If I am on a steady throttle at about 2750 rpm I get what feels like a pulsing sensation. As if the car is hesitating. It only does it when the engine is cold. Any ideas? It's a P1. Cheers.

 

Really. So that's what's wrong with it. Thanks

 

Its sort of normal.
Mine does it all the time. Its even worse when the air really cold and dense. I suspect its something to do with the ECU being in Open Loop? so the ECU is controlling the car form memory rather than real time live sensor data when the engine has warmed up (Closed Loop).

Hope this helps. (or maybe somebody may correct me)

Thanks
Gavin

 

Close but not quite. It's because the ECU switches over to reading the lambda sensor before the sensor is really up to temperature. This is done for cold start emissions. What you are feeling is the ECU rocking the mixture back and forth across the ideal point, which it does all the time during closed loop running, but when the lambda sensor is cold, it is a bit sluggish and unresponsive to read, so the variations in mixture are bigger, and slower than they should be. If you fit a lambda link or other AFR gauge you can see that the surging goes in time with the changes of the mixture, holding back when it's rich, pulling when it's lean.

Took me ages to find out what this was when I got my Scooby.

Normal and nothing to worry about if it goes away when it's properly warm.

 

Cheers mate.

 

IIRC you could disconnect the lambda when cold and switch it back in when warm. Not tried it but it was discussed a few years ago. You would need to put a switch in the ECU sensor lead.

F

 

Ok, IF the pulseing remains, even when the car is warm, and ONLY at around 3000PRM, is the Lambda sensor knackered, or is it the MAF????

 

Hi chaps, my sti4 type R does the same i've only recently noticed it with the cold weather wev'e been having of late just posted a thread should of looked here first, so what your saying is if the engine is warm this should not happen. cheers

 

I get this at times with MY00 Classic - I have an AFR and what Avalanche has said is spot on the AFR rocks back and forth and at times I can feel a slight pulsing - however this soon goes after a minute or so

 

On mine it goes away when engine is warm. So hopefully it is ok.