DTC CODES!! A LIL HELP PLZ

[88gt373]

HEY FELLAZ... I JUST FINISHED A REBUILD NOT TOO LONG AGO AND JUST FOUND OUT THAT 1988 MAS-AIR CARS DONT HAVE AN 'ACTIVE' CHECK ENGINE LIGHT SO WHEN I PLUGGED UP MY SCANNER TO THE ENGINE PLUG HERES WHAT I GOT:

DTC: 33
DTC: 12
DTC: 94
AND.... 'CYLINDER 8'


I GOT ALL MY SMOG STUFF HOOKED UP ALL HOSES GO TO THE RIGHT PLACES ALL WIRING ETC...

 

[jrichker]

Please take the Caps Lock off when you type. It is very annoying to read.

Code 12 -Idle Air Bypass motor not controlling idle properly (generally idle too low) - IAB dirty or not working. Clean the electrical contacts with non flammable brake parts cleaner at the same time.

Recommended procedure for cleaning the IAC/IAB:
Conventional cleaning methods like throttle body cleaner aren’t very effective. The best method is a soak type cleaner used for carburetors. If you are into fixing motorcycles, jet skis, snowmobiles or anything else with a small carburetor, you probably have used the one gallon soak cleaners like Gunk or Berryman. One of the two should be available at your local auto parts store for $22-$29. Take the solenoid off the body and set it aside: the carb cleaner will damages some types of plastic parts. Soak the metal body in the carb cleaner overnight. There is a basket to set the parts in while they are soaking. When you finish soaking overnight, twist the stem of the IAB/IAC that sticks out while the blocker valve is seated. This removes any leftover deposits from the blocker valve seat. Rinse the part off with water and blow it dry with compressed air. The IAC/IAB should seal up nicely now. Once it has dried, try blowing through the bottom hole and it should block the air flow. Reassemble and reinstall to check it out.

Gunk Dip type carb & parts soaker:

Code 33 - Insufficient EGR flow detected.
Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold. Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the passenger side wheel well. Using a test light across the electrical connector, it should flicker as the electrical signal flickers. Remember that the computer does not source any power, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.
Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the computer: you should have less than 1.5 ohm.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif


EGR test procedure courtesy of cjones

to check the EGR valve:
bring the engine to normal temp.

connect a vacuum pump to the EGR Valve or see the EGR test jig drawing below. Connnect the test jig or to directly to manifold vacuum.

Do not connect the EGR test jig to the EVR (Electronic Vacuum Regulator).

apply 5in vacuum to the valve. Using the test jig, use your finger to vary the vacuum

if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.

if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.

if engine stumbled, connect EGR test jig to the hose coming off of the EGR Valve.
Use your finger to cap the open port on the vacuum tee.
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 2-5 in vacuum?
if not the EVR has failed

EGR test jig

The operation of the EGR vacuum regulator can be checked by using a test light applied across the wiring connector. Jumper the computer into self test mode and turn the key on but do not start the engine. You will hear all the actuators (including the EVR vacuum regulator) cycle. Watch for the light to flicker: that means the computer has signaled the EGR vacuum regulator successfully.


Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks.

Revised 28-Oct-2009 to correct code definitions and operation.

Code 44 RH side air not functioning.
Code 94 LH side air not functioning.

The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves. When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and the O2 readings increase. By toggling the dump valve (TAB), the computer tests for the 44/94 codes.

Failure mode is usually due to a clogged air crossover tube, where one or both sides of the tube clog with carbon. The air crossover tube mounts on the back of the cylinder heads and supplies air to each of the Thermactor air passages cast into the cylinder heads. When the heads do not get the proper air delivery, they set codes 44 & 94, depending on which passage is clogged. It is possible to get both 44 & 94, which would suggest that the air pump or control valves are not working correctly, or the crossover tube is full of carbon or missing.

Testing the system:
Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them

 

[88gt373]

Ok.... So i checked all my vacuum lines and found that one was leaking pretty bad... when i put the car back together, i kind of had to used a bunch of mis-matched vac lines from the junk yard... anyway, i code 94 is is gone... 1 down 2 to go... Thanks for the write ups....very detailed.


Any idea of what "Cylinder 8" means?

 

[jrichker]

Codes can be dumped with the ignition on but the engine not running.

If you dumped the codes with the engine running, fix the idle speed problem code 12 and the 8 cylinder may go away by itself.

 

[88gt373]

Codes can be dumped with the ignition on but the engine not running.

If you dumped the codes with the engine running, fix the idle speed problem code 12 and the 8 cylinder may go away by itself.

Ok... so here is my update:

my EGR solenoid switch was bad... so it was giving me a code for that. I replaced it today and ran the scanner again and that code was now gone. Another code 94 came back then after shutting the car off, re-ran scanner and code 94 wasnt there.. NOW there is just a code 12 and "cylinder 8".

JRICHKER, how do i fix the idle speed problem or go about diagnosing it..Or are you saying that if i dump the codes while the motor is running, that should make both codes go away?

 

[jrichker]

Ok... so here is my update:

my EGR solenoid switch was bad... so it was giving me a code for that. I replaced it today and ran the scanner again and that code was now gone. Another code 94 came back then after shutting the car off, re-ran scanner and code 94 wasnt there.. NOW there is just a code 12 and "cylinder 8".

JRICHKER, how do i fix the idle speed problem or go about diagnosing it..Or are you saying that if i dump the codes while the motor is running, that should make both codes go away?

Are you saying that you got an cylinder 8 with the engine not running? If so go back and read the instruction book for your scanner. The 8 cylinder may mean it is an 8 cylinder engine.

See the "Surging Idle Checklist for help with all your idle/stall problems.

The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

 

[Mustang5L5]

Cylinder 8 could be just an engine Id code. When running a cylinder balance test, your result for a problem with cylinder 8 is "80".

So you can ignore the cyl 8 code...especially if it comes as soon as you initiate the engine running test

 

[88gt373]

Are you saying that you got an cylinder 8 with the engine not running? If so go back and read the instruction book for your scanner. The 8 cylinder may mean it is an 8 cylinder engine.

See the "Surging Idle Checklist for help with all your idle/stall problems.

The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

The engine IS running when i run the KOEO test after i put my OBDI/OBDII scanner to the port

"cyl:8
cylinder number"
is on of the screen. Along with code DTC 12.

the car runs fine and idles real good.. theres good power and it revs great, it runs/sounds great. The smog guy just wont smog me with the car having codes..so im wondering how to get them gone. Could it be a problem with my throttle sensor? i think its aftermarket or would that give a different code?

Thanks for the help

 

[88gt373]

Cylinder 8 could be just an engine Id code. When running a cylinder balance test, your result for a problem with cylinder 8 is "80".

So you can ignore the cyl 8 code...especially if it comes as soon as you initiate the engine running test

it makes sense that cyl 8 code is a description because when i ran the balance test nuthin came up just a code 12. im gonna see if my tps is outta range because it was removed when i got the motor.

 

[jrichker]

The engine IS running when i run the KOEO test after i put my OBDI/OBDII scanner to the port

"cyl:8
cylinder number"
is on of the screen. Along with code DTC 12.

the car runs fine and idles real good.. theres good power and it revs great, it runs/sounds great. The smog guy just wont smog me with the car having codes..so im wondering how to get them gone. Could it be a problem with my throttle sensor? i think its aftermarket or would that give a different code?

Thanks for the help

The "Surging Idle Checklist has the IAB/IAC idle speed cleaning and adjustment procedures needed to clear the code 12

 

[88gt373]

The "Surging Idle Checklist has the IAB/IAC idle speed cleaning and adjustment procedures needed to clear the code 12

Alright fellaz. Im pretty much stuck now. I went through the check list, adjusted my TPS, cleaned my IAC, got another IAC from the JY and cleaned that too. Cleared the codes with my scanner and used a jumper and undid the neg batt terminal. Im stumped that i still have a DTC 12. I even adjusted my idle to around 750 rpm (per these janky stock gauges, still have great vacuume about 17" @ idle).

I have power to the IAC, power to tps, egr all related sensors, car runs like a top.. i have noticed the idle will stumble slightly at start up when cold after i adjusted my idle and TPS... but not close to dying and no bogging..


IDEAS? would timing make a code 12 happen? thanks for all the replies

 

[jrichker]

If the timing is too far advanced, the engine will stumble and surge. Best bet is 10-14 degrees set with a timimg light.

Setting the timing:
Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

10 degrees BTC is towards the drivers side marks.

Simplified diagram of what it looks like. Not all the marks are shown for ease of viewing.

ATC ' ' ' ' ' ' ' ' ' '!' ' ' ' ' ' ' ' ' ' BTC
---------------- > Direction of Rotation as viewed standing in front of the engine.

The ' is 2 degrees.
The ! is TDC
The ' is 10 degrees BTC
Set the timing 5 marks BTC. Or if you prefer, 5 marks towards the driver's side to get 10 degrees.

To get 14 degrees, set it 7 marks BTC. Or if you prefer, 7 marks towards the driver's side to get 14 degrees.

The paint marks you make are your friends if you do it correctly. They are much easier to see that the marks machined into the harmonic balancer hub.

At this point hook up all the wires, get out the timing light. Connect timing light up to battery & #1 spark plug. Then start the engine.

Remove the SPOUT connector (do a search if you want a picture of the SPOUT connector) It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT
Warning: there are only two places the SPOUT should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.

Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

 

[88gt373]

If the timing is too far advanced, the engine will stumble and surge. Best bet is 10-14 degrees set with a timimg light.

Setting the timing:
Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

alright. ill do the timing check when it stops raining!!! this weather sucks here in the cali bay area.....
BTW i was reading over the whole post again and i noticed when on the checklist code 12 usually means the idle is too low..... on my scanner it said 'idle out of range/high'.... could that point me some where else? what are the chances of the IAC/IAB i got from the JY be bad too? thanks

 

[88gt373]

Alright.... so did the timing and it was at 14* already and luckily my timing light is so bright it was pretty easy to read.... so like i said the timing is ok, idles well no backfiring or surging, tps is at .998 volts, but heres the thing. i went to adjust my idle lower (because of the dtc 12 out of range/high) and if i went any lower than what i did, the damn screw would be out on the TB!!! i mean right now the screw is barley touching the linkage and if i backed it out all the way theres NO difference in the idle... is that normal?

DTC 12 SUCKS!!!!!

 

[Mustang5L5]

You need to unplug the iac when you back the screw out.

Unplug the iac, lower the idle down (it should stall if you go low enough) to the point it barely wants to run. Then, disconnet batt for 20 mins to reset computer. Plug the iac back in...and restart. Anytime you adjust the idle screw, you must unplug the iac to adjust, and then reset the computer.


Your tps will need to be readjusted, but shooting for 0.98 volts makes NO difference...just leave it anywhere between 0.5 and 1.1 volts. Adjusting to .9999 is useless. Rear the post stuck at the top of tech forum for more info

 

[jrichker]

Evidently you didn't read all the Help me create the "Surging Idle Checklist" - Mustang Forums at StangNet . In it is the proper way to set the idle speed, set the TPS and clean the IAC/IAB.

Just because the first few lines don't fit your specific problem does not mean that the information you need isn't in there. Checklist procedures are designed to cover a lot of possiblities, and contain information on as many solid fixes as possible.

 

[88gt373]

You need to unplug the iac when you back the screw out.

Unplug the iac, lower the idle down (it should stall if you go low enough) to the point it barely wants to run. Then, disconnet batt for 20 mins to reset computer. Plug the iac back in...and restart. Anytime you adjust the idle screw, you must unplug the iac to adjust, and then reset the computer.


so i do i approach fixing this now that i backed out the screw w/o unplugging i IAC/IAB?

 

[Mustang5L5]

You can still do it. More than likely, of you unplug the iac with the engine idling, it will stall.

If it does, leave it unplugged....crank the throttle body screw in a good amount and start the engine. It will probably idle at 1500 or so....then back the screw out to drop idle. Go down as low as possible and then reset the computer like I stated before

 

[88gt373]

You can still do it. More than likely, of you unplug the iac with the engine idling, it will stall.

If it does, leave it unplugged....crank the throttle body screw in a good amount and start the engine. It will probably idle at 1500 or so....then back the screw out to drop idle. Go down as low as possible and then reset the computer like I stated before

UPDATE:
I unplugged the IAC and lowered the idle to barley running. then after having the batt unplugged for about 30 minutes, i plugged the harness back to the IAC then started (with the TPS is withing range) the car and ran my OBD2 scanner and code was gone!!! * the IAC is brand new btw *

soooo.... i took the car around the block, ran great, idled WAYYYY better so i gassed it it first and did a tiny burnout (didnt even hit my rev limit) then came to a stop and i idle was stuck at 2,000 rpm! wtf... WHAT COULD THAT BE????

then i unplugged the IAC while running... nothing! (has voltage)
i unplugged the TPS.... nothing.. (has voltage)
i even unplugged the MAS AIR FLOW plug and nothing.. (didnt check for power but looks ok)

did i F*** something up ? i even cleaned up my TB... i ran my obd2 again and the code comes back (dtc 12) and goes away, and back. last time i ran it this morning there was nothing. im goin to run again later and see if its ok... any ideas? did i fry my computer?

 

[Mustang5L5]

Take the IAC off and clean the piss out of it. Make sure the internal plunger can move freely. They tend to gum up and hang open.

Repeat the idle reset and try it again. You might have to replace the iac if it hangs open.