Help me create the "Surging Idle Checklist"

stackz said:

ok, I just followed the above post and I must say it is severely lacking lol.

does not mention half the time that the engine needs to be running to test the solenoids...AND...it doesnt mention that when you are testing the second solenoid you need to have the first solenoid grounded so its passing air to the second solenoid so you can test its action....

also, what is the natural state of the first solenoid? when the engine is cold should it be closed or open? mine is closed. I have to manually apply vacuum to get it to pass air.

also, when I ground the first vacuum pot's solenoid and then release the ground...it stays active for about 10-20 seconds before closing. is this normal??

same applies for the 2nd solenoid. I apply ground and it stays going after I release ground for 5-10 seconds. however, when allowed to go by itself, it doesnt flow either way lol. I can remove the vacuum pot and manually blow on it and I feel air going to the bottom port. but when engine running and it hooked up, no flow out of either port until I started grounding it.

makes me think they were both simply stuck from sitting for 2 years...I dunno.

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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.

ViperPunk said:

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!

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Thank your your input, new thoughts and votes of confidence are appreciated.

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.

Cory Berg said:

Well that's odd and useless. What controls the check engine light? The computer?

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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.

Cory Berg said:

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?

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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 http://www.stangnet.com/tech/cluster87-93.pdf for more help on the instrument cluster details.

Cory Berg said:

You really do have an answer for everything...

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Not by any means, just like all the rest of us, I'm still learning....

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.