Strange issue - whining (and not from the owner!)

OK, a bizarre one that has manifested itself in 2 issues - possibly related, but tbh not sure. OK, #1 - I've noticed a pitched whining that's related to speed and throttle position. Location is from the front centre - so the only things in this area are the fuel pump and front diff (Carrera 4)..... Only is noticeable from about 50 - 60 mph in mostly 5th/6th..... Now, #2 I've also started experiencing some starting issues - it'll crank over very nicely, but struggles to fire. It WILL fire though with some encouragement. SO, I'm ruling out crank position sensor (surely it wouldn't even start then) I'm leaning towards fuel pump, BUT I can't hear any noises on idle on the driveway - only under load and in those conditions stated above. Aside from that the car is in good health - all liquids and heating is fine. Drives well etc etc. No juddering or wobbling. Any thoughts? DAn

That happens to me when the Mrs is in the car :dont know: :grin:

:floor: Yeh, mine stays in her own car now.

I did have some odd whiny noises between certain rpm that seemed to come from the front that were related to the aircon. Had the gas topped up and it shut up, along with the grumbly compressor noise from the engine bay.

#1 - does it whine if you stick the car in Neutral on Idle and freewheel at 50/60mph? If yes then I suspect front Wheel bearings.

My guess . The noise on its own and i would say probably front diff bearings .. similar to wheel bearings but i find the noise for those tends to alter on cornering. I would run the car up on a ramp to confirm which was at fault or worst case a test drive with chassis ears . Poor starting .. i assume you mean spinning over but not catching .. this could well be the fuel pump .. i would tend to expect lack or performance at high rpm though .. still its a possible . Crank sensor .. if the car is hot it can give a weak signal which the car struggles to read so it is possible but on the rare side ... usual fault is not start when hot but fine when cold . If we were to combine the faults to get a single item then a fuel pump again is possible .. But i think not .. The pump is submerged in fuel .. a sound deadening material and it would have to be screaming for you to hear it . On paper and yes it could be related .. in real life and i feel it isn't .. Running issues .. First check is fault codes , fuel adaptations and just looking at what the various sensors are doing with a tester .

Thanks for the all responses. To answer accordingly:- Aircon - all working fine. No untoward noises tbh. Whine sound (we're not talking a very loud sound tbh) - it's only present under load (gear) and with the throttle depressed (checked if level of pedal-mash made any difference - none at all). I'm going to treat the two issues as unrelated for the time-being then. I'll check the whine when I get out on the road with it - I live in the countryside so cornering at 50/60 is quite simple to acheive. But I like the idea of the diff - might be a ramp-job then. Starting issue - well, due to the unreliablity, I've not been driving it, so the attached video link is literally from starting the car cold. This is the 2nd start - ironically, I'd tried about 30 mins earlier and the bl00dy thing started first time! This subsequent time was a little more like how it is. (should be uploaded in about 30 mins - youtube is on a go-slow!) What about temp sensor? I've got a meter and fault reader, so I'll look at it at the weekend now. Thanks for your help Dan

I can't get the youtube vid to work im afraid . Temp sensor .. that's there for fueling so rich mixture when cold and weaker mixture when hot .. the car well knows what it should be .. if open circuit then it knows and will flag a fault code along with dropping out the temp gauge . i would be surprised shall we say if it's that ... rule of thumb with fault like this and you check fault codes then actual values of the sensors .. including the temp sensor. You would also look at the fuel trim adaptions . if no codes and nothing obvious with the sensors you move on to things the car can't see .. fuel pressure it can't see along with a poor crank angle sensor signal . Can you post a direct link to the video ... or email me it to me and i'll see if i can get it to work .. or if it works for everyone but me then please pray for my computer as i'm going to beat it a bit .

So after looking at this post - http://www.911uk.com/viewtopic.php?t=124928&start=120&sid=cbad4b0cd9ce8c5a7acdfa135bae56ab We've just found this on my car - Should it be connected and where?

The other one being some potential discrepancy on the coolant temp sensor.... Any ideas what the resistor values could be before I buy a replacement? Also, there's 2 part numbers - neither for a MY00 C4..... 996 606 405 01 (M96.01/02/04) 996 606 410 00 (M96.03) Cheers, Dan

Pipe would seem to be the resonance valve .. it opens at something like 3K rpm to allow better air flow or a different path for the intake airflow into the cylinders. In this sense there would be an air leak at 3K which the car will easily adapt for. No idea the temp resistor values but MC has mapped them for his project so perhaps give him a nudge ... a tester just reads out the temps . The part numbers to me indicate one is for model year 03 with the other being years 1,2 and 4 . There is normally a part number on each item so have a look at what's fitted to yours to be sure .

Thanks buddy, I noticed that the temps from the diagnostics in the AC panel were quite out (the 6c setting), but just wanted to double-check the data prior to ordering the sensor. As for the pipe, yeh, that's what it looks like - as only 2 places have dealt with the car (and one of those was Hartech when they rebuilt the engine!), someone's got a bit heavy-handed with it! grr. Looks a bit of a pig to re-fit too. TBH, I'd not noticed any difference in the meantime. Dan

I'm not going to say your starting issues is not the temp sensor .. it's just i would be surprised if this item was the cause . All i can say is i've not seen it so far with no code or no drop out on the temp gauge . Did you get a better link for the video ? or can you email me your video so i can have a look / listen . [email removed]

Appreciate your response and thoughts buddy. Just emailed you the link Thanks again, Dan

Ok .. That is a fueling issue .. its too rich on startup .. some cyls fire but not all of them .. when it does finally fire up its misfiring due to over fueling .. that slowly clears so that it runs on all cylinders . So .. the issue .. there are several things i can think of .. Fuel pressure . Leaking injector .. should have other issues but it will drop the fuel pressure on startup .. Temp sensor .. Maf sensor .. Air leak between maf and engine but i feel that would give other issues .. a look at fuel trims would help there . I'm trying to think of a spark issue .. i can't really see a CPS fault .. cam sensor and again not really .. both of these are outside possibilities shall we say . If no fault codes then im leaning towards a fuel pump issue .. i think i would remove the pump and have a look at the base of it and inside the tank .. any debris . I would also have a pressure gauge attached .. maybe the car is not holding pressure overnight .. draining back and it takes a few seconds to build up pressure again . Some thoughts anyways .. the sound clip helped me a lot :thumb: