CA18DET camshaft question

[04xr6t]

Hi
I have been having a heap of problems with my silvia after the head gasket was redone,
I had fully qualified techs do the repairs but ever since i got it back, the thing wont idle on cold start up.
They have played and played with it and replace everything
1/ Injectors
2/ stepper motor
3/ tps
4/ throttle body
5/ wiring harness
you name it its been done (by different techs along the years)
My question is
Is it possible when the head gasket was done the techs swapped the inlet can and the exhaust cam around (put exhaust cam into inlet spot?)
I have googled my guts out but no where shows if they can be "mistakenly" put in the wrong spot

Cheers in advance

[float_6969]

No the cams can't be swapped and have the car run at all. There are splines in the exhaust cam that the CAS go into.

If the issue is only during cold start and it's fine everywhere else, it's the idle control valve under the throttle body. I don't remember what Nissan called it. Something stupid, LOL.

[04xr6t]

Hi thanks for your feed back
the only reason i was thinking camshafts was due to the fact it has only happened since the head gasket was done.
idle speed control motor has been replace, even the wiring harness has been replaced.
One thing that does appear funny is the voltage too the idle speed control motor (its low)

Thanks

[float_6969]

This motor doesn't use any idle speed control motors. They're solenoids. Also, it doesn't have just one, it has 3. One for cold start fast idle, located under the throttle body, the primary one, located on the side of the intake manifold (short and round), and one for the A/C fast idle, located on the side of the intake manifold above the primary idle control (Long and octagon shaped).

[cbh148]

Nissan calls the cold-start/fast-idle valve the "Air Regulator".

[boost_boy]

Just because they did your headgasket doesn't mean they can't make errors. You could have leakage at the valves or the compression could be low or it could very well be a faulty regulator. The list is too long to cover, so we that call ourselves "CA18 fluent" will need a bit more info on what your motor is or is not doing to better assist you. Have you checked for leaks at the intake manifold gaskets or butterfly valve seals? It's alot to cover, but hopefully we can help you.

[04xr6t]

Thanks for your feedback guys, i will try to brake down whats been done
CA18DET engine (stock)
5 speed manual
Cam timing spot on
ignition timing seems to have to run very very advanced to start and run
slight chattering noise from crank angle sensor (at times) key way looks in good condition
1/ Head gasket (full reco including valves and guides)
2/ new engine wiring loom (as most connectors were broken)
3/ new air bypass valve (was not operating)
4/ new cold start injector
5/ reset throttle position switch
6/ compression tests good (170psi all 4 cyl)
7/ leak down test fine
8/ all engine earths rechecked (using resistance)
9/ engine revs increase whe warmed up
10/ engines revs increase when a/c turned on (hot or cold)
11/ found now idle speed drops if you push gear selector forward or back) when aleady in gear (manual) when hot
12/ found now fan speed gets interrupted if you push gear selector forward or back) when aleady in gear (manual) when cold
Basicly it appears the idle circuit is stuffed when cold

So have i confused you yet? ha ha

[Buddyworm]

11/ found now idle speed drops if you push gear selector forward or back) when aleady in gear (manual) when hot

This one is pretty easy to explain. ECU uses different timing maps for neutral idle and in-gear driving and the switch that triggers the transition is near the shifter "gate". In my car I can get a similar effect by trying to gently pull the shift lever into gear with the clutch pedal out.

4/ new cold start injector

Are you sure you're calling this by the right name? Because I'm 99% sure CA's don't have a cold start injector. ECU just increases pulswidths when cold.

[cbh148]

This one is pretty easy to explain. ECU uses different timing maps for neutral idle and in-gear driving and the switch that triggers the transition is near the shifter "gate". In my car I can get a similar effect by trying to gently pull the shift lever into gear with the clutch pedal out.

Any idea how/if idle is affected if one doesn't have those transmission sensors plugged in?

[04xr6t]

Cheers Buddyworm, i will check this switch near the shifter gate (any ideas how many pin connector?)

4/ new cold start injector

Are you sure you're calling this by the right name? Because I'm 99% sure CA's don't have a cold start injector. ECU just increases pulswidths when cold.[/quote]

I call it a cold start injector (its the large solenoid on the highest point of the throttle boy) sitting by its self (i believe its a 2 pin connector)

[cbh148]

I call it a cold start injector (its the large solenoid on the highest point of the throttle boy) sitting by its self (i believe its a 2 pin connector)

I'm assuming that by throttle boy, you meant throttlebody, but were actually referring to the intake manifold.

That's actually the FICD solenoid. All that does is raise the idle a bit when you turn on the A/C.

[04xr6t]

Cool, ok im getting closer now
terminology is always hard between different people
So the air bypass is the only item that actually controls the idle speed (hot and cold?)

[boost_boy]

Cool, ok im getting closer now
terminology is always hard between different people
So the air bypass is the only item that actually controls the idle speed (hot and cold?)

Only when cold. If it's stuck midway, it will cause all sorts chaos. If it's stuck closed, you car will not fast idle when closed and not be all that happy when warmed-up. The solenoid at the highest point of the intake manifold controls the idle-up feature for when the a/c is engaged.

[Buddyworm]

This one is pretty easy to explain. ECU uses different timing maps for neutral idle and in-gear driving and the switch that triggers the transition is near the shifter "gate". In my car I can get a similar effect by trying to gently pull the shift lever into gear with the clutch pedal out.

Any idea how/if idle is affected if one doesn't have those transmission sensors plugged in?

Good question! I'm not sure what the default mode of the switch is (ie: does the ECU read normal in-gear timing map when unplugged or the idle timing map when unplugged) but I have a feeling it defaults to "in gear" if there's no signal/the connector is detached (I don't have the time to research right now). If that's the case then driveability should be fine, but I would expect the engine to idle a tad rough and too low with unstable AFRs.

Cool, ok im getting closer now
terminology is always hard between different people
So the air bypass is the only item that actually controls the idle speed (hot and cold?)

Page EF & EC 12 of the FSM outlines the functions of all the air regulator solenoids.