Idling / Accelerating Issues

[PACEY]

Right then, for the first time in 2 and a half years my car is doing some interesting things.

1. When idling if i put the clutch in and put it in gear, leave my foot on the clutch, the revs increase by like, 300rpm. Then when i take it out of gear but still leave my foot on the clutch, it returns to normal.?????????Doesn't happen all the time though.

2. The worse of the two. While travelling down Orrong? road yesterday, while acceleration the revs dropped to 600 (idling). Then after about a 2 sec delay it came back up to the rpm i'd expect to do at 80kmh. ?????? It did it about 4-5 time in the space of about 10mins. I filled the tank up after work on the way home and it didn't do it again. What the?????????

Any suggestions?

[bully]

how low was your fuel tank??

May have some non fuel in it - i had this problem with water in fuel in a suburu my father in law owned.

We put a cup of metho in the tank, filled the car with fuel and then we could run it dry . the metho apparently stops the fuel and water seperating - we then ran it out completely never had the problem again.

[Boostzor]

Temp sensor or something confusing the cold start in the ecu?

[Steve]

What mods do you have? the revs picking up at idle sound like they may be the NVCS kicking in. If your idle isnt stable, it 'may' activate it once the neutral switch has been deactivated.

Second problem could have been fuel surging due to not enough in the tank.

More info would be good, mods, settings etc.

[PACEY]

Mods, cat back. Yer i was thinking a fuel surge. I had about 1/8 of a tank maybe when it was doing it.

NVCS ???????

Thanks

[Steve]

NVCS is the system nissan use that advances timing on the intake between 1050 and 4500rpm. If the revs at idle get near 1050, and the car is in gear, the NVCS will activate, advancing the timing and the revs will go up.

To test if this is the problem, just unplug the NVCS and put the car in gear. The NVCS plug is front drivers side of the head and has a brown plug. Or, you could just get someone else to put it in gear while you listed with the hood up - there will be an audible click noise when the NVCS activates.

For only a cat back it shouldnt cause dramas. 1/8 of a tank shouldnt cause dramas either with stock fuel pump.

[PACEY]

Thanks Steve

[PACEY]

Oh dear, the problem just got worse. Now when i come to a stop at the light and stuff the car just slowly drops revs and cuts out. It will happen 3 out of 5 times. When the car is stationary the rpm needle is constantly searching on the dial, if that makes sense. What the **** is wrong with my car? It seems to me like a computer issue. Like one of the senses has shat it's self and the computer is therefor going ?????? what the?.

Any ideas?

[Steve]

It could be your AAC - that is your idle control solenoid at the back of the plenum. It has a brown plug hanging off it. Check the plug is properly in place, try removing the plug and cleaning the electrical contact with brake cleaner or electrical contact cleaner.

Next step is to remove it and give it a good clean. Three bolts, pretty easy. You will also need to disconnect the purple plug to do this, its the AC idle solenoid. Once removed, give it a bath in brake cleaner.

Another thing to try is keep your ac switched on, as this uses an additional solenoid to bleed extra air into the plenum - may keep you out of trouble for the while. If it helps you will need to keep the aircon turned down to coldest setting so it is on most of the time (climate control will cycle on/off to maintain the set temp).

Another thing that is vital is to check ALL your vacuum hoses, intercooler pipes etc as well. Most skylines are old and the hoses tend to perish and crack.

Hope it helps. Sorry but I am somewhat taking stabs in the dark. Most fault finding is a process of elimination.

G/L

[PACEY]

Thanks Steve i'll give it a crack tomorrow and tell ya how it went.