ScionFred

iTrader: (1)

I've got my setup tuned about 90% with the FIC but I still have some issues that have me stumped.

1) When I start the car cold my LTFT & STFT total roughly -20% but after a long drive when the engine is hot, LTFT & STFT total roughly +20%. This seems backwards to me. When the engine is cold, it's drawing denser air but trimming a lot of fuel, then when it's hot, it's adding a lot of fuel. Is this normal or indicative of a specific problem?

2) My base fuel trim for the 440cc FIs is currently -18% and my overall LTFT is roughly -5%. If I subtract 25% fuel my LTFT is close to zero but I end up with a lean, stumbling idle AFR when hot (LTFT=0, STFT= +20%, AFR=17:1).

3) Tonight I turned the ignition on while I booted my netbook and connected my OBD2 scanner. It was on for a few minutes and when I tried to start the engine, it took 3 tries and when it finally started it ran rough, AFR was richer than 10:1 and it stumbled a little. It seemed as though fuel had leaked through the injectors and flooded the engine. Fuel injectors aren't supposed to leak like this, are they? I have new DW 440cc FIs installed.

4) After driving around for weeks without any CEL codes, I got two P0335 crank codes tonight related to the engine flooding. Is it common for AFR related misfires to cause a CPS failure CEL?

Could a pre-AFR sensor exhaust leak cause symptoms like these? Could the injectors be leaking fuel when cold but not when hot? Any ideas or suggestions are welcome. TIA.

ScionFred

iTrader: (1)

Oh well... I'm still stumped by #1 and #2 but apparently my brand new $400 fuel injectors (or at least one of them) is leaking and needs to be repaired or replaced after <10K miles. Kind of goes hand in hand with the $150 AFR sensor that failed after <30K. I had the same problem starting my car tonight because of the engine being flooded. Just what I need... raw gas dripping out of an almost-new FI past the rings and contaminating my oil. I suppose I'll have to remove the DW FIs, reinstall the oem Densos and send the DWs back for warranty testing, repair/replacement. I may as well remove my $500 harness and $300 FIC while I'm at it. Don't really need them with stock injectors and 6psi. Man, this Scion boosting is fun... I sure am glad I didn't buy a trouble-free factory performance car instead of boosting an econobox and having all this fun.

BTW, $5000 invested in performance parts now but if you count my time at the same rate I earn at work, $10,000 invested in a car that still falls flat on it's face compared to at least a half-dozen factory cars costing under $30k new.

crush02342002

iTrader: (2)

here is just some advice that may help answer a little bit of your questions..

when tuning idle i found its easiest to get the engine warm (20 min of idle or 5miles of driving..justa rough guess), park it and shut the engine off, disconnect batt for a few minutes and touch the cables togather, reconnect and start car, ltft should be zero from the start if they are not then the ecu didnt clear (retry), short term should read high and this is the moment to start playing with your fuel map. It has to be done fairly quickly before the ecu starts changing the st to lt. The reason for this is to tune for a warm engine and not a cold engine, on cold starts the ecu may add an extra amount of fuel or leaner in order to ease starting. If starting is an issue you may look into playing with the fuel map around (14.7 is ambiant pressure for me, so use what is ambiant for you) 14.7 psi and 0-800rpm's. its something youll have to play with to see what works best for you. Even after initial start the ecu runs in open loop for a few seconds so playing with the 02 map in this area wont work. also something els you can think about is the maf map in the 14.7 (ambiant) and 0-800rpms, notice if its the same accross the entire 14.7 colume...one would think you should be less in between the 0-800rpm area becouse you are not getting that much air into the engine at start up. However if you do plan on tweeking the maf map be very carefull not to make large changes and also save a copy of the map before you attempt anything.

crush02342002

iTrader: (2)

oh and leaking injectors suck...lol

ScionFred

iTrader: (1)

Thanks Crush. I suppose you're right. Since I haven't had any cold engine idle or afr problems, only hot engine, I should just ignore the cold fuel trims.

It still seems odd to see -20% trim at 14.7 afr when cold and +20% when hot. My FIs are 20% larger than stock, I'm pulling 18% with the FIC, my overall fuel trims average about -5% yet hot idle seems to require 20% more fuel to maintain stoich. If I add fuel (-15%), my overall trims will be be closer to -10% but hot idle will still be about +15%. Seems weird to me.

Do you think it's possible for a FI to leak when cold but not when hot? I need to pull my plugs and test my FIs for leakage.

speakerboy

Not to doubt your ability, but have you looked into taking this to a reputable tuner in your area? It may be worth the peace of mind to pass it off to someone else, and then blame them if anything goes wrong.

coryjames

i hold the highest power customer xb all self tuned fred is a very keen guy and knows his stuff.

as for the crank code i get it on very cold days when starting with the eth i start slow and throw that code thats what it will do if it takes a while to crank i have tried to change it fix it manipulate it with no luck so i just deal with it i figure its hard for my car to get fuel pressure and eth is a bear to start cold lol

crush02342002

iTrader: (2)

fred the best thing i can tell ya is to use the o2 map and place in the desired cells 3.2volts or whatever voltage is stoich for you. I assume yalls o2 sensors are the same as ours if not very similar so voltage should be almost identical. set the o2 map to voltage as well. set your o2 map and try to match it with your fuel map. This has been a standard for me dealing with fuel trims.

ScionFred

iTrader: (1)

I may end up taking it to P-Tuning eventually. I understand how it all works, what to do and have the tools necessary but they probably know some tuning tricks that I do not. Also, a dyno would certainly expedite the tuning process. The down side is that a dyno can't replicate all the conditions experienced during normal street driving.

ScionFred

iTrader: (1)

Thanks Cory. I haven't had another P0335 so it was most likely caused by the engine being flooded by that leaking FI. Other than the recent crk code, I've been code-free for a very long time now. The P0335 code seems to get set quite easily for various reasons.

ScionFred

iTrader: (1)

I think I just figured out my lean hot idle afr problem. What seems to happen is that when I reset the ECU and start the engine cold, the ECU sets the idle LTFT to a negative value between -5 & -10%. Once the engine is hot the ecu still tries to use that negative LTFT and the STFT maxes at +20% which is still too lean. If I give the ECU more time to learn, it changes my hot idle LTFT to between +5 & +10% and the hot idle afr is maintained at stoich. In the future I'll follow your advice and reset the ECU with the engine hot instead of cold.

I still don't know why my idle fuel trims vary so much between cold and hot but I suppose it really doesn't matter. I can just tune accordingly instead of trying to figure out why things don't always behave as I think they should. To that end I'm gonna try adding some fuel in the idle vacuum cells.

Now my biggest problem is that $%#@ leaking FI and the 30F temp outside... Thanks man.