Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 40

Thread: IAC got stuck again.

  1. #11

    Default

    When it idles up high, and the TPS is showing 0%, have you tried to push closed on the secondaries? I had that problem with mine. The secondaries were staying open just a little which was making the RPM run high. The TPS is connected to the primary shaft, so it will show 0% even though the secondaries are open a little. There should be a thread on here somewhere about it. I basically rest the butterflies to center them in the bore and added another turn on the secondary shaft spring.
    '73 K5 Blazer, built 350 SBC 375 HP/425 TQ, 12" F/18" R suspension travel. Deaver springs with King shocks, D44/12 bolt, 3.73 gears, lunchbox locker F/Auburn Posi R, crossover steering, 35" BFG Mud Terrains, Vintage Air system, PRP suspension seats, lots of custom work, all built by me.

  2. #12

    Default

    DJ: I was thinking the same thing. Is there a phenomenon in the Sniper that could cause it to read rich on AFR when fuel flow is inadequate? Oddly when I floor it, it reads rich on AFR. It can get as low as high-9:1. My fuel lines are one piece -6AN from the filter, which is located about a foot from the tank. Maybe the filter is the restriction at this point. Fuel pump is rated at 35 GPH. Is that adequate? I’d guess my engine to be well under 400 HP.

    Greg: when shifting into gear the AFR leans to 20:1 momentarily. Not sure if that’s normal or if increasing Minimum Injection Opening Time may solve it. Yes, on the datalog posted the IAC sticks open at the end. As previously stated, it has only done this three times in 1500 miles. Odd because there's no wiring near the IAC motor. The closest electronic device to the IAC is the distributor and there's nothing I can do about that. The video posted is typical operation, with the IAC functioning normally.

    Crusty: my secondaries were fully closed. The IAC was wide open. In other words, if I placed my finger over the triangle hole, it would idle down to normal again. Cool squarebody Crusty!
    Last edited by HeavyChevy; 09-12-2019 at 10:51 AM.

  3. #13

    Default

    Quote Originally Posted by HeavyChevy View Post
    Yes, on the datalog posted the IAC sticks open at the end.
    In the datalog, the highest IAC reading is 40% and the lowest is 0%. You can click on the actual IAC line then look above the graph and the box will show the parameter, the min, max and average for the entire datalog.

    So if you're certain the IAC is stuck open, but the computer is reading 0%, then you should probably replace the IAC and see what happens.

    If you're not certain the IAC is truly wide open when the computer reads 0%, then maybe you have leaks around the linkage in the secondaries like cCrusty mentioned?
    69 Camaro
    400 SBC, ProCharger D1SC

  4. #14

    Default

    With it being such an intermittent problem, it’s going to be difficult to diagnose. If it happens again, I’ll be sure to record it with my phone.

    Greg, just to be sure I’m not reporting incorrectly, when the triangular hole is sucking violently to where it’ll suck a very sticky and very strong piece of tape down the hole; that’s the IAC at wide open, correct?

  5. #15

    Default

    Keep in mind, an IAC that's barely open or even closed, but not perfectly sealed, will have equal pull (vacuum) as a wide open IAC will. It just won't have the same volume of air as it would wide open. So make sure you differentiate between pull strength and volume of flow. Hope this makes sense as I'm not the best writer.

  6. #16
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,748

    Default

    Correct, it'll have the same force (inHg), but not the same flow (cfm). An IAC valve can be deceiving.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 tires.

  7. #17

    Default

    Stacked, that makes perfect sense. Vacuum at idle is mid to high 20s kPa. Though when open (controlled vacuum leak) it’s at a higher RPM pulling slightly less vacuum at that point. So it’s definitely volume, not pressure that’s sucking the tape into the hole. When there’s a restrictive aperture, it just takes longer for the pressure on the suction side to equalize with the other side. So eventually there would be the same vacuum on the piece of tape with IAC “closed”, the vacuum pressure just equalizes much faster with it open.

    Which makes me wonder, what the heck kind of tape are you guys using and how long will it stick before being pulled down that hole? I realize most people have a more performance oriented engine than I with lower vacuum at idle.

    I just spoke with Holley Tech and they suggested that I turn A/C IAC Kick down to zero percent. While I don’t have A/C and all wires from that harness are deleted except my white Points Output wire and that harness lead is about as far as it can be from the IAC motor, I’m not 100% convinced that’ll solve the issue. He said if it ever happens again to call back, as it is likely a malfunctioning IAC motor.

    While on the topic, is there a discernible difference in quality from the IAC motor that Holley sells on their website vs the Standard Motor Products AC416?
    Last edited by HeavyChevy; 09-12-2019 at 12:13 PM.

  8. #18
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,748

    Default

    Quote Originally Posted by HeavyChevy View Post
    While on the topic, is there a discernible difference in quality from the IAC motor that Holley sells on their website vs the Standard Motor Products AC416?
    No, same quality.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 tires.

  9. #19

    Default

    Quote Originally Posted by HeavyChevy View Post
    DJ: I was thinking the same thing. Is there a phenomenon in the Sniper that could cause it to read rich on AFR when fuel flow is inadequate? Oddly when I floor it, it reads rich on AFR. It can get as low as high-9:1. My fuel lines are one piece -6AN from the filter, which is located about a foot from the tank. Maybe the filter is the restriction at this point. Fuel pump is rated at 35 GPH. Is that adequate? I’d guess my engine to be well under 400 HP.
    At what pressure? At 400 HP you'd need 32.41 GPH at 58 psi for the Sniper.

  10. #20

    Default

    Specs say operating pressure of 62 psi, but also lists a max pressure of 85 psi.

    Oddly enough, at WOT the system goes much richer than necessary. Which I understand is likely a tuning issue, but (perhaps falsely) assures me that fuel supply is not an issue at my lowly HP rating. Holley tech agrees, but I realize he & I are far from infallible.

Page 2 of 4 FirstFirst 1234 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us