1.9 Tdi Running rough when cold.

[redfive]

This 1.9 Tdi in a Sharan idles rough like a misfire when started from cold but when the engine heats up, switch off and restart the engine it is ok. I'm thinking a sensor somewhere will be the culprit. It has recently had a MaF meter too. Ideas please, thanks.

[ralton]

Hi redfive and other forum members,
My 1996 VW Passat Tdi has been suffering a very similar problem to the one you are describing for a few years now.
My car's 1Z engine problem is such that only when the engine is stone cold (ie first thing in the morning and in the evening to come home from work, either summer or winter) it will sometimes stop firing on one cylinder.
I have found from living with the problem for some time now that if I straight away give a little gas to reach around 2000 rpm during the first 10 seconds of start up, I can avoid the problem 90% of the time.
If however I allow the engine speed to remain around tickover during the crucial first 10 seconds of cold start-up then more often than not, one of the cylinders will drop out completely with white smoke (unburnt fuel) being emitted from the exhaust. Once the engine is in this dead cylinder state, I must either wait anywhere from 1 minute to several minutes on three cylinders for the dead cylinder to wake again. This reawakening will happen gradually. The process being speeded up by running the engine at higher revs for a while. Sometimes, like you also said, I have found that if I just turn the engine off for a while, say about a minute or two, then try starting again, the engine will start as if nothing ever was wrong. In either case once the engine has run smoothly for 10 seconds atleast, then I can stop and start and drive around without a problem.
Does this sound like your problem? If so, did you manage to cure it? Or has anyone come across such a problem asthis one?
The engine has done about 145,000 miles. It has had a new reconditioned cylinder head about 20,000 miles ago after a valve follower disintegrated. This I suspect happened due to a skimpy cambelt failure repair which was carried out before I owned the vehicle and either the repairer overlooked either a bent valve or damaged valve follower. As I did not purchase the replacement head or carry out the work, I am not sure whether new valves and followers were used or whether the old ones were re utilised.
I am suspecting either a sticky valve / follower / leaky hydraulic adjuster problem? or an injector / pump problem. I am also aware that injectors can become sticky but as I don't experience any smoke once all four cylinders are running I am reluctant to have them reconditioned?
Any help would be greatly appreciated.
Richard

[lovesacar]

try to check the vw oxygen sensor (http://www.vdubpartsdirect.com/vw_oxygensensor.html), fuel pump, catalytic converters. by the way, have you done tune-ups lately? might be its time..

[dergrossen]

Hey lovesacar..you sure you know what you are on about pal?:cool:

[user]

02 sensor would be my guess