I have a Holley sniper, it sounds to me like the oxygen sensor is shot. Check the bung where they welded it in it needs to be on an angle or it will burn out the sensor. If it isn't get an extension bung. I had a similar issue and used the bung and haven't had an issue since.
do you know what the afr was when the car has this issue ?

Bosch part number 17025

Amazon.com: Innovate Motorsports 3729 Heat-Sink Bung Extender HBX-1 : Automotive

Buy Innovate Motorsports 3729 Heat-Sink Bung Extender HBX-1: Oxygen - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

If I was in your shoes I would drive the car minimally until I got the car back to the original shop that did the engine install and setup, you don't want to run a brand new engine in a lean condition. Not sure that is happening now but better to be safe. It's hard for me or anybody else on this side of the keyboard to pinpoint exactly what you car needs so I would wait swapping parts out now until further notice.
You or the shop/ tuner need to do a log of the engine functions to gauge how the engine is performing and make any necessary adjustments. There are many areas to check with regards to the issues you mention, decel fuel cutoff, idle rpm, clutch selection. I can't say for 100% that this is the answer but a competent tuner that knows his stuff should be able to get things in the ballpark where they should be.

How To Take A Data Log From Your Sniper EFI System

Someday you may need to take a data log from your Sniper EFI system. Today I'm going to discuss two different ways you can take a data log using your 3.5

www.holley.com

With that said the tuner should be able to tune the car to a variety for performance levels, strip, street cruising, fuel economy it really depends on your driving habits and this should be conveyed.

 

If I were you, I'd take it directly to the tuner just down the street from the restoration shop and have them address your current EFI issues, and then plan on taking it back again for a final tune (if you need to) when you've got more miles on and experience with the car and the other issues have been addressed by the restoration shop.

 

the 02 bung needs to be welded in...not the drill the hole compression fit way or "clamp on" way

 

I agree with the above. Also, I had one where we needed to center the throttle plates, secondary binding. Also they make a progressive linkage set up that makes driving a stick shift much easier. All four open at once the way it comes out of the box.

 

I agree with getting the shop who did the work getting it right 100%.
From my experience and a lot of reading the o2 sensor is a common issue.
just fyi My AFR was around 30-35 when my car had the issue.

on a different note, also I suggest keeping your battery well charged these systems don't like low voltage.
Can't hurt to check for a vacuum leak too.
Nothing worse when new work gets done and there are issues.
Best of luck

 

Are you sure about that AFR number? It should be near 14.7.

 

it is around that now but when my car had the issue it was 30 plus.

 

Thanks everyone.....as I said, I was looking for some inputs and advice.......reading looks like a lot of things that may need to be addressed. I'm going this afternoon to the shop and have a talk with the owner with my list of concerns. All I can say at this point is the EFI does have the progressive linkage, but the O2 sensor is clamped onto the header. Does the little handheld tuner box that came with the EFI have that data log? If so, it is in the glove box, and I will get it and see what is going on. Is there software that I can download to my home PC to read this? I agree about not driving until these issues are resolved. I really appreciate all the input. As I said.....I know nothing about EFI. I'm 68 Y/O and have been wrenching on Camaros since I was in my teens .... this is totally new to me. At what mileage point would you feel comfortable with to do WOT runs on the computer/dyno? The Tremec 5 speed from the company, has ATF for break-in and it is recommended at 500 miles to change to regular gear lube....so I was thinking doing the engine break-in oil change at the same time.....and then the dyno?
Again....thanks and once I get more info (now that I almost know what I'm looking for) and report back.

 

but the O2 sensor is clamped onto the header.

The Tremec 5 speed from the company, has ATF for break-in and it is recommended at 500 miles to change to regular gear lube....so I was thinking doing the engine break-in oil change at the same time.....and then the dyno?

First thing to do is get the 02 bung WELDED, ideally at or right behind collector. that clamp on POS is absolutely letting in air so 02 sees false reading and EFI dumps fuel. I suspect your A/F ratio is way off.

Secondly check for vacuum leaks....which cause high idle.

EFI is never plug & play. If A/F is off due to exhaust leaks pre 02 (read like your clamp on 02) or fuel pressure is too high or low...you need to fix those issues.

Sadly, many shops just know how to "bolt" parts on but not "tune" them. You need to go to a shop that is VERY experienced with doing EFI tuning adjustments. Not just some strap and pull dyno WOT first pull...as boom can happen.

I am not a EFI guy on motors that carbs belong on (and make less power than carbs) but they do, when set up right, offer quick starting and supposedly better milage. More modern engine platform where engine management is computer, they are fine but tuning them, especially on built motors is a learned and practiced skill which requires data logging, adjustments, repeat.

Change trans fluid at 500mi...but confirm type. IDK about the TKO but my T56 takes ATF, not "regular" gear oil.

Do oil change on motor at 500mi, then dyno is OK, not before break-in.

 

Andrew could get that sorted with a remote tune. You just need a laptop with the Holley EFI software loaded. If there is an issue he will identify it.

projectgattago@gmail.com

Don

 

Don, thanks for your help! Do you have a link to the software?

 

Found the software download.....let me see if I can get the handheld to download. Thanks

 

I have learned the hard way. Every Sniper needs to be tuned by a professional. Well worth the money spent.

 

No so sure. The 3 that I've done worked out ok without professional tuning.

 

The farther an engine strays from “stock”, the more likely it is that it will need tuning imo….

Self tuning is just adjusting the fuel trims afaik. It is counting on the baseline tune selected by the owner being close enough. It’s a bit of a stretch for me.

Don

 

Holley Snipers also have a known issue of the throttle plates on the "secondary" side hanging open. I use quotes because there are really no secondaries per se. They all open at the same time. The fix for that is winding the spring on the secondaries another time around.

The issue with the throttle being touchy is also known. It feels like you go to give it throttle and nothing happens then all of a sudden the throttle releases and you are at 30-40% throttle. They make an arm you can attach to your throttle to give your rod or cable more leverage. It greatly reduces this issue.

I had all these issues and more on the one I had.

 

The progressive throttle link makes the TB work more like a 4 bbl. With 2 bbl opening 1st then the 2nd 2 bbl later. Smoother throttle response.

2 of the 3 I did were BP SBCs 1 383 and one 400. So relatively mild builds. We did not use time control.

The 3rd was a 350 moderate build with timing control. We did additional tuning in it to get it where we wanted it.

 

He says he has the progressive linkage. Gphusker reminded me of the secondary throttle. We had to center all the throttle plates and increase the spring pressure also.

 

I want to thank everyone for giving this old guy some insight as to how this works. I went and got the handheld from the car yesterday and the SIM card is there, I just don't have a reader for my PC....so I ordered one from Amazon and should be here tomorrow. Hopefully when I get it, I can download the existing tune and can get some help. I do plan to have the engine professionally tuned in the very near future. I guess if I get too frustrated with this.....I still have the 850 carb that came with the crate engine and will just convert back to the carb. I do think it is interesting that none of the ECU settings (I think) start working until the engine is above 160 degrees. I guess you deal with it until it warms up. Will provide updates once I can see the data log from the SIM card. If anyone knows someone who can get the right tune and is in the Baltimore, MD area, please let me know.

Thanks so much in advance.

 

The settings work, it just doesn’t go from open loop to closed loop control until 160 degrees. Closed loop is when the ECM is using the O2 sensor to adjust fuel trims etc.

Don

 

The settings work, it just doesn’t go from open loop to closed loop control until 160 degrees. Closed loop is when the ECM is using the O2 sensor to adjust fuel trims etc.

Don

My understanding is that it tries to go into closed loop most of the time, even when cold (it adjusts the fuel to hit the programmed AFR in your table). It just doesn't go into learn until you hit 160 degrees. It pops out of closed loop during acceleration and deceleration.

 

Interesting. 🤷‍♂️Might be the case but either way OP was misunderstanding when he thought settings are not used until 160 degrees.

 

Talked to s tuning shop yesterday.....I asked the cost of the tune.....$1000. OUCH!

 

Seems to me you have two possible issues - is the Sniper properly installed and fully functional - that's on the shop that installed it; is the tune right - that's on you. I don't know if the Sniper has any self diagnostics, where it can tell you where it hurts or if someone here can look at a data log and spot installation/function issues.

 

This guy comes recommended and is only $400: TRAINING & TUNING | fast-man-efi

 

This guy comes recommended and is only $400: TRAINING & TUNING | fast-man-efi

I second that. I used him last weekend. Very good. He sets you up but also explains everything. It was like taking a fuel injection class.

 

Sniper EFI is not plug & play, especially with modified motors. "tuning" per your build is always required. No it's not like Spinal Tap where you turn everything up to 11.

I have a modified computer controlled EFI car (not a Camaro) and tunes were $350 back when I did get them. The $400 source noted is good considering today's market. Especially if recommended by someone who has used them.

 

Let me just start by saying I know there is an EFI forum here, but reading the moderators explanation of what they want to see in that forum.....is people's experience doing the install.....not advice to solved issues so I put this concern in the engine section......Moderators please move if needed.

So Here I go! I had the Sniper installed on my brand new ZZ 502/502 engine with Tremec 5 speed 12 bolt with 3:75 posi in my 67 RS/SS. This installation was done at a restoration shop that installed the drive train. I'm a complete idiot to the EFI world. If it was an old fashion Holley.....I'd be all over it. The shop is scheduling me to drop of the car for some other items (not related) to be fixed, as I would expect after a 2-year restoration, nothing major. The below is from a Word document that I'll be giving the shop concerning the EFI.

• There are times that the EFI will not idle down, like going to a stoplight…..push the clutch in, foot off the accelerator pedal, apply the brakes……the RPM’s stay between 1800 and 2000 RPM, if that is the RPM I was running at (5th gear). Bump the accelerator and it still won’t come down, put the brakes on and it will settle down once you get almost to a stop and it will go idle (read below). I don’t know anything about EFI and the different ports and settings. At this time, the car is not fun to drive.
• I’m not sure if it is me…. but there is no way to do a gentle/smooth take off from a stop….it almost instantly goes to a high RPM. The car idles at 11-1200 RPM (not sure if the factory replacement tach is anywhere close to accurate) ……based on reading, shouldn't it be around 850-900 RPM? I think the start from a stop would be a lot smoother.

So I guess my questions are:
I have read on the Holley EFI forum to put miles on the engine to allow the EFI to settle down. So what is considered the number of miles.....I have about 200 miles on the engine now and as said above it is not fun to drive. When I picked up the car was told it was tuned for "Street/Strip". I was also told that the tuner came in with his laptop and did the tuning. I have no idea who it was.

I will say there is a very competent (?) turner just down the street from the restoration shop that will put it on the dyno and tune it. I just wonder who many miles do I need to put on the engine before I do that (which has been my plan all along).

The 502 crate engine came complete from GM with a Holley 870 CFM carb that I still have and if this can't be figured out, I will remove the EFI and install the carb. The oil pan to fit a first gen with the 502 is another story.

So before anyone starts the questions about AFR and other settings.....I don't know, I wasn't there when the initial tuning was done.

Hopefully I can get it back to the shop soon....get everything fixed and then to the dyno shop for final tuning and get some good readings about RWHP.

I know without the tuning numbers kinda hard to diagnosis......would just like some thoughts on this from some people who have firsthand experience.

Thanks for any help, suggestions, or advice.

I went down this road with a pretty stock L48 (350/300hp). My initial problems with the sniper were the coolant temp sensor and the idle air control were both defective, and I couldn’t get a smooth throttle response. I went to the setup wizard multiple times and started over but after a few minutes run time my idle would creep up to over 1100, set at 750 initially. I would shut it down and restart and it would be fine for a while and then creep up again. The temp sensor went over 200 deg right away. The engine was still cold so I knew that sensor was bad. After replacing both, the car settled in. I cured the throttle issue with a linkage extension piece I bought from EFI Pro in Florida, it made the point where the throttle lever attached about 1 1/2 inches longer. So now I had a nice easy acceleration with the stock linkage and the high idle issue went away. I tried the progressive linkage but it never worked for me for whatever reason, even after changing the setup to include it. I went back to the regular linkage.

I had another issue with the sniper but holley fixed it, even after the warranty expired. So it’s been 3 years now and it never failed to start under any condition. Hot, cold, wet, whatever….

Chris Meter/ EFI pro in Florida offers tuning services at different levels, depending on what you need/want. They do that remotely. The prices seemed pretty reasonable. Maybe they can help? You’ve got a high performance big block, but how are you going to use it? Heading to the track? If so get it dyno tuned. If not, maybe that’s overkill?

Whatever you end up doing, good luck with it. The IAC control replacement fixed my idle issues. It’s a cheap part from rock auto. The Holley sniper forum has all the part numbers to replace all the sensors in the sticky at the beginning of the forum. They’re all standard EFI parts used on most cars. My headers have a port for the O2 sensor so I never had a problem with it. Hope this helps a little.

 

I went down this road with a pretty stock L48 (350/300hp). My initial problems with the sniper were the coolant temp sensor and the idle air control were both defective, and I couldn’t get a smooth throttle response. I went to the setup wizard multiple times and started over but after a few minutes run time my idle would creep up to over 1100, set at 750 initially. I would shut it down and restart and it would be fine for a while and then creep up again. The temp sensor went over 200 deg right away. The engine was still cold so I knew that sensor was bad. After replacing both, the car settled in. I cured the throttle issue with a linkage extension piece I bought from EFI Pro in Florida, it made the point where the throttle lever attached about 1 1/2 inches longer. So now I had a nice easy acceleration with the stock linkage and the high idle issue went away. I tried the progressive linkage but it never worked for me for whatever reason, even after changing the setup to include it. I went back to the regular linkage.

I had another issue with the sniper but holley fixed it, even after the warranty expired. So it’s been 3 years now and it never failed to start under any condition. Hot, cold, wet, whatever….

Chris Meter/ EFI pro in Florida offers tuning services at different levels, depending on what you need/want. They do that remotely. The prices seemed pretty reasonable. Maybe they can help? You’ve got a high performance big block, but how are you going to use it? Heading to the track? If so get it dyno tuned. If not, maybe that’s overkill?

Whatever you end up doing, good luck with it. The IAC control replacement fixed my idle issues. It’s a cheap part from rock auto. The Holley sniper forum has all the part numbers to replace all the sensors in the sticky at the beginning of the forum. They’re all standard EFI parts used on most cars. My headers have a port for the O2 sensor so I never had a problem with it. Hope this helps a little.

Thanks for the input......I'm taking it to a professional tuner next week.....hopefully they can get it figured out! 🍻

 

A couple of things I learned from the tuner that Holley doesn't tell you. He said if you have the hood clearance, use a one inch spacer. And do not run a PCV breather hose to the base of the Sniper. If you have a hose coming off a PCV valve, run it to a catch can.

 

You just need to use the small orifice PCV valve that Holley recommends. The stock valve leaks too much vacuum….

Don

 

Not to mix up applications here but my LS engine uses this PCV valve for about $5.00.
More Information for ACDELCO 19313318
It probably works on most Chev applications to a 3/8" hose and straight through design.
Its has the small orfice and I don't use a catch can and there's no muck in the intake.

 

Thanks everyone for their help and suggestions. I have one more question and will leave this alone until after I have it tuned on the 12th of Oct. The shop really wants to do the Sniper tuning on their dyno but will do the basic tuning not being on the dyno, if needed. I told them that I didn't think the motor had enough miles to do WOT on a dyno. The motor probably has 150 miles on it! So, what does the brain trust here think about putting it on the dyno? I think I'm ok either way!

 

Do what you feel is right for you.
New engines are dynoyed all the time.
For instance,
I don't think Blueprint Engines drives the engine around for 500 miles before dynoing it and shipping it to the customer.

I think my first dyno run was maybe around 300 or so miles.