Once you confirm the operation of your IAC then it's time to read my article on Solving RFI Problems. That's what you're seeing. Have you checked your fuel filter and made sure it's not plugged?If both of these are okay you're going to have to find a way to monitor your fuel pressure while under load. Going in the direction you did (higher) is going to reduce the acceleration fueling that the engine sees. Remove the tape from the IAC breather hole and restart the engine. I installed the Holley Sniper in my Chevelle this winter with a brand new BluePrint 496. Idle quality is great, RPM is good, sometimes IAC is now between 2 and 5 exactly where it should be. It is probably that your RPM above the maximum point at which ramp-down can occur. Since that has long been corrected we have moved that information to the bottom of the article.). I don't want to go on too long here but once you know if you're trying to add or remove fuel, there are a couple of ways to go. No power at the programmer and no fuel pump running. If I were there in person I would test the function of the IAC (see this article.) My sniper is doing two thingsFirst issue, the idle is set at 800 and will idle fine, then There is a glitch in the system. What must remain foremost in your mind is that the only thing that can cause the idle to increase is additional air getting into the engine. knowledge with the sniper efi setup. Sniper setting is Stock camshaft. When you first posted this I had no idea how to respond. We are using Target AFR of 9.0: 1, Fuel Base approximately 40% higher. Not that I noticed. Another suggestion is to add an extra turn to the spring built into the linkage to increase the closing force on the throttle shaft. If I block off the iac with tape , I can get it to somewhat idle, but its not consistent. And the rather cavalier "Absolutely!" and when I close the IAC's hole with his finger, the engine is normal.The data on the touch screen I see are:AFR, A / F = 35.6 I ask because I'm using a PCV valve with my Sniper and have random idle issues as well. If you patiently adjust this over the course of days you will get it just right.Again, glad this is working for you and look forward to a good report in the future! While this video is not meant for the Sniper EFI user it does provide a great overview of how your ethanol tuning adjustments must be made not only to the base fuel map but to the other configuration settings. Once engine is warmed up been driving for awhile. It only lowers to 2-6% when I take my foot off the gas. The IAC going to 30 is normal. When I drive with warm engine the IAC is at 30% when pushing gas, but shouldn't it be at 0%? At that point the tps is pretty high, then shut the ignition off, pull the tape restart the engine and idle goes into hold mode and idle is through the roof. Engine has never stalled with Sniper system, once placed in Drive it just goes!!! After talking to Holley tech, I replaced the factory regulator and problem solved.The regulator had what appeared to be a film or something almost clear embedded in some of the screen, maybe from factory or from install, but that was my issue.PS : this page and other forums have helped me a lot. )Take a look at your AFR during the starting process. The throttle blade adjustment is at 2-6% at hot idle, and with warm engine 185F. So, clearly, the "No" answer is wrong. Reply Quote. Ensure that the secondary linkage is completely closed (both visually and manually.). This is very disappointing as people love to hear the motor while the hood is open.Thanks Jon. Having a TPS that won't go lower than 9% will affect the acceleration enrichment correction, and could create a stumble at the first moment of throttle opening.Yes, the IAC can and will fluctuate depending on changing conditions. Overview. What might cause the TPS to go to 2%? I have verified that there are no vacuum leaks, not to mention the car runs to good to have a vacuum leak bad enough to make this noise. Without it you are working in the dark. Hello Chris. An undersized or partially plugged fuel filter is a classic EFI installation mistake. There's a procedure there I can share with you if you'd like.. Sniper is still learning so it will continue to improve.Second, you may have heard the phrase, "correlation is not causation." When I covered the IAC with my finger, the RPM dropped so low it stalled. I've made all the adjustments, all the settings, and the IAC issue is driving me crazy. Consider adding fuel in the AE vs TPS and/or AE vs MAP ROC tables in the area where the stumble is occuring.Since this is happening at such low TPS levels it is possible that your engine would prefer a lower (richer) target AFR number at idle. Take it a step at a time. I can have it working fine (5% to 10% at target idle at operating temp.) Since it is unlikely that anything else changed it is most likely the IAC is problematic or the butterflies are not shut all the way. The team at EFI pro are some of the best I have ever dealt with when coming to ordering parts or having the knowledge to answer any question you may have. Start engine let it warm up to 160, learn mode is learning. Don't know if I should put this in a separate post. Though it started and ran good, it was dumping fuel and would not lean out to AFR set points. The noise is definitely coming OUT of the throttle body. I do know that the reference angle is 57.5, the inductive delay says 100.0. The IAC reads 36 when at idle fully warmed up. With everything else being right and since you can make it start by adding fuel it seems like you must have some sort of fuel pressure issue. Car has run perfect every time and has never hesitated or stalled since. The problem I believe this is creating is after I start vehicle (and its still in park), the IAC drops down to my hold percentage of 10% (since throttle % is not 0) before engine is warm and therefore causing the engine to stall out. Start with the most gradual throttle input you need to launch well, then slightly increase until you feel some stumble. The problem was RF interferance . When stopping, the brakes are unable to overcome the engine so I go to neutral just to stop fighting the engine. Hi Chris, I have a lean stumble on throttle tip in 2-3% tps taking off from a stop light the afr will go to 19afr and the engine will stumble for a split second. If you're having issues with your Holley Sniper IAC getting stuck at 20, there are a few things you can try to fix the problem. We can not hit it at all, we hit the pedal abruptly, the engine gives a lot of excess fuel, the AFR gets super poor at first, the car stops, then the AFR gets super rich and the car runs until it cleans up. When I removed the tape and started it again, it was idling at 1400-1500 RPM and sucking a bunch of air through the IAC, even though it showed 0% on the sensors screen (pic attached). Closed Loop Compensation rises to 100%, Do I just keep pushing it the same way to Some suggestions: i did have the same problem.try lengthening the lever of the throttle.meaning the length from the center of the throttle to the point where you attach your cable or your rod from the peddle. If you haven't confirmed that they it is worth checking. I did check for the lightning under the hood but all was well. Enjoy! Edit I just ordered a Holley return / regulator and cap for the sniper ouletOh, this is not an OEM Master Kit, but the fuel pump should be the same EFI Pro shipped this kit. I keep wondering how it was running so good with But once you come off the throttle there is a minimum RPM that the ECU wants to see before it releases the IAC from the park position and that is normally 1000 RPM over the target idle. A common issue we see is a result of poor fuel pump grounding running a eyelet from the pump ground to a rusty or painted surface. The only way to confirm RFI problems is by doing a data log. My IAC was constantly at 100% at idle. You are looking in the right area but I would probably not change the ROC blanking. After speaking with Holley Tech Support and Tech Support from where I purchased the systemthey decided to replace it. Maybe Holley will add Fuel Prime Multiplier to Terminator X later. But as you see from the recent revision I did above you seem to be having a fixable issue. engine works beautiful, the car runs a lot, but suddenly, the engine does that. I took some pics of the sensors page this morning after the car warmed up. Suddenly, the engine accelerates alone, hears a great deal of air being sucked in, When the system is up and running the fuel pressure regulator inside the Sniper is making a rattling sound like a shaking a paint can. After manually making the sensor go through the full range a few times, I reinstalled it and now my TP will read anywhere from 0% to 4% when I key on. Interesting situation you have. Its just at low speeds, not sure if its loading up or leaning out. Do please let us know what you find out! When I start the motor I have to push on the accelerator pedal for the motor to start. It's pretty hard to get the header tubes glowing at idle with a lean AFR. The engine makes very low vacuum at idle. I hope everyone enjoys this v. If this is the case then I would look particularly close at the IAC hold position and IAC ramp start.Let us know what you find and what works for you! I have a 406SBC that does most everything right with this sniper setup. Using the handheld, navigate to Tuning > Basic > Basic Idle and ensure your target idle speed is set to the RPM you desire. Given the circumstances I would say that it is either the IAC motor itself or RFI but you seem to have ruled both of those out. I also raised idle at Park a bit with the idle screw. Resistance results in heat and heat results in more resistance. The "PC Text" indicates what will be shown on the PC/Laptop data monitor or data logger. At idle my IAC is 3-4, AFR around 13-14, TPS is 0, timing 15-17. Once you know that then you can work on those problems. If you drop it too far the engine will stumble or stall when coming off the throttle with the car out of gear, so you'll know when you've gone too far. As you have noted, each time the idle goes up. The idle will not return to the set value.The second issue is the same as the first but the motor will stall out. When I am coming to a stop, the rpms will hang at 1200-1500 rpms. As soon as I got the new one installed and wiredit fired right up and did everything it was suppose to do with no issues. Then do it just a bit faster--just enough for it to bog a bit. I presume your idle speed table doesn't increase at 200 degrees? So the issue Im having is low idle. Thanks for the information you have provided on this site. Holley Idle Air Control Motor Idle Air Control Motor Fits the Following Applications: Sniper EFI 90 mm, 92 mm, 102 mm Throttle Bodies Digital Pro-Jection Systems Avenger 4-bbl TBI Commander 950 Terminator TBI I'm so glad you found this helpful--that makes my day!Don't get too concerned about the specific learn percentage. Incorrect connections will result in excessive resistance. Hope this helps! I had a customer recently with a high idle problem that he eventually traced to pad plug on one of the vacuum ports. I did buy the Sniper from you guys and the service was fantastic. Hello, I am having a tps and idle issue. It's a Chevy 350 bored .030" over it has a cam in it what I was told is the cam has the firing order swapped. To keep it running in gear, I have to bump the neutral idle up just over 1000 RPM. The fuel pressure regulator in the Sniper is fairly simple and not prone to failure, as far as I know. No matter what do, my idle will not drop below 1350-1400 RPM when the engine warms. Price Point: $$, Robust, feature-rich multi-port EFI systems offer easy plug-and-play late-model V8 engine swaps. Repeat until that stumble goes away, and then try a bit more throttle. Setup: 1965 Impala SS; ZZ6 Crate Engine, EFI Distributor. This curve runs fom -40 degrees to 260 degrees, and gradually reduces the RPM along that range. Should I just disable idle timing control? So glad this was helpful. This minimizes installation time and packages really well on a diverse group of engine applications. It is how the engineers allow you to clear a flood condition when you detect it. The warmer the motor, the higher the idle will be at this point. I set the AFR at 13.5 and all is good now. But you've got to find where air is getting into your engine.The reason it's going up as high as 2400 RPM is because once you press the throttle beyond 1% the IAC opens to the park position. You're going to have to get this fixed or it's going to cause even more problems than the high idle. I think that your Sniper system is working fine but would definitely check ouf the fuel pump. If your fuel pressure regulator has failed (and they often fail by blocking return fuel and maxing your fuel pressure) then it could lead to rich idle, particularly until your engine gets up to temp. itself out and hold idleeventually stalling. The small rubber plug had a leak. If you see that the ECU is commanding the IAC to 0 but there is air entering the IAC port then it's time to refer to my article on IAC Testing Procedures, Hello,I installed my sniper system on a 65 mustang, with a 302. As I would slow down for a stop sign or stop light, the car would run really rough and the idle did not want to come down. There are a few tell-tale signs that can help you diagnose the problem. My issue is that when Im in stop and go traffic, I can let off the clutch and the engine revs and doesnt quite want to come back to idle. I have one customer who is having some similar issues and his AFR is down at 9.6:1 when it won't start. So what--you're never going to drive in minus 40 degrees, right? It wont fire up. If the engine idles at 750 RPM with the throttle plates all the way closed and the IAC at zero then there is some sort of an issue. 2. So something is triggering the ECU to be in Open Loop. Changing the rpm curve and target rpm has no effect. Jun 12, 2021. I have an adapter on the manifold for squarebore to spreadbore and then a phenolic spacer. Worst case you'll have a spare on hand, and if the TPS is faulty you will have solved the mystery. See these. Then follow all of the instructions above, including confirming the idle speed curve setting at -40 degress as well as following my 10-step process for setting the idle. back to trying to zero down an idle. Your issues are likely related to one of these two things. So if you are trying to achieve a stoichiometric mixture in ethanol (which is achieved at an AFR of 9.0:1) then you should continue to target 14.7:1 since that is what will be displayed.
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