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Discussion Starter · #41 · (Edited)
One more - possibly related issue, when the car does run, and gets hot, it tends to run on after shut down, For a moment until it’s out of fuel. I have checked for vacuum leaks, so far nothing noted in the intake or under the sniper. All vacuum ports on the back are plugged. What did I miss?
 

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Not only does your power wiring have to be battery direct, you also must set the ignition system type in the controller from what I am reading. Maybe set a different type of inition in there to override the current setting then switch it back after ignition key on off on off a few cycles... I'm strongly leaning on the Holley being the issue here with the jumping miss... It is the only thing that makes sense at this point as it appears the misses are consistently timed with injector pulse.


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I also agree with Stroker on this one, I'm glad you were able to start narrowing it down to which system is causing your issue. I think the Sniper is a good system however in some respects a carb may well be easier to dial in, self-tuning is a total misnomer, sounds great in theory however. Most importantly is wiiring that system perfectly, keeping wires away from RF interference and making sure power and ground are directly off the battery. The tuner I use for all my LS builds told me he would not talk to me anymore if I used one on the 496 for my Chevelle. I have opted for the terminator but that being said it will be dialed in on the dyno with him setting it up.
 

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When I started out with my Sniper Unit I didn't have the issues you are experiencing but it seemed to stumble and run rich. What I did was to take a short drive and record a data log. Posted a copy of the data log on the Holley forum and sources there were a big help in helping me smooth out the fuel curve, isolate functions I were not using, etc etc.

From the data log they can also help you identify if there are any RF issues and air/fuel issues. May be something you want to try before giving up on the Sniper. I got couple thousand miles on mine now and I have no complaints.
 

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I also agree with Stroker on this one, I'm glad you were able to start narrowing it down to which system is causing your issue. I think the Sniper is a good system however in some respects a carb may well be easier to dial in, self-tuning is a total misnomer, sounds great in theory however. Most importantly is wiiring that system perfectly, keeping wires away from RF interference and making sure power and ground are directly off the battery. The tuner I use for all my LS builds told me he would not talk to me anymore if I used one on the 496 for my Chevelle. I have opted for the terminator but that being said it will be dialed in on the dyno with him setting it up.

Bruinfan I send you a message, thanks!



Any updates with your misfire?
 

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Discussion Starter · #50 ·
Good suggestion @railroaderman - sadly the car runs so poorly I can barely get it out of the garage. I contacted Holley direct and explained my situation, they agreed to bring it back for inspection and (hopefully) resolution.
While I’m waiting for it to come back I changed the oil and opened the filter - there are no signs of metal, etc. so hopefully the cam is still in good shape!
 

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I looked at your list of things you replaced and looked at but have you replaced your distributor cap? They can look great but have a crack in it. I also had problems with MSD distributors having to have, I believe 12v, if will not run properly or not run at all
 

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do you have a buddy that can loan you an Edelbrock carb just for testing purposes?
I'm in agreement in that it seems something is wrong with that Sniper, especially if you put new plugs in and they fouled that quick with those compression numbers.
I would think that overall compression should be a bit higher, but maybe since it's not broken in yet, it'll come around.
 

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Safe to assume you have eliminated the simple stuff like verifying the firing order, checked the plug wires, injector wires, etc? My son had an Impala once and we couldn’t figure out why it was running rich and misfiring so bad. Popped the hood in the dark. It looked like the Fourth of July there was so much sparking going on. Ended up the cheap plug wires were firing on each other and the manifolds.
 

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Discussion Starter · #55 ·
Thanks to everyone for your help troubleshooting this problem! This took a while but I was able to contact Holley, explained the situation and they took my sniper efi back for warranty inspection. The process took about three weeks but the unit came back functioning flawlessly! I had the opportunity to log another 60ish miles last weekend and my car is running better than ever!

it was a little rough getting up to temp but as the self-learn started taking effect you could see it pulling a TON of fuel from the learn table.
Unfortunately I didn’t get feedback from Holley as to what was wrong but I’m very happy they took it back and warrantied the unit even though it was well out of their traditional warranty period, I’m a happy camper!
 
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