high idle with strange findings...

[greengoblin95]

alrighty, i couldnt get my car dyno tuned soon enough so i swapped out my 42 lb injectors and maf with 24's and my maf that i had on the car. the car would idle decent with the 42's but would stay high rev'ed for a bit before coming back down due to the abundance of fuel. now that i have the 24's in with the maf, the car idles at 2100-2300. the fuel pressure is at 34 with the vacuum hooked up. its not a vacuum leak because i disconnected the intake tube that goes from the throttle body to the supercharger and the idle came back down to 850-1000 and i could rev the car without any problems, and the power was there. but if i include the whole air intake system that circulates through the maf, blower then the intake tube, the idle jumps up again. could this be a sign that the maf is not responding well to the 24's? I looked up the maf number and its used on 95 cobras (that have 24's) and 95 gt's (that have 19's). im just baffled by this. and i dont have the blower belt hooked up yet.

 

[Chythar]

Well, the Cobra uses the same MAF as the GT and V6, which is calibrated for 19lb injectors. The Cobra PCM compensates for the different calibration. So, right now your injectors don't match your injectors. I'm not saying that is the cause of your high idle, but it is an issue.

 

[final5-0]

I looked up the maf number and its used on 95 cobras (that have 24's) and 95 gt's (that have 19's). im just baffled by this. and i dont have the blower belt hooked up yet.

What is making this difficult to understand is

You are thinking aftermarket methods of meter/inj calibration
and
Ford does not use that method to match up meters and inj's

Like Matt said

Its all about what values Ford put in the pcm
and
Not about a certain meter will go with a certain size inj

If I understand what all you have done

You got an untuned pcm with 19# inj values
but
You have installed 24# inj's

You should be too fat

Then again ... You got all those hot rod parts so they are throwing
the pcm a bunch of false data ... thus ... ya need a tune

Grady

 

[greengoblin95]

i thought if there was an issue with the electronics portion, that the car would search for idle and not just stay high. my buddys car that i have worked on in the past has almost the same setup as me minus the heads and cam and head unit. he used his stock maf that was setup for 19's and didnt bother his car one bit with his 24's that are in the car. someone suggested turbulent air possibly, have any of you heard of that

 

[final5-0]

i thought if there was an issue with the electronics portion, that the car would search for idle and not just stay high. my buddys car that i have worked on in the past has almost the same setup as me minus the heads and cam and head unit. he used his stock maf that was setup for 19's and didnt bother his car one bit with his 24's that are in the car. someone suggested turbulent air possibly, have any of you heard of that

Just a couple things here Sir

Yes ... our pcm's have an adaptive strategy
but
They can only compensate so much

If you consider the COMPLETE range it is like 24% IIRC
but
Most consider it to be 12% when looking at it from a perfect setting

Kinda like ... 12% compensation one way or the other

Your buddy with the OEM meter and 24's

Once again ... I wanna point out

Ford DOES NOT make a meter calibrated for a certain size inj

I know I keep making that point over and over
but
That kind of thinking leads to so much confusion with OEM meters :Word:

Yes ... I can see how he might have gotten it to run with that mismatch
but
Something working ... and ... Something working correctly

Well ... Some of the time ... One ain't the same as the other

Last thing ... About that turbulent air question

You can some of the time make headway with that by doing this

Clock the meter like 1/8 of a turn one way and try it
If no help ... go another 1/8 of a turn

and of course

You would need to try it by going in the opposite direction

Kinda hard to do with the OEM flange setup

anyway ... Just a random thought or two

Grady

 

[greengoblin95]

Just a couple things here Sir

Yes ... our pcm's have an adaptive strategy
but
They can only compensate so much

If you consider the COMPLETE range it is like 24% IIRC
but
Most consider it to be 12% when looking at it from a perfect setting

Kinda like ... 12% compensation one way or the other

Your buddy with the OEM meter and 24's

Once again ... I wanna point out

Ford DOES NOT make a meter calibrated for a certain size inj

I know I keep making that point over and over
but
That kind of thinking leads to so much confusion with OEM meters :Word:

Yes ... I can see how he might have gotten it to run with that mismatch
but
Something working ... and ... Something working correctly

Well ... Some of the time ... One ain't the same as the other

Last thing ... About that turbulent air question

You can some of the time make headway with that by doing this

Clock the meter like 1/8 of a turn one way and try it
If no help ... go another 1/8 of a turn

and of course

You would need to try it by going in the opposite direction

Kinda hard to do with the OEM flange setup

anyway ... Just a random thought or two

Grady

thanks for the help bud, one of my buddies is going to bring me a matching maf calibrated for the 24's. once its in place im going to go to a tuner and see what he can do. im not trying to question your statements, i see what you are saying and trust me, a tune is coming. its just aggrevating. the car is this close and im having electronic issues. the motor is strong, just needs a lil doctoring.