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Help! Car Leans Out Gradually After 5000Rpm..

rondofj

By rondofj,
in Engines & Forced Induction

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rondofj Veteran

rondofj

Posted
Posted

Hi SAU, I need your help / suggestions...

Took my car to my tuner today to get my ignition timing advanced a few degrees, (road tune only) we found that my R34GTT leans out gradually after 5000rpms, sometimes around 4500 onwards, no matter how much fuel my tuner is adding, it still does this.. I have also noticed previously that it dosen't have any top end (its constant and smooth but not 'weld-me-to-my-seat'). That was with our previous tune. We then loaded the stock R34 maps and started from scratch and it still does this even with the stock maps.

As a matter of fact, we backed off and will be taking it to the dyno next week to check if the fuel pump, fuel reg is playing up? Now the pump is a new Walbro GS3442 that was installed and re-wired not more than a couple of months ago, it has a factory sock which has a bit of play where it meets the pump. The car has the usual FMIC, exhaust, 12psi (which holds constant from 2800 onwards), cold airbox, Nistune. So I will be driving in low rpms for now hehe..

Someone please throw in your suggestions as to what could be the cause of this?? ECU retarding timing in high rpms?? We detected no knock thank god, never did, even with previous tunes.. Fuel pump?? I hope not, its the newest item on my car, and it gave me a lot of noticeable power gain after the install, more than anything else.. Fuel reg?? what what.. :(

rondofj Veteran

rondofj

Posted
  • Author
Posted

Could it be my AFM is dirty? - its the stock one.. BTW just wanted to add that before the Nistune and fuel pump, my car was hesitating and had the flat spot at this SAME 5000rpm band - something like 4700-5700rpm - a flat spot zone, Nistune has fixed that, the flat spots gone, acceleration is smooth but theres just no power in this zone - ie I dont feel the turbo pushing me hard in my seat..stock turbo 12psi... before I could feel it, from 6000-7000rpm it felt the strongest then.. And now this leaning out from 5000rpm onwards..

rondofj Veteran

rondofj

Posted
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Posted

Having a read here:

http://www.evoxforums.com/forums/archive/index.php/t-35897.html

one guy says:

"Don't rule out a bad sensor for your AFR guage. The last two I had fail both started reading lean by almost 3 full points. Funny thing is, they would read okay in closed loop, just not when you got on it."

another says:

"Try ur fp relay first. I seen another post with a guy using blue fpr, same problem, switched to syock, problem solved"

and the answer is:

"found the culprit it is a missing fuel freaking pump relay in my fuse box in the engine bay ! i took the horn relay and put it in the fuel pump relay and my afr was PIG RICH.

really weird and i dunno why evo x over here does not have a fuel pump relay.

been busy @ work but will load up a map and see what happens from there on.

but nevertheless i will double check all hoses again but afaik everything's tight and will do another full boost leak test.

will keep everyone posted soon."

How good to have internet and good people!.. But I still havent found my answer yet.. duh

femno Grand Master

femno

Posted
Posted

Connect a fuel pressure and flow guage and monitor pressure and flow while its playing up.

Will save you a fuel pump if theres plenty of pressure and flow.

Also monitor response of the fuel reg - could have a hole in it and not increasing rail pressure with boost.

If he knows what hes doing, your tuner should know to do all these things without you having to find out for yourself on the internet.

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

One is a dampner Ron.

Need to get it on the dyno with the fuel flow/pressure tester as discussed with u. Its extremely unsafe to do this on the road.

I need to check ur install on the fuel pump. Last time this issue went after filling the tank full.

Have even loaded the fully stock factory map and the issue is still there

Ur car had the same or similar issue with ur old tuner and old fuel pump.

Wiill get it sorted for u. Just harder because u cant leave the car with me

rondofj Veteran

rondofj

Posted
  • Author
Posted

Have heard pple sayin to check the afm, but if that was dirty, we would get less clean air into engine per unit of fuel which means its running rich, but its not, its the opp ie, running lean, dont understand this one

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