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Re: Interpreting data. VS s3 Log
Posted: Fri Apr 28, 2017 1:23 pm
by Dylan
If it needs throttle it's likely to be rich. Injectors leaking maybe a place to look? Smoke out the exhaust when it starts?
Set the base idle could help with the IAC. 10-20 step's when warm is usually ok.
Re: Interpreting data. VS s3 Log
Posted: Fri Apr 28, 2017 4:21 pm
by Whyzee
I've already replaced injectors and fpr, and had tune adjusted so it gives less fuel on startup. No smoke at all.
I don't really know where else to look? I was thinking that maybe the IAC was stuck closed or something like that.. still, sometimes starts straight away without hesitation and other times it's a pig. Would a video help?
Re: Interpreting data. VS s3 Log
Posted: Fri Apr 28, 2017 5:55 pm
by Dylan
Post up a log or check out the IAC trace. Key on engine off put into diagnostic mode that'll fully extended the IAC solenoid. They key on and off it will return to it's park position.
Re: Interpreting data. VS s3 Log
Posted: Sun Apr 30, 2017 11:27 am
by Whyzee
So, I changed the IAC and cleaned the throttle body. It's different now.
If i turn the key quickly, it will crank and won't normally start unless I stab the throttle. BUT if I turn the key to the on position, then off and then try to start it, it'll fire straight away...
Maybe it's just an IAC problem?
Re: Interpreting data. VS s3 Log
Posted: Sun Apr 30, 2017 11:44 am
by Dylan
Maybe lack of fuel, priming the lines twice sounds to help
Re: Interpreting data. VS s3 Log
Posted: Sun Apr 30, 2017 1:34 pm
by MAGP
Dylan wrote:Maybe lack of fuel, priming the lines twice sounds to help
I agree, the fuel pump, injectors, or regulator, aren't holding pressure.
Re: Interpreting data. VS s3 Log
Posted: Sun Apr 30, 2017 6:18 pm
by The1
Fuel pump anti drain back valve is common if pump isn't running the line drains back to tank
Re: Interpreting data. VS s3 Log
Posted: Sun Apr 30, 2017 7:15 pm
by Whyzee
It'll still do it immediately after turning it off too, which is why I wouldn't expect injectors/fuel pump to be a problem (plus they're new).
Thing is, I can crank it for 5 seconds or 30 seconds and it wont start. Turn the key off and back on and it starts without hesitation...
Was never a problem with the old 424 pcm. It's only been a problem since I've had the 531 PCM... Anybody know whether these use different IAC's or any differences in throttle bodies from VS to VS s3/VT?
Re: Interpreting data. VS s3 Log
Posted: Sun Apr 30, 2017 8:10 pm
by The1
relay perhaps? Or can you hear pump running?
Re: Interpreting data. VS s3 Log
Posted: Mon May 01, 2017 8:15 am
by MAGP
The IAC is the same from VN-VT1. The throttle bodies are the same from VN-VT1 except for the ecotecs which use a shorter throttle body and the throttle blade opens in the opposite direction of the normal throttle body so the TPS is also different for the ecotecs compared to all the other V6 and V8s from VN-VT1.
A fuel pressure reading would be able to assist discount fuel pump etc.