5.3LS single turbo with TerminatorX, worked fine with 55lb injectors and updated to SEP 1000cc and since day one, been having issues with dropping cylinder over time... to the point where anything 1/2 throttle and it would not fire in at least 1 cylinder.
I had a feeling something funky was going on, so I took the plugs, #6 and #8 where really black while the rest were descent. I cleaned them up good, went for a 10mi test and tune session, couple hit at 13 psi, and all seemed fine, then as time went by it started to degrade to then start missing again.
Parked it, next day I yanked the plugs and well...y'all be the judge but I think two injectors ain't flowing the same as the rest!
I'm thinking 6/8 are going so rich at 1/2 to WOT that it literally miss fires. bellow 1/2 throttle it seems to hit on all 8.
Car did not do this with the previous injectors....
I know I can adjust each cylinder fueling but this would seem to be a bandaid when all the other cylinder look exactly like #2 in the pic

#2 and #8

2/4/6/8 (right to left)

 

Replace the 2 bad injectors

 

Yeah working on that with SEP, just sucks to have two bad one right out of the box!

 

They have a lifetime, transferable warranty.
I had a set of the SEP1000's in my car last year, that worked great. Ran my best ever ET/MPH.
Replaced with some SEP1500's as an "upgrade", and car had a low rpm/cruise rpm misfire from Day 1...
I thought it was a tune issue, and/or that I screwed up the new tune, or skipped some data input, or something.
Had a local guy put them in his injector cleaner/flow machine, and at anything other than WOT, 3 of them did not function.
Needed the car back together for a race, so no matter what, SEP wouldn't have time to receive, check out, and warranty my 1500's back to me.
Bought a set of Bosch 210's, which I'll never outgrow, and car immediately started, idled, and drove great with minimal tuning.

In the end, they did send me a brand new set of injectors, but I had no choice but to sell them to recoup some of my money back.
They were very apologetic, but sorry's would not have rebuilt my engine.

So...the warranty issue was fixed pretty quickly...
But along with that, here's why I'll never be an SEP customer again....
Less than a week later, they sent me a complete 2nd set of injectors, this time brand new Multec 1000cc ones, for a truck??
I could have easily been a dick, and kept and sold those as well, (since I had to pay to ship the faulty ones from Maryland, to Hawaii [$26], and pay the local guy to check/flow them [$80] prior to me mailing them back), but instead emailed them for a return mailing label, took time to leave work so I could go to the Post Office, and ship them back.
They never even thanked me for being honest (which I think was pretty shitty)
Instead, their last and only email, simply made an excuse as to why I got a 2nd set...

Oh well...at least the 1st set worked good.
Hopefully, when all's said and done, it works out for you.

 

It's good to hear they stand by their warranty. I'll pull them off and mail them out. They said it's not a flow issue, so I don't know what else it could be since previous injectors didn't do that. I'd guess they stick open longer than commended....either way I ain't firing it back up, don't need them to decide to stick open and hydrolock my motor!

 

I would have another company take a look at them and test them before you send them back for warranty. If they replace them under warranty, thats all good i guess. Hopefully the next set doesn't have issues as well.

 

i hope so as well… everything is new on the car (the whole car), put about 15 miles on those injectors, had 120 trouble free miles before that set.

 

SEC received my injectors, cleaned and tested them. Found that 4 did not pass their quality test. They are mailing me a whole new set.

 

Good deal. Hopefully, 2nd set are trouble-free for you.
Just out of curiosity, when did you buy your original set?
I just looked back and mine were ordered/paid for on November 19, 2020.
Was just wondering if there was a bad batch, or just bad QC

I also really wonder how it is even possible, to test AND "Flow Match" every set, as they claim, yet almost immediately have 3 or 4 (barely used) ones fail a "re-test"...4 of yours, and 3 of mine, and we're just 2 random people who happen to be on the same car site.

This is the reply I got back after they "re-tested" mine:

Since I run E-85, I actually bought myself an inexpensive injector cleaning/flow/test machine to maintain my personal stuff, and a few others (who will ultimately pay for the machine)
​​​​​​​

 

I bought mine 1/30/2021, could be a bad batch. I also wondered how can 4 be bad with 15 miles, they'd have to be bad from the start which I feel is what happened as the car not only sounded like it had more cam in it, but I would also get the modern car exhaust pop on decel which was never there with my 55lb.
EFI is great until it's not, heard more people blowing **** up from injector malfunction than carb'd guys blowing **** up because of a "bad carb" (talking aftermarket efi/injectors)....making me re-consider my set up...

 

So, some companies say they test and flow match each set. But that's not entirely true. Some just test 1 or 2 in a set, and if those are good, they assume that the rest of the set is fine. Speeds up production but sacrificing quality.

 

Yeah many factors here, good quality sampling plan is only one step of faster production that still has good quality. Not sure what they do at SEP. Maybe they got a batch or a change in overseas production that they weren’t told about. But it’s not a good biz plan to have lifetime warranty if you don’t believe the product is at least up to a certain qa standard.
i would wager that the overseas production had a change in one of the internal parts they use (diff source) and it’s causing a quality issue (could be very small and i happen to draw the short straw)

 

100 % agree. Ever since Covid, things have changed. Especially with oversea shipping and shortage of materials. A lot of companies had to make changes in order to keep up with demand and unfortunately some product just isn't the same anymore.

 

Second set is no better, #3 misfires (or doesn't). That's on new plugs too. Did the usual checks: swapped plugs, wire and coil between 1 and 3 just to be sure it wasn't something silly, wouldn't be lucky that way....SEC wants me to send this set back...so they are packed and ready to go, meanwhile I got a set of FIC850 ready to install...I don't have time to play this game....takes 2 weeks turn around (that's what it took the first time, 4 days to get there, 3days to test, 2 day shipping -at least that was nice of them to use 2day shipping).
Hope the FIC works out.

 

If that's the case, then they are being fraudulent in their claims of all sets being flow-matched. With every set of their injectors, comes a "dyno" sheet, which shows flow rates for all 8 injectors at various speeds/rates. Not saying you're wrong at all, and with one guy getting TWO complete sets that each set has problems, would actually lean towards you being 100% correct.

That sucks!
It's a shame you don't have access to an injector machine. I had mine flowed prior to even contacting them, so that I KNEW what was happening (and couldn't be bullshitted), and we 100% verified/confirmed that 3 of them were not functioning at low load/flow. Basically, sticking closed, and/or very intermittently working at low RPM cruise, but would open up and work well enough at WOT.

Anyway, best of luck to you with the FIC's. Please post back with the results of trying those...

 

yup, I will update...(as threads that are left with no closure are a huge pet peeve of mine). I'd have it running by now except I had a tough time with the o-rings on the FIC to fit into my intake, ended up with one getting pinched and cut, had to get new orings... nothing's easy these days it seems!

 

Probably should have swapped injectors around before buying a new set first just to verify if that was really the issue with fouling plugs.

 

would have been pointless for the first set, issue was pretty clear and validated by SEC that two where bad. 2nd set, also irrelevant, you can tell from the brand new plugs that #3 it's not firing at all or very well compared to the rest (1/5/7). 60F cooler on header tube #3 compared to #1 and #5 will also tell me it's not firing (or not firing well), and that was right out of the gate (I had also noted header temp on all 8 with set 1 and 3# was within tolerance then).
It is pretty obvious at this point that this is all injector related. If SEC was local (on same continent) then I would have entertained a 3rd set but at this point, I'd like to drive the car sometime this year lol.

 

Companies have preset data sheets for each of their flow sizes. This is the issue when they just test a couple and call it good. Makes no sense to the customer when they receive their injectors and end up having a couple defective. They look at a data sheet and they think "well they did test them, all the data is there". Just bad QC and poor effort on testing each injector in the set. I've been around fuel injectors since 97' so I know a thing or two lol.

 

Be sure to lube the O-rings if you haven't. We like to use a little Vaseline on the O-rings, works best in my opinion. Good luck