Engine Hunting after start-up !!!!

[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.

[APA]

i know this is a long shot, since you just put the z32 AFM on but your AFM woulnd't be faulty or ****ed would it?

adrian

[Revhead]

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?

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?

[Guest Works Auto]

Yep its been retuned for the AFM and injectors.

[Guest Works Auto]

The car runz fine. on the move its really good its only on startup . Its just something that annoys the shit outta ya.

[FIL]

cold start settings perhaps? might be time to talk to the tuner about getting that particulary part of the map sorted out properly...

[adam 32]

simon did lumpy do it for you? id be asking him - i bet he would know

[Nate]

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.

[GOT BOOST]

push the choke in a bit sounds as though its too fat : Þ

time for cube increase bite the bullet go the big one too

[puckish]

Sounds like AFM or TPS. If you only run the AFM and the injectors does the same problem happen ?

What voltage are you getting the the TPS test points ?

[MrMayhem]

.....................soft

[N I B]

Let me plug a 3D in and i can check every thing out then put the

old ECU back after fixing the problem We test a lot of cars out

like this as all the info comes up on the laptop, work well.

[Nizmo]

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. its really annoying me. Its a fairly stock auto.

[N I B]

Sounds like a TPS problem.

[MrMayhem]

my coins on TPS for Works 32 also

[N I B]

Simons got GTR injectors so it may be over fueling on cold start.