Check for codes, clean your intake with some carb clean or seafoam, if all that doesn't come up with anything replace the forward bank O2 sensors.

 

Thanks Auditech79, that's extremely fast response. I just checked codes, therewas nothing there. I tried to use VAG-COM to find out the O2 sensor readings, got some numbers but don't know if they are of any significance. When you say clean the intake, can you explain a little more? (sorry about my knowledge, just started learning and excited about fixing the car I like).

Also, if the O2 sensor fails, would it not give me a code?

 

A bad O2 sensor should throw a code and we don't typically replace O2 sensors in a '99 car (for the most part).

What acutally happens on a cold start? Do you turn the key all the way and nothing happens? Or does it crank but not turn over for 5 seconds or so?

BTW a faulty fuel pump can go anywhere from complete failure to intermittant to occasional failure. I have one customer that just banging on the fuel pump was enough to "fix" it for a little while longer (this is not our usual MO though we tend to do permanent fixes). On the other side you could have a fuel pump relay that's faulty but typically it would fail a little more often.

How long has this problem been happening? Where do you live, is it truely cold in the morning (we're in SoCal and it really doesn't get that cold here)? If you have a failing relay ambient tempurature could play a role.

Sorry for all the questions but I can't just replace parts to find a problem I try to ask as many questions that can help identify a problem and even little details can help. Like what if the car sits ALL day from after a morning commute and you work late into the evening does it start quickly or slowly?

 

Thanks for the input. When I went through the forum, I find people are complaining about engine hard to start when it is warm, mine is on the other side, usually takes longer time to start when it is cold. It will start, just cranks a lot longer time (say 4-6sec v.s. 1sec). This problem first started 3 years ago, where the car just would not start. Then it became somewhat OK, but it has not been as bad as it is this year. Even last winter was OK. Once it is started, it is fine.

Just in case it means anything to you, I can feel my engine vibrates through the steering wheel when it is idling (I mean significantly more vibration than my other cars). A couple of weeks ago, when I stopped at light, the engine stopped (or you call it stalling?), never happend before.

I live in Windsor, Ontario, where I don't consider it is really cold. I have a garage too.

Your last question, when I start the engine in the evening, it starts slowly. But if I restart the car within, say 30mins of last drive, it will start normally.

Thanks again!

 

Thats some crazy stuff your describing, it almost sounds like you have carbon build up on the valves causing it to idle wierd and hard start up but it starts normally when its hot?
I would still clean the intake and try to clean the carbon build up off the valves.
The old school approch to cleaning it is have someonefloor the throttle wide open and you spray chemtool carb cleaner down the intake until the can is empty, this will make the engine bogg down and cause miss-fires until the can is emtpy but it should idle better than it everdid after your done. Give it a try it will only cost you the price of the can.

 

when you say spray down the intake, where exactly do you mean? Thanks.