unclefester

Weird that you don't get a CEL .... have you actually connected an OBD reader to it again to see if there is a CEL recorded but just not showing? If you do clean the IACV out, don't forget to put an old towel under it as you do get a little bleed of coolant out when you disconnect the pipes.

Oh and this is a good time to check if the throttle cable tension is correct

BenRNBP

I'm erring towards a sensor but maybe not the O2 one - they tend to throw pretty good codes. Do you have any way of datalogging (can Scanguage do this - or even check what the value the sensor is giving in real time ?) as I wonder if it's the intake temp sensor suffering from heat soak and giving erroneous readings to the ECU ?

I've had similar problems also with crank position sensor before (not on my S2000) but with that the problem was constant rather than intermittent

unclefester

On mine when the crank sensor went it did similar things but the sensor had almost completely unscrewed from the engine - it wouldn't rev past about 2k under load ... and it sounded awful but was fine with no load although it did throw a code as soon as it went.

I didn't think the crank sensor was related to temperature though .... could be wrong however.

IACV was always the one for me that affected initial throttle response - that said it could be any number of the sensors, MB' idle thread was invaluable in diagnosing the issue.

S2KIP

I think it'll be the O2 sensor.

ian_6301

You need to be aware of HOW the O2 sensor and the CEL work.

The CEL light and the corresponding fault is triggered by a reading from the cell that is outside of the expected limits, set in the ECU.

If the O2 sensor fails open circuit, the ECU will see 0v, which is outside of limits and will produce a fault and a CEL.

If the sensor fails such that there is a reading, which is within limits but not accurate, then you would not get a CEL or a fault, but the mixture would be out of whack, which would cause the symptoms that you are experiencing.

A very swift Google found this site: http://www.lambdapower.co.uk/diagnos...c_index.asp#q7

As before, swap the sensor out for a known good one and see if the symptoms go away...

BenRNBP

Same argument applies to most of the important sensors though; throttle position, intake temp and MAP can all be giving signals "within the expected range" but still be too low/high for the actual conditions.

markforrester99

- Bad Engine Earth
- Loose or corroded battery terminals

O2 sensor wont make the car cut out or seem like its going to stall. It has limited effect on the fueling and when it does it only does it under certain conditions. When you push the throttle to the floor the O2 adjustments are ignored so the problem would go away.

Your issue sounds electrical to me and before changing endless sensors check the basics like the battery and the earths.