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This '''audi 5cyl works''', but experiences "idle fluctuation problem" We've created this editable page to be able to help him, summarize the findings, suggestions in a thematically organized way. * does it rather happen with cold air/warm air ? ** cold engine / warm engine ? We've experienced that '''similar idle problems are often caused by VE table'''. Can be very sensitive in some cases. Because of the wideband measurement and EGO delay it's hard to diagnose properly (the leaning shows up later in the log than the actual problematic loadsite). In '''many cases the idle fluctuation was cured when the VE was fixed at the right loadsite'''. * Temporarily '''disabling EGO correction''' (or even permanently for idle) also worths a try. ---- * injector size= ?? ** req_fuel= ---- '''History''' - Mattias wrote on chat: * some guy with an Audi 5 cyl posted on [http://www.vemssupport.com/forum/index.php/topic,1503 this forum] * he was having trouble with the engine falling through when letting it down to idle http://www.savarturbo.se/~mattias/motor/vems_data/log-pics/overrun-1.png http://www.savarturbo.se/~mattias/motor/vems_data/log-pics/overrun-2.png At that point, fuel should be resumed after overrun, shouldn't it? Expression grid says ecu pulse width = 0, and so it is.. but the overrun fuelcut settings don't say so http://ranz.planet.ee/idle2.vemslog In the log he tries at first with no overrun fuelcut, later with the ones in my screenshots ---- '''Things to check...''' * too low overrun_fuelresume ? * or maybe lowmap ? but overrun_fuelresume=1800rpm (maybe not always ? Possibly not true for at all part of the log ?) and fuel back at 1173rpms Other strange thigs: * and mat/tps(fuel) table is strange, also mat/tps(retard) is not too safe for turbo * and boost target is abouve fuel cut Log analyse (http://ranz.planet.ee/idle2.vemslog) Interesting thing after tps pulse (rpm falling) and pw: * There are 3 tps pulses in the log. After the tps pulse when the rpm is falling the pulse with is not 0 and match with the VT calculations but the 2 other cases in falling rpm the pw is 0 and not match with VT calculations. I saw the modification around 22sec in the log (you can see the marker in the multigraph): *'''overrun fuelcut''' *pressure based: 0 -> 18kPa (maybe this explains the VT pw calculation mismatch ) *Fuelcut rpm: 8000 -> 2500 rpm *Fuel resume rpm: 500-> 1800 rpm ---- '''The log/config has some config errors which WILL cause idle problems.''' (Reidar, some of these were suggested in the forum thread already. All the config changes are in the log file, you only saw the first part with no overrun fuelcut - scroll and put the marker at the last blips of throttle in the log and you will see the overrun fuelcut enabled, the marker from the config change is visible at the bottom of the log viewer.) IAC PWM Frequency: is set to 250hz. 25hz works fine on the audi aan/aby/adu/3b Set the whole idle area in the Ignition table to the same ignition advance.. 15deg on idle or so. The PID settings is somewhat off in my opinion and experience with these cars. P= increase this. could try value: 70 I= Lower this value. Could try value: 3 D= Increase this value. A really High D often helps on cars with AirCond where they got stall issues when AirCon active. (just experience) Try a value of 150 Use the ignition based idle control to get a steady idle. I usualy tune it a bit rich on idle. 0.95 or so.
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