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k_d_ch

Member Since 02 May 2013
Offline Last Active May 19 2014 07:30 AM
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Posts I've Made

In Topic: Co Emissions High: Overfuelling?

18 May 2014 - 11:00 PM

FOCA - the above post gave us reason to believe there was an air leak around the inlet manifold - we have to rely on the information you give us and draw our conclusions/ make our suggestions from that   

FOCA - So the air leak in the inlet/ manifold was a "blind alley" - the garage has direct access to the car - we have to rely on the info you post     

I am sorry if you feel that it was a waste of your time. I am grateful for your air leak comments: I personally have learnt from them and shall take them on board in the future. The garage that said it was an air leak was different to the garage where I took the car in the end (I was wating for my appontment with them at the time). There are garages to just do an emissions test and there are garages to solve a challenging problem! By the way, the guy who did the job said that there is no air leak, he checked it first.


In Topic: Co Emissions High: Overfuelling?

17 May 2014 - 09:16 PM

By the way, can anyone suggest where I can get a fault code reader for my Escort (1995)? Apparently, OBD2 readers work for

cars from 1996 onwards. It seems a bit bizzare, but my Escort's ECU has got a socket that OBD2 plugs into (and even tries to start when plugged) but then gives an error message and is of no further use. 


In Topic: Co Emissions High: Overfuelling?

17 May 2014 - 09:05 PM

Problem sorted. It was an ECU glitch, apparently. It was not supplying the required voltage (0.5V) to the lambda sensor.

The garage guy who fixed it said everything was in order once he probed (i.e. gave an extra ground) the signal wire that goes from the ECU to the lambda. Many thanks to everyone!


In Topic: Co Emissions High: Overfuelling?

15 May 2014 - 09:07 PM

Not quite. What actually happens is that the air goes through the inlet manifold and then escapes.
 
To keep the emissions good it expects (for descriptions sake) 1 part fuel to 3 parts air. The air goes through the airbox and the car knows at this point, there is three lots of air in the system, but as it passes through the manifold, half the air escapes. By the time that the engine gets the air and fuel, its now at a 1:1.5 not 1:3 ration. in essence, to keep it balanced the car should inject half the fuel (0.5 parts for 1.5 of air) but its not, its actually injecting twice that, hence the overfuelling.
 
If it is a leaky inlet, then it would be best taking it off rubbing it down and finding the leak. It might be something cheaply repairable, or may just need a new one.
 
How confident where they that this was the case?

I can see the logic in your explanation. I saw on a website (I think it was about Polos though) that the pressure inside the manifold can be lower than outside (is this what people mean when they use the word "vacuum" in this context?), hence the sucking in when an "air leak" occurs. It may well be that on Escorts it is the other way round, or that they were ill informed...
Regarding the garage guys, I would not put too much money on their claim. They were in a rush, as many of them usually are. At the time another problem occured as we spoke: the fan connector on the fan switch stopped working. It had not looked very healthy for years and now finally gave way. Following which I got a new connector from a scrapyard, which was lucky, and the fan is cutting in fine.
I then went back to the emissions guys to ask them to give the emissions test another go, which they offered to do free of charge in the first place. (This was kind of them, but also explains why they would not want to spend too much time on my problem.) At that point they said that there was no point in retesting since the first time round it was an air leak and the fan connector and switch could not have been a reason for high emissions, which seems fair enough to me.

In Topic: Co Emissions High: Overfuelling?

15 May 2014 - 06:09 PM

I would start by having the Lambda sensors checked, if they are not correctly calibrated or working then this is likely the cause of the issue. The engine temperature sensors will have little to do with overfuelling as this is purely used for controlling engine cooling behavior.

Many thanks for your comment. 

Today a guy at a garage sprayed some stuff (they said "brake cleaner") around the inlet manifold and the emissions on the computer shot up. The guy suggests there is an air leak in the inlet manifold. Just to check: my understanding is that an air leak like this would make the oxygen sensor send a signal to the ECU to inject more fuel, which would be the way it overfuels. Would this logic be correct, were there to be an air leak?