1989 Fox Runs Rough When Cold And Code ?s

tjmi69 · Apr 1, 2015

Hey all. I'm new to the forums and new to the foxbody. My car runs really rough and alot of popping in the exhaust when cold but then when it hits a certain temp it clears right up. I bought a code reader and ran the koeo and got codes 22,31,81,82,84 and 85. I am really confused with the koer test. It said the reader would display my cylinders first and it displayed 6 cylinders. Is this just error because the koeo codes weren't fixed? The codes it sent for koer is 12,13 and 21. I'm new to all this stuff so any help would be awesome. Thanks

FoxMustangLvr · Apr 2, 2015

What have you done recently to your engine? Any modifications? Please give us a run down of you car please.

Did you remove the EGR, purge cantister, and Thermactor air system?

12- Idle speed control out of specified range
13- Normal idle not within specified range
21- Coolant temperature sensor out of specified range
22- MAP sensor out of range, did you change this recently? May need to be cleaned.
31- Canister or EGR valve control system, did you remove this or disable?
81 & 82- Thermactor air circuit, integrated controller circuit
84- EGR control circuit
85- Canister purge circuit or transmission shift control circuit

tjmi69 · Apr 2, 2015

Just bought it last summer. Haven't done anything to it except change the coil. I'm pretty sure all that stuff is removed. the guy I bought it from had it as a drag car so I'm sure everything was removed. It seems like I've lost alot of power too. It has heads from a 69. E303 cam, 75mm pro-m maf, 24# injectors. Not sure on the intake.

FoxMustangLvr · Apr 2, 2015

Lots of people hack these cars up. Can you post a few pics of the engine bay?

tjmi69 · Apr 2, 2015

I sure will. I'm at work right now bUT I'll snap some tonight when I get home.

jrichker · Apr 2, 2015

Since most of the emissions equipment has been removed or tampered with, the code 22 is the one code that will negatively affect performance. If there is emission testing in your area, you bought yourself a big headache.

MAP/BARO sensor operation and code 22

Revised 14-Nov-2014 to add wire colors for frequency & voltage testing and engine sensor wiring diagrams.

On a Speed Density car, the MAP/BARO sensor is connected to the intake manifold and acts to sense the manifold pressure. Lower vacuum inside the intake manifold when combined with more throttle opening measured by the TPS means more airflow through the engine. As airflow increases, fuel flow through the injectors needs to increase to keep the air/fuel ratio where it needs to be. When manifold vacuum increases, the engine is either decelerating or idling, and it needs to reduce the fuel flow through the injectors.

On a Mass Air car, the MAP/BARO sensor vents to open air and actually senses the barometric pressure due to changes in weather and altitude. Its purpose is to set a baseline for the computer to know the barometric pressure. As barometric pressure decreases, it leans out the fuel flow to compensate for less oxygen in the air. When the barometric pressure rises, it increases to add fuel since there is more oxygen in the air. The fuel requirements decrease as altitude increases, since the atmospheric pressure decreases.

Disconnecting the MAP or BARO sensor will set code 22.

Misconnecting the BARO sensor to vacuum on a Mass Air car will cause the computer to lean out the fuel mixture.

Code 22 or 126 MAP (vacuum) or BARO signal out of range. The MAP or BARO sensor is pretty much the same sensor for both Mass Air & Speed Density cars. The main difference is where it is connected. Mass Air cars vent it to the atmosphere, while Speed Density cars connect it to the intake manifold vacuum. Its purpose is to help set a baseline for the air/fuel mixture by sensing changes in barometric pressure. The MAP or BAP sensor puts out a 5 volt square wave that changes frequency with variations in atmospheric pressure. The base is 154 HZ at 29.92" of mercury - dry sunny day at sea level, about 68-72 degrees. You need an oscilloscope or frequency meter to measure it. There a very few DVM’s with a price tag under $40 that will measure frequency, but there are some out there.

Map sensor wiring:
black/white - ground
orange/white or +5 volts power
white/red signal out.

Measure the +5 volt supply using the orange/white and black/white wires
Measure the signal using the black/white and white/red wires.

The MAP/BARO sensor is mounted on the firewall behind the upper manifold on 86-93 Mustangs.

Baro or MAP test using a real frequency meter - run the test key on, engine off. The noise from the ignition system will likely upset the frequency meter. I used a 10 x oscilloscope probe connected from the frequency meter to the MAP/BAP to reduce the jitter in the meter's readout. And oscilloscope is very useful if you have access to one or know of someone who does. With an oscilloscope, you can see the waveform and amplitude.

If it is defective, your air/fuel ratio will be off and the car’s performance & emissions will suffer

Some basic checks you can make to be sure that the sensor is getting power & ground:
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery cable. It should be less than 1.5 ohm.

The following power on check requires you to turn the ignition switch to the Run position.
Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or EGR sensors. Use the black/white wire for the ground for the DVM.

Diagrams courtesy of Tmoss & Stang&2birds

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs

tjmi69 · Apr 2, 2015

Nope. Live in michigan. No emissions testing. The map has been bypassed.

jrichker · Apr 3, 2015

tjmi69 said:
Nope. Live in michigan. No emissions testing. The map has been bypassed.

I think you don't understand. The MAP/BARO sensor is not part of the emissions equipment.
Bypassing it will put the computer into limp mode with reduced power and economy.

The MAP sensor is on the firewall behind the upper intake manifold. Re-read the technical description I posted for the Code 22.

Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles Probst :ISBN 0-8376-0301-3.

It's about $25-$50 from Borders.com see Amazon.com: Online Shopping for Electronics, Apparel, Computers, Books, DVDs & more . Select books and then select search. Use the ISBN number (without dashes or spaces) to do a search. Try searching using M-1832-Z1 instead of the ISBN number if you don’t get any positive results. You may only be able to find a used one, since the book is as old as the cars it covers. Or you order it from your Ford dealer as SVO part no. M-1832-Z1.

Use the ISBN number and your local library can get you a loaner copy for free. Only thing is you are limited to keeping the book for two weeks. It is very good, and I found it to be very helpful.

tjmi69 · Apr 3, 2015

Thanks. That response was to the guy who said I was in for a headache if there were emissions testing in my state.

tjmi69 · Apr 3, 2015

So if I get a bap hooked back up I should be good? Why would anyone bypass it?

FoxMustangLvr · Apr 3, 2015

tjmi69 said:
So if I get a bap hooked back up I should be good? Why would anyone bypass it?

Do you have an aftermarket computer? Some type of programmed chip? I think there's more info we need. The map/baro talks to the MAF, you can't have one and not the other when running a MAF type setup unless you are speed density.

The missing sensor could be your problem or at least one of them.

tjmi69 · Apr 3, 2015

Pretty sure it's the stock cpu and no chip. I will get a bap and see what happens

jrichker · Apr 3, 2015

tjmi69 said:
Thanks. That response was to the guy who said I was in for a headache if there were emissions testing in my state.

That's me. I have been driving and fixing EFI 5.0 Mustangs for 23 years now. Over 15 of those years have been spent here on Stangnet reading, learning and teaching others how to fix these fun cars without busting their budget or banging their heads against a brick wall....

tjmi69 · Apr 3, 2015

I appreciate all the help. People like me are sure glad people like you are around.

tjmi69 · Apr 4, 2015

tjmi69 · Apr 4, 2015

I found a map sensor off a 5.0 lincoln towncar that I was told would be the same and it didn't change anything. Still runs rough when cold.

jrichker · Apr 4, 2015

The air filter inside the engine compartment is a big no-no. The turbulence and hot air off the fan causes problems with the airflow though the MAF. The stock airbox and flat panel filter is miles better than that. At a very minimum, the air filter needs to mount inside the wheel well where the stock filter pulled its air supply from.

Clear the codes and dump them again. The instructions for clearing codes should have come with your code reader. If not, turn the headlights on and disconnect the battery for 5 minutes. Turn the headlights off & reconnect the battery. Then drive at ~55MPH for 15 minutes & dump the codes again. Anytime you put a replacement sensor on an EFI engine, you need to do the disconnect battery thing. This cause the computer to go into "learn mode" to lean the new sensor settings.

Is your rough running just at idle or all engine speeds?

tjmi69 · Apr 4, 2015

if I floor it then it cleans up but then alot of popping out of exhaust when I let off

jrichker · Apr 6, 2015

tjmi69 said:
if I floor it then it cleans up but then alot of popping out of exhaust when I let off

Fix the obvious problem first - the air filter location. Some PVC pip from Home Depot, Lowes or Ace Hardware is a good place to start to fabricate your own setup.

tjmi69 · Apr 6, 2015

I don't have the tools available to cut a hole in the fender wall at this moment but that is definitely a future project. I don't think that's causing my problem cause it would seem like that would start causing problems when everything heats up under the hood. I understand what your saying though and I do plan on changing it.

1989 Fox Runs Rough When Cold And Code ?s

New Member

I love my Pimp

New Member

I love my Pimp

New Member

StangNet's favorite TOOL

New Member

StangNet's favorite TOOL

New Member

New Member

I love my Pimp

New Member

StangNet's favorite TOOL

New Member

New Member

New Member

StangNet's favorite TOOL

New Member

StangNet's favorite TOOL

New Member

Similar threads

Privacy & Transparency

Privacy & Transparency