Idle And Initial Takeoff Probs

[rondofj]

Good Day...R34 RB25det with power fc and Precision 5558 here running 98.

Had this problem for a while. Stopped at lights I need more throttle to take off normally or it will vibrate, half stalling or in the worst case jerk / lurch extremely violently, coughing/gasping. Push in clutch and /or apply bit more gas it will recover n drive normally. Cold starts are perfect, cold driving for first ten minutes are always smooth and car purrs like a cat with lotsa low down torque. Once warm it runs and sounds rough, loses some low end torque. Doesn't purr smoothly anymore. Only stalls /feels like stalling when taking off with not much throttle. Boosting is fine, no hesitation or misfires, revs clean all the way, goes MUCH harder on colder days. Oh and car idles/runs a bit rougher with O2 feedback off, so I always have it on. Car has 1 sec or sometimes 2 sec LAG from stop to go most times. Very annoying. Have to keep feathering throttle.

Tested n fixed couple vac leaks, changed fuel filter, found tiny leak on wastegate clamp where it sits on turbo housing. (Tiny soap& water bubbles in that area when idling). Coolant temp sensor seems to be working cos the commander displays change in temp from start first couple mins about 25C and then goes up n normally sits at 72C or up to 80C boosting hard for a cew mins on warmer days. Idle air control valve (IAC) has been removed n cleaned twice, m sick of it. Used a gasket paste though so not sure if leaking, spraying WD40 there and on joints/suspect areas doesnt change engine note though. TPS is 0.46V at idle and voltage changes with accelerator stabs so assume its fine. There could be more minor vac leaks though as this test was done sometime ago. But prob was there then even after fixing leaks. Havent fixed the tiny wastegate leak though, tightening v band n it still leaks slightly, holds boost well though.

Kinda lost here on what it could be.. Fuel pump is a walbro, directly wired. Air filters clean and Z32 is plugged in tight and joints re-soldered, sensor element cleaned.

Edited July 25, 2015 by rondofj

[rondofj]

Have to add that during driving or slowing down/ stopping etc, there are NO stalls or feeling like stalling, only from stop to go.

[Ben C34]

Can't beleive that you haven't bought a wideband yet.

[Sinista32]

What is the upper as well as the lower voltage of the tps. Can you get that measured. Have you had your tuner look at the tune. Checked the water temp sensor.

[rondofj]

Ben, remember when you guys once suggested to get the afrs checked, well had that done sometime ago at unigroup, was all good. TPS at idle is 0.46V and pedal to floor ( keyjust at ON) from memory is around 4.8V or something- will check

[hardsteppa]

Whats the section of the map like that you're in when taking off? Might need a bit more fuel, which would not be as evident when aided by cold start enrichment, and if its only that small section of the map you wouldn't hit it when driving otherwise, only at takeoff.

[rondofj]

Just tested -TPS idle is 0.46V and pedal to floor is 4.07V.

Coolant temp sensor at 18-20degs is around 1800+ ohms and dropping roughly an ohm a second as engines running/warming up. Was around 1490 ohms after say 5mins and showing 41degrees hot on commander

[rondofj]

How do I check that section of map, are you talking about the load vs rpm table where the black bar jumps across. Or the fuel/ignition maps

[rondofj]

Timing at this point is usually 25ish or less degrees when stopped after 5-10min drive, taking off it drops to 15-16degrees.

[rondofj]

[hardsteppa]

I have no idea about power fc's sorry, someone else would need to input there. I just had a similar issue on my other car which runs a Wolf 3d V4, low in rpm range under light throttle. Quick look at the fuel map showed it had a nasty hole lol, smoothed out that section and never looked back.

[89CAL]

To me, their are fairly decent jumps in the ignition cells as it jumps up from N01 to N02 and then N03. From memory my N01 and N02 cells were set at a number down to about L04 or L05, 20 degrees I think is what I had there. The Power FC does its own thing with timing at idle (has its own idle map that you cannot access), but I think I found that playing with these cells made my idle a little bit nicer

It wouldnt hurt to try at this stage, just take photos of what you are changing (assuming that you dont have FC-edit and a Datalogit or FC-Hako) that way you can set it back to normal if it makes it worse

I'm no tuner, so I'm not giving you a 'this is definitely the problem' answer, hopefully it is a helpful suggestion anyway.

Fueling, its hard to say without a wideband, and I don't feel comfortable telling you to change your fueling without knowing what its at and where it is going. Shouldn't really make much of a difference at idle, but none the less

[Dose Pipe Sutututu]

those jumps are normal, you need a wideband... possible your throttle enrichment table is off its chops.

[rondofj]

Sorry app doesnt allow me to load straight but here are the afrs

[rondofj]

Did come up ok, test wasdone last year but car had same issues then n nothings been changed since

[Ben C34]

That info is as good as useless for your problem

[Dose Pipe Sutututu]

you need to monitor what your afr reads on and off throttle and also on transient throttle.

Ben and I have told you plenty times get a wideband