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ECT , 0.55 volts dc on one single wire to a good ground ?
The other wire should read 5 volts to ground
Your mechanical coolant thermostat should keep the coolant slightly above 88 C or about 90 C ( 0.65 volts )
So 0.55 volt is a Temp above that , but not a worry ( if correct reading method )
On the brake booster hose , it does not prove a whole engine or brake booster absolute no leak at that brake booter test point , only that the leak ( ? ) increases with an open hose
You could be going from no leak to a leak
Or a small leak to a leak
There is a hose on the top of the fuel pressure regulator and a hose attached to the underside of the 2nd or 3rd from the front intake manifold , look for hoses on the EVAP components under the engine air filter box
Which brings us to FPR leaking extra fuel into the intake by way of the vacuum hose , hose dry ?
There are some cruise control hoses / components in the area that are independent / isolated from the engine vacuum lines
One CTS wire was giving me 0.65v measured with one pin on the wire, one pin to a ground in the engine bay.
The other wire was not giving any signal. This is supposed to show 5 volts? I tested the continuity of the female end of the connector and the paper clip I’ve shoved in the rear, so it should be returning something?
0.65v means your coolant is 90C, was the engine warmed up when you tested it?
Can you check it when it's cold as well?
When you check it, just backprobe the two wires.
Engine was warming up when I tested it, so that’s the voltage I’d expect. It started at 0.7v, then as I waited a bit longer it went up to the final reading of 0.65 or below. All looks good to me.
MAF will read 1.2 volts DC on the middle wire at the correct idle speed and increase toward but not on 5 volts on throttle up
Vee had a suggestion to give the connector pins / blades a slight twist so your MAF does not drop out intermittently driving you crazy
Idling at 1050 RPM according to OBD, engine warm. MAF voltage from the centre wire with an external ground is 1.45v.
That is functioning correctly then.
Last on the list then, TPS reset and new O2 sensors. Got a TPS reset booked in on Weds, then a free MoT retest on Monday hopefully. I’ll hold off on sensors until after that, the TPS may solve the emissions too? Need to get CO down and Lambda up a bit.
When fully warmed up and idling, there is a faint white smoke from the exhaust, like when you start a car on a cold day. It smells a little bit rich, but not massively so. Giving it a little rev causes a more dense white cloud to come out the back.
Last edited by tobywood13; 06-10-2024 at 02:23 PM.
'You can clean the O2 sensor connectors and the small wire grounds ( left and right ) on the rear engine firewall.' - I will clean these up.
'There is a thing if the sensor connectors are swapped they can throw off your engine regulation
On the car side of the connectors there are 3 wires of the same color , the 4th different deter mains correct position' - I will check these are in the right connectors, thanks for the diagram.
'Ensure the one fuse for the O2 heaters are good ( fuse 10 , or 12 , 14 , 16 in that group )' - Checked one earlier in this process, fuse 14 I think, but I'll have a look at the other ones also.
'you can read with a meter the heating element in the sensors to know if that is defiantly bad , pins 3 and 4 and not the Greek Lambia symble' - I assume you read the continuity between the two pins? If not, how do you test the heaters?
'Faint white smoke can be a coolant leak into cylinders fouling the O2 sensors ( sensors cleanable ? )' - I don't think it's this, as after a longer drive today there was no smoke. I assume yesterday evening's white smoke was just condensation burning off. It definitely didn't smell like coolant.
Thanks for these next tips, I will update once I've had a look this evening.
Look for resistance on pins 3 and 4 on the sensor side and they should be close to the same
Do you do this with the engine running? Does it matter if they are cool or hot? Or is it just a check that the resistance is the same from the sensor's wires, no matter the temp? Do you read the resistance between the two wires, or is it from each wire to an external ground?
I.e. high resistance when cold on both wires, low resistance when hot on both wires. (Just an example, it might be the other way round in reality).
I will be surprised if the TPS Reset does not cure your problem.
It’ll probably sort the idle out, but the tremendously high CO emissions and low Lambda could be another issue, hence suspicious towards O2 sensors.
There's an emissions test at idle, which wasn't done as the idle was obviously idling too high.
There's also an emissions test at 2500 rpm, which my car also failed with 15x too much CO, a bit too little Lambda, and acceptable hydrocarbon (not sure how this was ok with the CO quantities present however).
In theory, even with my fast idle speed the emissions should have been ok at the fast idle check. So that could be another issue, likely O2 sensors.
Last edited by tobywood13; 06-11-2024 at 11:11 AM.
Don't overthink things. Right now you have a car that's idling high because it's being artificially overfuelled. That can cause the results you are seeing.
Let's get that TPS reset first. I believe it will resolve everything.
The resistance would be from pin to pin ( each sensor wire pairs ) , hot or cold as they will be very very slightly higher at higher temp but still close to the same comparing sensor to sensor
If you do find a fault it may save a trip and time to the emissions center plus the TPS resetting ( money )
As you do hone it in ( tune ) you will save money on fuel
Had the TPS reset done by J-Cat in Norwich, for any UK people reading this I highly recommend them. Very friendly, knowledgeable, and the whole thing took about 3 minutes, and they charged for half an hour’s labour which I thought was fair enough for cramming me in to their schedule (They’re booked up until August otherwise!).
The car is now idling at 650 rpm, and averaged 24 mpg on the one hour drive home which is much better than usual. Hopefully, it remains at this correct idle after a cold start tomorrow morning. I’ve got my MoT re-test booked on Monday, fingers crossed the idle speed was also linked to the poor emissions. We’ll see.
Thank you all for your help so far, hopefully this is the end of the saga for this issue. Now, I need to go get the handbrake working for the MoT also, at least that should be simple…
06-07-2024, 12:39 PM
