GS300 mk3 2005 - transmission issue and misfire

[andyb63]

3rd gen GS300 with 98k miles has occasional rough idle on start up as though not running on all cylinders. It clears under load quickly and is very intermittent.  Car has been serviced and had new plugs about 6 months ago.   No fault codes showing up.

It also seems as though the transmission changes to a higher gear too early. i.e to 5th or 6th at around 1200 rpm at modest speed when it feels like it should hold it for longer.  No other problems with the transmission and changes seem smooth enough and works fine on sport/manual shift mode.

Seems more like electrical gremlins than mechanical. 

I have a got a slight blow on the exhaust at the very rear but I cant see that affecting transmission or idle at start up.

Any thoughts or obvious things to check. I am not familiar with the GS300 engine and it baffles me how a transmission fluid can be 'for life' and I cant check it.

Thanks 

[Mihanicos]

Merry Christmas to all.

Not all trouble codes are displayed on the instrument panel. To eliminate all guess work, I would use the Techstream scanner, the Mongoose or the one used by Lexus.

Intermitent faults usually indicate bad contacts at the connectors. By removing and reconnecting the connectors a good contact is restored.

Never believe that anything in this real world lasts for life! My car's owner's manual states that the gearbox is sealed for life and no maintenance is required. However if you refer to Techdoc ( Lexus repair manual ) it specifies that the gearbox oil should be changed every 72 months or some 60 000 miles, I am not quite sure of the mileage but is around there.

Refer to Techdoc for your car and follow the directives. I would most certainly  change the oil with the recommended oil by the manufacturer and not by any other claimed to be superior, better etc.

I would also disonnect and reconnect all connectors to the gearbox. Also check any damage to the multicore cables pertaning to the gearbox and repair as necessary.

Moisture and water is the cause of all electrical and electronic equippment.

Kindest regards,

Chris.

 

 

[Rayoh123]

On 22/12/2017 at 4:07 PM, andyb63 said:

3rd gen GS300 with 98k miles has occasional rough idle on start up as though not running on all cylinders. It clears under load quickly and is very intermittent.  Car has been serviced and had new plugs about 6 months ago.   No fault codes showing up.

It also seems as though the transmission changes to a higher gear too early. i.e to 5th or 6th at around 1200 rpm at modest speed when it feels like it should hold it for longer.  No other problems with the transmission and changes seem smooth enough and works fine on sport/manual shift mode.

Seems more like electrical gremlins than mechanical. 

I have a got a slight blow on the exhaust at the very rear but I cant see that affecting transmission or idle at start up.

Any thoughts or obvious things to check. I am not familiar with the GS300 engine and it baffles me how a transmission fluid can be 'for life' and I cant check it.

Thanks 

Hi Andy, did you ever get sorted? My 2006 gs300 seems to be doing the same thing, and also when im cruising along at 50-60mph and let the throttle off and put it back on, the car lets a 'thump' noise from the rear, but only when the engine is warm. Vsc light comes on now and again, and when coming to a stop the car sometimes stalls, im wondering if it is all related? Smooth shifts in manual/sport which makes me think its not something serious, maybe a sensor?

[The-Acre]

25 minutes ago, Rayoh123 said:

Hi Andy, did you ever get sorted? My 2006 gs300 seems to be doing the same thing, and also when im cruising along at 50-60mph and let the throttle off and put it back on, the car lets a 'thump' noise from the rear, but only when the engine is warm. Vsc light comes on now and again, and when coming to a stop the car sometimes stalls, im wondering if it is all related? Smooth shifts in manual/sport which makes me think its not something serious, maybe a sensor?

Have you done a diagnostic?  I was reading just recently that blocked cats or duff 02 sensors can cause stalling and misfires.  

[Rayoh123]

Yes had diagnostics done and only code came up was something to do with clutch/gearbox/torque converter/and something else to do with transmission, though it didn't specify what it was! Although this was not related to the engine management and vsc light being on the dash...and neither of them lights had codes stored to say why they were on.

My mechanic was baffled by it and suggested the only way to figure it out was to start eliminating things even suggesting a new transmission which I don't want to do!

[The-Acre]

I'm guessing a main dealer diagnostic would be your best bet. The initial outlay may pay you in the end. Have you got the code number that came up?