Jump to content
SAU Community

Recommended Posts

Hey all,

Sorry to start another one of these threads, but I've done a search and didn't find anything that quite matches my symptoms, so I was hoping someone here may be able to point me in the right direction. To cut to the chase, here is what my engine is doing:

http://youtu.be/-g0nValrfZY

Basically it struggles to return to idle after a quick blip of the throttle, and under higher load (longer rev or while driving) it stalls as soon as it comes off throttle. Now normally I would say this is pretty symptomatic of a vacuum leak, however my car is running on a MAP sensor. I really don't have any experience with how an engine functions on MAP sensors, but I was under the impression that air leaks would not cause the car to stall, is that correct? Is this more likely to be something like the IAC valve? If I turn the air con on and give it a quick blip, the engine will stall; so that leads me to believe it is the IAC?

A bit more of a background, I have JUST finished putting the engine back together following a full cylinder head recondition. The only things that have changed since I last drove the car are Tomei Type-B poncams (possible timing issue??), valve springs/retainers, and bronze valve guides. I have checked for air leaks, but everything seems tight and as previously mentioned, the car is on MAP. My external wastegate is also a leak at the moment as it seems to be stuck permanently open, but I didn't think this would cause the stalling issues?

Thanks for any help,

Martin.

Link to comment
https://www.sau.com.au/forums/topic/409075-car-stalling-on-decel/
Share on other sites

Probably need to get computer tune touched up. Maybe because of the new cams and flow rates of your head. Could have put

your ignition out of wack. Used to happen to my GTR, got it retuned and now I dont have any problems. But, then again it really could be something to do with getting your head put back on.

Yeh, that's what I'm worried about. If it's an issue with the tune then that's fine, I can get it to the tuners and they can do their thing. But I'm HIGHLY reluctant to give my car to the tuner when it's got issues, lest they then be stuck trying to sort out my shit :/

If your wastegate is stuck open this would mean it has no vac/boost signal? So maybe the vac line you have hooked up to it is leaking through the wastegate straight to atmo? Causing both issues?

Try raising the idle screw on IAC. Make sure its plugged in.

Be sure ignition timing is correct. But it sounds as tho its just in the tune.

Did u have cams last time it was tuned?

Not being experienced with MAP tunes, but does it utilise a deceleration fuel cut like AFM based ECUs?

I had a mate fully ulleh BOV and increasing the deceleration fuel cut rpm stopped it stalling off throttle blips or hey cruising.

Unfortunately with the Plazmaman, adjusting the idle screw on the IAC is impossible. But I guess if it's quite possible it's an issue with the tune being out then I'll sort out the wastegate and just get it to the tuners.

No not at all, it was perfect. But it's had some pretty major work done since it's been driving, and it's the first time I've removed/reinstalled a cylinder head. With the car running on MAP, I wasn't sure what I should be looking for; didn't want to take it to my tuner with potential leaks or other problems all over the place.

Problems like this:

560354_10151017032802541_1906570586_n.jpg

Anyone else seen a bent valve on a Turbosmart wastegate before, or know whether replacement parts can be had? I'm confused about how it happened, but I have a suspicion. The car backfired on start-up the other day, found a massive patch of soot directly under the screamer pipe afterwards, so it's clearly backfired through the wastegate. No idea why, or if it would cause this damage.

Ahhh true, I just had a look at the Turbosmart product info, and yes I'm missing the valve seat! I don't even remember it at all... Now I wonder where that could have got too :unsure:

That's a relief though, thanks Scotty! :D

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

    • Yes to both! Yes to standard ECU and tune, but exhaust is aftermarket. Unsure on brand. Actually have it sitting in at my desk haha! I have to set it up on my laptop but this is a great next step, will do. So I generally try to shift before 4.5K RPM most times. I largely don't do a lot of high-rev driving, but I will take it up to red 1-2x a week max, as I know the occasional "Italian tune-up" is good for these cars.  Oh wow, is this way better than what I'm getting. Does this mean there's a good chance I have an issue?   Thanks for all the info so far guys.
    • Old Son, did you re-use the Holden ABS in the new shell or try a different module?
    • Yeah, nah. I had the actuator rod off it today. The arm will not move at all. Neither out, nor in. Yeah, you'd think so, but I've been thinking about that. Even when the actuator rod fell all the way off at the beginning of this saga, it would build more boost and faster in lower gears than it would in higher gears, and you'd think that that was the opposite of what should happen. But I strongly suspect that there is a thing with the gearing getting the revs to rise faster, that there must be some transient effect with the gas flow rate rising quickly, that you don't get with the more steady state case of the higher gears. Keep in mind - the gate is not shut in either of my weirdnesses. So things are not "normal". We normally think about a turbo spooling up (below the wastegate target) with the gate shut. I have all sorts of mental models running now where the gate is a little bit open, and having it stuck open allowing gas out while it should be going through the turbine has all sorts of weird effects (in these mental models). I'm thinking in the higher gears, the ex mani pressure builds to the point where enough gases spill out the wastegate to just prevent the pressure rising much more at all, or just creeping up, all the whole the revs are increasing and getting closer to the point where a gear shift becomes necessary.
    • Is it possibly wastegate actuator itself is sticking, or even the rod to flapper? Otherwise I reckon things are getting a bit rusty/worn   Also odd it won't boost in 3rd to 5th, but will in 1st, I'd expect the other way around with it slightly open as there's more time on your way to redline for it to spin up
    • Does anyone know ow what these two plugs are for and if they should be unplugged? Just put the dash back together and can't remember if these were plugged in before or unplugged! (Blue and white plugs) 🤦🏽‍♂️
×
×
  • Create New...