Hi everyone I hope I can find some help here as this is now starting to do my head in. My car failed it's mot and I've replaced everything literally. New spark plugs new rocker gasket new timing belt and pump new crankshaft pulley. Took a straight through exhaust off and replaced with a second hand exhaust system with a middle box and a back box fitted new lambda sensors. I even added catalclean and an engine flush and the fast idle CO reading came back at 0.29% with the allowed limit being 0.20% we gave the car a good run out and heated it up and took it back in for another try and it changed to 0.28% everything else was within the limits and there are no warning light or fault codes on at all. so now we're stumped it's left me the mechanic and the not dude lost for a solution I wonder if anyone can help. It's a ford fiesta 1.2 duratec 16v 2009 3 door. 

Sounds like a knackered cat.

See I have thought this. But wouldn't it have failed the emissions for what was coming out of the exhaust? It's the fast  idle CO. The MOt tech said its could be something to do with the new sensors not mixing the correct fuel. So we reset them. And they are working correctly. 

Are they looking for the right results?

Is your car a late Mk6.5 and the tester looking for early Mk7 figures

With what you have changed, try E5 petrol, change the oil and filter, change the air filter (even take it out for test😘) and clean the MAF sensor and try again

CO fails are generally just caused by a faulty cat.  It's main job is to turn CO into CO2.

HC's are generally produced by burning oil so wouldn't expect those from a knackered cat.

And lambda is effectively the measure of a 'clean' petrol burn.  As long as the lambda sensors are fine and there are no exhaust leaks, that shouldn't be affected by a faulty cat either.

How would I know if it was a late mk 6.5 compared to an early mk7. It was built in 2008 and first registered in 2009. It's also had a fresh service kit and oil change prior to the test. 

26 minutes ago, DaveT70 said:

Are they looking for the right results?

Is your car a late Mk6.5 and the tester looking for early Mk7 figures

With what you have changed, try E5 petrol, change the oil and filter, change the air filter (even take it out for test😘) and clean the MAF sensor and try again

How would I know if it was a late mk 6.5 compared to an early mk7. It was built in 2008 and first registered in 2009. It's also had a fresh service kit and oil change prior to the test. 

3 minutes ago, Deano.87 said:

How would I know if it was a late mk 6.5 compared to an early mk7. 

If it looks like this it's a Mk 7

7 minutes ago, Eric Bloodaxe said:

If it looks like this it's a Mk 7

 

2 minutes ago, Deano.87 said:

 

Mk 7 it is then!😀

5 minutes ago, Eric Bloodaxe said:

Mk 7 it is then!😀

Yeah I thought it was. Where about are the MAF sensors on these do u know? 

Have you just recently bought this car ? Just wondering what it's history is like.

28 minutes ago, Deano.87 said:

Yeah I thought it was. Where about are the MAF sensors on these do u know? 

There isn't a MAF on the 1.25.

There's a tMAP under the plastic intake manifold.

19 minutes ago, Deano.87 said:

Where about are the MAF sensors on these do u know? 

Normally would be found adjacent to the airbox on main pipe leading to the engine. I seem to recall having seen mention somewhere that not all 1.25 Fiestas have one, though?

 

2 minutes ago, TomsFocus said:

There isn't a MAF on the 1.25.

Ah, beat me to it as usual!😀

23 minutes ago, TomsFocus said:

There isn't a MAF on the 1.25.

There's a tMAP under the plastic intake manifold.

Yeah I thought as much. I couldn't find 1. What does the tMAP do then? Basically now the car is running lumpy on idle and cuts off sometimes on startup so we were thinking it's a sensor. We've spent a fortune on this car in repairs and it's starting to do our head in tbh.

46 minutes ago, unofix said:

Have you just recently bought this car ? Just wondering what it's history is like.

We bought the car a few months ago it's got high mileage and we've had to replace all sorts on it. The car itself was cheap and we expected to spend a few quid but it seems we do 1 job and another needs doing there a small engine so can't be much more to do to it tbh. We reset all the sensors the other day there are no warning lights. But car is running lumpy on idle now on cold startup and seems to want to stall. Just started it up since Thursday last week. Once it's warm it runs okay. 

1 hour ago, Deano.87 said:

Yeah I thought as much. I couldn't find 1. What does the tMAP do then? Basically now the car is running lumpy on idle and cuts off sometimes on startup so we were thinking it's a sensor. We've spent a fortune on this car in repairs and it's starting to do our head in tbh.

The tMAP measures intake air temperature and pressure.  Whereas a MAF measures intake air flow.  Some engines use both, others only use one or the other.

37 minutes ago, TomsFocus said:

The tMAP measures intake air temperature and pressure.  Whereas a MAF measures intake air flow.  Some engines use both, others only use one or the other.

Ah okay then. So do you think that could contribute to how the car is running on startup and when at idle? And where abouts is this sensor located? 

1 hour ago, Deano.87 said:

Ah okay then. So do you think that could contribute to how the car is running on startup and when at idle? And where abouts is this sensor located? 

Not personally no.  Generally the engine massively overfuels as a failsafe when the MAP sensor fails.    If that was happening, the MOT lambda reading would be out of tolerance.  However that is the main fuelling sensor for this engine.

It's under the plastic intake manifold between the central branches on Mk7.

 

I'm not sure what's causing the problem unfortunately.  

Being cold start should rule out the lambda sensors, as they're not used until they've warmed up.

Throttle body may need cleaning or relearning.

Temp sensor may be faulty.

Vac pipes are worth checking for splits, though that would generally cause a lean mixture which world put the lambda reading out of spec in the other direction.

If it had a straight through exhaust previously then it may have been remapped.  Although gains are very minimal from temps on this engine.

17 minutes ago, TomsFocus said:

Not personally no.  Generally the engine massively overfuels as a failsafe when the MAP sensor fails.    If that was happening, the MOT lambda reading would be out of tolerance.  However that is the main fuelling sensor for this engine.

It's under the plastic intake manifold between the central branches on Mk7.

 

I'm not sure what's causing the problem unfortunately.  

Being cold start should rule out the lambda sensors, as they're not used until they've warmed up.

Throttle body may need cleaning or relearning.

Temp sensor may be faulty.

Vac pipes are worth checking for splits, though that would generally cause a lean mixture which world put the lambda reading out of spec in the other direction.

If it had a straight through exhaust previously then it may have been remapped.  Although gains are very minimal from temps on this engine.

Throttle body may be the issue now uve mentioned it as we reset all sensors maybe so that would have reset the throttle body settings? Will check the vac pipes and do u know how I'd tell if it was remapped previously. Your a star for the help so far given me alot to check over and speak to my mechanic about tomorrow. Thanks man. 

33 minutes ago, TomsFocus said:

Not personally no.  Generally the engine massively overfuels as a failsafe when the MAP sensor fails.    If that was happening, the MOT lambda reading would be out of tolerance.  However that is the main fuelling sensor for this engine.

It's under the plastic intake manifold between the central branches on Mk7.

 

I'm not sure what's causing the problem unfortunately.  

Being cold start should rule out the lambda sensors, as they're not used until they've warmed up.

Throttle body may need cleaning or relearning.

Temp sensor may be faulty.

Vac pipes are worth checking for splits, though that would generally cause a lean mixture which world put the lambda reading out of spec in the other direction.

If it had a straight through exhaust previously then it may have been remapped.  Although gains are very minimal from temps on this engine.

Don't suppose there's a way to relesrn the throttle body manually in these is there? 

2 hours ago, Deano.87 said:

Don't suppose there's a way to relesrn the throttle body manually in these is there? 

I believe that you can run a reset / relearn programme using FORScan

Yes, I'm wondering if it's been remapped

13 hours ago, Deano.87 said:

do u know how I'd tell if it was remapped previously.

Not easy to tell if a car's been remapped unfortunately.  Quickest way to check is ask the previous owner.

 

13 hours ago, Deano.87 said:

Don't suppose there's a way to relesrn the throttle body manually in these is there? 

There was a manual relearn procedure for the Mk6, I don't know if it still works the same on Mk7.  

Disconnect the battery for long enough for all circuits to drain (or short circuit between the leads to speed that up).  Reconnect battery.  Do not touch the throttle pedal.  Switch on the ignition for around 60 seconds until all the clicks and whines stop.  Then start the engine and let it idle for around 10 minutes.  Do not touch the pedal at all during this time.  After around 10 minutes when the idle had settled to an appropriate level then take the car for a drive, ideally using the throttle as much as possible in as many different driving situations as you can.

Alternatively, as above, it may be possible through a garage diagnostic, though I doubt they'll be using Forscan if it's just an independent garage.