How smart are modern engines ?

jCarroll · Dec 29, 2010

50 years ago a good test for leaking intake manifolds or vacuum lines was to spray WD-40, starting fluid, or propane where you were checking, and listen for the engine to speed up if there was a leak and it sucked more combustible substance into the engine.

Are current engines with fuel injection, lots of sensors, etc too smart to be fooled with such a test, or does it still "work".

guido · Dec 29, 2010

Hello,
Yes, anything that is combustible, introduced in the intake system, would change the engine R.P.M.'s.
Guido

kseaton65 · Dec 29, 2010

still use that test quite often, can of brake or intake cleaner works well

Jerry/MT · Dec 29, 2010

I think you maybe right. If the O2 sensor senses a rich condition, it can lean the mixture, IF it can update itself quickly enough. I"ve never tried it, however.

BCnT · Dec 29, 2010

well for one thing...WD 40 doesnt have a flammable propellant anymore so youre gonna be chasing flies with no honey.

carpman15 · Dec 29, 2010

(quoted from post at 14:43:21 12/29/10) I think you maybe right. If the O2 sensor senses a rich condition, it can lean the mixture, IF it can update itself quickly enough. I"ve never tried it, however.

it should work just fine because the o2 sensors can not change that fast esp if you do it right after starting it while its still "cold" it goes into "open loop" where the o2 sensors dont matter - thats what ive been told anyways -

either way it will change rpms too fast for engine to compensate for that change in speed -

tom-ky · Dec 29, 2010

You need to unplug the Idle control, depending on what vehicle as it will try to adjust the speed right back. When doing balance tests you also have to do this.

Anonymous-0 · Dec 29, 2010

The propellant on my WD-40 is co2, isn't that what is causing ALL the warming trouble? obviously not flammable.

Hobo,NC · Dec 29, 2010

Depends on how massive the air leak is... depends on were the leak is,,, depends on the engine temp,,, depends on whether its affecting one cylinder are all of'em,,, depends on were the leak is in the airflow stream...

Yes its difficult to find a air leak,,, a smoke machine is a must have tool to find them most of the time... After I brought one I could not live with out one...

If the leak is with in the parameter of the PCM to adjust for it you are not gonna find it with old shad tree ways unless you got a real sharp eye...

Its called fuel trim Google it,,,, Long term (LTFT) and sort term (STFT)...

Jiles · Dec 29, 2010

For years, I have used a small spray bottle filled with water. Cheap and effective.

patsublett · Dec 29, 2010

WD40 use to use butane for a propellent. That is why you could use it for that purpose as well as a starting fluid. It wasn't the WD40 but the butane propellent that worked. They quit using butane in it in about 1994 so it won't work anymore.

Hobo,NC · Dec 30, 2010

(quoted from post at 22:43:21 12/29/10) I think you maybe right. If the O2 sensor senses a rich condition, it can lean the mixture, IF it can update itself quickly enough. I"ve never tried it, however.

Is 1/10 of a sec. fast enuff fer ya,,, if so that's what you are dealing with...
Folks will B chit out of luck if they depend on their shade tree ways to eliminate a air leak on a EFi system that's up to par... Sometimes ya gets lucky tho...

How smart are modern engines ?

jCarroll

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guido

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kseaton65

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Jerry/MT

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BCnT

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carpman15

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tom-ky

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Anonymous-0

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Hobo,NC

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Jiles

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patsublett

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Hobo,NC

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