2001 Yaris T Sport Intermittent Lack of power

[Pooley86]

Hi guys

Ive got a problem with my Yaris t sport 2001, there is an intermittent lack of power that happens anywhere in the rev range and at all speeds, if I keep my foot in the same place it’ll suddenly come alive and gooo. Sometimes the car is flawless and pulls well and sometimes it acts like this. I’ve checked all the love data of the o2 sensors and maf etc... however the timing advance seems to jump around quite a lot, I was wondering if anyone has had a similar issue or wether there’s common issues with the vvti system.  

 

Thanks in advance 

[Johan Damitha De Silva]

No, and I have been here for many years and not seen this reported in our cars.

Presume it has had a full service including fuel filter and no engine management light then to me, the problem could be a fuel pump issue but replacing random parts will be too expensive. Sadly no mechanic wants to invest in time looking for intermittent issues that they may not be able to locate.

The car has a timing chain so will not be a belt issue.

Do try and run the car on a full tank of Shell Petrol V-Power for its cleaning properties (very easy to pick up the Diesel V-Power nozzle by mistake!)

Good luck, it's a great little car.

[Silver Yaris]

When was the last time that it had a service? 

I know you've said you checked the MAF & O2 sensor but there also other simple things that could potentially cause what you are describing such as a damaged / bad connection on the main earth strap or loose / bad connections on your Battery although you should notice this at night as your lights will flicker when you have the loss of power. Could be dirty injectors so a bottle of injector cleaner in a tank of fuel is worth doing anyway. Gunked up spark plugs or faulty coil packs would typically cause a misfire rather than loss of power but it would do no harm to check them.

[bathtub tom]

2 hours ago, Pooley86 said:

 however the timing advance seems to jump around quite a lot

 

How do you know that?

[Pooley86]

2 hours ago, Johan Damitha De Silva said:

No, and I have been here for many years and not seen this reported in our cars.

Presume it has had a full service including fuel filter and no engine management light then to me, the problem could be a fuel pump issue but replacing random parts will be too expensive. Sadly no mechanic wants to invest in time looking for intermittent issues that they may not be able to locate.

The car has a timing chain so will not be a belt issue.

Do try and run the car on a full tank of Shell Petrol V-Power for its cleaning properties (very easy to pick up the Diesel V-Power nozzle by mistake!)

Good luck, it's a great little car.

Well that’s not good to hear 😂. Yea I serviced it about 300 miles ago(Trd oil filter,plugs) however I did not replace the fuel filter as I was told it’s not a servicble item as it is in the tank. No eml light on, it was on recently for a po125 but I found a pin pulled out on the lambda sensor so I repaired that and it hasn’t been on scince. I’m a HGV mechanic myself so I don’t mind investing time in it just not too much money. A couple of days ago I ran some injector cleaner through it but I’ll try some v power aswell now.  Sometimes it’ll perform problem free and has all the power and other times it’ll bog down. It’s done it scince I replaced the starter motor last week, but I’ve checked I’ve disturbed no wires and the sensors. 

Yea there lovley cars and quite surprising! I’ve owned it a year and a half now and only replaced radiator stater motor and clutch. (150000 miles)

thankyou for replying! 

[Pooley86]

1 hour ago, Silver Yaris said:

When was the last time that it had a service? 

I know you've said you checked the MAF & O2 sensor but there also other simple things that could potentially cause what you are describing such as a damaged / bad connection on the main earth strap or loose / bad connections on your battery although you should notice this at night as your lights will flicker when you have the loss of power. Could be dirty injectors so a bottle of injector cleaner in a tank of fuel is worth doing anyway. Gunked up spark plugs or faulty coil packs would typically cause a misfire rather than loss of power but it would do no harm to check them.

About 3000 miles ago, I’m going to try cleaning the earth strap as it got covered in coolant when it overheated(blocked radiator) I’ve recently put some injector cleaner thought it but going to try some v power next. Yea I checked the spark plugs the other day and they do look extremely white which could indicate a lean burn, however I thought if it was ignition related it would do it all the time and not intermittently like you said. 

Thankyou for replying!

[Pooley86]

1 hour ago, bathtub tom said:

How do you know that?

Watching the live data of timing advance while driving along, if I keep my foot to the floor sometimes it jumps around from 7-33degrees of timing. There’s not a constant increase or decrease, but it may just be how it is. It’s just something I noticed.

 

[bathtub tom]

48 minutes ago, Pooley86 said:

Watching the live data of timing advance while driving along, if I keep my foot to the floor sometimes it jumps around from 7-33degrees of timing. There’s not a constant increase or decrease, but it may just be how it is. It’s just something I noticed.

 

That doesn't seem good to me, but I wonder if it's just the knock sensor retarding the ignition?

[Pooley86]

Possibly, I’ll double check the connection and wires as I think it sits near the starter motor and I replaced it last week and seems to be when this problem started. Maybe I’ve knocked something 

[Madasafish]

As a matter of principle I would check the camshaft sensor..

 

And the crankshaft one as well...

and the wiring to them.

[Johan Damitha De Silva]

Pooley86, let us know how you got on 🤗