recian

I got my s4 back on the road last week after a lower intake blowout. During work i replaced injector orings and such along with connector pigtails since they crumbled. Car ran great before aside from intake leak. Had 3800 hesitation but 4k+ was strong. Now that its all back together the car bucks and stumbles over 4k and cant get over 5.5k.. at least i dnt wana push it past that. I read about potential weak fuel pump. Could the intake leak have hidden that? I know it runs way better under 3k but seems to be starving for fuel. Secondaries arent hard to get to. But could it be primaries by any means? I had issues with their connectors also

rx_214

Sounds like secondary injector issue, could also be your fuel pump if you're running stock.

Also, check the 5th and 6th port: How To Test Your 5th and 6th Ports

recian

i am running a stock fuel pump but it didnt have the issue until after replacing intake gaskets. That's why im not sure secondaries or 5/6 ports. I can actuate them i'll try the grease trick tomorrow. Injectors are the same p/n which means theyre the same cc. I swapped primary and secondary injectors when i put the rails back. (it may sound stupid but i wanted to run the secondaries as primaries to get them used and actuated more since the original owner didnt use the secondaries so much) I had a harsh vibration under 2k rpm before when in gear, now that's gone but i've got the 4k+ issue. Now riddle me this.. The car ran great before exept intake leaks. If it was an injector problem wouldnt it have showed up before? I mean it doesnt matter now which injectors are primaries or secondaries since i swapped them. They both open in each rotor over 3500. So say i had a sticking primary and swapped it to the secondary spot.. Yeah a sticking secondary would cause this but that sticking primary would have caused me an issue before hand also would it not? Yea it could be related to the duration of 500-3500rpm as opposed to 3500-7000 but both injectors run to redline so... I would have noticed that prior. Hell if they werent so expensive i'd just buy 2 new ones lol or if i had a running good car to take em from.. I'm trying to find me a S5 instead of this S4 tho or a TII

recian

well i did more work to it today. Funny thing is it didnt wana act up today exept from 6-7k. Couldnt make it past 6k without fear of damaging the engine. I noticed it's easier to get past 4k with more throttle. (not full open throttle) so i checked my tps today. 1.2k at rest and 4.89k at full open so i know that's good. I checked my 5th and 6th today. Theyre working perfectly. Pushed grease all the way to the top of the rod. Now i'm leaning to fuel psi or injectors. Sucks i dont have the tools to monitor fuel psi at such high rpm. It only does it in gear not at idle. I dont have long enough fuel hose to do that lol

rx_214

Good to hear that things are progressing... I remember you mention in other post that the fuel filter was changed right? Now we are closer to find out what the actual culprit would be for your issue.

Might very likely be the secondary injectors, and if the tank had sitting fuel then that could possibly clog the injectors.

recian

Yeah fuel filter isnt new but it's not original. It's still odd that i could rev to 8k prior to this but now I cant get past 6k without sputtering. Injectors i think can be the only culprit. Theyre the only part that was moved during the repairs. Fuel pump wasnt touched it just wasnt used for about 3 weeks since the car wasnt running. I'd just like to know for the guy buying my car. He's somewhat mechanically inclined. I want toget a TII