NX300h cold start - engine misfire/hesitation/lumpiness

[paulrnx]

Hi

Has anyone suffered from a lumpy / poor running / hesitating petrol engine on their NX300h when started from cold for the first 2-3 miles? I have this problem now but it comes and goes and only appears when outside air temp is low. Seems ok when outside air temp is above about 7-8 degrees. Problem goes away when engine is warm. Another symptom is the car doesn't like a constant speed during the first 2-3 miles when the petrol engine is on and has a slight judder but always ok under acceleration. Had mine checked at a dealership and nothing logged in terms of fault codes and all settings have been checked against another vehicle. Just curious to see if anyone else has experienced similar. I always use BP Ultimate or Shell V-Power so I was thinking about doing a few tankfuls of 95 RON fuel to see if this makes a difference. Probably won't be an issue as the weather warms up mind

[C Mclean]

Nothing like that on mine..

[rayaans]

3 hours ago, paulrnx said:

Hi

Has anyone suffered from a lumpy / poor running / hesitating petrol engine on their NX300h when started from cold for the first 2-3 miles? I have this problem now but it comes and goes and only appears when outside air temp is low. Seems ok when outside air temp is above about 7-8 degrees. Problem goes away when engine is warm. Another symptom is the car doesn't like a constant speed during the first 2-3 miles when the petrol engine is on and has a slight judder but always ok under acceleration. Had mine checked at a dealership and nothing logged in terms of fault codes and all settings have been checked against another vehicle. Just curious to see if anyone else has experienced similar. I always use BP Ultimate or Shell V-Power so I was thinking about doing a few tankfuls of 95 RON fuel to see if this makes a difference. Probably won't be an issue as the weather warms up mind

Used to get this with my RX. 

Talked to a few people. Turns out its intentional misfiring to warm the catalytic converter up quicker when really cold to meet emission regulations

As long as it's smooth when up to temp you have nothing to worry about. Roughness when at operating temperature is bad

[paulrnx]

17 hours ago, rayaans said:

Used to get this with my RX. 

Talked to a few people. Turns out its intentional misfiring to warm the catalytic converter up quicker when really cold to meet emission regulations

As long as it's smooth when up to temp you have nothing to worry about. Roughness when at operating temperature is bad

Cheers. Spot on, was hoping to hear something like this. The Lexus tech did intimate something like this and nothing to worry about. Thx Rayaans

[Ian J. Parsley]

Just out of interest, there'll be many others more expert than I about this, but I gather there is no point in using special fuel (BP Ultimate or whatever) with a hybrid/CVT. Others may be able to confirm/refute this!

[NemesisUK]

No point other than to help keep the engine cleaner due to the additional detergents etc..

I've feed mine with nothing other than V-Power from new. But then I had a pump with my name on it from running the CLS55 ....

[paulrnx]

Thanks everyone. I was wondering about the premium fuel. I wondered whether the Petrol engines used in Lexus hybrids are capable of continuously adjusting to take into account the higher RON rating. If not, there is no performance gain to be had. Still an advantage in terms of keeping the engine cleaner but whether that in itself is worth it, maybe not.

[fogey]

I have only noticed misfiring on start up of my 400h once in all the 7 years I have owned it. It soon disappeared and ran smoothly on idling before I even drove away. It sounded to me as if the mixture was too rich. I would have thought that misfiring over any extended time would soon start to poison the cat, so rather than being good it would be very bad indeed. This is the main risk if you miss the 60k plug change, you may end up with a very expensive bill for a new cat of course !

As the plug wear is more related to mileage, then it may not be so risky to miss the 6 year plug change if you do  very low mileage. Unfortunately you cannot use that logic for the rather costly10 year cam belt change, unless you have enough cash reserve to buy a new engine !

[paulrnx]

Had mine checked out a few times and all is ok or appears to be ok. The problem comes and goes and is only there when cold and not all the time when engine cold and ambient cold. Doubt it's going to cause a problem because it only does it occasionally and only for a very short period of time. I'll live with and I'm sure it'll be fine. Not sure how we got on to missing 6 year plug changes and 10 year cam belt changes mind?