Need help on 2009 audi q7 3.0 tdi codes P0087, p0269, p067 codes different glow plugs at different times....p0191....also has a long start alot of times and sometimes white smoke but goes away

 

You can easily Google all those codes by adding Audi Q7 TDI after them. Scantools like the OBD-Eleven actually will Google search it for you from the scan interface. If you are going to DIY on this car, get the VCDS cable system/Ross-Tech software, as it gives you the best insight and access required to both repair and maintain this car.

Those codes say you've likely got multiple related issues going on. Glow plugs don't last forever. If you are using a standard OBD2 scanner, then you aren't seeing all the trouble codes stored in your Q7; this car requires a VAG-compatible scantool to read everything and perform maintenance functions. A bit of white vapor out the pipes is normal at cold start on a TDI until it begins to warm up and reflects low cylinder & exhaust temps.

The purpose of the glow-plugs is to preheat the air in cylinders prior to engaging the starter on a cold engine, as the TDI is a compression engine...the compression stroke heats the air in cylinder to where it spontaneously combusts when fuel is injected, etc., and the white 'smoke/vapor' is indicative of a cold/incomplete burn. White-colored/coated exhaust tips, on the other hand, indicates an Adblue dosing/system issue. If your glow plugs are going out, you will get long crank cycles to get enough heat in the cylinders built up to support sustained compression ignition. The same can occur if you turn on the ignition to 'accessory', but do not immediately start the car, then attempt to start the car later w/o turning the ignition off fully and recycling it so that the glow-plugs and normal diagnostics will be engaged in the starting cycle again.