Sluggish when cold. What's up?

[wret]

After installing upper IC pipe I have a dramatic performance improvement and higher boost, but when starting cold, for a couple of minutes I have zero low rpm power. I can step on the throttle and it goes from zero to wheel spin but nothing in between. It goes away in about a minute.

Any ideas?

 

[DSM90AWD]

The increased boost combined with the cold air (which warms up after a few mins) could be pushing you to fuel cut.

Check your UIP connections and make sure yout BOV is plumbed back to the intake properly.

 

[wret]

I haven't ruled out a leak but I couldn't think of any reason why a leak would only be evident when cold and under no/low boost situation.

 

[AWDPetmitsu]

I have the same thing happening to me every morning and my car is stock. I'd floor the gas pedal and it's sluggish for a second, and then I'd get a sudden rush of power. This goes away after two to three shifts and then everything seems normal. I'm not really concerned with it but I do wonder what's going on.

 

[wret]

I think I may have it figured out. Someone correct my logic if it's off.

In the couple minutes before the O2 sesor warms up the engine is running pretty rich. If I still have a small boost leak somewhere, a small amount of boost might not make it to the throttle but the additional fuel does and creates an overly rich condition. The small air leak is compensated for once the ECU gets good oxygen readings.

 

[DSM90AWD]

Originally posted by wret
I think I may have it figured out. Someone correct my logic if it's off.

In the couple minutes before the O2 sesor warms up the engine is running pretty rich. If I still have a small boost leak somewhere, a small amount of boost might not make it to the throttle but the additional fuel does and creates an overly rich condition. The small air leak is compensated for once the ECU gets good oxygen readings.

As an FYI.. there is an ECU-Controlled module on the firewall that shuts down vaccume to the FPR for the first minute or so of startup which effectively boosts fuel pressure for that duration.

This could exaggerate any boost leaks (e.g. metered airs) impact on AFR as during this time the car would normally run richer.