Engine speed instability at fast idle

[JM19723]

I have a problem where at fast idle 1200-2000rpm the engine dies and recovers before it stalls. This continues on this cycle until the revs are increased or the throttle is released and engine goes back to idle. Switching the engine off then starting again seems to fix the problem for a short time until the fault goes away of its own accord. This is accompanied by a knocking sound during low to mid range accelleration. Got me stumped

[bspec]

I have the same problem with an 05 B Spec. The dealer has been playing with it for 12 months and Subaru had it for 6 weeks but still no fix. The engine light also comes on occasionally and on the fault is always the cam positioning sensor. Subaru has changed O2 sensors and the throttle body but the problem still comes back. Has anyone else had this same problem and was there a remedy?

[bspec]

Still got this very annoying intermittent problem and Subaru cannot fix it. Any suggestions from anyone?
Thanks.

[kleinerbastler]

You wrote that the error was for the cam position sensor, but why Subaru didn´t changed this sensor?
The symptoms sound like camshaft or crankshaft sensor, but also try to log the neutral switch from the manual transmission.

[Tradewind]

I had this problem also about 2 months ago.

It stems from running the engine in a near stall engine speed, basically I have found in a manual trans car you can bring this problem into play simply by lugging the engine from about 650rpm in say 3rd or 4th gear, do this several times and sure as night follows day you will get engine light and fault will read as cam angle sensor.It took me a couple of restarts and some constant speed driving and it cleared itself after about 15mins. You may find that the engine will not go past about 5000rpm while this condition is occuring

So ..... my thoughts are that the counts/cycles that the ECU is looking for are dropping below a preset minimum value and then ECU is simply believing the cam position sensor is simply not working - hence the code. ECU then appears to go into a protective mode and limits engine RPM.

Thats what I have found, was freaking worried first time it did it. Yes the uneven running, knocking etc are all part of the deal too


All I do now is ensure that engine rpm is above 1500rpm at all times and I dont allow the engine to near stall speed, no more issue

[Tradewind]

A further thougth

I bet that its only occuring on manual cars, I believe it would never occur on an automatic trans car

[kleinerbastler]

Yes, because only MT has this neutral switch. If this sensor fails (goes on and off), the camshafts go to position 0. So log the behavior in RomRaider.