; even cleared the buffer down, replicated the problem, and interrogated again (at the dealer) - still no clue. As a precaution we have changed the ICV, the temp sensor, the impulse sensor, and it had a new air mass sensor not long before I bought it - can't think of much else, except perhaps the starter which incidentally can be screechy, but again only when on the slope....(I wonder). However, the starter otherwise seems strong. Did wonder about the fuel pump/fuel pump relay, but that's venturing into spondooliks I'd rather not spend territory, unless I can be sure it would fix the problem. The inclined angle somehow plays a part so I'm speculating that if its not electronics, it might be some sort of physical/mechanical problem - is there anything like a non return valve in the fuel flow that could be susceptible I wonder? Any suggestions or similar experience (and resolution!) much appreciated. Thanks. Julian

I think this is a similar problem that Steve suffered from http://www.porscheclubgbforum.com/tm.asp?m=612015 He has sold his 911 but still pops in from time to time.

Julian! It does sound more like a fuelling issue to me. Nose-up, the tank will be higher than the engine, so I would be tempted to look at the fuel lines, to see if there are any non-return valves in the flow or return pipes which might be sticking open. However, it does sound really strange, and I have never heard of this before. When I had my '98 996, I had two occasions in 4 years of ownership where it was reluctant to start and took lots of cranking and throttle teasing before spluttered into life. It was on the level in my garage. I have heard of a couple of other people experiencing the same, but never a consistent and frequent occurrence like you are experiencing.

Thanks for that - but I'm having trouble following that link - even logged in I'm getting access denied?

It is in our member's only section, which you won't have access to. It describes how to change the crankshaft position sensor, which when it fails inhibits the ignition coils. When they start to fail, it causes difficult starting, but it would likely throw a fault code. Although a possibility, I can't see how it would be affected by the slope. To me, your symptoms are more like those of flooding.

To get to that link you have to be a Porsche Club GB member - you appear to shown as a "Guest" at the moment. If you are actually a member and haven't linked your account, then follow the instructions in this link ---> http://www.porscheclubgbforum.com/tm.asp?m=235860 to get your account upgraded.

Ah - well we already changed that - or at least I thought we did - the impulse sensor yes? Also, I am a member, and I thought I set up my login/forum id using my membership no. - has something gone wrong there, or have I messed it up somehow? Appreciated.

Actually - my link has the old info (I'll go and change it!) This is the correct link http://www.porscheclubgbforum.com/tm.asp?m=446453 Did you email admin as requested there to get your access upgraded?

Just done that email - hopefully get access soon - thanks.

...also had another thought - Richard mentioned possible flooding - mindful it starts ok cold, I wonder could the emu be misreading the warm engine and squirting too much fuel through? Though I'd have thought that would have been a consistent problem with a warm engine and not just on the slope....?

Only other slight clue is that intermittently the car will fire up and then immediately fail to idle and stall - corrected by a restart and a blip on the throttle. That can happen under hot or cold conditions - that's why I changed the ICV, but that problem still presents - again I suppose it might be indicating some sort of inconsistency in the fuel flow on start. Any further comments or thoughts/best guesses appreciated.