ECU tune?

[Quiny]

My 818 is ready to go cart but I'm really not happy with how it's running. It starts right up and runs pretty good until it gets to closed loop. I let it run for an hour, at idle not so bad but it really hesitates when you hit the gas. I have only one code P1507 "idle air control". I did check the basics, compression is good about 150 in all cylinders. Checked for vacuum leaks found none, neutral switch was bad and replaced it. Checked grounds and so forth. My assumption is that the tune is so far out that it is causing the hesitation and lean condition. I do have a tactrix cable and Romraider and I am tempted to make some changes but I thought someone else may have already been down this road and have some words of wisdom. Since the exhaust is different, the intake is completely different, and the fuel pump is different I just didn't know where to start. MAF first then injectors or the other way around. What about a good base map to start with?

[STiPWRD]

Do you have any bends right before your MAF? If the flow isn't laminar, this will cause issues. You mentioned you're running lean, can you elaborate? Is it lean at idle as well as the upper rpms? Are you running a wide band AFR and if so, what sort of numbers are you getting, maybe upload a data log? Also, what are your long term and short term fuel trims?

[Turn In Concepts]

First off what motor setup is in yours? 2.0L wrx, 2.5L wrx, 2.0L STI, 2.5L STI? All could have this code and all will be caused by different things.

Tony

[Quiny]

I'm running a 2.0 wrx. The O2 sensors are stock. I'm going to do some logging today and get some readings.

[Turn In Concepts]

You likely have a stuck idle air control valve. THey get quite gummed up and need to be disassembled and cleaned thoroughly. Problem is they can be a pain to take apart due to the strange 5 point star screw they use. Typically needle nose vice grips work best. You will also need a new gasket which we have as when you take it apart the gasket will expand greatly due to the coolant it has been soaked in.

Check out this video.

https://www.youtube.com/watch?v=Egp1Uhp1DVA

Tony

[Quiny]

I did have a 45 degree elbow directly before the MAF. I just plumbed it so it is a direct shot from air filter to MAF. It's running like a whole different car way better. Code is also gone. I love this forum. I do think I need to scale the MAF but at least I can drive it now. Here is a screen shot of it idling to 1500 rpm.
34666

[Buzz Skyline]

Our WRX and STI both used to do this when a particular vacuum line connection broke. It's right in the middle of the top of the engine. On ours, it was a blue t-connector that is easy to break when doing other maintenance, but it's hard to tell it's cracked by just glancing around the engine. I'll try to find a picture. I can take one tonight when I get home.

If that's your problem, replace the connector and you're good to go. They're cheap and available at most Subie dealers because they break so often.

[Buzz Skyline]

Look for this connector

34667

[Buzz Skyline]

Except that it's usually buried under a tangle of vacuum hoses like this

http://forums.nasioc.com/forums/showthread.php?t=2166862

[Quiny]

I did have that problem but I found it when I rebuilt the engine. I had all kinds of brittle vacuum lines. I ended up buy an entire new PCV hose and tee setup since mine was like glass. I'm sure my problem was what STiWRD said, the elbow directly before the MAF. Just to prove it I switched it back and had exactly the same issue. I cant believe it makes so much of a difference.

[Buzz Skyline]

Oops, I didn't read down to where you solved it.

Yep, this forum is indispensable.

[Quiny]

Is it ok to leave the fuel tank temp sensor open? I think it is only used for emissions testing but I could be wrong. Does anyone know if it gets used in the A/F calculations?

[Bob_n_Cincy]

Is it ok to leave the fuel tank temp sensor open? I think it is only used for emissions testing but I could be wrong. Does anyone know if it gets used in the A/F calculations?

Take a look at Tony's post #6 in this thread. He says you need the temp sensor.
http://thefactoryfiveforum.com/showthread.php?15946-P0183-Code&p=173662#post173662

[STiPWRD]

Glad to hear you got the problem solved. I had put a bend in my intake right before the MAF a few years ago when putting in some fmic piping for the wrx and had this exact issue, except my car was running super rich. I played around with my utec and tried tuning the ecu leaner but even insane amounts of fuel adjustment (25% correction) did not fix the problem. I ended up calling turboxs and they turned me onto the whole don't put any bends before the MAF tip.

As far as the fuel temp sensor, I'm not sure. Do you still have the old sensor? and if so, can you measure the resistance on it? I'd connect it and tape it to the side of the fuel tank but I haven't gotten this far along in my build yet. The best solution would be to have an in-line sensor in your fuel line that replicates the oem signal.

[Jaime]

The fuel temp sensor is about 2.5K ohms at room temperature.