car not running right...

DSM1G · 11-23-2004

I just put 550cc injectors in my car and now it does not run good at all. It starts up and then kills. If i give it gas it will stay running but run rough. I played with the SAFC, but nothing seems to be right. I checked all the vacuum lines, fuel lines, and spark plug wires and everything is plugged in. I even took the fuel rail back out a second time and checked to see if all the injectors were spraying, and they all were. Anyone know what my problem could be?
Its on a 93 eagle talon tsi FWD, at.
mods are: QPR built motor, evo3 big 16G turbo, walbro 255 fuel pump, IPT torque converter,SAFC, ported 2G exhaust manifold, 2.5 custom downpipe to 3inch exhaust with high flow cat, K&N filter, boost gauge, egt gauge, and now 550 injectors.

Thanks,
Adam

carltalon · 11-23-2004

What are your afc settings?

DSM1G · 11-23-2004

its at -10 for 1000 and 2000RPM. i tried everything to get it to idle, or run decent.

**Kracka** · 11-23-2004

What sort of MAS are you running? If its a stock one, you'll need to take out a whole lot more than 10% fuel (should be around -25%).

joem · 11-23-2004

Are you on low throttle setting are hi?
joe

Alpine TSi · 11-23-2004

I had 550's with no fuel control on an A/T ECU and the car ran but got shit milage because it was running rich.
I can't imagine the car not being able to even maintain an idle would be related to the AFC settings.

**Shane@DBPerformance** · 11-23-2004

550s are about 41% bigger than the stock 390s. Set you throttle switch over points at something like 20% low and 50% hi. Then if you have a stock MAS try setting you low throttle settings from 1000-7500 at -35%. If you have a 2G MAS try -20%. If you have a severly hacked 1G MAS then 0% to +25% at 1000, 0% at 2000 and maybe -5% the rest of the way up. You probably need to change your spark plugs by now also, if it has been running extremely rich. Pull them out and see if they are covered in black.

niterydr · 11-23-2004

Like I said, try -20, and see if that help out a little bit, if it does keep taking it out down till -30.
Or just wait to get that 2g one in there and start around -15.

DSM1G · 11-23-2004

thanks guys for your help. Im not sure what was wrong but I decided to pull the 550's out and just put my 450's back in, and it ran just fine. Im guessing the injectors might be messed up or something. Oh yea I dont have a stock automatic motor, there was a 6 bolt manual motor swapped in there before I bought it, so it has the 450's not the 390's.

Adam

**Shane@DBPerformance** · 11-24-2004

If it still has the automatic ECU, then it is tuned for 390cc injectors. 450s aren't a huge jump so the O2 sensor can probably still handle it, but the jump to 550s might be too much.

12-03-2004

Quote:

Originally Posted by ecoli

If it still has the automatic ECU, then it is tuned for 390cc injectors. 450s aren't a huge jump so the O2 sensor can probably still handle it, but the jump to 550s might be too much.

In closed loop the ecu can adjust for larger injectors up to 40% in 91+ and 30% in 90s IIRC but I am almost certain in dsms that when the ecu switches to open loop under hard throttle it is running off pre-programmed maps and the fuel trims do not update or have any affect on the fuel being injected. Correct me if I am wrough though, the dsm cd doesn't go into detail about it.

**Shane@DBPerformance** · 12-03-2004

The long term fuel trims still have some effect on the 2G ECU up to 4500 RPMs in open loop, but yea the DSM ECUs run off of hardcoded maps and don't us the O2 sensor at high load.