Engine coolant temperature - 4 cylinder 1.3

[Automike]

I have 2010 iQ 1.3 which currently has a misfire on cylinder 4 (P0304 cyl 4 misfire detected). My diagnosis path has included swapping ignition coils 3 with 4, fitting a new plug, checking cylinder compressions but still I get the same fault code appear in the defect memory after a short drive. One observation I have noticed is that the engine coolant never seems to circulate around the system. I can go for a 5 mile drive then leave the engine running for 30 minutes after which time the top hose is very hot, but the bottom hose is still cold to the touch. I have removed the thermostat to satisfy myself that it opens at 82 degrees, which it does (heating water in a saucepan method). I know the next stage would be to remove the thermostat and run the engine to see whether the water pump is actually operating by checking the flow at the rad filler cap, but as this job is quite labour intensive, I was hoping another fellow iQ 1.3 owner could confirm whether they all do this. There are no signs of any external water loss. Once this has been confirmed, I intend to swap injectors 3 and 4, and then perform a cylinder leakage test in case the head gasket has failed. I would be very surprised if it has as the vehicle has only done 7,200 miles!  If anyone has got any ideas from previous experiences, I'd  welcome to hear from them.

[TomdeGuerre]

It seems you still have some investigation to do about the P0304 misfire. Have you tried injector cleaner in the fuel or when you swop your injectors are you cleaning them by squirting cleaner through them with electrical power on?

As far as the question of water circulation, I take it the car never actually boils over and doesn’t use water? I’d think an engine that’s only running on three cylinders won’t be able to get up to / maintain proper operating temperature. Does your car heater work OK or do you think there’s any airlock in the system? When you had the thermostat out was it the type with a jiggle pin? Sometimes they have to be correctly oriented when you refit the thermostat to avoid air locks.

[Automike]

Thanks for your reply. I haven't gone down the injector swapping route so far, but that's my next step to see if I can transfer the fault to another cylinder. Whilst I previously stated, there are no signs of any external water loss, I do recall the first time I became aware of the fault, I had driven about 40 miles and noticed the engine hesitating very intermittently, as though a coil was breaking down. This happened no more than three times during the journey, in which time, the yellow engine warning light came on. When I got home and lifted the bonnet, I saw a small puddle of coolant around the radiator filler cap. When I squeezed the top hose, coolant was escaping from the seal of rad cap. The expansion tank also was a little low, so I topped it up. The cap was inspected but no faults were found with it and it re-seated correctly. I can only think the pressure release valve had been activated.

Since that time, I have only driven the vehicle on short road tests to try and establish the cause, but other than the reoccurring misfire, no further water has escaped. The engine will misfire when driving from low speed whilst under load. According to the diagnosis counter the fault has occurred 75 times and always cylinder 4. The engine runs smoothly at idle and never misfires. I have to say, my overall suspicion is that the head gasket could have failed due to a water circulation problem, but at no time have I ever experienced any overheating warning messages on the dash. This is also supported by the engine diagnosis which shows the ETC (Engine Temperature Coolant) does not go higher than 194 degrees F / 90 Celsius even after prolonged running.

Just to answer some of your questions, the heater works perfectly and the thermostat, is the type which is sprung loaded and held in position by two steel lugs within the plastic casing. It can be fitted in one of two positions, 180 degrees apart but I can't see how this could cause a heating problem if it was installed 180 degrees out.

What would be really appreciated is if an iQ 1.3 owner could run their engine up until its warm and then check to see if the bottom hose is still cold. That might give me the answers I'm looking for, to decide my next stage of diagnosis.

Thanks again for your feedback.

[tarquin]

Just a quick point of information. 

I was in the Toyota spares dept  recently  and. Mechanic/technicial from Aston Mattin came in and bought a waterpump for the cynet (1.33) version of the iQ. (Same engine). I know the guys in that department and made equires. Seems they have used at least 10 to his knowledge stating the impeller wears out

just thought i would share that

 

David

[Automike]

Hi David, thanks for your information regarding other known water pump failures. I shall definitely keep this in mind as a possible route to explore.

Mike.

[Automike]

Okay, here's a further update to my continuing engine misfire saga. I ruled out a faulty fuel injector last week by swapping injector 4 with injector 2. Same P0304 (Cylinder 4) fault code registered after a short road test. Thinking it must be a head gasket problem, I decided to bite the bullet this week by purchasing a Combustion Leak Detector. A nifty tool at £34 courtesy of eBay, it connects to the radiator cap and flags up the presence of any exhaust gases in the coolant by changing a test fluid a different colour (blue to yellow). After multiple checks, the test fluid remained unchanged (blue). Phew I thought, at least the head gasket hasn't gone. As I can't get my head around why the bottom hose is always cold even after an extended run, I am going to remove the water pump later this week to check its operation.

In the meantime, has anyone on this forum ever had to change a water pump on an iQ3? According to my local Toyota dealer in Sandhurst, they have never stocked or sold one before for an iQ3!

 

 

 

 

[alan333]

43 minutes ago, Automike said:

I can't get my head around why the bottom hose is always cold even after an extended run

Isn't that what it's supposed to do?  When the thermostat is open, hot water flows to the top of the rad, then gets cooled by ram effect of the car (or by the fan) as it travels through the rad, then that cold water is drawn back to the engine from the bottom hose.