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Thread: Marine 454 IAC setting unknown variables.

  1. #11


    OK, so we got water ran to one of them today. Got it up to 160°F, it went to Learn but only got to 21% before we had to shut it down. Noticed at idle IAC was at 100% idle was like 650ish. Tried to bring it up a couple times and got backfire through the TBI. We don’t know what cam is in it, boat is new to us. We're guessing it’s a mild cam. Going to throw a vacuum gauge on it tomorrow and see what it says. Then maybe set a different one. Hard to say. We will see. Not sure when it’s going on the water for the season to actually run it like it will be everyday.

  2. #12


    Turn in the idle speed screw a turn or two.

  3. #13
    Join Date
    Dec 2009


    Quote Originally Posted by Don Petrey View Post
    Got it up to 160°F, it went to Learn but only got to 21% before we had to shut it down.
    The purpose of the Learn Table is not to achieve similar values, high/low values (0% or 100%), or any value in particular. It's simply indicating the amount of tuning applied to the Base Fuel Table. Read this thread (LINK), that's what it's all about.

    Noticed at idle IAC was at 100% idle was like 650ish.
    Opening the throttle blades (idle speed screw "in"), decreases the IAC Position at hot idle.
    Closing the throttle blades (idle speed screw "out"), increases the IAC Position at hot idle.
    If the idle speed screw is unscrewed too far, the engine is inhaling air from an additional source - vacuum leak. (Initial Checks & Adjustments - Read Steps #1-#6!)
    May God's grace bless you in the Lord Jesus Christ.
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  4. #14


    OK guys, got another one running today got it up to temp and adjusted idle, but still can’t get it to 800. It looks like the handheld has a default of 950. Which I guess we can be OK with, but can’t put a load on it till it’s in the water to get it to Learn. So put a vacuum gauge on it today and was 8-10 inHg. Here's a question, we pulled numbers off of another cam 2296 & 1094, can anybody tell me this cam profile? We're shooting blind, seems to be a street/strip. Also threw a timing light on it and it was all over sometimes before sometimes after. Set a different cam and the mark is nowhere in sight. Tried to bring it off idle backfires like crazy and dies. So I’m thinking we are off a tooth on the cam rest seems to be OK. Another question for you guys, is can these Holley pumps pull through a Racor filter. The reason for this is it’s a boat and we run water block filters to save pumps and such we can also add the factor low pressure lift pump and see.

  5. #15


    Don, the Sniper has a feature where the ECU adjusts timing to attempt to get a smooth idle. It is called "Idle Spark" control and can be turned on or off. Sounds like yours is on. When on you won't get a steady timing read with a light until you use the "Static Timing" check feature. It's in the instructions and there are Holley videos as well. Basically you tell the ECU to set the timing at whatever you choose (15° is a common choice) then you put a timing light on the balancer. If the timing on the balancer is not at 15°, turn your distributor until it matches. Once complete, you have now "synced" the ECU timing with the engine.

    Regarding idle speed, the ECU will adjust the idle to meet the programmed RPM if it's able. If you want it to idle at 800 you need to program that. Then adjust the IAC on a hot engine until the IAC stays around 2-10%. This is also in the instructions. If you're not tuning with a PC, I highly recommend you do. The handheld is nice, but you can't beat tuning on the PC.
    69 Camaro
    400 SBC, ProCharger D1SC
    1.302 60', 5.95@116.4 on pump gas

  6. #16


    Thanks Greg. We're were just starting to get it to idle and get the IAC set. As for PC tuning, not sure about doing that. These need to be a bulletproof setup, we have two more boats to possibly do so that’s six more units. If there's too much of a hassle, we won’t do them. We'll check over the Idle Spark and do that. Still not sure which cam is in it. These engines say for 10 years. Any of you guys run these in a boat, since they are coast guard approved? That's what we're dealing with. Thanks tons for the help.

  7. #17


    OK so UPDATE GUYS. Today I went to get one of the to run and check them out. Tried maybe a dozen times a couple times it ran for maybe 1 minute not smooth or anything back fire a few times and die. So the other day we had it running and threw the timing light on it and it was all over sometimes before TDC sometimes after, but all over. So tomorrow we're going to pull the distributor and back it up a tooth and set the phase and then go from there and see if it'll settle out. So if it’s set with rotor at #1 and dropped in the system should either show 0° or 15° if it’s set through the unit. Still doesn’t make sense, nothing changed from Friday till today and at least we had it running long enough to get to 160°F on Friday. Any help would be great.

  8. #18


    Don, please read Greg's post. You will need to set timing using the Static Timing function. It'll be most beneficial if you can post the Config File for us to look at. I understand your frustration, but I need to see the .Sniper file or else you'll continue to shoot in the dark without reading the manual, and Greg's post.

  9. #19


    OK, I did that and can’t find the Idle Spark on the handheld anywhere. As far as the manual, we have one for the distributor one for the TBI and one for the HyperSpark. And none of them mention this so it seems like we only got part of the whole manual. I’ll try to get it downloaded and printed tomorrow. As far as getting a Sniper Config File, the boat is some miles from town so maybe we can get them soon. Problem is I have no way to upload them don’t have a card reader, and the other mechanic is under quarantine for two weeks now. He has a card reader. As for the static timing, I set that at 1, 5-10-15, no change, still backfire and no idle. Like I said I’ll get the manual downloaded and printed and take it out with me to the boat and try things from there.

  10. #20


    You need to step back, take a deep breath and relax. Then open up the Holley website and read the full installation manual for the Sniper. Not the Quick Start guide, the big 75 page manual. Read it two or three times and pay attention to it. Sounds like you have some expensive hardware that you're working on and you're in over your head. So slow down and figure it out before you mess stuff up. This isn't rocket science, you just need to calm down and pay attention to the instructions.

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