Chasing idle issue may be a MAF problem?

[R100RT]

Hi Tuners, My car is a '94 T4MO, 331 mild stroker. I'm running a 76MM C&L.
My idle is stable except until the fan comes on. Once in a while, the ICS catches the additional load but most of the time, the engine dies. I data logged this and saw that the MAF voltage went up as the RPMs went down. see below

Normal idle is 800 RPM, about 22 KG/HR, .7 volts, 15% loadx.

RPM 800 700 600 500 400 300
MAFV .7 .71 .72 .78 .8 .85

Maybe it's time to give up on this C&L meter and go back to stock or a Pro Air meter. FYI, the MAF wires are clean.

Input?

Thanks, Eric

 

[tjh566]

first off, did you change the "ISC Neutral Idle Airflow" Function to work for you combo?

Another note the C&L's are know to be inaccurate, dunno if that would be the cause of your idle issues or not.

 

[final5-0]

Hello Eric

I will admit to really bad mouthing C&L meters in the past

These days, a good many self tuners have had good results
with them.

A lot of that is because you can find transfer curves for them
now a days.

See if you can find a curve for your meter here

http://eecanalyzer.webhop.net/

Clint has done a good bit of work with them

btw ... have you ever considered moving over to a j4j1 cal file

It can be more forgiving than the t4m0 with a combo like yours

Grady

 

[R100RT]

first off, did you change the "ISC Neutral Idle Airflow" Function to work for you combo?

Another note the C&L's are know to be inaccurate, dunno if that would be the cause of your idle issues or not.

Yes, I have. However, this wouldn't cause the MAFV to increase as RPM decreases.

I have also tried different MAF sensor and clocking the meter. The only thing that helps is setting the idle up to 850 RPM, which shouldn't be required with my mild cam.

Thanks, Eric

 

[R100RT]

Hello Eric

I will admit to really bad mouthing C&L meters in the past

These days, a good many self tuners have had good results
with them.

A lot of that is because you can find transfer curves for them
now a days.

See if you can find a curve for your meter here

http://eecanalyzer.webhop.net/

Clint has done a good bit of work with them

btw ... have you ever considered moving over to a j4j1 cal file

It can be more forgiving than the t4m0 with a combo like yours

Grady

The meter works great at anything above idle. I am confident in the curve. It's the MAFV output thats wacko. I also tried reclocking the meter. I have also noticed the the MAFV changes with ACT. In other words, at 50 DEGF ACT, 870 RPM gives .7VDC, at 100 DEGF act, 870 RPM gives .65VDC.


To test further, I will install the stock MAF, and retune. If the problem goes away, we can say the C&L meter tube is the problem.

Thanks, Eric

 

[final5-0]

I have also tried different MAF sensor and clocking the meter. The only thing that helps is setting the idle up to 850 RPM, which shouldn't be required with my mild cam.

Thanks, Eric

I don't know if I could be so confident in saying an elevated idle speed is NOT needed here Eric.

You do talk of a mild cam and I do see you are forced with turbo so I would have to think you do not have a good bit of duration as I and most others I have worked with have had to deal with

But ... When it comes to idle issues and modded Stangs .................
Most of the time ... You will see peeps run an idle speed of 800 or better

Your throttle body air flow scalar and as was talked about above, neutral air flow function points will greatly help to stabilize idle.

Working with inj slopes, offsets and the like to cause your K's to hug that 1.00 line closely will also help things.

Like my GT ... I've seen many say they have had better idle results with a bit over rich idle ratio as opposed to lean one

I found some help with injector timing also
It took a GOOD BIT of the cam lope away

Grady

 

[R100RT]

I don't know if I could be so confident in saying an elevated idle speed is NOT needed here Eric.

You do talk of a mild cam and I do see you are forced with turbo so I would have to think you do not have a good bit of duration as I and most others I have worked with have had to deal with

But ... When it comes to idle issues and modded Stangs .................
Most of the time ... You will see peeps run an idle speed of 800 or better

Your throttle body air flow scalar and as was talked about above, neutral air flow function points will greatly help to stabilize idle.

Working with inj slopes, offsets and the like to cause your K's to hug that 1.00 line closely will also help things.

Like my GT ... I've seen many say they have had better idle results with a bit over rich idle ratio as opposed to lean one

I found some help with injector timing also
It took a GOOD BIT of the cam lope away

Grady

Hi Grady,

My sig combo is another Mustang I have. I have five cars.

This one is the $600 Vert, '94 GT 331, Cobra intake, 24#, 65MM TB, 76Mm C&L, Stage 1 cam, GT40Y heads, 1.7:1 Crane rockers.

I'm not sure, with the T4MO, how to influnce idle A/F ratio, unless you run OL all the time. I know the engine will idle, at 600 RPM, with a rich idle.

My K's are running near 1. I data logged a typical stall, if you want me to e-mail it.

Another thing I have wondered about:
When I come up to a stop, idle will come down to 900RPm, until I get almost stopped. Then, I see the RPM blip up, about 100RPM, and then come down to normal 800 RPM. Why does the idle blip up? Why doesn't it just go down to 800 RPM?

Eric

 

[final5-0]

Hi Grady,

My sig combo is another Mustang I have. I have five cars.

This one is the $600 Vert, '94 GT 331, Cobra intake, 24#, 65MM TB, 76Mm C&L, Stage 1 cam, GT40Y heads, 1.7:1 Crane rockers.

I'm not sure, with the T4MO, how to influnce idle A/F ratio, unless you run OL all the time. I know the engine will idle, at 600 RPM, with a rich idle.

My K's are running near 1. I data logged a typical stall, if you want me to e-mail it.

Another thing I have wondered about:
When I come up to a stop, idle will come down to 900RPm, until I get almost stopped. Then, I see the RPM blip up, about 100RPM, and then come down to normal 800 RPM. Why does the idle blip up? Why doesn't it just go down to 800 RPM?

Eric

Eric

So many things can influence the idle on a 94-95 Stang and the frustrating part of it all ... some of them are most likely not causing a problem what so ever.

But ... one or more of them may be the guilty dog causing you to be an unhappy camper here.

You end up just looking at all those various things to see if anything looks outta whack I guess you could say.

I'd start off with mechanical adjustments first.

You want the tb blade stop screw just barely holding the blade off the side of the tb bore ... Really ... that is its main function as opposed to setting the idle anyway

As you know ... the idle is really set by the pcm.

The bleed screw on the tb can cause the famous hanging idle if open too far. I have seen peeps have good results in a range or two to three turns out.

IIRC, I've seen the most stable idle with an isc duty cycle at around 35

You are supposed to have a slight increase in idle speed until you almost come to a dead stop ... but not anything like 500 rpm or more like you see if that bleed screw is too far out.

Dizzy at 10 with spout in place of course.

Now for some pcm discussion

First thoughts are a surging idle is usually a sign of being a bit fat

Since you got those 24# inj's ... I'd move to the j4j1 file faster than a heartbeat
It really works nicely with modded Stangs that have moved away form OEM inj's and meter.

That TFS stage 1 cam ... while I would not call it radical ... it ain't no super wide valued lsa or milk toast cam if you ask me. IIRC ... its like 110 lsa ... or ...
am I not remembering correctly

anyway .......

The more narrow the lsa ... the more you may have to work with various adjustments is what I've seen be the general all around rule of thumb.

I looked to see if you were running LT's as they can sometimes cause a bit of grief
with idle issues.

I gave a fellow some help in a very round about way about a week ago who like you was dealing with idle issues. I've heard nothing back from him so maybe it worked out for him.

He was running the j4j1 file like me so I looked at my values and a couple other files of similar combos and just gave him some percentage of change values.

These are based upon an unmodified j4j1 file btw

TB airflow scalar ... add about 70%
ISC Neutral Idle Airflow points ... add about 10%

Now ... There are procedures you can go through to get closer but you could easily try these to see if you find some help.

You have loaded in the offsets for those 24's ... Correct
If not ... Go over to the Tweecer site for the values and load em up.

You say your K's are running near 1
however
Here is where you can't be talking in a ball park kind of way as you use the values to determine if your fat or lean at idle from an adaptive perspective.

Values < 1.00 means the adaptive is pulling fuel cause you're fat
Values > 1.00 of course are opposite here

You could certainly + or - the maf cells (depending on what your K's are telling you) at idle and like 1 above and 1 below to see if you find some relief.

Man ... I almost forgot ... You have loaded in your new cubic inch size ... Correct?
If not ... your load at idle could be a bit off.

Try some of this stuff Eric
and
If I didn't make sense with some of this ... holler back

Grady

 

[R100RT]

Updated info C&L testing

Hi Stangers,

I got tired, of messing with the 76MM C&L and decided to go back to the stock MAF. My plan was to get the car running real good and then try the C&L.

I was able to get the stock MAF running fine. Without changing any mechanical adjustments, I put the C&L back in, tweeced the new MAF curve, and gave it another shot. The tune was really close but I could tell the idle was not as good. The KMRFs were perfect though.

With the stock MAF, I was able to disconnect ICS, and the engine would drop to about 700 RPM. Trying the same trick, with the C&L, stalled the engine right away.

If you recall, my problem was that the engine would stall almost every time the low speed fan would come on. After I went to the cobra tune, with my stock MAF, those problems went away.

So, what do I think I have learned? Well, for one, the idle MAF was the same for both the C&L and the stock MAF. That tells me the MAF calibrations were good. By the way, I used Clints 76MM black tube 24# 70MM sensor curve from the EECA.

I think the C&L has problems at the low MAF flows, because the larger flow area, and the way the tube only looks ,at flow in one spot. the stock MAF sorta averages it because of the divider that goes across the MAF.

Where to go from here? The stock MAF is getting to about 4.8 Volts WOT. I suppose I could live with it. I probably will given that spending $200 would only get me about 10 HP. I probaly will put a K&N fliter in and call it good.

 

[final5-0]

Where to go from here? The stock MAF is getting to about 4.8 Volts WOT. I suppose I could live with it. I probably will given that spending $200 would only get me about 10 HP. I probaly will put a K&N fliter in and call it good.

Close to pegging that little stocker meter
I done did that myself as well

You can up the maximum something or the other scalar (the exact name eludes me at this moment ... but ... it will be obvious when you look for it) that talks about airflow to 4.99999 volts for a bit of more upstairs kinda room with your curve.

At this 4.8 volts ... What is your af ratio

Grady

 

[R100RT]

Hi Gardy, The MAF max voltage is already at 4.9999

I don't know hat the A/F ratio is, no WB, but the car doesn't show any signs of running lean.

I know you had to change your stock MAF but you also have better heads and cam.
I'm just trying to decide where to go from here.

Eric

 

[final5-0]

OK ... The max maf voltage has been put into place

You might still find more room at the top of the curve for these reasons

The fuel table is quite fat at the top as delivered from Ford

If you look at the values you see like 12 to 1 with the GT and 11.5 to 1
with the Cobra IIRC.

Now remember ... these values in this table are NOT your actual fuel ratio
but are LAMBSE values which ARE your commanded fuel ratio.

LAMBSE values and Wide Band values can be quite different

If using a WB and you found you were in fact fat ... You would most
likely find room at the top of the curve since you decrease airflow
values to lean things back.

Some of the time ... You will find you are lean and then you will loose
room at the top of the curve in your efforts to fatten things up.

anyway

I usually try to stress that WOT fuel stuff is best to leave alone until
one does two things:

1) Obtains a stable Closed Loop Tune
2) Obtains a Wide Band

Grady

 

[R100RT]

Thanks for the input, Grady.

Just to make sure we are not misleading others, who are following this thread, I wanted to exspand a little more on MAF sensors.

For a given air flow, if the sensor output is near 5 volts, there is nothing that can be done to reduce this voltage. You are right that changing the fuel tables could find more power and a WB would be good to use. You are also correct that leaning the MAF curve would reduce the indicated airflow but the MAFV still stays the same.

I know you ran a stock MAF a while. What I would really like you to way in on is if you think a new MAF would be worth the $200.

Eric

 

[final5-0]

Thanks for the input, Grady.

Just to make sure we are not misleading others, who are following this thread, I wanted to exspand a little more on MAF sensors.

For a given air flow, if the sensor output is near 5 volts, there is nothing that can be done to reduce this voltage. You are right that changing the fuel tables could find more power and a WB would be good to use. You are also correct that leaning the MAF curve would reduce the indicated airflow but the MAFV still stays the same.

I know you ran a stock MAF a while. What I would really like you to way in on is if you think a new MAF would be worth the $200.

Eric

Well Eric

I ran the OEM meter and 30# inj's because the Tweecer afforded me
that opportunity.

I will say if you are too fat you are gonna have to work with fuel tables
and the curve so things are gonna change but lets just say you usually
have to go larger with a meter if you are close to pegging it ...
but ... not in every case.

Some things are just so important, you want the very best quality you can
find when talking about them.

Since the meter is used to determine load and our cars pcm is load based,
the maf certainly falls in that important category.

This is one area one really should not scrimp on IMHO.

Lightning meters are very nice units and as I understand it ........
they can be found for an attractive price.

I've had very good luck with my ProM shorty 80mm and their 77mm meter
has been a solid unit with peeps for years now.

About that Q of ... Is a maf worth $200

Several years ago I got mine for $250 and I felt it was a bargain

I'll put it this way my friend

Since you got a way to custom fit the maf curve to your specific combo
needs, It just seems natural to me that you want a meter that has
given proven positive results for peeps in the past who have done
what you now seek to do.

Quality first and price is secondary in this case is how I see it.

Grady