Poorly Z

[Coopers-swb]

Hi mate.

We do have a sister site for the 300zx specifically with some knowlegable experts on it that may be able to help.

Join up and post this problem up.

Welcome to 300ZX-Club - the UK Owners Club for the Nissan Z32 and Z31 300ZX

I started off thinking it was a MAF problem but you have replaced that.

Good luck with it.

Darrel

 

[RobZ32]

Have you checked the colour of the spark plugs to see if ALL cylinders are rich on the RH side? If so it must be (assuming all three injector base O ring are not leaking) the ECU controlled injection duration or an air intake flow restriction on the one side. The fuel pressure is common to both banks so it cannot be the problem (assuming no fuel line restrictions).

The ECU responds to each sides O2 sensor so it can increase/decrease injection on either side independently. With the engine stopped disconnecting the battery will wipe the ECU memory resetting the correction back to zero on both sides. Try this and see if it’s better immediately after restarting.

Airflow restrictions will create conditions that the ECU will try to compensate for as it is supposed to, but at some point it will not be able to cope with the differences. Are both throttle valves opening equally, Is the crankcase ventilation system OK, Is the idle valves and balance tube working OK, Is there a lump of rag stuck in one sides air intake hose or the hose been squashed. Are they’re any leaks on the air intake pipes etc

 

[Hammer67]

Thanks Rob, all good suggestions. Will pass them on to my mech. The bastid thing is going in the sea soon.

 

[Hammer67]

Right, the Z lives again. My mech, an ex Nissan man, has finally sorted it. Turns out a combination of poor base set up, the RH oxygen sensor dropping in and out and a dead AFM was the cause. Here`s some advice ~ don`t buy a pattern AFM. A used genuine item has transformed the thing and it now drives better than when I bought it 2 years ago. Hopefully the fuel consumption will now return to normal.

It`s good to have a toy to play with again as my Triumph came out in sympathy with the Z and set fire to it`s wiring harness a couple of weeks ago.

 

[pmac]

Right, the Z lives again. My mech, an ex Nissan man, has finally sorted it. Turns out a combination of poor base set up, the RH oxygen sensor dropping in and out and a dead AFM was the cause. Here`s some advice ~ don`t buy a pattern AFM. A used genuine item has transformed the thing and it now drives better than when I bought it 2 years ago. Hopefully the fuel consumption will now return to normal.

It`s good to have a toy to play with again as my Triumph came out in sympathy with the Z and set fire to it`s wiring harness a couple of weeks ago.

glad you are up n running. You just cant beat a nice NA when all is in good order.
Interesting about the pattern AFM. wot woz wrong with it??
i know someone who bought one off ebay and it was duff.
MrF. has now started selling pattern ones.

 

[Hammer67]

Well, my original AFM was dead, the engine ran like a bag of nails and unplugging the AFM made no difference ~ as if it wasn`t there. Bought a pattern AFM which improved things but not completely so my mech went looking for other faults and found the RH oxygen sensor was failing and lots of base settings had been messed about with. Again things improved but still not 100% ~ horrible flat spot between 2 and 3K revs and horrific fuel consumption etc. He produced a voltage output printout from the pattern AFM and advised it wasn`t right and to fit a genuine one. I was a bit sceptical to be honest but I got a refund for the pattern one using the printout as evidence and sourced a genuine unit. Fitted it and bingo ~ like a new car.

 

[RobZ32]

Sounds like you had the wrong pattern AFM that would need the VQ map changing in the ECU to tune out the differences. VQ map contains a logarithmic scale to equate AFM output volts with actual air flow. The curve of the VQ scale is critical to the amount of fuel delivered and the smooth operation of the engine.

 

[Hammer67]

Rob, thats quite possible. The pattern unit was allegedly the equivalent to the OEM part number 22680-30P00 but who knows. I`m just glad the thing is sorted and I can use it again, certainly had enough of Mrs H67 whining about it!! And Rob, thanks for your input, most helpful and appreciated.