Help me create the "Surging Idle Checklist"

Discussion in 'Fox 5.0 Mustang Tech' started by jrichker, Apr 10, 2005.

  1. This is an equal opportunity forum where everyone has an opportunity to make a positive contribution. Any time you think you can do a better job than I have, you are welcome to try. I will watch from the sidelines and applaud your efforts.

    It stands to reason that in order to check the flow of air through a series of valves, there must be a source of air of sufficient volume and pressure. I would think that the appropriate source would be the Thermactor Air pump AKA, smog pump. If that principle escaped you, there is very little I can do about that.

    Please note that in order to have vacuum present, the engine must be running or you have connected an external vacuum source. Since most of don’t have a vacuum pump capable of delivering a constant 16”-20” of vacuum, the running engine is the vacuum source of choice.

    The tests are arranged in order so that the first item tested must be functional before you proceed the next test item.

    You also made an incorrect assumption that testing the vacuum control TAB & TAD solenoids was accomplished by observing the air flow through the control valves. That is not the case.

    The control valves are tested first by the application of vacuum to them individually and observing the airflow switch from one path to the other.

    The vacuum control TAB & TAD solenoids are tested by the application of a ground to the proper wire. At the time the ground is supplied, you should be checking for the absence or presence of vacuum at the solenoid valve’s output port that connects to the control valve. You can use a vacuum gauge or feel the suction on your finger as you cover and uncover the output port on the valve.

    If the logic of all this escapes you, there is very little I can do to help you.
  2. just wanna say thanks to jrichker for this thread! took a yr and a half to read through it but one tps sensor and a thorough IAC cleaning later the car is idles like a dream! PS I heard that you can clean your O2 sensors by soaking them in gas overnight and the reason why I thought about trying this was I pulled codes for the sensors and wanted to try it before buying new ones!
  3. Thank your your input, new thoughts and votes of confidence are appreciated.
  4. No prob lol, but any ideas about soaking O2 sensors in fuel to break up deposits or prolly just internet bs?
  5. yep. you sure did earn your title.
  7. AND another thing.

    I was recently plagued with a hestitation at 1800=2000rpm thinking it was another fuel pump going bad.

    I ran the test again and got 31. Turns out that means low voltage on the EGR attachment. So I bought a new one for about $37 and no surprise the car runs perfectly again.

    J. Richker is still king.
  8. It took 3 years to get to the final point where I can honestly say: "I now know what it was like to drive an 86GT when it was new." Wow.

    I am a BIG fan of J. Richker as mentioned above.

    Here are the things that made my still original barn find Stang finally run like brand new in the last month.

    1. Repaired/replaced the original defective "Spout" connector on distributor advance wire.
    2. Replaced fuel filter for a second time in as many years.
    3. Solved all engine codes permanently over 3 years on sale.
    4. Thinking TFI and PIP were in need of replacement "just because they were on sale" I got a new Accel TFI (which turned out to be defective so I returned it) and bought on sale a guaranteed remanufactured distributor as I don't have tools for disassembling one to replace the expensive PIP. When replacing the 3 yr old reman distributor (one of the very first things the shop did for me) I discovered they missed a tooth when installing it at the shop. ARRRG. So for all these years the minor idle issues and remaining minor topend miss was the fault of a pro in a hurry to go home. Sad. Amazing the ECU can overcome a base timing error like that and actually run very well for the most part.

    SO. If I ever take a car to the shop and still have issues when I get it back. AFTER checking engine codes. My new rule #1a will be to pull the distributor cap. Mark #1 plug wire and rotate the engine to TDC. If the rotor points to #1 plug wire I'll move on from there. If not I'll have my answer and a 15 minute permanent fix.

    Great fun to still be successfully racing an original 27 year old foxbody at the autocross.

    **I just got a new TFI from Latemodel Restorations online delivered for $40. Works great right out of the box and they sell both manual and AOD units. "Burned in" electronics, high temp, includes heatsink silicon and really good instructions to test other things like coil, wires and plugs. Car now runs flawlessly at all temps and speeds. This is way better than paying $200 for a Ford TFI. They also have a performance version for $69 if you have a hopped up engine.

    **I recently reviewed an old post from two experts including J. R. explaining that it is "impossible" to be one tooth off when stabbing the distributor on a 5.0 as the timing light will put it in the right place with the "spout" disconnected. My bad. You'd have to be so far off that you couldn't turn the unit far enough to correct it is all. GOOD to KNOW. So all I will have to do in the future is check with a timing light!!
  9. So I was in my car today in between classes, turned the key into the on position to get some music and noticed a check engine light. I have an '87 and your checklist states that there wasn't a working check engine lite until some versions of the '88. Any ideas on that?
  10. The bulb turns on when the engine is first started so that you can be sure it isn't burned out. Odd feature for a bulb that doesn't work, but it is there.
  11. Well that's odd and useless. What controls the check engine light? The computer?
  12. Yes.

    The wiring to make it work on 86-88 Mustangs is not present. Somewhere I have a description of how to make it functional.
  13. Interesting...
    So when I do the MAF conversion, can I set up the wiring to make the light work? Or is it not that simple?
  14. Yes.
    I still can't find the how to document in my Stangnet Docs library. Basically you tap into pin 17 (tan wire) on the computer harness and run it to pin #9 on the instrument cluster connector C250. See for more help on the instrument cluster details.
  15. You really do have an answer for everything...
  16. Not by any means, just like all the rest of us, I'm still learning....
    Cory Berg likes this.
  17. I appreciate your humbleness. :)
  18. So I got my EFI 5.0 up and running and just pulled the codes. I'm using an rjm harness so I think some are relate to removal of the smog and egr stuff but I just need some help figuring out what needs fixing. I'm having rough start problems. Here's the koeo codes.




    Thanks for any help!

    Also just ran a koer test and it said code 6 for cylinder count. Is this correct? Shouldn't it be 8?
  19. With no emissions control, the 8x series codes are to be expected. If you don't have a cat converter H pipe, they can be ignored. Just expect the car to sink like gasoline, since the Thermactor air system, the cat converters and the fuel tank vent system eliminate that problem.

    The code 10 is a spacer code that pops up before the rest of the codes start to be dumped.

    The 6 code for the cylinder count is an anomaly that occurs in many of the 5.0 Fox body cars. Someone at Ford coded it wrong and it is meaningless.

    The 96 code is a fuel pump electrical problem. Since you didn't list the year model of your car, I can't give you the correct code definition and wiring diagrams. Repost with the car year and I will post the proper code definition and wiring diagrams

    Here's some additional help on running a cylinder balance test that may help find some of your problems.

    Cylinder balance test: use this to find dead or weak cylinders:

    Revised 25 March 2012 to add necessity allowing the KOEO tests to finish before starting the engine and the need for a properly functioning IAB/IAC to run the cylinder balance test.

    The computer has a cylinder balance test that helps locate cylinders with low power output. You’ll need to dump the codes out of the computer and make sure that you have the A/C off, clutch depressed to the floor and the transmission in neutral. Fail to do this and you can’t do the engine running dump codes test that allows you to do the cylinder balance test.

    Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

    Be sure to turn off the A/C clutch depressed to the floor, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

    Here's how to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.



    If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.


    The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

    89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.


    The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

    WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

    What to expect:
    You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and drivability problems

    Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

    Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, clutch depressed to the floor and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

    Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

    Cylinder balance test

    If you have idle or IAC/IAB problems and the engine will not idle on its own without mechanically adjusting the base idle speed above 625-750 RPM, this test will fail with random cylinders pointed out every time it runs. The IAC/IAB must be capable of controlling the engine speed to run in the 1400-1600 RPM range. Playing with the base idle speed by adjusting it upwards will not work, the computer has to be able to control the engine speed using the IAC/IAB.

    Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Let it finish the Key On Engine Off (KOEO) code dump. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. Remember to keep the clutch pedal (5 speed) depressed to the floor during the test. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures.
    Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure

    Do a compression test on all the cylinders.
    Take special note of any cylinder that shows up as weak in the cylinder balance test. Low compression on one of these cylinders rules out the injectors as being the most likely cause of the problem. Look at cylinders that fail the cylinder balance test but have good compression. These cylinders either have a bad injector, bad spark plug or spark plug wire. Move the wire and then the spark plug to another cylinder and run the cylinder balance test again. If it follows the moved wire or spark plug, you have found the problem. If the same cylinder fails the test again, the injector is bad. If different cylinders fail the cylinder balance test, you have ignition problems or wiring problems in the 10 pin black & white electrical connectors located by the EGR.

    How to do a compression test:
    Only use a compression tester with a screw in adapter for the spark plug hole. The other type leaks too much to get an accurate reading. Your local auto parts store may have a compression tester to rent. If you do mechanic work on your own car on a regular basis, it would be a good tool to add to your collection.

    With the engine warmed up, remove all spark plugs and prop the throttle wide open with a plastic screwdriver handle between the throttle butterfly and the throttle housing. Crank the engine until it the gage reading stops increasing. On a cold engine, it will be hard to tell what's good & what's not. Some of the recent posts have numbers ranging from 140-170 PSI. If the compression is low, squirt some oil in the cylinder and do it again – if it comes up, the rings are worn. There should be no more than 10% difference between cylinders. Use a blow down leak test (puts compressed air inside cylinders) on cylinders that have more than 10% difference.

    I generally use a big screwdriver handle stuck in the TB between the butterfly and the TB to prop the throttle open. The plastic is soft enough that it won't damage anything and won't get sucked down the intake either.

    A battery charger (not the trickle type) is a good thing to have if you haven't driven the car lately or if you have any doubts about the battery's health. Connect it up while you are cranking the engine and it will help keep the starter cranking at a consistent speed from the first cylinder tested to the last cylinder.

    See the link to my site for details on how to build your own blow down type compression tester.
  20. Took your advice and ran the pin 30 wire to ground to dump the codes. Here is what I got. KOEO, code 11 ok, code 10 cylinder #1 low, code 34 EVP sensor voltage above closed limit(what is the EVP, I can't find it in any of my books?), KOER, code 12 cannot control RPM during self test High RPM test, code 21 ECT circuit volts out of range, code 91 Heated O2 sensor signal lean left side, code 33 EGR valve opening not detected.
    Figured I would clean and /or replace the EGR valve, test the O2 sensor and do a compression test. Not sure what to do with the rest. Any Ideas. Thanks Russ