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76 280z, low idle, low vaccum


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#21 jthom5147

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Posted 12 July 2016 - 12:03 PM

Push it in and apply some high temp silicone around where it enters the block.
ORANGE BULLET - RIP
BLACK 260Z in progress, done right this time.

#22 NewZed

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Posted 12 July 2016 - 03:48 PM

Follow the arrows.

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#23 NewZed

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Posted 12 July 2016 - 06:41 PM

A little more help - the air space under the valve cover is the same air space that that breather tube connects to.  The rocker area and the crankcase are the same space.  If you're going to seal the bottom you need to seal the top also.  Or just seal the intake manifold (where the PCV valve is and where that big tube ends up).

 

You have a bunch of different problems to work on.  Your 12% over-rate injectors are probably making up for the extra air.  When you seal up the vacuum leak that you're working on, you'll have cut off that extra air.  With no idle speed control the engine probably won't idle anymore.   And you'll be running rich becuase the injector rates are higher.



#24 Turbo_the_world

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Posted 12 July 2016 - 09:12 PM

Well, I have the car running at 800rpm at idle now, was a combination of timing and the fact I found a throttle set screw. Still having problems with it on the road, in my garage the throttle is fast and runs fine through all rpms. Under load, the car gives out at 2k rpm, no power and seems to stumble a little.

#25 Turbo_the_world

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Posted 12 July 2016 - 09:27 PM

I believe that problem is the tps though, so I will be testing and possibly purchasing on of those.

#26 Chickenman

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Posted 13 July 2016 - 06:25 AM

Pull the plugs and post up some pictures of the firing end. Use a good Camera and turn off the flash.

 

I'm suspecting that the plugs are fuel fouled. If they are, then throw in some fresh plugs. BPR6ES gapped at .032". The factory " Trignition " on these cars is notoriously weak. ( Matchbox module is light years better in technology ) . Breakup under load but OK under no load is usually Ignition related.

 

BTW. What does " give out " at 2k mean. It won't rev at all above 2K????


Edited by Chickenman, 13 July 2016 - 06:37 AM.


#27 Chickenman

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Posted 13 July 2016 - 06:35 AM

A little more help - the air space under the valve cover is the same air space that that breather tube connects to.  The rocker area and the crankcase are the same space.  If you're going to seal the bottom you need to seal the top also.  Or just seal the intake manifold (where the PCV valve is and where that big tube ends up).

 

You have a bunch of different problems to work on.  Your 12% over-rate injectors are probably making up for the extra air.  When you seal up the vacuum leak that you're working on, you'll have cut off that extra air.  With no idle speed control the engine probably won't idle anymore.   And you'll be running rich becuase the injector rates are higher.

^ Agree 100%. My engine has a bit larger camshaft and pulls like a SOB to 7.000+ on the stock 188cc injectors. Quite surprising actually.

 

It's been running so good, that I've a complete Haltech system that I've put off installing. Been too busy with other things, and I've just been enjoying driving the car. My normal DD ( Audi A4 ) has been down for over two months with a coolant leak issue, and frankly I don't care. Driving the Z has just been so much fun.

 

Sometimes you can " Tinker " too much....  My bedroom is starting to look like a Parts Warehouse though. ( Coil over kits, Camber plates, Rear disc conversion, Speakers and Amps, ECU's, engine harness, W/strips, H/Lite covers  )



#28 seattlejester

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Posted 14 July 2016 - 01:41 PM

What are you using for fuel control?

 

What are your timing values?

 

How are you controlling timing?

 

Stock throttle body doesn't have a TPS.

 

Numbers and facts. Give them.



#29 Chickenman

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Posted 20 July 2016 - 11:48 AM

^ Actually the stock throttle body does have a TPS. It's just an very early style and quite crude.  But it still has to be adjusted properly



#30 seattlejester

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Posted 21 July 2016 - 04:31 PM

Not really what we call a TPS now days, it is more akin to a WOT switch although it does know when you are off throttle and not on WOT yet, I guess a 3 position switch is more accurate. 

 

If you put the stock TPS on an aftermarket throttle body on a stock ECCM with uprated injectors with an aftermarket cam it wouldn't be surprising that the engine is stumbling on acceleration.

 

I think the correct problem description is insufficient acceleration enrichment, or excessive acceleration enrichment seems like the idle problem is mostly figured out.

 

If you are using a stock ECCM there is a very limited amount of things that can be done. Other then making sure the fuel system is in tip top shape (good line pressure, fuel pressure gauge, good flow) not much else you can do other then playing with the injector size, which still isn't much of a solution, more of a way to trick the ECCM.

 

If you are running an aftermarket system, you would go under the accel enrichment tab and add or remove injector pulse width based on your AFR readings based on your TPS rate of change, which you wouldn't be useful at all if you were using the stock TPS as that cannot communicate correctly with an aftermarket ECU.

 

This is of course with the assumption that the timing is running on a stock curve on a stock system. If the timing is off car can feel sluggish or feel like it is bogging, at which point it would be moot playing with the fuel until the timing is figured out. 






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