BlackFox

Just swapped my engine myself with the help of my brother after dropping a valve.

Engine and cylinderhead is new, everything else (electronics, intake, exhaust, ...) is from the old engine.

Engine will start and idle, but as soon as i hit the throttle and release it, it will bog down and stall.
Startup again is also an issue, usually needs a little throttle. Then it won't idle and stall again as soon as I release the throttle.

Keeping the revs up is not a problem, and after a while it will idle nicely.. Untill I hit the throttle and it stalls again.

Already cleaned IACV, reset the ECM and cleaned the map contacts and used a tie wrap to keep it in place. Nothing seems to help.

Spark plugs are brand new, airfilter is a recent K&N, no CEL and no errors if I read it out with an OBDII app.

Possible timing issues or valve adjustment issues? The previous owner only used this engine briefly for some track days and then swapped it out for a Toda engine. It did had ITB's and possibly a dfferent head. So I don't know if the timing has been touched.
However all the electronics and intake are now from my old standard engine...

I'm really at a loss here...

s2000maniac

Make sure the ground on the back of the head is tight and clean.

BlackFox

Not sure if it's very clean, but I think it is.
It's in a hard to reach place, so not that easy to do a quick check. However, the ground is wedged between the screw and the black metal plate. Is it supposed be between the head and the plate? Could this make a difference?


I've also just performed a check that was stated in the workshop manual (page 11-91). If the car stalls when you put your fingers in the holes of the throttlebody, you should replace the IACV.

Mine does stall when I do that, so that would mean my IACV is bad? Any other way to check?

BlackFox

I've attached the ground on the back of the head in the right place now... no change.

Beginning to suspect the throttle position sensor, but that would be strange since we didn't touch anything on the intake manifold.
Possible vacuumleak? Or air leak at the manifold itself? 2 lower bolts were at very hard to reach places, we probably didn't torque them up to the right spec. The rest however is. Might still give problems?


Disconnecting the IACV connector wil actually make it run nicer... up untill the moment I touch the throttle. Then it will shake all over the place, but it least it won't stall. As soon as I reconnect the IACV, it will stall.

Sceanzo

Did you mix up the MAP and TPS sensor? As I recall they are the same plug.

DeeKay

look for o ring under map sensor.

BlackFox

Map and tps sensor haven't been touched, since this all came with the intake manifold from the old engine and worked just fine up untill it dropped a valve.

Someone suggested my valves are too tight.
This engine has titanium valve retainers, so someone definitly worked on them. It also had ITB's and the spark plugs were black with soot, is it possible it ran on a different mapping without the owner noticing the valves were too tight?

BlackFox

Did a valve adjustment last night (were a bit tight), made sure the intake manifold was tightened down and checked vacuum lines.

Still nothing.

Car starts and idles fine when cold, as soon as the coolant gets up to temperature the troubles start.

Seems like the ECU reacts to slow when it's going to stall.
Vtec works, but it's definatly down on power, seems to hold back a bit.

Timing might be off?

apme123

Double check the IDLE CONTROL VALVE, maybe clean it

SpitfireS

What intake manifold gasket did you use?
Is there a possibility the coolant flow through the intake (and IACV, throttle body too?) is blocked?
Or maybe the head is modified to not have coolant flow through the intake - it had ITB's.. right?