webtechy

Hi there, did you get to the bottom of this out of interest?

Ali007

Guys my Q7 hard starts usually doesn't start on the first attempt.sometimes emits white smoke from the exhaust on start up.im from the Caribbean so it can't be cold weather.I've changed starter and I used some fuel additives and still nothing has changed any other suggestions?please help..ive also changed the EGR valve and the the glow plugs

alexdei

hi Franklin Andrada, where are you from, I believe I did all those things as well. Did the problem fix on your end?

j4g3d

Recently i've noticed a possible starting problem on mine.

Mine is tuned up.

Lately on cold starts, using the start button (keyless) i have not tried this in cold with the key in the car... the car would crank over for a few seconds longer than usual. It almost sounds like the battery/starter stopped working a split second before it then fires up fine. Hard to explain, but you know when a car is turning over, making that 'turn over' noise, well it almost stops turning over, as if its dying, but then it fires up ok. Once its going its fine.

The battery was replaced and coded properly 3 months ago. So is brand new.

Any ideas?.

Q7Jazzy

Same here, my 2007 TDI will crank just fine a hundred times in a row, but the hundred-first is a dud and I have to restart, followed by plumes of white smoke as described above. No errors in VCDS.I have noticed something interesting: the first attempt is typically a dud (a 10 second crank), but if I press the accelerator 3-4 seconds into the second attempt, the engine starts immediately. This tells me one thing – the engine is not getting air (it is getting fuel, and plenty of it - thence the white smoke). In my case, I would rule out fuel- and battery-related problems, glow plugs, injectors etc. I preemptively checked and cleaned the throttle body a month ago; the plastic cogwheels are all fine. Is it possible that the flap remains stuck closed after the last engine shut-off? I occasionally hear a buzzing noise from the flap after an engine shut-off. What else should I look at in the air intake assy (I cleaned the MAF sensor and the flap) that could cause this but not throw an error?

Matt83

Hello, have you found the problem since? I have exactly the same problem (difficult starting hot or cold) thank you 😉

Q7Jazzy

Look into the following:

• Throttle body stuck in the closed position due to gunk and/or worn cog wheels, this happens occasionally and results in a no-start -> clean, replace cogwheels
• Weak and/or badly coded battery -> replace and code properly
• Cam sensor and crank sensor and their signals/correlation when cranking -> replace
• Air pockets in the fuel lines (including HP fuel lines) and common rail reservoirs on both banks -> bleed
• Main positive cable voltage drop due to copper oxidation (anything above 0.3V is considered bad, mine was 0.6V!!!) -> remove the cable (what a job!) and dip the copper around the lugs in molten solder
• Main negative cable connection to body -> clean
• N290 defective/sticking -> replace
• N276 defective/sticking -> replace
• Weak/old starter motor -> replace
• Glow plug relay in the engine bay fusebox -> replace

Unfortunately, I didn’t identify a single root cause or something that would make me say: yea, that’s it!! It's rather a combination of the above. I did it ALL, and mine is starting fine now.

Matt83

thank you for your answer I will look, I forgot to specify it is an a5 that I have. I have researched further, my symptoms are - slight smoke when the engine is idling and sometimes a few jerks when the engine is at 90 in temperature. - cold start problem and more difficult when hot (10-15sec) start engine pilot starts. above was made: - EGR valve - 4 out of 6 injectors - starter - intake flap - PMH flywheel clutch... - revision with filter the previous owner tells me that the problems came when he did the overhaul with the filter + accessory belt + hp pump belt + intake flaps. Also there is a stall on the hp pump?? the rail injection pressure has just been tested, it is ok, no particular fault apart from p008700 injection pressure too low.. thank you !

Matt83

[QUOTE=Matt83;25693694] merci pour votre réponse je vais regarder, j'ai oublié de préciser c'est un a5 que j'ai. J'ai fait des recherches plus approfondies, mes symptômes sont - une légère fumée lorsque le moteur tourne au ralenti et parfois quelques secousses lorsque le moteur est à 90 degrés de température. - problème de démarrage à froid et plus difficile lorsque le pilote du moteur de démarrage à chaud (10-15sec) démarre. ci-dessus a été fait : - vanne EGR - 4 injecteurs sur 6 changé - démarreur - clapet d'admission - embrayage volant moteur PMH... - révision avec filtre l'ancien propriétaire me dit que les problèmes sont venus lorsqu'il a fait la révision avec le filtre + courroie d'accessoires + Courroie de pompe hp + volets d'admission. De plus il y a un décrochage sur la pompe hp ?? la pression d'injection rampe vient d'être testée, elle est ok, pas de défaut particulier à part p008700 pression d'injection trop basse.. merci ! [/CITATION]

Matt83

thank you for your answer I will look, I forgot to specify it is an a5 that I have. I have researched further, my symptoms are - slight smoke when the engine is idling and sometimes a few jerks when the engine is at 90 in temperature. - cold start problem and more difficult when hot (10-15sec) start engine pilot starts. above was made: - EGR valve - 4 out of 6 injectors changed - starter - intake flap - PMH flywheel clutch... - revision with filter the previous owner tells me that the problems came when he did the overhaul with the filter + accessory belt + hp pump belt + intake flaps. Also there is a stall on the hp pump?? the rail injection pressure has just been tested, it is ok, no particular fault apart from p008700 injection pressure too low.. thank you !