32 Gtr Hesitation/flat Spot

[confuzion]

Hey guys wondering if any one has some advice for me on a problem i have been having.. Running rb26 with n1 turbos, power fc

While driving sometimes i lose throttle, the motor sounds like it is still running (revs stay where they were), however when i apply gas, instead of going forward, it feels like it pulls BACK instead, keep trying and it does the same thing, so i pull over and it stalls straight away.

Try starting it and it just cranks and cranks. If i turn it completley off for 5 seconds and restart it starts fine and i drive away again.

Its intermittent and can happen anytime, maybe once every 5 drives?

The other day i went over a speed hump and it stalled (started ok through) which would indicate loose plug/wireing which i have checked and all look fine in the engine bay.

Also sometimes while driving there is a flat spot occasionally, not sure if its tune related but its happening more often latley..

I have taken out the AFM's and cleaned them with the electronic contact cleaner spray stuff and checked all plugs where in and sprayed them too.

With key turned to ON (not started) i get on the power fc sensor check screen:

AFM-1 0.25v

AFM-2 0.15v

02-1 0.04

02-2 0.06v

With car started and idling

AFM-1 1.20v

AFM-2 1.23v

02-1 0.04v

02-2 1.26v

Obviously i have a dead o2 sensor but that wouldnt be causing this would it? its always been dead (was told when pfc was installed) and these issues have only shown up recently. AFM voltages seem ok?

Have changed plugs, checked electric plugs are plugged in properly etc, any other ideas? Have not swapped afms yet as i dont really know anyone with a gtr that would, and the problem is intermittent so id have to borrow them for a while

grrr cheers guys

[confuzion]

now that i re-read that, sounds like fuel pump?

[confuzion]

chucked stock ecu (rom'd) in yesterday and it still stalled pulling up to a set of lights so rule out ecu :|

[Cubes]

Has it had a SAFC or the ecu wiring fiddled with at any time?

I installed a safc in to mine quite some time ago, upon removing it I connected up the bullet plug, over time this some how developed a bad connection occasionally cutting out.

Do a ghost trace of the afm signal, when it cuts quickly check, get some one in the passenger seat or even better your self while some one else drives and monitor all the sensor outputs.

[confuzion]

From my knowledge its never had a SAFC, it came with the stock ecu which has been rom'd in japan, which i changed for a pfc.

About 3 months later its been doing this and i have put in the ecu it came with and ill have a look at the error report tomorrow night with a mates consult port thingy, see if that sheds any light.

I will also try what you suggested, ill put the pfc back in and monitor the sensors etc especially when it cuts - cheers

[JimX]

I have a very similar problem, and thought I'd just reply here so that we can have any info more easily available. Confuzion seems to have sold his GTR, so hopefully we get some ideas happening for those of us who still own one

The main main additional things I can think of are -

- When it stalls and I try to start again, it will attempt to fire instead of just winding over like Confuzion's car did. And then it will usually not start for a lot longer than 5 seconds.

- When I change the air flow meter setting in the PowerFC menus to RB25 AFM setting, it sometimes got the car up and running so I can hobble home when I couldn't start it before. But this is getting less and less reliable and I don't like using the wrong AFM map anyway even if the knock sensor reading is low.

- The plugs are definitely not fouled as was my first theory when it first happened. They are a perfect light brown colour. I changed them anyway but it didn't get any better or worse.

- Maybe most importantly, when the car is in "conk out mode", BOTH o2 sensor readings seem to stay stuck on zero volts and then both go back to normal if the engine starts running properly again. Maybe the unburnt fuel is causing them to drop to zero, but it seems to switch off and on so fast.

I need to get the PowerFC tuned anyway so I might let the mechanic handle it. But if anyone has any ideas I could try first, please let me know!

[infamous_t]

- Maybe most importantly, when the car is in "conk out mode", BOTH o2 sensor readings seem to stay stuck on zero volts and then both go back to normal if the engine starts running properly again. Maybe the unburnt fuel is causing them to drop to zero, but it seems to switch off and on so fast.

Maybe bad electrical connections to the o2 sensor, similar to the problems ppl are getting with afms.

Check and resolder if they look suspect.

[cherp]

I also get this with my rb20...

[JimX]

Maybe bad electrical connections to the o2 sensor, similar to the problems ppl are getting with afms.

Check and resolder if they look suspect.

I thought that at first due to the obvious coincidence of both sensors dropping to zero, but then I thought it wouldn't be dying at idle speeds because it's not using the O2 sensor then. Also if I disable the O2 sensor in the PowerFC hand controller, it makes no difference to the running, it just uses more fuel and doesn't cruise as smoothly when disabled.

A guy at work I was speaking to suggested a fuel supply problem because he's had a similar problem on his BMW. His was a faulty fuel pump, but after more discussion we also thought that it could be a faulty fuel pressure regulator, or dodgy wiring or relay for the pump, or a problem with the igniter or CAS. Any wonder why I haven't pulled anything apart yet? It'll take me weeks to go through all these one by one

Another one we thought of that seems a bit too complicated to be likely but may be possible, is if there is an intermittently leaky injector that disrupts the pressure to the other injectors when it leaks. But I don't think that could bring down the whole engine as easily as a faulty reg or pump or associated wiring/hoses etc.

I have a spare reg and new injectors to go in, I guess those will be the first things I change and see what happens. Just need to find new o-rings!

[arbess]

This might sound a little left field but, have a look at your earthing cable from your engine to your chasis.

Also wouldnt hurt to check your batteries age.