A/F ratio when idling?

[McMsk]

Hi Guys,

I still seem to have a pressure leak. This seems to be causing strange a/F ratios. What should it be when idling? I during idling used to have three line on my aem wideband --- showing it to be too lean to show. And when cruising it used to be between 14 and 15. Now also during cruing it partly shows --- that mean to lean. At first I thought it might be the wideband not working properly, but when i step on it and get to the range where the apexi regulates it shows between 10 and 11. any idea what might be cauing this problem? What should it show while idling?

Thanks

Mark

 

[isnms]

~14.7

 

[McMsk]

That mean, that when idling my boost leak problem drwas too much air, correct?

 

[isnms]

what is your a/f at idle in numerical format?
what is your VF at idle?

yes sounds like you're drawing in unmetered air.

 

[McMsk]

What do you mean in numerical format? The aem only displays between 10 and 17.9, so it must be more than 17.9 when it shows ---

What is VF?

 

[isnms]

...I during idling used to have three line on my aem wideband --- showing it to be too lean to show....

I don't know what "three lines" is.

VF

 

[McMsk]

The three lines means, that the measured value is either below or above the amount than can be displayed. The range it can display it between 10.0 and 17.9 I believe. and when it shows the three lines --- it is something like 18.5 or worth, which is not displayed. Then my supra was setup stock it also showed three lines --- under boost because the ration was richer and 10.0 so like 9.5 so it would not display it but show --- till oyu leaned it out enough to show a value like 10.5

 

[isnms]

ahh, then that sounds like you are drawing a lot of unmetered air

 

[IHI-RHC7]

What are your mods?
It does sound like you are drawing unmetered air, or your fuel pressure is too low.

 

[McMsk]

I have a greddy fmic with hardpipes, a hks sportturbo, bic downpipe, random tec cat, tanabe, apexi safc II, profec e-01.

if it would have too little fuel pressure, then the ratios would not be correct under boost, i would say

 

[IHI-RHC7]

If it were injesting unmetered air, you would suspect the same thing...

 

[McMsk]

what do you mean? I believe, there is some boost-leak somewhere, and when the engine cruises, it has underpressure, and where air normaly goes out, when cuising air goes in. But where might this be. I built a pressure test, but could not tell where it is coming from. Might i have blown the intake manifold gasket?

 

[jetjock]

Gotta agree with the others in that it sounds like pirate air. The AFR should always be right around 14.7 during steady state cruise and idle. Some engines idle just a tad leaner but not very much.

 

[isnms]

Today's actual instructions on consumer goods:

On a Swedish chain saw: "Do not attempt to stop chain with your hands or genitals."

:rofl: :rofl: :eek3:

 

[McMsk]

Where might this priate air be coming from? Can this be caused by a damaged intake mani gasekt?

 

[isnms]

^yes it can, happened to me.

 

[McMsk]

what were your sympthomes? were they in anyway similar to mine?

Can't find any other leak anymore. Found some, but still the same problem, and when i use the pressure tester, I hear sometinhg from near the intake but can't tell. did you guys ever use this kind of spray which is supposed to help you find pressure leaks? I have no idea what it is called in english, bit i guess you know what i mean. I bought some, but didn't try it yet.

 

[isnms]

yes, I had a very lean idle and a very rich wot.
the unmetered air that was being drawn in ad idle was being pushed out at wot. so the expected amount of air was not being delivered to the cylinder for the supplied amount of fuel.

 

[McMsk]

The first round i used the pressure tester, i discovered that my stock bov was broken, and i had left it in the car only to close the hole. So I was able to boost 1.3 bar without fuel cut, and i was very suprised by this. But Now I removed it and closed the hole, so it must be someting else. Thats why I guesed it to be the intake manigasekt? Did you every use the kind of spray i mentioned, or maybe i should go ahead and remove the intake many and have a look.

 

[isnms]

yeah, I tried the spray, I tried the homemade pressure tester, I checked over all the hoses. Finally I took it down to the local Goodyear shop and had them put on their smoke machine. That's how the hole in the intake manifold was discovered.

retrace your steps before you take off the intake manifold. What did you work on from the time it had good a/f till now?