Jump to content
SAU Community

Recommended Posts

Hey just a small annoyance with my cold start. When starting the car up for the first time on the day the idle goes to like 600,700rpm kinda stumbles then just revs out kind of wakes up and then just warms up normally and yeah everything else is fine i know kind of picky but yeah just abit annoying. For the rest of the day turn the car on when cold warms up normal but if its not driven for more than a day or two then yeah does it again could be the cold but also wondering if it may be related to the tps?? It use to play up all the time but got it fixed but wondering if for like the first 5 seconds when cold this is going funny. maybe its something else but yeh what could it be.

Link to comment
https://www.sau.com.au/forums/topic/124145-cold-start-annoyance/
Share on other sites

The way I understand this situation is,

a 'cold' air/fuel mixture is richer because of more denser air,

a 'cold' combustion chamber is hard to ignite,

a slightly lean air/fuel in a cold chamber is even harder,

whereas a slightly rich mix will wet/flood the chamber,

if the rev range is increased the mix is easier to predict/control,

this is the basic problem with any air/fuel mix.

I also suffered cronic problems lately in the cold, the coil packs were cracked which usually shows up in the high rev range when each pack is firing around 16 times a sec, but on a cold DEWY morning everything is damp and the cracks act as conductors until the heat disperses it.

apart from your aac valve on the manifold plenum there is a valve UNDERNEATH the inlet plenum/manifold that adds air according to coolant temp based on maps in your ecu... this valve can destroy itself and cause all sorts of problem!!!

this is diagnoed by crimping hose and listening for idle rpm change ie: should drop.

if this is the case.. you best plan of action is to make sure that this valve stays shut!!!

hopes this helps!!!!

stock as a rock besides a full exhaust and soon to have an apexi pod. and it only when i turn the car on the first time on a cold start. If i leave the car for like 3-4 hours in the cold and then start again then nothing. wait a day or two without starting then yeh goes funny in cold start for a few seconds then all good again. wierd ay.

  • 2 weeks later...

I had a similiar cold start issue on the stock ecu... It would fire then stumble requiring either a second or two for the rev's to raise or a slight tap of the accelerator.

I dropped a pfc in to it and bumped up the PFC's cold start cranking time and its now perfect. Cold start flicks straight to 1500rpm where it sits then slowly drops as the car becomes warm.

The std pfc's cold start values had it cranking over for some time before it would fire, I bumped it up more, it then fired straight away but would stumble as the stock ecu would, bumped it up a little more and now its all good.

The stock ecu also had slight idle hunt where as the pfc has a nice solid idle that vary's only 20-30rpm max.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • @Kapr Haha yeah thats the one. I missed that you had a built up engine, I wouldn't want to run it on there either then. It was good in my situation just to replace the original turbo on a stock engine. @MBS206Yep definitely not a replacement for anything name brand
    • You are selling this? I have never bought something from marketplace...i dont know if i trust that enough. And the price is little bit "too" good...
    • https://www.facebook.com/share/19kSVAc4tc/?mibextid=wwXIfr
    • It would be well worth deciding where you want to go and what you care about. Reliability of everything in a 34 drops MASSIVELY above the 300kw mark. Keeping everything going great at beyond that value will cost ten times the $. Clutches become shit, gearboxes (and engines/bottom ends) become consumable, traction becomes crap. The good news is looking legalish/actually being legal is slighly under the 300kw mark. I would make the assumption you want to ditch the stock plenum too and want to go a front facing unit of some description due to the cross flow. Do the bends on a return flow hurt? Not really. A couple of bends do make a difference but not nearly as much in a forced induction situation. Add 1psi of boost to overcome it. Nobody has ever gone and done a track session monitoring IAT then done a different session on a different intercooler and monitored IAT to see the difference here. All of the benefits here are likely in the "My engine is a forged consumable that I drive once a year because it needs a rebuild every year which takes 9 months of the year to complete" territory. It would be well worth deciding where you want to go and what you care about with this car.
    • By "reverse flow", do you mean "return flow"? Being the IC having a return pipe back behind the bumper reo, or similar? If so... I am currently making ~250 rwkW on a Neo at ~17-18 psi. With a return flow. There's nothing to indicate that it is costing me a lot of power at this level, and I would be surprised if I could not push it harder. True, I have not measured pressure drop across it or IAT changes, but the car does not seem upset about it in any way. I won't be bothering to look into it unless it starts giving trouble or doesn't respond to boost increases when I next put it on the dyno. FWIW, it was tuned with the boost controller off, so achieving ~15-16 psi on the wastegate spring alone, and it is noticeably quicker with the boost controller on and yielding a couple of extra pounds. Hence why I think it is doing OK. So, no, I would not arbitrarily say that return flows are restrictive. Yes, they are certainly restrictive if you're aiming for higher power levels. But I also think that the happy place for a street car is <300 rwkW anyway, so I'm not going to be aiming for power levels that would require me to change the inlet pipework. My car looks very stock, even though everything is different. The turbo and inlet pipes all look stock and run in the stock locations, The airbox looks stock (apart from the inlet being opened up). The turbo looks stock, because it's in the stock location, is the stock housings and can't really be seen anyway. It makes enough power to be good to drive, but won't raise eyebrows if I ever f**k up enough for the cops to lift the bonnet.
×
×
  • Create New...