Low Power under 2krpm, then Surge

[thenomisf]

Hi All,

I recently converted my S12 from auto to manual, but ever since it has had a weird "feature".

Under 2000/2500 rpm the engine feels good, but very dead on power (as you are pulling away), as soon as it goes over there is a very noticeable and sharp (almost feels like you have been rear ended) increase in power. It feels a lot like suddenly adding 5-10 degrees of timing.

This happens regardless of boost level or throttle position (and no its not just the turbo coming on, its a very sharp sudden change).

I have checked all my sensors and wiring, removed the auto trans electronics, I have no boost leaks. I can only assume there is a difference in timing map for the auto for smooth pull away (?) but I am told the maps are identical.

I am trying to get a timing light to check, but the service manual says auto/manual CA18ET should be timed the same ?

I am aware the knock sensor becomes active at 2200 RPM, but I would have though that would make it feel slower if it was retarding timing , but who knows!

Any ideas would be appreciated!

[thenomisf]

Think I figured this one out.

The adjustment pot/variable resistor on my MAF was dead and not giving a signal to the ECU (0 volts). This was making the idle mixture super rich.

The idle mixture according to some on the US forum is referenced up to 2000 rpm, found some gear in the service manual to support this.

I fitted a spare MAF I had, and adjusted the pot and it seems to have reduced the severity of the issue, if not completely cured it.

I have a timing light on the way to me so I can check that too!

[northerner]

Did you disconnect the Auto ecu box thingy inside the NSR inner arch?

[thenomisf]

I did yeah , as far as I could tell it only has a single feed wire back to the ECU which the ECU takes to ground when it wants to block lockup (cold start etc).