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Discussion Starter #1
Here is the problem, the car starts up with a slightly fast idle around 1150 rpm and smooth, as it warms up the idle starts to get faster as the fuel air ratio goes down (11:1) and then the fuel air ratio goes really lean around (20.6:1) and then the engine slows down. So the fuel air ratio displayed on the wide band goes up and down with the rpm surge: Here is the back ground: The engine was taken out for major overhaul and everything was touched. Throttle bodies were match bored and no the shafts are not leaking air as I tested for that. The throttle stops were all backed off so the butterfly’s seat on the bores in an attempt to get the idle down. Yes I know this is bad but I am trouble shooting. The Air regulator for idle control is electrically disconnected in an attempt to get the idle down. The AAC idle control for the A/C is electrically disconnected in an attempt to get the idle down. There is now no fuel tank canister and the air bleed for it is blocked at the front throttle body. There are no Narrow band O2 sensors in the pipes but I never had them in before the engine was out and I programmed around their absence. There is a wide band but not hooked into the computer. The MAF’s were working fine before I took the engine out but you never know? I have Nistune and can program it but I have gone through it line by line changing values and getting no fix to the problem. Personally I think it is the fuel air ratio is changing for some reason and I am at a loss as to what it is causing it ? I do have some Z32 MAF’s but I have to wait for wiring plugs and silicone hoses to arrive to try that idea out. Is there anyone out there who had something similar happen to them cause this is getting to me? . . :flame:
 

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Discussion Starter #2
Well it's not the MAF's cause I changed them. after it warms up I get the same thing.
 

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What's the idle RPM once it finally warms up?
Disconnecting the air reg electrically won't eliminate it as a potential vacuum bleed, they can stick open (constant high idle) and even when working properly, engine bay heat will gradually close them off, same as the 12V does.
An item simply not required here in Aus, might be different in your country though.
Sound to me like a manifold or throttle body gasket problem, lots of them to leak.
 

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Discussion Starter #6
What's the idle RPM once it finally warms up?
Disconnecting the air reg electrically won't eliminate it as a potential vacuum bleed, they can stick open (constant high idle) and even when working properly, engine bay heat will gradually close them off, same as the 12V does.
An item simply not required here in Aus, might be different in your country though.
Sound to me like a manifold or throttle body gasket problem, lots of them to leak.
The Idle was below 900 while warming up but once warming started then it starts to surge and the surge increases to 1850 rpm. once warm it surges between around 1150 to around 1850. While this is going on the wide band is going rich to really lean as it follows the surging. I was hoping not to have to take the intake off but this is looking more and more like what your saying . I will have to take out the idle control valve and while I am there I will clean out and check the ACC and plenum too. I need that plenum for BOV's and my A/C and what ever else is still hooked to it. I took a propane torch and went all around the throttle bodies and gaskets and shafts and got no increase in speed so I took that as a sign of everything sealed. I will have to revisit all of that again for a triple check while the Greddy intake plenum half is off.
 

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I've never had any luck with gas when checking for leaks, engine fan blows all mine away.
The fact yours is temperature related points to a gasket, top of the list at least.
1850 is high, you'd experience a full cut until the rpm dropped?
Might be worth checking if the TPS set correctly?
 

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Discussion Starter #8
I will check further into that. When at idle it did show zero at idle on the Nistune dash board but i don't remember what it said as I increased the throttle .
 

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I always use dieselstart gas when searching for leaks, its easy to spray all over, but also pinpoint.
 

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Discussion Starter #10
OK I found it !
It was a blown Fuel pressure regulator diaphragm. It was passing raw fuel into the the intake and moving around from cylinder to cylinder. Thus causing an undetermined cylinder over fuel/rich mixture. Which cause the varying cylinders to misfire. Holly Crap! I can't believe it was so simple to fix. I put another fuel pressure regulator on and instantly it ran good. On the Dyno the guy wanted to set the fuel pressure and as soon as he pulled the vacuum line off the regulator it started to piss fuel out of the tomei fuel regulator. Holly Crap I can't believe I missed that and spent thousands of dollars chasing the problem for a $120 fix.

Everyone watch for this one!
 
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