bionic_oosty Donating Members 241 Member For: 12y 10m 11d Gender: Male Location: Sydney/Wollongong Posted 16/04/12 04:36 AM Share Posted 16/04/12 04:36 AM (edited) Hey all,I have this weird problem my car now has since it's tune..When in 4th, 5th, 6th gears (only) under load at about 3000rpm, it all of a sudden loses all power like a boost cut feeling and then continues to shudder when u try to just put your foot slightly back on the power to keep driving. This lasts about 5-10 seconds after the original power cut..I was thinking valve springs MAYBE??But you can literally flog the thing to 5500 rpm in all other lower gears and it will never do anything wrong...Plus it does not do the shudder after backing off after powering hard..The main problem is the actual complete power loss when your foot is left on the throttle half way into boosting up..Any ideas or people who have had this issue?Cheers, Josh Edited 16/04/12 04:40 AM by bionic_oosty Link to comment Share on other sites More sharing options...
Paulie2256 Donating Members 7,441 Member For: 16y 2d Gender: Male Location: SE Melbourne Posted 16/04/12 04:56 AM Share Posted 16/04/12 04:56 AM (edited) Yeah probably valve springs. They don't always have a problem in the lower gears because there isn't as much load on the engine. The power loss you are feeling is there because the valve is being forced open at the power stroke. The less load on the engine, the less air and fuel is need so the pressure during the power stroke inst big enough to cause issues. Edited 16/04/12 05:02 AM by Paulie2256 Link to comment Share on other sites More sharing options...
bionic_oosty Donating Members 241 Member For: 12y 10m 11d Gender: Male Location: Sydney/Wollongong Posted 16/04/12 05:04 AM Author Share Posted 16/04/12 05:04 AM ahhh bugger....Just suprises me because it's at really low rpm levels when just trying to overtake on the highway in 6th from lets say 90-120kms.I agree that it's gotta be valve springs, but from previous reads on the forum I just figured valve springs was after u backed off hard..Not midway thru boosting!Cheers again Link to comment Share on other sites More sharing options...
Paulie2256 Donating Members 7,441 Member For: 16y 2d Gender: Male Location: SE Melbourne Posted 16/04/12 05:10 AM Share Posted 16/04/12 05:10 AM Before replacing valve springs do the other cheaper things first. When is the last time you replaced spark plugs, are they at the correct gap to suit the tune?When were the coils last replaced?When was the boost solenoid or throttle body last cleaned? Link to comment Share on other sites More sharing options...
dre Resident idiot. Donating Members 2,068 Member For: 14y 2m 4d Gender: Male Location: Melbourne Posted 16/04/12 05:10 AM Share Posted 16/04/12 05:10 AM Ive found if there is less than half a tank of fuel the BF I'm driving does this at around 3000rpm. Its giving me the sh*ts, I Was thinking a surge tank is the answer. never even thought of valve springs as the car is standard.When my valve springs in the FG started to complain I found it was more of a problem when the car was restarted as it just would not idle for a minute Link to comment Share on other sites More sharing options...
bionic_oosty Donating Members 241 Member For: 12y 10m 11d Gender: Male Location: Sydney/Wollongong Posted 16/04/12 05:28 AM Author Share Posted 16/04/12 05:28 AM These are some good opinions,I never thought of plugs as they are brand new done for the tune! But they did tell me they re-gapped them for the tune...And it does run like a bucket of sh!t at cold start.I also have not had over half a tank of fuel since tune to my knowledge..Coils to my knowledge are originals..Boost solenoid & throttle body never cleaned.They put on a new turbo actuator for the tune..Are they commonly faulty or have issues?? Tuners also did fuel pump, bigger injectors, actuator & custom gapped plugs.... Seems like it could be many months b4 I could possibly source the issue Link to comment Share on other sites More sharing options...
bionic_oosty Donating Members 241 Member For: 12y 10m 11d Gender: Male Location: Sydney/Wollongong Posted 16/04/12 05:50 AM Author Share Posted 16/04/12 05:50 AM I had a quick look just checking hoses and lines etc and found this (picture below)It was about half way out when I first touched it...What is this?? I can see oil below it in the hole. Is this meant to be air tight or is it no biggie?? If u don't think it has anything to do with my original problem just disregard this post lol...Just thought I'd check. Link to comment Share on other sites More sharing options...
Paulie2256 Donating Members 7,441 Member For: 16y 2d Gender: Male Location: SE Melbourne Posted 16/04/12 06:01 AM Share Posted 16/04/12 06:01 AM Positive crankcase ventilation valve. Push it in all the way. Sometimes they need to be replaced. Link to comment Share on other sites More sharing options...
bionic_oosty Donating Members 241 Member For: 12y 10m 11d Gender: Male Location: Sydney/Wollongong Posted 16/04/12 06:34 AM Author Share Posted 16/04/12 06:34 AM no worries mate, I put pushed it back in all the way.I'll just start checking things bit by bit and see how it reacts..Hopefully just plugs or the below half tank of fuel thing.Cheers people, appreciate the ideas!! Link to comment Share on other sites More sharing options...
bionic_oosty Donating Members 241 Member For: 12y 10m 11d Gender: Male Location: Sydney/Wollongong Posted 16/04/12 09:11 AM Author Share Posted 16/04/12 09:11 AM After doing a fair bit of google searches, I'm thinking (hoping) the problem is coil packs considering the car has 140,00kms and just got tuned...But just to be sure - Would a dodgy coil cause a fierce SHUDDERING after the initial miss while under load in the 4th 5th 6th gears??I'm preying it's not a fueling issue as I just paid up big money about 4 weeks ago for brand new walbro pump, fuel filter and injectors.It also has a constant miss at idle and even worse so on cold start. Coils???? Link to comment Share on other sites More sharing options...
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