my ongoing miss- I still need help

[wymjym]

Too much information can make for messy guesses!

In my quest to eliminate a nagging miss at idle I data logged many parameters the other day but the ones that stand out to me are:
1 throttle position is never less than 18% and never more than 93%
question: is this typical? I had already checked and set the tps voltage maybe there is a physical restriction limiting its sweep?

2 the maf flow rate was .84 when started (at idle) but after warm up it was typically 3.5~4.5 lbs per min.
question: isn’t this high?

3 the maf at WOT and 4900 rpm was 18.32lbs per min
question: what is the typical range (output) for the maf on this car (1997)

note:
after driving for a few miles I pulled over to the side of the road, put it in park and it idled pretty smoothly
I then raised the hood and unplugged the maf, the engine immediately dropped in rpm but recovered in less than 1 second to what sounded like the exact same idle…look at the chart!!!!!!!


I’m looking for guidance here, is the maf in question or do I need to keep looking?

And lastly…this is a 1997, with a 1997 engine and pcm etc….notice something ‘wrong’ with this photo?


This is the maf that was/is on the car when I purchased it (from a ford mechanic)
I had replaced it with another maf (black plastic housing) early on trying to eliminate my miss but it ran the same so I put the ‘original’ unit back on. How much difference would the maf outputs be? Does the data chart indicate that the maf is functioning properly?

Thank you!!!!!!!
wj

 

[Mr Anonymous]

Do not use the plastic MAF. The correct MAF for a '97 has an aluminum housing and a different electronics pack. If you've been running a plastic MAF on your car all along that's the first thing you need to correct immediately. The MAF outputs are very different since the 96/97 PCMs and 98/99 PCMs run at different clock speeds.

What are you using for data logging? It looks like you're logging PID's which don't have anywhere near the update rate of DMR's. For the MAF you want to log MAF counts, not lbs/min and for TP log relative not absolute.

 

[wymjym]

Hi Chris,
I located a used one that is ....sortof...local and will pick it up later this week. Is there any way I can confirm that it is functional before paying my money?
make sure the wire is not broken, measure resistance?

I purchased Autoenginuity in 2007, not sure if it will read/right that fast but will find out.
wj

 

[mustangracer91]

When I'm trying to diagnose a faulty maf or map sensor, another pid I look at is the calculated load...at idle in neutral with nothing on, and your calculated load is high, over 10-20%, you've got a problem with that circuit, or a restricted exhaust.

 

[SHOZ123]

Check the Short Term Fuel Trims. This will tell you if the MAF is properly calibrated in closed loop. Be sure to clear the KAM first as this will be adjusted by the adaptive control over time.

On a warm engine you will be in open loop at idle for under a minute. This should show you a rich commanded fuel value.

Data logging the MAF flow rate is not much help unless you know the MAF tables.

The plastic MAF will run lean on < '98s and should be setting a DTC for a lean condition (limit on fuel added reached).

 

[mustangracer91]

IIRC, the housing itself doesn't matter on the maf, it's the element that screws into that housing right? I know some places just sell the element and you're suppose to reuse your old housing...so technically couldn't he just swap to the correct element and be done?

 

[SHOZ123]

Unless you are getting an OEM element then they are all off.

There is a difference in the internal bar that shields the element between the plastic and metal OEM MAFs.

 

[wymjym]

Unless you are getting an OEM element then they are all off.

There is a difference in the internal bar that shields the element between the plastic and metal OEM MAFs.

My local wrecking yard no longer has the metal maf!
The AZ and Oreily's offer rebuilt Cardone units...is this a safe bet?

The engine sets no codes except sometimes a rich one p174. The long term is always pulling huge amounts out of bank 1 and when it can't pull enough the code sets.

The short term for bank one shows more negative readings than bank 2.

wj

 

[mustangracer91]

Unless you are getting an OEM element then they are all off.

There is a difference in the internal bar that shields the element between the plastic and metal OEM MAFs.

I'm a little confused, by element, I'm referring to the core sensor section that's held in by two tamperproof torx screws...are you referring to the different internal bar is actually cast into the metal housing?

as mafs are a somewhat common failure point, where can us v8 sho owners go to source a correct brandnew one? or do we no longer have that option?

 

[Mr Anonymous]

I'm a little confused, by element, I'm referring to the core sensor section that's held in by two tamperproof torx screws...are you referring to the different internal bar is actually cast into the metal housing?

as mafs are a somewhat common failure point, where can us v8 sho owners go to source a correct brandnew one? or do we no longer have that option?

The sensor sections of the electronics packs are different. The 96/97 version uses a sample tube that is part of the MAF housing. The 98/99 version uses a plastic sample baffle that is an integral part of the electronics pack itself. Thus, the electronics packs are not interchangeable between aluminum and plastic housings.

Cardone remanufacturers the MAF sensors, just go to Rockauto.com.

'96/'97 Aluminum MAF:

'98/'99 Plastic MAF:

 

[Mr Anonymous]

My local wrecking yard no longer has the metal maf!
The AZ and Oreily's offer rebuilt Cardone units...is this a safe bet?

The engine sets no codes except sometimes a rich one p174. The long term is always pulling huge amounts out of bank 1 and when it can't pull enough the code sets.

The short term for bank one shows more negative readings than bank 2.

wj

Cardone is OK, but personally I'd want to peel back the label they place on the front of the electronics pack to verify the correct P/N. I've seen a few of the Cardone units on customer cars and most were the correct electronics but a couple were not.

You can also try Kirk at NESHO 508-963-5899, or www.car-part.com to search your local recyclers.

 

[mustangracer91]

thanks guys for clearing that up and the directional guidance...

 

[bacernate]

Refresh my memory here. Does it go rich at idle? A bad maf or a dirty one will run very rich at idle and then very lean as rpm increases.
Does the car go into open loop under full throttle, if it does I wouldn't worry about the tps sweep.
Can you change the maf to read grams per second and voltage on your laptop scanner?
That's what I'm used to seeing.
Also what's your baro reading in hertz? Should be in the 145 ish. Any lower than that is also a good indication of a incorrect or faulty maf.
Let me know, email or pm me if you would like.