Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Slowly increasing idling in 3L V6

Today I noticed that upon taking away my foot from the accelerator ( and pressing the clutch) the revs came down (as normal) but then gradually increased during a few seconds to about 2000 rpm This happened a few times. One time I saw that the rpm slowly came down again. Also, the normal idle was not exactly stable on one occasion. Engine was warm and running fine otherwise. This is on my 3.0 L 3V6 Roadster from 2009. I did not notice this behavior before. I was in traffic and could not experiment any further, also it occurred only a few times.
Any ideas why this happens?
Thx,
Bert

I had the exact same symptoms on my Nissan 180sx and I fixed it by replacing the plug on the wiring harness that connects to the throttle body position sensor.

I hope that helps.

Check the integrity of all the vacuum lines and fittings. A cracked hose can result in unpredictable idling.

regards,
Phil

I would start by gently cleaning the Mass Airflow Sensor in some solvent

The electronic throttle is the place to start. If cars arent used fairly intensively you get problems with the throttle position sensor.

Might sound daft but I'd be inclined to sit in the car in the garage engine off, and depress and release the throttle a hundred times just to make sure it was working as well as it can. On the Lotus there was a procedure for re-calibrating it which I think was no more than ignition on but engine not started and pressing the throttle fully open and fully realeased a couple of times. Ignition off then start the engine.

If the problem persists then garage and diagnosticks.

Throttle shaft partially seizing is another one. Usually triggers management light as well though.

I have the same problem on my 2011 Roadster. The throttle is still cable controlled on these models. Can anybody explain where to find the MAF sensor?

Well, I thought that this would be an easy lead, so I checked the lines and found one with a kink in it and corrected it by loosening a near tie wrap. Today I took the Morgan to work for a test drive and I could not reproduce the error. So perhaps... this did the trick.
Thanks for all the follow up!
Bert