new turbo, new plugs... acceleration probs. continue

[plymouthtalon]

I posted awhile ago about my car accelerating slow sometimes. Every once in awhile I floor it and all the way through the rpm range the car accelerates just like my old n/t would under WOT. People suggested plugs. I figured what the hell, and I shelled out the cash for some Denso Iridiums. Others said turbo. I agreed, especially after the turbo locked up. Used-car warranty got me a new T25. I thought the problem went away, but now it's doing it again.

What could it be, wastegate maybe? I still have the stock boost gauge, and boost seems to build at a normal pace when the slow accel. happens. Everything seems exactly normal, except for the slower accelerating. No jerking or hesitation-type movements, just smooth (but way slow) speed gain. Usually I can make it go away by letting off the gas and flooring it again. Help?

 

[bobgeorge]

have you,changed the fuel filter?

 

[DSM90AWD]

What boost are you running? Stock?

Sounds like the car is retarding timing due to knock (lean or rich).. as when you let off off the gas it will resets itself.

There is a list on yahoo onelist called Phantom Knock which this could also very likely be.

Get a datalogger and see what affects on KnockSum, Timing and O2 voltage you get.

 

[plymouthtalon]

Havent had this car for long - its stock except for the SSQV. I removed the dumptube restriction and also the BCS restrictor, so boost might be a little above normal. I run premium fuel of course. and the BOV's vented back to the intake so I don't know about running rich. Can you hear knock at all? Cuz when the car goes slow like this nothing out of the ordinary seems to be going on besides the slow accel.

 

[DSM90AWD]

Your knock sensor will pick up knock before it is audible and retard timing so really the only way to pin it down is via datalogging.

I'd also try pressure testing your intake as even stock you can have significant boost leaks which will affect performance. For ex.. if your system leaks 2psi your T-25 (which is already inefficient to begin with) will have to run 18psi at the compressor to get 16 at the intake (ok 19.5 with the pressure drop from the stock SMIC).

Also try swiching to a different gas station as (especially during winter) gas can get contaminated with water.

Throw in some dry gas in the next tank.. then change the fuel filter.. then run a decent injector cleaner.