Stall and hesitate problem

[GTRFAN]

My r32 gtr has had the head redone as a few valves were broken due to sucking in some water. We also replaced bearings, cam belt and sensors.

We also changed the o2 sensor, which I believe is in the top of the exhaust. The engine runs great but sometimes it hesitates and even stalls when just cruising along not under boost.
My mechanic says it's a sensor playing up, and it needs time/temperature to start to work properly? What do you think?

It feels like it starves for fuel for a few seconds. I.e. power loss.

All I need to do is just let it idle for 30 sec or switch it off and back on and it goes on fine.

Airflow meter/s?
O2 sensor/s?
Dirty contacts?

[TINDUCK RACING]

....THE USUAL SUSPECT.......dodgy AFM......

Jon.

[GTRFAN]

I discovered that if you dissconnect either one of the AFM's then the engine will stall but can be started again with little effort, but will only rev to 2000rpm's ! It's kind of a limp home mode which is good to know. Well if it is the AFM's then I guess I better try one for a while and see how it goes OR bite the bullet and get the Z32 big suckers.

[YCEE]

I have a similar problem as well, and the car will run lean, switch it off and start it back on and then it is fine. Problem will occur mostly when air-cond is switched on, and even you off the air-cond it persists, but if I do not on the air-cond at all it will run fine.

I changed the fuel filter, and plan to change a NISMO high flow fuel pump as some mechanic suggested that the fuel pump might be weak. Don't think is the AFM cause the car idles perfectly and if you had an AFM problem you might get misfiring alot or foul plugs.

[TINDUCK RACING]

Quote: Don't think is the AFM cause the car idles perfectly

.....pull the plug from your AFM when your car is running fine: it will still idle perfectly without it connected at all........just my 2 cents

Peace love and horsepower,

Jon.

[GTRFAN]

TINDUCK RACING, what is the best way to find the source of my problem? Most of the time everything is fine so it's hard to find.

Another interesting thing is when it idles from the initial start, after a few min it starts to vary the idle from 1200 to 2000 rpms by itself! But as soon as I start to drive everything settles down to a normal idle?!? Does that sound like the AFM is getting the wrong signal? What else could have an effect on idle speed???

[TINDUCK RACING]

.......hopefully about 30 people who know more than me will correct me if I'm wrong, but I seem to remember reading somewhere on the SDU forums that an intermittent fault with an AFM can cause the ECU to go into a Limp-home mode, where it will misfire and struggle to rev, but will idle at 2000rpm..........sound familiar?

......the cheapest way to see if the AFM(s) are the culprit, is to persuade someone to lend you theirs for a bit......swap them over, and see if the problem stays or goes....

....hope this helps,

Jon.

[Ethan_R33]

GTRFAN,
i had EXACTLY the same symptoms. Tried everything, found out it was the air flow meter.
Try getting a new one, or maybe a good 2nd hand one if u can get em anywhere.
Good luck mate.

[GTRFAN]

Yeah thanks guys.

I already put up a post about borrowing a AFM with no replies!

I wonder if converting to MAP is a better option than Z32 AFM's?

Can a power fc handle a MAP reading like a Motec can?