Interesting situation you have. Start engine let it warm up to 160, learn mode is “learning”. Start with the most gradual throttle input you need to launch well, then slightly increase until you feel some stumble. After the start process, If the idle speed is higher than the target idle then the IAC should begin closing as long as the TPS is below 2%. I also tried changing roc/map to 8 from 15 again no change at all.My ve table is smooth and tuned I even changed my AFR to 13.5 from 14.2 and no change at all. Unless you have ignition control enabled, that is the only thing it can do to reduce the idle.Realize the only things that can cause the car to idle up as you describe are air and ignition advance. Strangely, what I've seen is that it idles too lean as the injectors are effectively shut off.Thanks again for the follow-up and glad to hear that everything is working well now. Once engine is warmed up been driving for awhile. 30 minutes later CTS reads 161, start engine Idle is jumping from 450 (almost stall) to 1500, IAC is jumping all over 10 – 90. Switch power to the Sniper on and crank the engine. Then your low idle problem will go away. Those don't impact the way the engine runs and can cause the whistle sound you describe. If that happens then follow my 10-step process shown above. I would not expect that an electric fan would create a noticeable load on the engine but if it did then you'd want to set the idle screw when the fan was not running. Thanks Again for your help. :-). That will happen occasionally, but less as time goes and on and the engine tune stabilizes. It sounds to me like it is way retarded.In the event that the timing is right then take a look at your AFR--the actual AFR, not the target. If it is not a problem with the Sniper EFI System itself then it could be an issue with some sort of harmonic involving the fuel pump. Idle when warm was 850-ish and IAC 3-4 just as when I readjusted it the night before. If I adjust idle screw out to get the tps to zero or even 1% the engine will not idle. Sometimes it sounds like it wants to crank at the start but runs out of gas. 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. That's a nice change of pace--a low idle issue! Thanks again. You mentioned going from 13.5 to 14.2 but you'd want to go in the other direction--maybe to 13.2. Take it a step at a time. Not to bandstand here but this is the point when where you bought your system is so important. 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. I have not heard of this. The data that you provide shows that you have at least two problems. For someone in your position, it will become an indispensable tool in your tool box. TPS% = 1 It is good to at least know that the Sniper fuel pressure regulator can have high pressure failure issues (contrary to what I posted to Scott back on April 13th!) However I do have a couple of issues I hope you can help me resolve. Is that normal? Chris...I finally got everything resolved. A couple of possibilities that come to mind in order of likelihood: I’m having an issue with what I think is the Iac. Make sure that your blanking level is _below_ that (being careful not to find yourself in the situation I describe above.) I have multiple datalogs, I have contacted Holley tech support and have received little to no help. This was an issue in the earliest version of the Sniper firmware. Everything was working perfectly and I shut off the engine. To start viewing messages, select the forum that you want to visit from the selection below. The manifold pressure increases with the throttle opening but the RPMs are still low. Put an end to cold start issues, hesitations, vapor lock, and flooding. The fact that it ran so (at times) with 90+ PSI fuel pressure is a testimony to the Holley's closed-loop technology. Holley has done all of the heavy lifting in putting together these 100% complete systems. I explain the steps needed to get your Holley Sniper to idle properly When I turn it off and try to restart it just cranks. when things aren't working and this provides just that. The on board fuel pressure regulator in the Sniper throttle body has a small filter clipped over one end . P.S. Thanks for your very detailed question! But before you adjust the ECU to lean the idle out, first confirm that your fuel pressure is right. Good luck! Another suggestion is to add an extra turn to the spring built into the linkage to increase the closing force on the throttle shaft. I'm going to jump out on a limb here and say you either don't have adequate fuel flow or pressure. Trademarks belong to their respective owners. Your AFR is pegged lean. Does that make sense to you? Now I have most of the bugs worked out it runs fine on the highway and around town it's just the idle. And thanks again for taking your time to answer these questions. !I called Holley today, and before I could even described the symptoms the 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. My primary reason for going EFI was drive-ability, (Startup and take off without waiting for the engine to warm up) and not have the occasional hesitation a carburetor has especially just barely opening the secondaries. If your fuel pressure is at or about 60 PSI then visually inspect the barrels of the throttle body while having someone key on the Sniper. If the minus 40 degree setting is lower than the setting to the right, simply move it up so that it looks something like this: The folks who have tried this have found that their idle speed control behaves much more as they expect. My problem with the sniper is the whistling and hard throttle pedal, I have a 700r tranny with a kick down cable. You will find a startup IAC percentage, an amount of time it holds at that percentage, and an amount of time it takes to idle down to the normal idle speed.By default, that number is 50% at normal operating temperature. We have shipped quite a few of these to customers in Australia and New Zealand so I know that there is becoming a good following there!We recommend this Inline 10-micron fuel filter to prevent problems like that. That is the default "Clear Flood" TPS setting and turns all fuel off until the engine cranks. I am extremely suspect of what you were told about the Sniper ECU monitoring fuel pressure, for several reasons. Once you've done this, the next natural step is to transfer the learn table to the base map, then go in and smooth out the sharp edges, which are going to be at these transitional states. I appreciate everything you are saying. But I still get the iac at 0 and the rpm at 1200. Hope this helps! The engine might run hot but if the timing is right it should keep that heat in the engine--which is where the damage turns up. I can have it working fine (5% to 10% at target idle at operating temp.) So as much as I can I have been taking off real slow and let it fall on itself to try to learn and its not learning its way out of it. Definitely would have went with you guys. There's nothing wrong with manual tuning, but at this point that is just compensating for an inadequate fuel map. Its just at low speeds, not sure if its loading up or leaning out. Has a good size camshaft can’t find any vacuum leaks. I installed my Sniper and the engine fired up great. See these. Get On The List for Emails Straight From Our Pro? The first thing I'd do is check your fuel pressure with a gauge like this. To start viewing messages, select the forum that you want to visit from the selection below. (Note: in the original version of this post we had a section about checking the idle speed curve setting. Trust me--you can handle it from here. Good luck! I have driven car about 200 miles. I called support line he said he would have to look into it and call back. have the system learn the higher speeds? Always had to set idle above 950. Engine has never stalled with Sniper system, once placed in Drive it just goes!!! When you open your IAC to 30% you are naturally going to have a high idle condition. Some have suggested the gasket might cause it but I've never heard of anyone fixing the whistle by adjusting the gasket (and many have tried. Hello Going in the direction you did (higher) is going to reduce the acceleration fueling that the engine sees. I can tell you that when things aren't working the way you wanted them to work that nothing beats knowing for-sure that you don't have a fuel supply problem. Observing the temperature on the 3.5-inch handheld (only), wait for the temperature to achieve 160 degrees F. Once above 160 degrees, turn the idle speed screw so that the idle is about 50 RPM below your target idle speed set in step 1, above. Im not sure what its doing, have messed with after start fuel, fuel at cranking. If your TPS has snuck up to 2% then your IAC will be at the hold position, which by default is 30%. Hi Chris. Anyway I have a 327 sbc in a 1987 Monte SS with a T5 5 speed and 3:73 posi rear. Changing the rpm curve and target rpm has no effect. Comp. The IAC is hanging open and not really at 0. So I have been doing the slow take offs and thinking that it would learn its way out. You could go either way.. And so glad you guys are enjoying the Sniper EFI system. 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! Really appreciate the amount of learning im getting off here. If they are closed, check the primaries. )If you rule out a fuel supply issue then we're going to have to gather a few more clues. I am new to the EFI scene but want to learn. Several good bits here. Jump on board now! It's pretty hard to get the header tubes glowing at idle with a lean AFR. Thanks for the great question! It reads 0 at idle and when I accelerate it goes up to 30 and makes a loud sucking sound that seems to be holding the car back. I am having an issue with the IAC on the Sniper. If the IAC number is increased during this high idle, review the points about high idle from tuning issues. that my Air/Fuel ration was 15:1 and I believe the target is 13.5:1. Purists will sniff that these are not accurate to the tenth of a PSI. https://peakauto.com/peak_10x/ Want to contribute to the growth of our channel? That is the IAC hold position. Mechanical Fuel Pressure Gauge on the inlet of your Sniper, now is the time. to. That way you can get into that part of the table that needs tuning, and you can watch your learn numbers grow. Duty Cycle% = 3 Nice to meet you. Hey Chris :-). Are these compatible enough? If your RPM is 2000, your TPS is 0, and your IAC is not closing, then there is some problem. It is working fine when you restart the car, controlling idle perfectly at 8 steps open so it is unlikely to fail when the car warms up--or correct itself instantly when you restart it..So, if you don't have any vacuum leak, and the throttle plates are fully closed, the only thing I can guess is something is causing your ignition timing to change. Now it registers zero and I have good idle but it will not register until it hits 60 and up. Let Then why don't you Get On The List for Emails Straight From Our Pro? The Sniper EFI 4150 2x4 system from Holley features 8, 100LB/HR Fuel Injectors capable of supporting 1250 HP on both naturally aspirated and forced induction applications. Throttle Tip-In tuning can be a bit of a challenge but I'm confident you can get this resolved, Mike.Let me start by saying that unless you've really done a lot of driving on the system in some useful learning situations then I would set this issue aside and not even think about it. Pricing was reasonable, shipping was prompt and Chris helped me with a wiring question during my install. Also for: Sniper efi 550-511, Sniper efi 550-516. First, I'm kind of insistent about not changing any of the default settings unless the vehicle absolutely will not cooperate enough to drive/learn, and only then if you have a specific understanding of the problem and a specific solution. You want to ensure that nothing is hung up in there.The only thing that I can think of that would cause the fuel pressure to spike when the motor starts is the increased fuel flow at the higher alternator voltage (jumping from 12.0 to 13.5 volts or so.) It then started working normally again. It is reliant on the data acquired by the included wideband oxygen sensor. I have replaced the IAC motor and the problem remains. View and Download Holley Sniper EFI 550-510 quick start manual online. If you have performed the adjustments above and still have RPM issues, it's time to look for clues. When fully extended, it completely blocks air from passing through the I… I then saw you guys have an awesome little gauge that can hookup inline to the snipers existing fuel feed?? With an assistant pressing the accelerator, you need to make sure that when the accelerator is pressed to WOT that the throttle blades are fully opened, and when accelerator is lifted the linkage is fully at rest against the idle speed screw. Shut off car/restart and it's back to idle at That is certainly not normal! Hot start it most of the time won’t start unless I give it a little throttle. So, if pressing the throttle is making it start, it's because you're flooded.Which is consistent with your rich idle condition comment, right? Shut off the engine, ensure power to the Sniper is switched off. If the TPS is even just 2%, the IAC will go to the hold position (normally 30%) and will not change until the TPS goes back below 2%.If you create a datalog you will be better able to confirm if something is not working correctly. So the issue I’m having is low idle. Top brands like MSD, Flowmaster, Hurst, Accel and many more make up the industry’s leading offering of enthusiast-driven products to deliver robust, complete performance solutions for builders, racers, and drivers. Occasionally, it will start and idle very well for a few seconds, but then dies as if someone shut off the key. It could be, but that seems unlikely.Instead, you need to look at the basics. I was 20 minutes into a drive yesterday when all of the sudden the RPM increased not commanded. As inconvenient as it might seem, I'd recommend keeping a timing light handy and checking your timing during the high idle condition and then again after restarting. And yes, monitoring the fuel pressure is the right answer. However, whenever you start changing things, you can get into a chain reaction. is jumping all over the place when you experience this condition, it does not I've abbreviated it just a little bit but am appreciative of the added insight your comments provided.Off-idle performance can really be a challenge to self-learn but be assured that it can almost always be done. What would cause the idle to faulter like that? Holley's EFI Hyper Spark Ignition system is a plug and play system for Sniper EFI. The fix? It will drop down to 400 RPM then climb 500 and then shoot to 900 and then come back sometimes two or three times then catch it self an idle just fine again. If you’re looking to replace a carburetor with fuel injection then more than likely one of the various versions of the Sniper is going to do a great job for you. Only in the unlikely event that your engine simply won't run well enough to drive and self-learn should you consider tweaking anything inside of the first several hundred miles. We offer some tips to help with that. I would suggest you take a look at that if you haven't already. There are two ways to address this--you can let the system learn or you can manually adjust the acceleration enrichment. Second, Holley just released over the weekend a video on how to implement a flex fuel sensor on their HP and Dominator ECU's. It will need to see it again and again. The throttle position should be zero. is the fuel pressure. Hi. Running new vintage air system so the is only a single power wire to compressor that’s why I asked if I needed to run input wire to ac relay or if iac would pick it up fast enough(which it’s not). Thanks for sharing that, Jason--great info! This instruction manual must be read and fully understood before beginning installation. By the way your site and your accessory products are nice. When you experience this, before you touch anything or shut the engine down, first look at your TPS and your IAC. This is a great time to visually inspect the overall Sniper EFI install. Properly configured, the Sniper does a fantastic job of responding to the transition from Park to Drive. I hold my foot steady in place it does this in 5 second cycles and if i let go of Ran 2 Holley carbs and an Edelbrock. If it creates an issue (not normally the case) then you'll know. Idle was back to normal but iac was at 0. Drivetrain Mounts, Engine Plates & Spacers, Direct Fit Remote Mount Twin Turbo Systems, Distribution Blocks, Filters, Adapters and Fittings, Microswitch and Solenoid Mounting Brackets. I installed Holley Sniper on three other Mavericks here in Brazil and the problem also exists.I did not make any changes to the parameters, only on Target AFR and the correction on the Idle Speed ​​Curve chart. 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