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I was tuning my TVS1900 LS1 GTO and it was misfiring underload mainly in cylinder #4. I did the typical coil pack, wire, plug troubleshoot but still had an issue. The car sat for a while so it was run with some stale fuel, so I sent the injectors (Mototron 60lb SV107) off to be tested and cleaned. The results came back and they have a lot of variation. I'm not 100% sure this caused the misfiring, but defiantly needs to be addressed. Do you think I should just purchase 2 and have them sent directly to the tester and make a better matched set or find a completely new set? Any recommendations on reputable places to buy injectors? Bmotorsports seems to have a good price, but I'm really leery of who to purchase from as I heard of knockoff injectors flooding the market. Home » Shop » Fuel » Injectors » Siemens DEKA IV ( DEKA 4 ) Mototron 60lb/hour High Impedance Injectors ( Short Style )
Personally, I wouldn't use 60# injectors in that. I don't know what kind of power your looking at making, but 60# injectors, with a blower, in my experience, run out. I guess if you're looking at 6-8# maybe, but over that, I think you're going to be running short.
I’m not so privey to injector girth and length. But if I were you I would like to know for sure I had the number 4 hole not missing. Before I put a set of bigger or smaller squirters. Just for ***** and giggles move the number 4 injector to another hole and see if the thing follows. Noid lights are pretty cheap as well. Harbor freight. Check your valve springs before you can’t check them. Then get you a perfectly sized injector set after you find the problem. I hope I’m not coming off as the all knowing super goober. Only trying to help.
I’m not so privey to injector girth and length. But if I were you I would like to know for sure I had the number 4 hole not missing. Before I put a set of bigger or smaller squirters. Just for ***** and giggles move the number 4 injector to another hole and see if the thing follows. Noid lights are pretty cheap as well. Harbor freight. Check your valve springs before you can’t check them. Then get you a perfectly sized injector set after you find the problem. I hope I’m not coming off as the all knowing super goober. Only trying to help.
I agree, check your valvesprings. When there is nothing left to troubleshoot for a cylinder's misfire, it almost always seems to be valvetrain related (broken valve spring or bent valve not fully shutting).
I have cured misfire by doing a crank relearn. I changed plugs, wires, swapped around injectors etc. chasing misfire. Did a crank relearn, solved.
A crank relearn does not stop an actual misfire, all it does it re-sync the misfire detection routine with the crank signal to more accurately detect what cylinder a real misfire is happening on.
I was tuning my TVS1900 LS1 GTO and it was misfiring underload mainly in cylinder #4. I did the typical coil pack, wire, plug troubleshoot but still had an issue. The car sat for a while so it was run with some stale fuel, so I sent the injectors (Mototron 60lb SV107) off to be tested and cleaned. The results came back and they have a lot of variation. I'm not 100% sure this caused the misfiring, but defiantly needs to be addressed. Do you think I should just purchase 2 and have them sent directly to the tester and make a better matched set or find a completely new set? Any recommendations on reputable places to buy injectors? Bmotorsports seems to have a good price, but I'm really leery of who to purchase from as I heard of knockoff injectors flooding the market. Home » Shop » Fuel » Injectors » Siemens DEKA IV ( DEKA 4 ) Mototron 60lb/hour High Impedance Injectors ( Short Style )
Here's the results of my flow test:
I'm actually impressed that a non-matched set only has a 7% deviation in a static test. That being said I am doubting that your injectors are the cause of your misfire but to be certain move cylinder 4's injector to another cylinder and see if the problem follows. If it doesn't then you have another issue, if it does I would ditch the entire set of injectors and buy a good matched set from Fuel Injector Clinic or Fuel Injector Connection and possibly consider the newer EV14 injectors instead of the SD60s.
A crank relearn does not stop an actual misfire, all it does it re-sync the misfire detection routine with the crank signal to more accurately detect what cylinder a real misfire is happening on.
I'm chasing this same issue on my 2500 HD. Swapped coil packs, did plugs and wires, checked fuel pressure, everything checks out. As soon as I hit 75 MPH on the freeway, I get the wonderful blinking CEL, which goes away as soon as my speed drops. I'm thinking it's possibly clogged injectors, so testing them is my next step. But I'm wondering about weak valvesprings as well. Thing is, there's no misfiring present at WOT from a dead stop, the engine runs like a champ. If my springs were weak, wouldn't that become more apparent at high RPM?
Well he did say specifically, "it was misfiring underload mainly in cylinder #4" which is why he started the whole thread asking for help. A crank relearn does not prevent nor fix a reported misfire, and I'm taking him at his word that he has a real misfire which was cause enough to send out his injectors to track it down.
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Chasing Misfires Issues, likely injectors? 
