Mass air connected, Car dies. Disconnected, Car runs???!?

1990Coupe

1990Coupe

Founding Member
Mar 11, 2002
1,462
132
114
Toms River NJ
#1
OK after getting the RIGHT computer and headligh harness, she runs :banana:

However, The car will not run with the Mass Air sensor CONNECTED... If i disconnect it, she'll run and idle just fine (however once she warms up i have a rather nasty idle surge). I have no EGR stuffs hooked up, the sensors are there and plugged in, just no lines running to them. I have never seen anything like thsi before anyone have any ideas? Im about to buy a new mass air sensor tomorrow, and a bunch of other little sensors like the Idle Air sensor, ACT, ECT, all those little ones.

(ps i set my TPS to .99 so thats good :) )

Here she is so you can see.

View attachment 295075
 

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#2
That is odd I had an 85 t-bird turbo coupe i used to run with out the TPS hooked up if i did it would run crappy...Maybe its a bad MAF? but why would it run with it off you got me on this one....Hope someone can help you im not that familuar with these cars sorry ...I need to learn about them myself...now that i have a 93 GT...Oh yeah the car sound good ...sounds nice what exhaust do you have?
 
#3
i had the same problem with my buddy 91. when it was plugged in the car ran soo rich that it actually would kill the motor. took a little while to figure it out but the maf was bad and caused the plugs to foul. leav it disconnected and get a new one when u can it wont hurt it driving it around for a lil while like that just remember when the maf is unplugged the pcm cant tell how much air is actually entering the engine soo its basically running off a back up fuel and timing map and guessing based on throttle position and engine rpm. gas mileage will suck too
 
#4
I was thinking it was a bad Mass Air however i thought that the car wouldn't run with it unplugged?? Im going to my local autoparts store today to pick up some misc sensors hopefully that will help against the idle surge, and i'll see how much the mass air sensors go for and maybe pick up a brand new one :shrug:
 
#6
I've had some friends drive there cars to my house because of that same problem. They had either a bad or dirty MAF that did that. They have cleaner that is made just for cleaning it. Try to barrow one from a car that runs good and see if that cures it.
 
#7
sigh,


The described condition does NOT absolutely mean the MAF is the failed component.
Start by pulling the codes.

If you go buy a NEW meter now, you are gambling... sometimes you win, sometimes you lose.



For the special MAF Cleaner.... that stuff is basically Brake Cleaner. Check the labels.
The specialty cans of 'Electronics Cleaner' are the same thing as well.
I've always used Brake Cleaner to clean my MAF meters.

good luck,
jason
 
#10
Justin--First, excellent job. The engine bay looks clean as hell.

Second...Clean the MAF sensor, and put the airfilter box on there. My black car ran like crap without the air box. It wouldn't idle at first, then after gassing it a few times, it idled from 400-600RPM. I put the box and filter on and it was perfect.

Third...you have a PM
 
#11
vristang said:
sigh,


The described condition does NOT absolutely mean the MAF is the failed component.
Start by pulling the codes.

If you go buy a NEW meter now, you are gambling... sometimes you win, sometimes you lose.



For the special MAF Cleaner.... that stuff is basically Brake Cleaner. Check the labels.
The specialty cans of 'Electronics Cleaner' are the same thing as well.
I've always used Brake Cleaner to clean my MAF meters.

good luck,
jason
Click to expand...

I'll have to pull codes in the tomorrow. It seems like it would be a bad or dirty meter. I plug it in, it dies, i unplug it runs fine :shrug: I wouldn't buy a new one per say, i'd pick up a used one from a salvage yard.

SVT32VDOHC said:
Justin--First, excellent job. The engine bay looks clean as hell.

Second...Clean the MAF sensor, and put the airfilter box on there. My black car ran like crap without the air box. It wouldn't idle at first, then after gassing it a few times, it idled from 400-600RPM. I put the box and filter on and it was perfect.

Third...you have a PM
Click to expand...

I had the airbox in there today. Even with it in there, it made no difference.

Thanks for the props!! :nice:
 
#14
Nope haven't fixed it. Today im going to head home and clean the MAF. If it still dies when unplugged I'm going to get another one from the salvage yard. Check my progress thread i posted a vid of its maden voyage down my street. I have it unplugged in that vid and listen to how good it runs :shrug:
 
#17
1990Coupe:
Hi!
It's GREAT that you posted the video. GREAT IDEA!!
It helps a lot in figuring out a number of things that are going on. And, it helps to identify some inaccurate information and misconceptions that may have been given you.'

So, let's handle the inaccurate information and misconceptions first:

o For a stock setup, stock TB, setting the TPS is a ricer mod, pure and simple. If you have an non Ford/FRPP TB, then you should check the TPS because the quality on non-Ford TB's sucks. Mustang TPS FAQ

o Is that a 100% stock MAF?
For C&Ls, people should shove those POS MAFs far up the *ss of the people that sold them the units and the people that suggested them. If it's an old ProM, then the old ProM sold most cr*p for most of the years. Still, at least their cr*p came with a flow sheet, so if people had a chip, they could adjust the MAF table to the POS quality control and electronics tuning that the old ProM used to do.

o Please, never ever connect or disconnect senors with the car turned on. And especially if the engine is running! That's a great way to fry the ECC, and/or fry the sensor, and/or freak out the EEC's control loop.

o You'd be lucky if even a 100% stock MAF works with it open on the end like that. You'll be getting a ton of fan wash. So, even if it did run/work, then it would work by luck and luck only.

o You must read the codes. Otherwise, you're guessing. If you want, you can replace every part of the engine one by one until you hopefully find the bad part. Or, you can start by seeing what the code readings are. Note: The codes give you an idea of where to start looking. They codes rarely tell you "part ABC is bad". But, the codes often give a good idea where to start.


As people said, without the MAF hooked up, the EEC goes into failure mode (aka: FMEM, limp home mode) and will run the engine pig rich as an emergency to help the person get home and not get stuck in the middle of nowhere. Do a Google search for ECC FMEM (e.g. How to Tune and Modify Ford Fuel ... - Google Book Search ).
 
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#18
stang&2Birds said:
1990Coupe:
Hi!
It's GREAT that you posted the video. GREAT IDEA!!
It helps a lot in figuring out a number of things that are going on. And, it helps to identify some inaccurate information and misconceptions that may have been given you.'

So, let's handle the inaccurate information and misconceptions first:

o For a stock setup, stock TB, setting the TPS is a ricer mod, pure and simple. If you have an non Ford/FRPP TB, then you should check the TPS because the quality on non-Ford TB's sucks. Mustang TPS FAQ

o Is that a 100% stock MAF?
For C&Ls, people should shove those POS MAFs far up the *ss of the people that sold them the units and the people that suggested them. If it's an old ProM, then the old ProM sold most cr*p for most of the years. Still, at least their cr*p came with a flow sheet, so if people had a chip, they could adjust the MAF table to the POS quality control and electronics tuning that the old ProM used to do.

o Please, never ever connect or disconnect senors with the car turned on. And especially if the engine is running! That's a great way to fry the ECC, and/or fry the sensor, and/or freak out the EEC's control loop.

o You'd be lucky if even a 100% stock MAF works with it open on the end like that. You'll be getting a ton of fan wash. So, even if it did run/work, then it would work by luck and luck only.

o You must read the codes. Otherwise, you're guessing. If you want, you can replace every part of the engine one by one until you hopefully find the bad part. Or, you can start by seeing what the code readings are. Note: The codes give you an idea of where to start looking. They codes rarely tell you "part ABC is bad". But, the codes often give a good idea where to start.


As people said, without the MAF hooked up, the EEC goes into failure mode (aka: FMEM, limp home mode) and will run the engine pig rich as an emergency to help the person get home and not get stuck in the middle of nowhere. Do a Google search for ECC FMEM (e.g. How to Tune and Modify Ford Fuel ... - Google Book Search ).
Click to expand...


:hail2::hail2::hail2::hail2::hail2::hail2::hail2:

First off thanks for that informative post :nice:

Second>. everything under the engine is stock, minus the exhaust, and the fact that i did not hook up the EGR system. All the sensors are there and plugged in, just no tubes running to them. I do have Cats, and i do have a smog pump hooked up to pump air into the cars (high flow x pipe). So TB, sensors, MAF its all stock.

Third> I've hooked up the airbox, plugged in the MAF with the car off. As soon as i start the car, she'll run then die. I then unplug the MAF with the car off, i start it and she runs good.

Forth> i've cleaned the MAF very well last night, still same thing.

Fifth> I have a code reader but i lost the book and i don't know when to start counting the blinking lights. I know i'll pull codes for the EGR until i have that programmed to turn off, but would the MAF throw a code if the engine only runs for a 1 or 2 seconds?



:)
 
#19
Dude, I have a 90 GT that does that too without the front aircleaner housing attached. Mine suffered from the Fan wash. Does it do that when you have the air cleaner attached? It seems that the factory fan blows a ton of air directly in to the MAF which drives the MAF out of range.
 
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