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Discussion Starter · #1 ·
Hi Alex,

The latest post in the Blown Motor Resource thread shows an FRPP-tuned motor blowing a ringland due a failed injector. And it seems there have been some other failures too due to bad injectors.

Is there any way we can use the AP3 to monitor for what might be an injector that is clogged or otherwise going off?

Thanks!
Mark
 
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Hi Mark there are a few areas to monitor and the tough part is that you have to monitor for a difference from the norm:

1. Fuel trims - both LTFT and STFT will be affected by a failed injector. However keep in mind that the O2 reading that drives these terms is done as an average of all 4 cylinders.
2. Knock - if one cylinder all of a sudden is more knock prone and repeatably so.
3. Checking spark plugs - coloration, signs of detonation etc. The older school stuff still works.
 

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Hi Mark there are a few areas to monitor and the tough part is that you have to monitor for a difference from the norm:

1. Fuel trims - both LTFT and STFT will be affected by a failed injector. However keep in mind that the O2 reading that drives these terms is done as an average of all 4 cylinders.
2. Knock - if one cylinder all of a sudden is more knock prone and repeatably so.
3. Checking spark plugs - coloration, signs of detonation etc. The older school stuff still works.

If you detect an issue, is it typcally something that can be fixed by removing the injector and having a shop clean them or does it need to be replaced? Would you recommend replacing as a set or individually, and would you go with OEM even with an upgraded turbo?
 

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Discussion Starter · #4 ·
Hi Mark there are a few areas to monitor and the tough part is that you have to monitor for a difference from the norm:

1. Fuel trims - both LTFT and STFT will be affected by a failed injector. However keep in mind that the O2 reading that drives these terms is done as an average of all 4 cylinders.
2. Knock - if one cylinder all of a sudden is more knock prone and repeatably so.
3. Checking spark plugs - coloration, signs of detonation etc. The older school stuff still works.
Thanks Alex, I'm old school and have done tuning of turbo motors with an exhaust gas analyzer up the tailpipe and stopping on the side of the road to pull the plugs after a pull (and then changing the jets, needles, emulsion tubes etc. on the Webers...). I already check the plugs each oil change so I'm good with #3.

#2 makes sense, so I've got 4 of 6 tiles on the AP tracking per-cylinder knock counts.

The remaining 2 tiles now track LTFT and STFT, and I'm presuming that an unusual INCREASE in these variables would be an issue. Please correct my presumption if it is wrong!

On my ST, in a steady state cruise (4th gear, 45 mph) after warmup, STFT seems to be around zero and LTFT is just under 12.

Would you consider those readings to be nominal?

Thanks again,
Mark
 

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If you detect an issue, is it typcally something that can be fixed by removing the injector and having a shop clean them or does it need to be replaced? Would you recommend replacing as a set or individually, and would you go with OEM even with an upgraded turbo?
There are very few places that clean DI injectors. For a higher mileage car (100k +) given the price of the injectors is not too bad, I would consider having them replaced. I would replace them as a set.
Yes I would go with OEM injectors.
 

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There are very few places that clean DI injectors. For a higher mileage car (100k +) given the price of the injectors is not too bad, I would consider having them replaced. I would replace them as a set.
Yes I would go with OEM injectors.
Do you happen to know if the o-ring kit has to be ordered along with the new injectors, or are the o-rings provided on the new injectors?
 
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