Author Topic: CVT low idle rpm when in D, fuel saving feature? (Read 8040 times)

DrShockr · « **on:** May 18, 2013, 12:34:24 AM »

Hi all,

Bought my 55 plate CVT jazz just 2 months ago, it had the CVT judder which I fixed by flushing the fluid DIY. I have noticed that once the car is warmed up and I stop at a traffic light, after a few seconds the rpms drop to about 300. This is with the car still in D and foot on the brakes. When I lift off the brakes, it takes about a second for the rpms to go back to normal (700-800) after which the car 'creeps' forward. Is this some sort of fuel saving feature of the car or is something wrong with mine?

When this happens, if I press on the gas straight away after lifting off the brakes, instead of waiting for creep to engage, the car sort of jolts into motion. This does not seem a normal way for an auto transmission to work but I've never had CVT before. Also, it seems this happens fairly often when warmed up and stopped in D, but certainly not all of the time, sometimes it won't do it and there's no lag between lifting off the brakes and creeping forward.

I have attached a photo of the dash when this is happening.

Would appreciate any suggestions....

[attachment deleted by admin]

chrisc · « **Reply #1 on:** May 19, 2013, 04:05:33 PM »

Normally the idle is 750 rpm. There must be a sensor giving a reading that tells the ECM to reduce the revs. Only diagnosis with an OBD reader will tell you why, and which one(s).

DrShockr · « **Reply #2 on:** May 20, 2013, 06:58:11 PM »

Thanks for the reply Chris.

I've attached my bluetooth OBDII reader but there were no fault codes stored in the ECU.

Could it be a symptom of a bad EGR valve?

I did plan to clean the EGR valve when I did the CVT flush but I couldn't for the life of me undo the bolts!

chrisc · « **Reply #3 on:** May 22, 2013, 05:00:50 PM »

Definitely worth a try. There are lots of posts about big improvements to be gained from cleaning this component

DrShockr · « **Reply #4 on:** December 08, 2013, 07:46:22 AM »

Just an update:

I removed and cleaned the EGR valve with carb/air intake cleaver but it had no effect on the low idle.

I finally got round to cleaning the throttle body and the problem has disappeared. There was a lot of black sludge build up behind the butterfly valve which must have caused some sort of airflow restriction during idle. Wiping up with a rag and eventually spraying the carb/intake cleaner directly into the valve cleaned everything right up.

culzean · « **Reply #5 on:** December 08, 2013, 09:23:03 AM »

The black stuff could either be from EGR gas going back into intake end of engine or more likely from PCV (positive crankcase ventilation) valve which routes oil mist and any gases from crankcase back into intake to burn it up and stops it being blown out to atmosphere. Maybe short runs or too much low speed running can contribute to this. Worn piston rings can cause excessive crankcase pressure, but this is a rare problem on Honda engines, but if the problem happens again maybe a compression check would be in order. Check the engine oil level regularly to see if any oil is being used, as the Jazz shouldn't use any oil between changes. Normally blue smoke from the exhaust when power is applied after engine overrun (going downhill in gear or using engine braking ) is a sign of worn piston rings, as oil is allowed to get onto the bore and burns off, flip-side is when under power the combustion gases can blow past piston rings into crankcase and pressurise it.