VR6 slow start and rough idle

[Kezbo 0]

93 corrado vr6

 

I'm having some trouble in that on startup the car seems to turn over for a few seconds before firing up, then when it fires it takes a few moments to clear its throat. Then once warm the idle seems rough.

 

I've had it on vag-com (lite) this morning and no fault codes found. I have replaced the fuel pump relay but that hasn't helped. I'm thinking it might be the crank sensor but want to be sure before spending much more money. Is there any way to tell without trial and error, what about the live data you can see on vag-com, is comparing that with typical figures of any merit (if so does anyone have normal figures?).

 

For example n a hot idle I'm getting:

Revs 680-740 (it's not bouncing around a lot but just doesn't sound ideal)

Timing 4.5-6 btdc

Co around 900

 

Any help or advice greatly appreciated to help my wallet!

[Mawrick 0]

I had intermitent startup problems with my VR6 (not rough idle though) and replaced quite a few things before I got info the fuel pump non return valve is notorious for failing - so much VW made a fix for it (basically a hose with a builtin non-return valve - but this is sadly no more available from VW.

 

I replaced with an ebay non-return valve, and some fuel hose (so I did't need to cut into the original fuel hose).

 

My problem was mostly a "hot start" problem - but j[ust thought I'd mentioned it as it's a quick/easy and cheap fix if that is the cause :)

 

[Kezbo 0]

Thanks.

 

That's interesting, I've never heard of that problem. Is there any way to test / identify if this is my problem?

[VW_OwneR_85 1]

seeing as you have access to vagcom get it on vagcom again and check out what coolant temp reading its getting ,

[Kezbo 0]

seeing as you have access to vagcom get it on vagcom again and check out what coolant temp reading its getting ,

 

It looked pretty normal when I had it on the other day, around 90 degrees. Are you thinking it might have been too low? Intake temp seemed quite high, about 30 degrees when ambient was 18, not sure if that's normal or not.