Advice on troubleshooting poor running condition?

Discussion in 'Fox 5.0 Mustang Tech' started by JasinC19, Apr 19, 2012.


  1. JasinC19

    JasinC19 What hole is this!?!

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    I've been trying to get my new build running smoothly.

    In short, I took the spout out, timing is 10degrees.
    I unplugged IACV/IAB, car running bad

    Read codes, got code 34 (I think it was 34) which is EGR malfunction. I capped off vacuum port on EGR valve and car ran smoothish.
    Can I keep my EGR capped off with no ill effects until I figure out this issue?

    Spout out, IACV disconnected I set idle down to 700 (got really choppy).
    Should my TPS be disconnected while I'm doing this?

    Reconnected everything, set TPS to around .91v and it dies when I start it. I can get it started if I hold the throttle down, but it won't idle. Am I missing something? I thought the IACV would kick in and rev her up.

    Also, my IACV whistles really badly.

    I definitely noticed a change in the idle quality when i clocked my MAF, so I am going to try to run stock airbox tomorrow and see if it helps. That is if the weeds on the side of my house haven't eaten it yet.

    Thanks for any advice.

    Noteworthy mods:
    Trick flow top end kit
    c&l maf for 24# injectors
    24# injectors
    a leaking exhuast system
    stock distributor
    bbk cai
  2. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    Do a cylinder balance test, note what codes come up.

    C&L MAFs are not designed to run with anything but the stock airbox.

    Cylinder balance test:

    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 cylinder 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.

    [​IMG]

    [​IMG]

    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.

    [​IMG]

    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.

    [​IMG]

    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, 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.

    See the link to my site for details on how to build your own blow down type compression tester.


    Sponsored Ad

  3. JasinC19

    JasinC19 What hole is this!?!

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    Thanks, I would love to do a cylinder test, but I'm having issues with the idle once I plug the IAC/spout back in.

    Another strange thing I noticed is that with the IAC unplugged and spout unplugged, the engine was struggling at one point, then the idle suddenly raised. It seemed like the computer figured something out or something, but I though that the only thing that changes idle with IAC/spout disconnected was the stop screw.
  4. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    You may have bumped what ever is causing the vacuum leak you have hiding in the maze of old lines and connections...
  5. JasinC19

    JasinC19 What hole is this!?!

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    At around 1000 rpm i have 15" vacuum, pretty constant. When I try to lower idle to 700-750 to set base timing, I get 5" vacuum that shakes along with the engine that is trying to cut off.

    Why would I have 15" vacuum at 1000-1500 rpm, but low vacuum at idle?

    Also, if my valves were adjusted to be too tight, would it be possible to achieve 15" vacuum?


    I wish there was an easy way to cap all vacuum lines to see if my problem goes away, then add one at a time.

    Thanks for the help and bear with me... this car is stressing me out!!!

    Here is my orientation of vacuum lines

    Upper intake:
    Source
    Fuel pressure regulator
    Long black plastic line that goes over to passenger firewall vacuum connector
    Charcoal solenoid line
    PCV to side of intake manifold

    My EGR valve is capped off. I blew in it when it was disconnected and a tiny bit of air blew through it, but barely any.

    I have the rest of the lines on the passenger vacuum connector thing capped off. I think one went to thermactor lines... the one that originally went to EGR broke, so I used the other white one (which is now capped anyways)

    I'm wondering if my valves are adjusted too tightly. I read that can cause low vacuum.
  6. JasinC19

    JasinC19 What hole is this!?!

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    Actually that isn't a bad idea if it is possible. Can I cap everything off (source to vacuum tree, EGR, Heater vacuum line, charcoal) to "start from scratch"?

    Also, this is the passenger side connector i was talking about. It's been a constant source of unfamiliarity for me.
    [​IMG]
  7. Blown88GT

    Blown88GT Founding Member

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    I'm sorry, but that's just not true. With the correct calibration tube, they will run with conical filter mounted directly to the MAF inlet. The cal tubes are different for the 2 configs. However, the MAF's are sensitive to inlet configuration, i.e. no bends within 6" of MAF inlet. I've talked to them a number of times because of the issues with mine. I have found that once the engine reaches full operating temp & it goes closed loop, the idle returns to normal. Will be experimenting with this again shortly.
  8. JasinC19

    JasinC19 What hole is this!?!

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    I have the stock airbox back on for now. It didn't help my issue.
  9. Blown88GT

    Blown88GT Founding Member

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    I've seen that vacuum connector on other Ford models, but not on my '88, unless it's buried inside the fender. I've got a bunch of those from the salvage yard with vacuum accumulator attached. Good for spares when the old plastic ones break. I've added a couple accumulators for the vacuum hogs, i.e supercharger surge valve. That one helped my idle vacuum a lot.

    If you post of pic of your inlet config, i.e. MAF. I might be able to help.
    C&L Calibration Chart, hope you have the right one for your configuration.
    http://www.cnlperformance.com/calibration.html
  10. JasinC19

    JasinC19 What hole is this!?!

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    Where does your EGR vacuum line come from?
  11. Blown88GT

    Blown88GT Founding Member

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    EGR Control Solenoid or EGR Valve?
    JRichker has posted the vacuum diagram many times. Can't find one right now.
  12. JasinC19

    JasinC19 What hole is this!?!

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    Valve. I am just asking because mine comes off that bunch of lines in the pic i posted and you mentioned you didn't have one.
  13. Blown88GT

    Blown88GT Founding Member

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    That one's easy to find on mine, broke it a couple months ago so different color. It comes from the EGR Control Solenoid upper port.
    [​IMG]`
    Yours will never function as currently plumbed. EGR Valve is not connected directly to manifold vacuum, it should be connected to the output of the control valve.

    Looks like it's all been re-plumbed by a previous owner. True?
  14. JasinC19

    JasinC19 What hole is this!?!

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    No it was me. I broke the EGR line, so I just swapped in the one that used to go to the thermactor solenoid.

    However, I currently have the EGR valve capped off. I still am not sure if the valve is leaking or not.
  15. Blown88GT

    Blown88GT Founding Member

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    I have a MityVac hand vacuum which makes testing a lot easier. It's been more useful than a code reader.
    BTW, the hissing noise at the IACV may indicate that it's leaking. Remove it, clean it, & inspect it. You can get them at the junkyard from '93-'94 Explorers. The connector is clocked a bit differently, but it will fit. Cost is about $7. You can get all the plastic vacuum hard lines at at the same time. Most won't even charge you for them.

    You don't need a Thermactor system for a good idle, but you do need a good solid vacuum. Also, blowing into a vacuum line is not a good test of anything because of all the check valves, both internal to the solenoid valve & the external ones shown in the pic.
  16. jrichker

    jrichker StangNet's favorite TOOL SN Certified Technician Founding Member

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    I may have to apologize for that misstatement, but if you carefully read all the information in http://www.cnlperformance.com/MAF_info4.html, you may come to the conclusion that as a general rule, it isn't too far off. It seems that there are a lot of "ifs" in C&L's design and documentation. Putting any old CAI kit on without consulting them first isn't the best plan. Their CAI may work perfectly but some others may not. If someone neglects to consider all the "ifs" they could end up with some very difficult to trace problems. Far too many people use what they have at hand and neglect to search out the manufacturers' instructions until it doesn't work the way they expected.
  17. Blown88GT

    Blown88GT Founding Member

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    Yes, especially these statements:

    On 1994 and newer vehicle applications, ALL of our aftermarket mass airflow upgrades are designed and calibrated to utilize a conical filter mounted directly on the end of the MAF housing...
    For 1989 to 1993 applications, however, things become much more complicated...There is a calibration tube chart provided on our website, but if you are unsure for your particular application, please contact us and we will be happy to assist you in determining what is appropriate for your particular vehicle

    Best to call C&L & ask for their recommendations for your particular application. I have done this, but it still doesn't work the way it should. I am using the C&L 76mm in a blow-thru configuration & the "Green" tube is specified.

    All these aftermarket MAFs were designed for optimum performance at WOT.
    For 1989 to 1993 applications, however, things become much more complicated
  18. JasinC19

    JasinC19 What hole is this!?!

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    Hey guys, I'm still trying to figure this out. I had the plugs out while I was adjusting the valves, so I took my handy digital inspection tool and took some pictures of the top of my pistons. The quality isn't super great, but what would you say we are seeing here? Rich running condition? Oil seapage? Water leak? Or normal?

    As a reminder, these are brand new forged pistons with almost no run time on them.

    [​IMG]

    [​IMG]

    [​IMG]
  19. JasinC19

    JasinC19 What hole is this!?!

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    Any takers?

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