Surfcast23 Posted July 5, 2019 Share Posted July 5, 2019 I have been experiencing violent bucking combined with/followed by a loss of acceleration from about 2500 to 3000 rpm. I have seen a few older posts with this problem and wanted to know if anyone has figured out a solution? Link to comment Share on other sites More sharing options...
Max Capacity Posted July 5, 2019 Share Posted July 5, 2019 How old are the spark plugs ? Have you done a boost/vacuum leak test ? Most likely a hose blew off a fitting. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Surfcast23 Posted July 5, 2019 Author Share Posted July 5, 2019 How old are the spark plugs ? Have you done a boost/vacuum leak test ? Most likely a hose blew off a fitting. Plugs are only a few years old. Have not done a boost/leak test. Will look for loose hoses once it cools down a bit m. Link to comment Share on other sites More sharing options...
Max Capacity Posted July 5, 2019 Share Posted July 5, 2019 If you need a great shop, up in Sterling MA is ESP, Enhanced Street Performance. For a leak test, block/plug the black hose from the air filter box with a pint size paint can, pull the small hose off the blow off valve, give that hose a quick blast of air from a compressor, then put you thumb over the hose, listen for leaks. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
FJuan Posted July 5, 2019 Share Posted July 5, 2019 Between 2,500 to 3,000 RPM is what we call the studder zone, which is common with the 4th gens. Some have fixed this with an upgraded fuel pressure regulator like an STI regulator and some have fixed it with a Tune. There are several threads on this topic. I was able to fix mine with a new LGT fuel pressure regulator and new fuel hoses to the intake manifold. Eliminating the OEM fuel connectors at the intake manifold. My wife's balls are delicious. Link to comment Share on other sites More sharing options...
bigBADbenny Posted July 6, 2019 Share Posted July 6, 2019 My bet is avcs solenoids. Log the vvt angles with Romraider or Btssm Link to comment Share on other sites More sharing options...
Surfcast23 Posted July 11, 2019 Author Share Posted July 11, 2019 I am also getting these CEL codes, p0345, p040, and p045 with occasional no start. Could these all be related? Link to comment Share on other sites More sharing options...
system60 Posted August 2, 2019 Share Posted August 2, 2019 Going through same issue, car studders bad and goes lean as hell. Only happens for me under light throttle or cruising, if I give it 50% or more throttle through the same range it's fine. My tuners spent a lot of time with no real improvement. Going to be doing new plugs at next oil change. PS. It only started after I had the engine built. I had DE 850s prior and did a topfeed conversion with 1000s(e85 eventually). Opensource tune by same tuner before and after. Sent from my PH-1 using Tapatalk Link to comment Share on other sites More sharing options...
system60 Posted August 27, 2019 Share Posted August 27, 2019 Add me to those that resolved with a new fuel pressure regulator. Ended up going with an Aeromotive and cleaning up the mess that is our feed/return setup. Sent from my PH-1 using Tapatalk Link to comment Share on other sites More sharing options...
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