Can't Figure out the problem.

Black 93 Fox

Active Member
Jun 1, 2003
1,995
0
49
Vancouver,Washington
Alright So I am running out of options. I can not figure out how to get my car to idle. I bought a chip didnt help, tried the TPS, thought it wasnt getting enough juice so I just upgraded the alt to 130 tonight and still wont change. Ok here is the problem. I will start the car it wont idle on its own and will surge and die.... once I baby it down to idle around 1000rpm it will run for about o 5minutes or enough to get fully warm then I hear the engine speed up and slow down about 3x's each time getting worse then it dies. The car is running rich I read in the Surge Idleing thread something about a fuseable link might cause this. Where is the fuse able link how do I fix that to see if that will cure it? I am about at my wits end here and ready to start hitting the car with a mallet.:mad: Any help or possiable idles would be greatly appricated thanks guys.


Here are all my mods:
Full Trick Flow H/C/I
FMS 30LB Injectors
Profesional Products 75mm TB(might be part of the problem it whistles)
255 in tank pump
Under Drive Pulleys( Not on the new alt yet)
battery relocated with kill switch and 150amp breaker.
SCT Chip ( not in car currenty took it out)
All the other bolt on's
 
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The injectors look a little large for a 303/306/308. The computer may have problems trimming the idle fuel without a custom burned chip.

The fuseable link is for the O2 heaters and is located in the main wiring harness near where the O2 sensor wiring exits off to go to the O2 sensors. You can use a voltmeter to look for 12 volts at the O2 sensor harness.
 
Yeah Intend to put a blower on it eventualy thats why I put the 30's on there. It is a 306 BTW, Is it possiable that it could be the fuseable link? think If I threw some 24's in it could that maybe cure the issue...

jrichker said:
The injectors look a little large for a 303/306/308. The computer may have problems trimming the idle fuel without a custom burned chip.

The fuseable link is for the O2 heaters and is located in the main wiring harness near where the O2 sensor wiring exits off to go to the O2 sensors. You can use a voltmeter to look for 12 volts at the O2 sensor harness.
 
Alright so I have been screwing around with it for a couple hours. I tried the TPS again I can get the car to idle but only when the TPS is set at .69, the frist time I did this it was idleing then the electric fan kicked on and it started surging again and died. So I started it back up and babyed the gas pedal down so it would idle( if you try to start it and leave it the thing will not even try to idle on its own) came out of the car didnt touch a thing and the electric fan kicked on again and it didnt surge this time??? I unpluged the IAC and it dided right off the bat. I started it with out the IAC plug in and that damn throttle body really started whistling it would not idle period. Would a bad ground cause this if so how would I check to see if there is a bad ground somewhere? Also I still have the chip just not in the car's computer would all this be able to be tuned out? I've been working on this problem for over a month an its really ticking me off.
 
You can chase your tail doing all kind of things in a random manner, or you can take an organized approach to troubleshooting. The best plan is to have your troubleshooting strategy laid out with a 1,2,3 approach. Do the simple stuff first. That means take measurements, dump codes, and do simple adjustments. If you make a change and it does not improve the problem symptoms, undo it and proceed to the next step.

The surging idle checklist is laid out with a 1,2,3 approach. Start with step 1 and go from there.

The best way to check the O2 sensor heater circuit is to use a voltmeter. Tearing up a wiring harness to find a fuse link that may be good is counterproductive. Unplug the O2 sensors and look for the 12 volts on the chassis side of the O2 sensor harness with the ignition switch in the Run position.

The TPS is supposed to be set with the ignition switch in the Run position with the engine not running.

The 75 MM TB is also too large for your displacement. It would be more suited for a 351 or larger engine.
 
Alright I'll try thoes thanks jrichker! I'll let you know what happens.


jrichker said:
You can chase your tail doing all kind of things in a random manner, or you can take an organized approach to troubleshooting. The best plan is to have your troubleshooting strategy laid out with a 1,2,3 approach. Do the simple stuff first. That means take measurements, dump codes, and do simple adjustments. If you make a change and it does not improve the problem symptoms, undo it and proceed to the next step.

The surging idle checklist is laid out with a 1,2,3 approach. Start with step 1 and go from there.

The best way to check the O2 sensor heater circuit is to use a voltmeter. Tearing up a wiring harness to find a fuse link that may be good is counterproductive. Unplug the O2 sensors and look for the 12 volts on the chassis side of the O2 sensor harness with the ignition switch in the Run position.

The TPS is supposed to be set with the ignition switch in the Run position with the engine not running.

The 75 MM TB is also too large for your displacement. It would be more suited for a 351 or larger engine.
 
Alright I cleaned the IAC( has 11.79 volts in run postion), set the TPS with the engine of but in the run postion I set it at .96, I bought a code scanner I ran the scanner with the engine off and the engine running ( waited till it was warm then ran the engine on scan) The car is starting to run better its not as hard to baby it down and get it too idle. Two things I noticed while doing the test first thing was after I did the key on engine off test I started the car and it started right up and idled on its VERY OWN! Thought that was werid then second thing I noticed while waiting for the temp to go up I accidently hit the headlight switch when i did it made my temp needle go up so I shut it off and sure enough it made it go down and I double checked it same result any thoughts on this? All the codes came up basicly emissions (car has no emssions), one was idle too low code 13 and the other is the Air Diverter soleiond fault? Code 81 and 82. The car didnt get to do the full run test I dont think it died but it came up with the codes below.

Key On Engine Off:34,81,82,85,84,34
Key On Engine On:8,94,44,34,13
 
Code 13 - Key on Engine off - ISC did not respond properly (extends to touch throttle then retracts for KOEO) – ISC

Key on Engine running - Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too high)

If your idle is above 725 RPM, the computer will set this code. Normal idle speed is 650-725 RPM. Higher than that means that someone has mechanically set the idle speed by use of the idle speed screw, and has effectively disabled to computer’s ability to control idle speed.

Code 34 Or 334 - EGR voltage above closed limit - Failed sensor, carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the flange side of the EGR by mouth. If it leaks, there is carbon stuck on the pintle valve seat, replace the EGR valve ($85-$95).

If the blow by test passes, and you have replaced the sensor, then you have electrical ground problems. 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 post. It should be less than 1 ohm.

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.

Let’s put on our Inspector Gadget propeller head beanies and think about how this works:
The EGR sensor is a variable resistor with ground on one leg and Vref (5 volts) on the other. Its’ resistance ranges from 4000 to 5500 Ohms measured between Vref & ground, depending on the sensor. The center connection of the variable resistor is the slider that moves in response to the amount of vacuum applied. The slider has some minimum value of resistance greater than 100 ohms so that the computer always sees a voltage present at its’ input. If the value was 0 ohms, there would be no voltage output. Then the computer would not be able to distinguish between a properly functioning sensor and one that had a broken wire or bad connection. The EGR I have in hand reads 700 Ohms between the slider (EPV) and ground (SIG RTN) at rest with no vacuum applied. The EGR valve or sensor may cause the voltage to be above closed limits due to the manufacturing tolerances that cause the EGR sensor to rest at a higher position than it should.

This will affect idle quality by diluting the intake air charge

Code 81 – Secondary Air Injection Diverter Solenoid failure AM2. The solenoid valve located on the back side of the passenger side wheel well is not functional. Possible bad wiring, bad connections, missing or defective solenoid valve. Check the solenoid valve for +12 volts at the Red wire and look for the Lt Green/Black wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the LT Green/Black wire for the solenoid valve.

See http://www.veryuseful.com/mustang/tech/engine/images/88Stang5.0Vacuum.gif for help on the vacuum line plumbing.

Remove the large rubber hoses from the rear of the aft vacuum control valve. One hose goes to the pipe to the back of the heads. The other hose goes to the pipe that goes to the cat converters. Start the engine and apply vacuum (steal a line from the manifold somewhere) the airflow out of the valve should switch from one outlet to the other. If it doesn't then the vacuum control valve is bad.

With the engine running, stick a safety pin in the LT Green/Black wire for the solenoid valve & ground it. That should turn the solenoid on and cause air to flow out the port that goes to the pipe connected to the cats. If it doesn't, the valve is bad. If it does cause the airflow to switch, the computer or wiring going to the computer is not signaling the solenoid valve to open.

Code 82 – Secondary Air Injection Diverter Solenoid failure AM1. The dump valve air diverter valve (front vacuum operated valve) isn’t working on the Thermactor Air System (smog pump). Look for broken or missing vacuum lines on the solenoid valve to the diverter valve Check the solenoid valve for +12 volts at the Red wire and look for the Red/White wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the Red/White wire for the solenoid valve


Code 84 EGR Vacuum Regulator failure – Broken vacuum lines, no +12 volts, regulator coil open circuit. The EVR regulates vacuum to the EGR valve to maintain the correct amount of vacuum. The solenoid coil should measure 20-70 Ohms resistance. The regulator has a vacuum feed on the bottom which draws from the intake manifold. The other vacuum line is regulated vacuum going to the EGR valve. One side of the EVR electrical circuit is +12 volts anytime the ignition switch is in the run position. The other side of the electrical circuit is the ground path and is controlled by the computer. The computer switches the ground on and off to control the regulator solenoid.

Code 85 - CANP solenoid - The Carbon Canister solenoid is inoperative. Check vacuum lines for leaks and cracks. Check electrical wiring for loose connections, damaged wiring and insulation. Check solenoid valve operation by grounding the gray/yellow wire to the solenoid and blowing through it.
The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.


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