The Honda PCX / Forza / ADV150 / SH Forums

Hi guys, newbie here looking for some advice.

I have a 2015 PCX125 that is struggling for the first few miles after a cold start. It starts fine but then then runs rough and seems to completely lack power until the engine is warmed up, and then its fine after a few minutes. It will be fine for the rest of the day on warm starts and then the next morning, same thing again.

I've changed the battery for a new one and it made no difference whatsoever.

Any suggestions?

Thanks
Chris

Hello Spoons and welcome to the forum.
How many miles/kms you have on the scoot. Has it been doing the same ever since new, or it is a kind of new development?
I'd check ignition, &spark plug first before venturing further.

How cold is the weather?Check spark plug. Few things here.. Is it stored outside ?? Could be condensation and possibly an stuck open thermostat. I think it could be normal based upon temperature and storage environment. Might be susceptible to your environment and so warm it up prior to loading it.

How long have you had it, did you buy it new?
Has it always done it?
Engine rough or transmission?

Thanks for the advice and the welcome.

Its been owned from new and has just started doing this in the last couple of weeks. It is stored outside but in a sheltered area. It has about 8,000 miles on the clock.

I'm from the UK so we don't really get a lot of really cold weather but it does get down to below zero on some nights. Its cold now but it actually started doing this whilst the weather was still warm so I don't think the cold weather is the explanation.

Sounds like a new spark plug would be a next thing to change.

According to service schedule the spark plug should be changed after every 5000 miles or 8000 kilometers- so in case it is still the original, it is about time to change it.

Not normal, they fire straight off and run fine in cold weather. Did you put some crappy petrol in it?

If it's a 2015 it should still be under warranty. Might be worth a phone call to the dealer.

Oyabun wrote:According to service schedule the spark plug should be changed after every 5000 miles or 8000 kilometers- so in case it is still the original, it is about time to change it.

That's Honda covering themselves - most spark plugs can go much longer than that - I'm over 10'000 miles now and my bike starts 1st time, every time and runs really well and gives great fuel economy - and I ride in sub zero temps early morning and evening.
Yes, it's cheap, but no, no point changing fully working parts for no good reason - when it needs changing I will change it with the spare.

It is definitely an electrical problem with one of the sensors that are being used during the Open Loop. If you really want to understand this all vs throwing your money at everything Google "Open Loop vs Cold Loop". You will see references to cars but do not ignore the information. These 4T scooters are basically cars minus a Knock, Cam and Crank sensor.

However if you have the money to spend. Buy spares of all the sensors on the bike so that you're prepared every time to quickly fix an issue on the fly. There are only 4 sensors related to the motor:

Air Intake Temp Sensor
Throttle Position Sensor
Coolant Temp Sensor
O2 Sensor

However my guess would be either a faulty Coolant Temp sensor or O2 Sensor. Double check your O2 sensor connector/s. I know on some PCX's the O2 sensor has 2 connection points that can come loose. One connector is at the end of the sensor(looks like a mini spark plug boot) the other connects to the harness on a bracket that is bolted to the left side of the cylinder block. Just double check that they are both snug, otherwise you may just have one connector.

What I do and my bike does almost the same thing. Bike will start right up but if I shut it off quickly I then start to have issues. My solution is to hold the brakes, hit starter button and blip the throttle. Yes the manual says not to do this but it works every time. One suggestion is to leave it idling for a few minutes once you first start it. Now if you have problems when starting right off the bat then something is not right.

Nosubstance wrote:What I do and my bike does almost the same thing. Bike will start right up but if I shut it off quickly I then start to have issues. My solution is to hold the brakes, hit starter button and blip the throttle. Yes the manual says not to do this but it works every time. One suggestion is to leave it idling for a few minutes once you first start it. Now if you have problems when starting right off the bat then something is not right.

Sounds like your partially flooding it and then following the almost 'flooded start' procedure in the manual.

I have a similar failure with my 2015 PCX 150 with Start/Stop here in Thailand:
If I start in the morning (never below 20°C), no problem with starting, but the engine runs very rough and the bike is shaking unbelievable while accelerating, speed about 5km/h. After some 100 meters, the green Start/Stop- lamp should indicate that the system is working. But it remains off. And Start/Stop doesn't work.
If I stop the engine and restart with warm engine, the Start/Stop system works and the shaking of the motorbike is much less than before.
I bought the bike as a new one, but I think it's shaking more than in the beginning (now I have about 10800 kms on it).
As I studied combustion engines at the university (a long long time ago), I can definetively say that the ignition comes too early, which is leading to a rough running engine.
What can I do to isolate this problem?

I'm in the UK and every week day I start the bike from cold and it's kept outdoors when all the cars and road has a frost cover - this is late at night near midnight or early hours of the morning, say 2am. Still on original spark plug/air-filter after 11'000 miles and 2.5+yr's of ownership with only a few oil changes and the bike starts 1st time and idle's perfect - however, now it's near freezing and after a minutes warming up, the bike is a little rough and does not pull away with much power for the 1st few seconds - after that it's fine. So definitely a problem with one of the sensors or something related.
I thought the ECU and feedback in the system was supposed to detect problems with the sensors and flash the warning light on the dash? I also believe someone said not all the sensors had ECU monitoring - perhaps it's one of those at fault?

I have been having similar issues. When holding in the brake and pressing the ignition button, it doesnt always turn over straight away. We have had silly cold weather at the moment, so I am thinking it might be the sparkplug or something?

@Iceman

I contacted my Honda shop and they said it is the winter fuel. They add 10% ethanol to the gas during the winter months, why? I have no idea.

I had similar issues with my truck and was advised to use some Lucas Fuel Injector Cleaner and it worked like a charm. Mechanic said that deposits in the injectors change fuel delivery from a mist to a squirt - not as efficient. It worked for me.

For a scoot or MC, you’d need to add some over several tankfills, because the mix ratio isn’t much.