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Loss of power when on boost also hunts tiny amount in idle

My r34 always has issues
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My r34 always has issues Newbie

My r34 always has issues

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Hi all I'm having a few problems with my r34 gtt rb25dett neo it's completely stock. It's done 200,000 just got rebuilt with forged rods and pistons. Running 7 psi on the stock turbo.  Iv driven it another 4,000 km roughly and I noticed about a week ago in 3-4 grand rev range in 2,3 and 4th gear it would lose power upon acceleration.  But I drove it today. And it's having the same sort of issue but only when I get boost like runs fine in first but if I hit second and get past 1 psi of boost it like jerks and loses pretty much all go to it. The original issue i couldnt hear the engine really struggling i just sort of felt the lose of power but the issue im having now i can definently hear the engine die. It also hunts slightly when idling I'm thinking it's a fuel issue iv ordered a pump, reg and coil packs. I was just wondering if anyone else has had this issue. It still gets boost if I power through i get to 6 psi and it doesn't feel like it changes or gains more power.

joshuaho96 Veteran

joshuaho96

Posted
Posted
  On 05/10/2023 at 1:00 PM, My r34 always has issues said:

Hi all I'm having a few problems with my r34 gtt rb25dett neo it's completely stock. It's done 200,000 just got rebuilt with forged rods and pistons. Running 7 psi on the stock turbo.  Iv driven it another 4,000 km roughly and I noticed about a week ago in 3-4 grand rev range in 2,3 and 4th gear it would lose power upon acceleration.  But I drove it today. And it's having the same sort of issue but only when I get boost like runs fine in first but if I hit second and get past 1 psi of boost it like jerks and loses pretty much all go to it. The original issue i couldnt hear the engine really struggling i just sort of felt the lose of power but the issue im having now i can definently hear the engine die. It also hunts slightly when idling I'm thinking it's a fuel issue iv ordered a pump, reg and coil packs. I was just wondering if anyone else has had this issue. It still gets boost if I power through i get to 6 psi and it doesn't feel like it changes or gains more power.

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Idle hunting is a sign of air leaks. It usually means the ECU is trying extreme measures to stay on target idle speed. Easy way to validate this theory is to unscrew the TPS adjustment and tweak it ever so slightly to bump the TPS voltage above idle. This will disable idle control. An engine without vacuum leaks either internal or external should experience a low idle or no change in idle when you do this.

GTSBoy Grand Master

GTSBoy

Posted
Posted
  On 06/10/2023 at 1:09 AM, My r34 always has issues said:

Could that also cause the issues that were occurring when driving. 

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Less likely. That's more likely to be something electrical/electronic. And that could also cause the idle problems too.

For helping look for vacuum leaks, grab a can of carby/brake cleaner spray and go over the various joints. If idle changes, you've found a leak.

My r34 always has issues Newbie

My r34 always has issues

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Alrighty my driving issues sorted not low on power no more I did check for a boost leak using carry cleaner awesome f*king idea BTW nothing happened, then checked the tps voltage was good and changed with the throttle position. I also unscrewed and tested it didn't get a change in revs. I changed the spark plugs and now it's all sweet. My idle still slightly varies about 50 to 100 rpm but not frequently.

Thank for the help BLOOODY LEGENDS 

joshuaho96 Veteran

joshuaho96

Posted
Posted
  On 06/10/2023 at 11:22 AM, My r34 always has issues said:

Alrighty my driving issues sorted not low on power no more I did check for a boost leak using carry cleaner awesome f*king idea BTW nothing happened, then checked the tps voltage was good and changed with the throttle position. I also unscrewed and tested it didn't get a change in revs. I changed the spark plugs and now it's all sweet. My idle still slightly varies about 50 to 100 rpm but not frequently.

Thank for the help BLOOODY LEGENDS 

Expand  

I have experienced what I would describe as idle dropping out in moments with counterfeit spark plugs but it wasn’t really idle hunting. It felt like a misfire almost. It would drop and then recover as the idle control caught it. Never stalled but noticeably felt strange and was fixed with new genuine plugs. 

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