Strange Start Issue

[SouthIndy_Talon]

Hello,

I have a stock 90 TSi. Lately, I seem to have a strange starting issue. If the car has sat for a long time (overnight or during my 8 hour work day), the car seems to struggle to start up (even worse when it is a bit cooler outside). I usually have to hit the starter two or three times in order to get it to fire up. Sometimes, it will start but begin to studder and I will have to shut it off and start it one more time. Once it does start, it tries to hold at 1500-1600 rpm, but will fall to normal idle after a few seconds and then will stall out occasionally. It would always idle a little high when cold until the car was warmed up. But now it seems like it is not able to hold that slightly higher idle while warming up. I am thinking it might be the FIAV? Car starts and idles fine (minus about a 50-100 rpm idle surge) once warm.

Car does have a new(er) ISC.

Have also noticed that in the mornings the idle will drop a little bit for a few seconds once I turn the headlights on. Not sure if that is related at all or not.

Thanks for any help that you provide!

 

[kamikazeredneck]

This sounds like a ISC issue. I removed mine and every time I start the car it's hard to start like you are describing. I would test your ISC motor and make sure it is operating correctly. It's a easy test and from what you are describing it sounds like that is the issue. I know you said that your ISC is new but I've had many parts be DOA or die after only a few hundred miles. If you have to replace it, make sure you get one that is from a reputable place and not one from a chain store. The chain stores might be cheaper but in my experience they break much quicker or are DOA.

Here is a YouTube video on how to check the ISC:

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[luv2rallye]

Another possibility: After sitting long time you may be losing fuel pressure in the rail (which you shouldn't) due to leaky fuel pressure regulator (usually), injector, or fuel pump check valve. Check rail fuel pressure after it sits 8 hrs (or since a fpr is so cheap and it's the usual culpret, you can just try replacing it).

 

[SouthIndy_Talon]

This sounds like a ISC issue. I removed mine and every time I start the car it's hard to start like you are describing. I would test your ISC motor and make sure it is operating correctly. It's a easy test and from what you are describing it sounds like that is the issue. I know you said that your ISC is new but I've had many parts be DOA or die after only a few hundred miles. If you have to replace it, make sure you get one that is from a reputable place and not one from a chain store. The chain stores might be cheaper but in my experience they break much quicker or are DOA.

Here is a YouTube video on how to check the ISC:

You must be logged in to view this image or video.

Thanks. I will double check the ISC tonight.

Another possibility: After sitting long time you may be losing fuel pressure in the rail (which you shouldn't) due to leaky fuel pressure regulator (usually), injector, or fuel pump check valve. Check rail fuel pressure after it sits 8 hrs (or since a fpr is so cheap and it's the usual culpret, you can just try replacing it).

How long does it take for the fuel pressure to come back up to normal? The car seems to struggle for a while after it finally starts for a few minutes. However, that might explain why it is hard to start in the first place. Maybe there are two different issues going on at the same time. I will check into that as well.

 

[steve]

How long does it take for the fuel pressure to come back up to normal?

Fractions of a second if the fuel system is up to snuff and working like it did to begin with.

 

[SouthIndy_Talon]

Fractions of a second if the fuel system is up to snuff and working like it did to begin with.

Thanks. Probably need to look into the fuel system components anyway. I believe everything (except for the injectors and fuel filter) are original to the car from 1990.