Jump to content
SAU Community

Engine Hunting after start-up !!!!


Recommended Posts

Guest Works Auto

Had this problem for 3weeks now and going insane.

Start car up and it revs to 2000rpm then when its meant to drop back to about 1000rpm it drops to like 300rpm and almost stalls. Then it proceeds to hunt for a while before it settles at around 1000rpm.

Now i think ive changed possibly every sensor in the car but still no luck. I even put a new inlet manifold gasket on.

one thing i noticed is that it seemed to happen after i put the gtr injectors and z32 afm in.

Another thing to note is that i have no crankcase pressure . The revs arnt dropping if i take the oil cap off like it used to.

Someone save me and shed some light on this as im going insane to the max. gonna kick panels in shortly.

Link to comment
https://www.sau.com.au/forums/topic/15647-engine-hunting-after-start-up/
Share on other sites

Sounds like a classic case of the ECU saying "WTF is happening to the mixtures??". What's probably happening is that it's using the fuel maps in the ECU, and when the oxygen sensor starts returning some absurdly rich numbers, starts winding back the mixtures until it idles. Stupid question, but you DID retune the car after making the changes? :D

If the AFM and injectors have been changed and the tuning remains as it was before the changes, then the maps in the ECU will be basically useless. The fuel will be too lean and, at best, the AFM readings will be out all over the rev/load range. At worst, the new AFM will have a completely different response curve (if that's a term you can use to refer to an AFM :) ).

If I'm completely off the mark and you HAVE had it retuned, I'd be taking it back and having them tune it again.

Another option is a leak in the intake piping, sucking bucketloads of unmetered air into the engine and thereby making the mixtures much more lean than the computer thinks they should be. A bad thing all round, and could cause the problems you describe. How does it run on the move?

I just had the same problem in my R31.. but it would stall at the lights when it warmed up! REALLY was pissing me off... found out it was the AFM. Thought it was the crank angle sensor though.. amongst other things... a COMMO :) owner told me he'd bet it'd be that... so i took his advice and changed it, and saved alot of cash from gettin a new dizzy and/or ECU... phew.

I have something similar with my car. start it up - idling revs are fine. Then after the engine is warm when it idles it will start dropping from 750 to about 400 - 550 and it starts shuddering and spluttering bounces the revs up a little then they drop again. :D its really annoying me. Its a fairly stock auto.

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

    • You’re all still going on about track cars, he has said multiple times doesn’t intend to take it to the track,  just stick to what was said at the beginning and do the pump and ecu, it’ll get you enough for 230kw at the wheels and has enough poke to be fun for what you want it for 
    • All of that is absolutely true. At any time in the history of these turbos the lottery has always been that it could die at stock boost treated exactly as the factory intended, or it could die when pushed to 10, or 12, or 14, or 16 psi, after a short time, or a longer time, or it could last seemingly forever. You have the combination of all the possible statistical (probably) normal distributions of manufacturing tolerances and quality outcomes, on top of the statistical distributions of failure modes (which might be normal, but are probably biased, like Poisson distributions). You get the lucky turbo and you can beat on it for years. You get the really unlucky turbo and it will crap itself as it rolls out of the factory gate. And every possibility in between. But you can definitely still kill the lucky turbo. It's just that most people didn't try, once they knew they really shouldn't try.
    • Maybe I have Stockholm syndrome but working on an M2 isn't that hard. Getting parts cheaply and quickly is hard, but getting parts same day isn't necessarily hard if you're willing to pay way too much for it at local dealers. There's a lot going on, you need to have a build of ISTA on a laptop and the right cable, if you don't have the mindset of "do it exactly right or not at all" you will probably start seeing cascading failures. Skylines are a little more tolerant in that regard. The car doesn't potentially trash itself if you bought the wrong oil filter like a BMW would. Or trash the entire cylinder head and potentially spin a bearing because someone took the anti-drainback valve out of the plastic oil filter cap. An M2 will also do just fine on track, zero oil starvation concerns, factory brakes are great if you change the pads for a high temp compound + flush with track-ready fluid.
    • The "ideal/formula" that used to be touted was death of the turbo is going to be caused by a combination of 3 things. Heat Speed of turbo (boost level you're pushing) Time   Basically, you can get away with high heat and high boost for short periods. But start doing long hard pulls, or circuit driving etc, and now you've increased time as well which will shred things. From memory when Adrian was drag racing he was running 17psi, on a stock turbo, and running insane speeds. But he also had other additives helping in the setup too. Some people have success at 14psi for a while, while others due to pushing the cars hard for long periods opt down to lower temps. But also, generate a lot of heat (let's say bad tune), for a long time, and you'll be okay, until you try to spin that little guy up slightly. It's the one advantage of dumping a lot of fuel in, you'll be reducing EGT a bit and helping with the heat portion of the above 3 areas.   And these days, stock turbos are that old that there's the possibility of just outright failures due to material age. I'm not shocked that even when used in factory spec that a stock turbo fails when 30 years old. It's a worn out "precision" "balanced" performance item, that's likely no longer precise, or well balanced
    • this... hence I said what I said previously, SMSP nights you see mainly Hondas, Evos, A90s, F80x and the odd VW. The 5 or 6 times I went, I only saw 1x R32 GT-R, and other than that I was the only one in a shit box Skyline.
×
×
  • Create New...