Weird Idle (1990 240sx)

[Vernal]

I just swapped my sohc to the dohc and everything runs great, but I have a weird idleing problem. When I turn on the car it idles at 1000 because I turned up the idle a little, but when I barely tap the gas pedal it revs up to 1500 or 2000 and stays there for 2 seconds and then drops back down to 1000. I have a different ECU (automatic Altima) so I don't know if it's that. Also when I come to a stop the rpm drops like normal but once I stop it sometimes revs up to 1500 or 2000 and stays there for 2 seconds and then drops back to idle. One of my friends said that it might be because the dohc brake booster might be different from the sohc (I have the sohc). Anybody have any ideas?

[rogoman]

- check the O2 sensor.- check for a sticking EGR valve.

[Vernal]

Ok, I actually dont have an egr sensor could that be it.

[rogoman]

It's not an EGR sensor but an actual EGR valve. If you got an EGR valve, it's bolted to the intake manifold at the back and there's an EGR pipe that runs around the back of the motor and screws into the exhaust manifold.

[Vernal]

If that was the problem what would i do.

[rogoman]

If you got an EGR valve, try moving it up and down manually by hand. There may be a lot of carbon in there causing it to stick. It can be removed and cleaned.

[Vernal]

Its not that because the engine has only around 60k.

[180fan]

I second the EGR.

[Vernal]

I'm almost sure its not. Plus the egr valve opens at 15 and 25 mph. It only revs up when I come to a stop or when I'm sitting there at rev it a little it will stay at 2k for a second and then drop. I'll try to post a video to better our diagnosis.