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Thread: No increased idle when cold

  1. #1
    Electronic Ignition!
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    No increased idle when cold

    I was having trouble downloading bin a while ago but with your help I got that figured out .

    I burned the APAB bin to my chip and set my timing, and my IAC steps to 40 with an idle speed of 600. When I start the engine cold, it starts then dies, the only way it will stay running is if I slightly press the pedal. It runs super smooth with pedal slightly cracked open. I am pulling 15in hg at idle. The engine does have a Comp cam in it, but nothing crazy. It should have an increased idle when cold correct? And decay over time with coolant temp?

    Even when warm the engine doesn't seem to idle well at all. Driving seems fine, it is mostly at idle that I have the problem. My wideband shows it idling SUPER lean, cold or warm at 17.5-off scale. I know it is a stock bin for a 4.3 and I have all this on my AMC 258, but that seems way off. Or is it typical for that much of a variance? It seems no matter what I do to the main fuel table it always comes back to the lean condition. Is that the ECM reading the O2 and pulling fuel from my table?

    Thanks for all your help guys. I know it is difficult to troubleshoot stuff over the internet, but any suggestions will be appreciated and tried.

  2. #2
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    I have never liked the 7747 / 4.3 calibrations. Most that I have seen do not trigger the injectors with each injection pulse, instead they use ecm logic to decide when to fire injectors. This always seems to cause issues for folks using the 4.3 cal in any "not a 4.3" application. My experience with 258 EFI retrofits was to work over a couple of fuel only swaps. The swap was designed for a stock cam and for the first project the engine builder opted for something different which I no longer have the specs for. I ended up using a 7.4 calibration as my baseline as the old, slow burn head and non-heated aftermarket intake just seemed to match the early BBC TBI parameters closer.

    With that said, GM uses both spark advance and increased airflow to effect higher idle. If you're running fuel only then you've lost access to the spark and will probably have to make adjustments to your calibration to add IAC counts. Why the engine runs lean takes a little thought to answer. If you have a "low end" cam, combined with the strong intake pulses of the 258, then the stock VE table may be a very poor match. The engine might not be getting enough fuel at idle. Increasing delivered fuel is a good way to check this. In your case it sounds like increasing VE values does not make a difference. Have you tried disabling closed loop and monitoring the WB to see if the changes actually show up in the exhaust? Spark advance can certainly affect O2 readings. Increasing advance gives more time for combustion to complete and generally shows as a richer mixture at the O2 sensor. Again, if you've gone with a fuel only conversion then you might want to consider adding spark control for better control.

    If you'd like to compare the stock 4.3 settings to what I'd used in the 258 fuel only swap you're welcome to. Here's a little bit about some of the engine differences that helped me choose the 454 calibration base:
    http://www.gearhead-efi.com/Fuel-Inj...ull=1#post7221

    Here's the post with the files:
    http://www.gearhead-efi.com/Fuel-Inj...ull=1#post7273

  3. #3
    Fuel Injected!
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    I'll try to remember but, this was so long ago. The 4.3L back then had a high complaint level of rotten egg smell. The 4.3 had some PROM and a hardware updates tp address this. The O2 was moved downstream to sense both sides in an updated y-pipe. The 4.3 also had rich and lean injectors in the pods to combat the fuel distribution. The 4.3 ran open loop at idle in some cals because the O2 would cool off and not maintain closed loop without the investment of a downstream heated O2 back then. I believe you are fighting a system you will struggle to correct and I wouldn't spend the time. I always begin with the last calibration released for the ECM used for the application regardless of model year. In this, I would move to a 5.0L, use the same injectors in both pods, and recal the bin for your engine and injector. Or you may use what was suggested above with another engine. I say this without knowing what your system has such as injectors, O2, wiring, what Ign ect.

  4. #4
    Electronic Ignition!
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    This is why I love this site! Everyone here gives straight forward answers. I should have given more info on the engine in my earlier post. Here is what the engine is: .060" over 258 block, the cam is a Comp High Energy 260H, 4.0L head, header, and 2.5" exhaust.


    The dist in locked out and the ECM is controlling spark. I can use either Tinercat or Tunerpro RT to disable closed loop, but what exactly do I do? Do I set "Rpm above which open loop idle is forced off" on Tunerpro to say a lower value than the 1000 that it is currently set?

    It also dawned on me that is it possible for the CTS to be malfunctioning and seeing a greater temp than is really there. I can verify that with WINALDL next time I hook to the Eagle.

    I will follow your links now and check out the fuel table. Thanks for the advice!

  5. #5
    Electronic Ignition!
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    I can use a v-8 bin correct? I need to change the number of cylinders to 6 right? I'll see exactly which injectors I am running. Thanks for your suggestions!

  6. #6
    Fuel Injected!
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    The IAC may be stuck. If you change the idle speed in the bin, does the actual idle speed follow?

    As for the lean condition, you should monitor the O2 sensor voltage just to see what is happening. The O2 can only read stoichiometric, so it shouldn't go lean while in closed loop. In closed loop, the O2 sensor voltage should constantly be swinging above and below 0.45V. If you see it doing that, then the PCM doesn't think/know it's lean and you need to figure out why the O2 sensor and your wideband are not matching.

    You have a header, so how far away from the head is the O2 sensor and is it heated or not?

  7. #7
    Electronic Ignition!
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    I believe the IAC is working, I can watch the step count and it does react, and I can hear a change in the sucking when I jab at the throttle. I have also placed my finger over it and can detect the sucking and its change during throttle position.

    The wideband and non-heated single wire 02 are in the collector. The header is more of a long tube design. Is it possible to install a heated 02 with the 7747? I will watch the 02 voltage next time I have WINALDL hooked to the car and observe the 02.

    It sucks I always get motivated to work on this thing in the winter when it's freezing out. Then when summer comes I live with how it runs and beat the snot out of it. My son and I are taking to Moab for the Jeep Safari next month and I would like it to start and idle well, it will work as is, but a little improvement would a long way!

    Thanks for your help!

  8. #8
    Fuel Injected!
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    Yes, you can use a heated O2 sensor with a 7747 and you should be using a heated O2 sensor with long tubes. The one time I tried the non-heated O2 in a collector, the system would go lean every time the engine returned to an idle after driving. If I left it long enough it would eventually throw an O2 code, but it took a minute or 2 of idling.

    Personally, I would use a 4-wire O2 sensor. The connectors and sensors seem to be more common. Also, it gets rid of using the header for the sensor ground by wiring it directly. The O2 negative wire from the computer is the tan wire which was hooked to the rear passenger side intake bolt on the stock V8 applications. I believe the V6 applications had it in the same spot. It goes to D7 in the computer connector.

    Part way down the page on this link is a table with the wire colors for different types of O2 sensors. Just match the wiring to the sensor you get. Hook the "heater" wires to switched power and ground, the "signal" wire to the old O2 purple wire and the "ground" wire to the tan wire.

    http://www.aa1car.com/library/o2sensor.htm
    Last edited by lionelhutz; 02-18-2016 at 07:36 AM.

  9. #9
    Electronic Ignition!
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    Quote Originally Posted by lionelhutz View Post
    Yes, you can use a heated O2 sensor with a 7747 and you should be using a heated O2 sensor with long tubes. The one time I tried the non-heated O2 in a collector, the system would go lean every time the engine returned to an idle after driving. If I left it long enough it would eventually throw an O2 code, but it took a minute or 2 of idling.

    Personally, I would use a 4-wire O2 sensor. The connectors and sensors seem to be more common. Also, it gets rid of using the header for the sensor ground by wiring it directly. The O2 negative wire from the computer is the tan wire which was hooked to the rear passenger side intake bolt on the stock V8 applications. I believe the V6 applications had it in the same spot. It goes to D7 in the computer connector.

    Part way down the page on this link is a table with the wire colors for different types of O2 sensors. Just match the wiring to the sensor you get. Hook the "heater" wires to switched power and ground, the "signal" wire to the old O2 purple wire and the "ground" wire to the tan wire.

    http://www.aa1car.com/library/o2sensor.htm
    Right on! Will do! Thanks

  10. #10
    Fuel Injected!
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    Trying to fix a similar rough idle issue, can you recommend a part number for a heated o2 sensor?

    Quote Originally Posted by lionelhutz View Post
    Yes, you can use a heated O2 sensor with a 7747

  11. #11
    Fuel Injected!
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    Question for No increase in Idle cold. The ALDL is in 10k mode which is designed to be used for "End Of Line Test" at the factory.
    This is done by placing a 10k resistor across ALDL Pins A and B.
    This involves the ECM to force idle to a set calibration value of 1,000. It eliminates the closed loop timers, adds a calibrated amount of ignition timing to the commanded/cal and provides the End Of Line test a fast test for the system to pass or fail. End of Line could blip the throttle and hear it spark knock hits or read this on the data stream so this part of the system would obtain a PASS. Other tests were done as well.
    The outcome we found for the Service Field is idle @ 1,000 RPM, rough idle, spark knock, early EGR application and stalling at idle in some cases. Some ECM's provide an Open ALDL mode to retrieve data and run in a normal mode of operation, some do not. I believe your IAC system may operate correctly if you remove the 10k or pull the ALDL off I think you'll find the IAC may run right - drive it.

    What you asked about the min Run spd, this is for many items. For ECM power saver to not turn on or activate outputs under the RPM to not drain the B+. Another is when software would run diag codes and activate systems off a timer as EGR and Canister purge just for some. But this isn't true in all cases and is dependent on the S/W, ECM, and system configuration. Without your sytem knowledge it is difficult to correctly answer.
    The RPM you se at 1,100 or so could be the wrong conversion OR the wrong label descriptor in your ADX file. Normally Run spds are close to 350-450 rpm generally speaking.

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