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  • Throttle won't return to idle.

    Something new started happening when I drive the truck. The throttle hangs and won't return to idle when I left off the gas. It only happens above 1800ish RPM. Anything below that and it's fine and above it hangs open. I did use these instructions to reset the idle on the truck and the IAC Position is open about 6% at warm idle.

    Chris's Idle Speed Adjustment Instructions*:
    1. Using the handheld, navigate to Tuning > Basic > Basic Idle and ensure your target idle speed is set to the RPM you desire.
    2. If you are using your Sniper EFI System to control timing, navigate to Tuning > Advanced > Advanced Idle > Idle Spark and ensure that the Idle Spark Enabled is set to Disabled. You can re-enable this after you have completed this idle speed adjustment process.
    3. Switch the power to the Sniper off.
    4. Put a strong piece of tape over the IAC breather hole, duct tape or something that couldn't possibly be sucked into the throttle body. No air should be able to pass.
    5. Ensure that the secondary linkage is completely closed (both visually and manually).
    6. Turn the idle speed screw on the primaries in about 2-3 turns after it makes contact with the linkage and starts opening the primary throttle blades.
    7. Switch power to the Sniper on and crank the engine.
    8. Use the idle speed screw to set the idle at a comfortable warmup speed.
    9. Observing the temperature on the 3.5-inch handheld (only), wait for the temperature to achieve 160F.
    10. Once above 160F, turn the idle speed screw so that the idle is about 50 RPM below your target idle speed set in Step 1, above.
    11. Shut off the engine, ensure power to the Sniper is switched off.
    12. Remove the tape from the IAC breather hole and restart the engine.
    *Note: If you are using your Sniper to control ignition timing then I recommend that before you start this process you disable Idle Spark control If you're trying to do this while the ECU is simultaneously trying to bring your idle under control by adjusting the advance it's going to be counter-productive. You can disable the Idle Spark control at the locations below. Be sure to re-enable it once you get your idle tuned.
    Software: Idle > IAC Settings > Idle Spark
    Handheld: Tuning > Advanced > Advanced Idle > Idle Spark

    I disabled and enabled Idle Spark control according to the instructions. It's not a mechanical issue because I can physically force the throttle shaft and it's closed and still at 2000ish RPM with the IAC Position at 0%. Now if I blip the throttle it will slow down to 1000 and come to rest at programed idle with 6% IAC Position. I don't notice it as much when it's cold and once it's hot 185F it will go away after a little driving at temperature from 140-185F it's consistent. Anyone have any thoughts on this?

  • #2
    Did your force just the front throttle shaft or both? It's usually the rear shaft that hangs. It may need one additional turn on the rear throttle shaft spring or the throttle blades may not be properly centered in the bores. To prove it's not the IAC, place strong tape over the IAC port. Even if the IAC hangs open, the tape will prevent airflow.

    Comment


    • #3
      I'll do that once it cools off. I just got home in it and it was consistently sticking until about 185F and then it was perfect. You have a good point though.

      Comment


      • #4
        https://forums.holley.com/forum/holl...ies#post274023. This thread discusses the rear throttle sticking and there are links further discussing the spring and the centering of the throttle blades. Also inspect the link bar between the front and rear throttle shafts. If length is off it can either prevent the rear throttle from closing or will not draw it closed when the primaries are closed. The link bar is simply adjusted by bending.

        Comment


        • #5
          I tested it with the IAC port taped off and it does the same thing. If the rear blades are sticking they are only doing it between 120 and 185 degrees. Not sure how that would be a thing. When they are closed there is some play in the linkage.

          Comment


          • #6
            The sticking is due to relative thermal expansion between steel and aluminum. Most likely your blades need to be re-centered, but you can try the spring wrap first. You want the link to pull the rear blades closed, but if you go too far it will actually hang the rear open slightly. The length of the bar is dependent also on how far you have to turn the idle screw in to get to your target.

            One thing you can look at is how far you have to turn the front throttle shaft before the rear starts to open. If there is a big delay, the system will start dumping fuel in the rear barrels when there's little airflow. So a little delay is normal, a big delay means that adjustment is necessary.

            If you decide to center the blades so some searches in the forum and as well with other search engines for pictures and/or videos. You don't want to pull the screws all the way out. They are staked or swaged to prevent them from falling out and into the engine. Only loosen them enough to get the blades centered. Using a light source pointing down the inlet side will allow you to see the gaps when looking from underneath.

            Comment


            • #7
              https://forums.holley.com/showthread...7846#post97846 (Throttle Blade Misaligned/Centering & Secondary Shaft Coiled Spring Tightness)​
              May God's grace bless you in the Lord Jesus Christ.
              '92 Ford Mustang GT: 385"/6.3L SBF, Dart SHP 8.2 block, forged steel crank & rods, forged pistons, Trick Flow T/W 11R 205 CNC comp ported heads, 12:1 comp ratio, 232-244 duration/.623" lift/114 LSA camshaft, TFS R-Series FTI comp ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, Holley 36-1 crank trigger, MSD 1x cam sync, PA PMGR starter, PA 200A 3G alternator, Optima Red battery, 100HP progressive dry direct-port NOS, R134a A/C, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, Earl's -6AN fuel system plumbing, Walbro 255 LPH in-tank pump & Pro-M -6AN hanger, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM C6 converter, B&M Hammer shifter, Stifflers transmission crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

              Comment


              • #8
                So I need to do this at what temperature? Cold, I call tell they're closed & centered, plus engine runs fine. Same as when it's at 185F. So I need to pull this when the temp is around 150F and check the center? If so, this doesn't add up to thermal expansion.

                Comment


                • #9
                  No, perform the repair with the throttle body cold.
                  May God's grace bless you in the Lord Jesus Christ.
                  '92 Ford Mustang GT: 385"/6.3L SBF, Dart SHP 8.2 block, forged steel crank & rods, forged pistons, Trick Flow T/W 11R 205 CNC comp ported heads, 12:1 comp ratio, 232-244 duration/.623" lift/114 LSA camshaft, TFS R-Series FTI comp ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, Holley 36-1 crank trigger, MSD 1x cam sync, PA PMGR starter, PA 200A 3G alternator, Optima Red battery, 100HP progressive dry direct-port NOS, R134a A/C, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, Earl's -6AN fuel system plumbing, Walbro 255 LPH in-tank pump & Pro-M -6AN hanger, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM C6 converter, B&M Hammer shifter, Stifflers transmission crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

                  Comment


                  • #10
                    Here are my rear blades. They look centered to me, but I could be wrong.
                    I may have to take back what I just said. If I tap slightly on the rear throttle blades, they will cause the throttle to stick. It could be they're out of alignment.

                    Comment


                    • #11
                      Shine a light from the opposite side. You may also see some scuff marks on the side of the throttle bores. If you can tap and get it to stick they probably are misaligned. There's a set screw throttle stop on the rear blades on some models. Sometimes that's not adjusted and the blades will stick in the bore when fully closed, but that usually causes it to stick when you try to open the throttle, not when you're trying to close it to get it to idle. You'll see the misalignment best if you look at it from below. You'll have to pull the Sniper, but you'll have to do that anyway if you need to center them.

                      Comment


                      • #12
                        I tried to center the rear blades this morning. Going into town in a little bit so I’ll know if it’s fixed. I did notice one of my return springs seemed to be getting weak so I swapped it out. Is there a good contained setup for a throttle return spring?

                        Comment


                        • #13
                          Did you add a wrap of the coil spring on the rear shaft? The front set can also be improperly centered, but because they're held open with the idle screw they rarely bind. Let us know if the idle situation is improved.

                          Comment


                          • #14
                            It was either the shafts or spring, but it's fixed. It created a new issue though. Now on a hot start it will fire up, and instantly stall and you have to hold it to the floor to get it to start. It's so rich you can smell gas. Black smoke comes out of the exhaust when it does finally catch and needs a second or two to clear up.

                            Comment


                            • #15
                              Capture a datalog of the start if you can. Excessive fuel pressure could cause this. Since you were possibly working with the return line connection the regulator may have a problem. Check your fuel pressure at the prime and during startup. The other possibility is a stuck injector. Looking down the four barrels watch when the ignition is turned on for four equal prime shots, and once started make sure you're getting equal flow through the injectors.

                              Download and post your Config File so we can look at your Cranking Fuel and After Start Enrichment %. Don't Transfer Learning To Base before you upload it here. It's likely either the pressure, an injector, or the tune so consider all three. How does it run after you get past the startup?

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