Low Idle issue - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 9 (permalink) Old 10-10-2019, 01:52 PM Thread Starter
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Low Idle issue

Good Morning every one,
Currently having issues with my 1983 280zx. I am having a weird low idle issue, I installed a pallnet fuel rail and added headers from MSA. With adding headers the EGR tube that goes to the intake manifold to the headers them selves doesn't fit. So I basically deleted the EGR by plugging up the holes that are in the header and the EGR port on the intake manifold. I started it up with open headers just to see if it would even start and it did, it ran rough for a minute or so but then sat evenly at 1000rpm. Which is what it sat at before these upgrades. It got up to operating temperature then ran super rough like it was about to stall out at 250rpm. I shut it off and started checking everything and all seemed fine. I started it up today and it is idling at 250rm still. Would this all be due to the EGR being blocked off at the bottom? anything would be greatly appreciated. Thanks

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post #2 of 9 (permalink) Old 10-10-2019, 03:19 PM
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sounds like a vacuum leak, make sure the intake manifold is plugged up where the EGR valve used to sit. a picture of what you have would be nice.
could also be a poor fitting manifold. I suggest you smoke test the intake manifold looking for leaks.
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post #3 of 9 (permalink) Old 10-10-2019, 11:23 PM Thread Starter
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Originally Posted by Dave M View Post
sounds like a vacuum leak, make sure the intake manifold is plugged up where the EGR valve used to sit. a picture of what you have would be nice.
could also be a poor fitting manifold. I suggest you smoke test the intake manifold looking for leaks.
I will post a picture in just a moment.
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post #4 of 9 (permalink) Old 10-10-2019, 11:41 PM Thread Starter
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Do I need to block off the EGR all together ?
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post #5 of 9 (permalink) Old 10-11-2019, 12:37 AM
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if you have blocked off the port where the pipe connected you should be fine. That being said I would still do the smoke test. Block off the throttle bottle inlet (a styro cup works well) blow smoke (a cheap cigar works fine ) thru a hose connected in place of the where the brake booster plugs in. You should feel resistance to air flow, keep puffing in smoke and look for leaks to the outside.
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post #6 of 9 (permalink) Old 10-11-2019, 11:48 PM Thread Starter
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Update** I did a smoke test and found two vacuum leaks and corrected them immediately. I started the car this morning and it was running how it should right around 1k rpm. It got up to normal operating temperature and still idled correctly. I tried simulated driving the car by holding the throttle lightly then increasing throttle to about 3k rpm. It then started to surge consistently while remaining at 3k rpm. I am a bit confused because I tried looking into this online and people are saying it could be a vacuum leak still ? Seems very weird to me but that is where I am currently at right now.
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post #7 of 9 (permalink) Old 10-12-2019, 08:51 AM
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Time to check fuel pressure, to make sure your hookup to the new rail are working with the FPR. You need to address one thing at a time. You got the vacuum leaks fixed, next will be the fuel pressure, then the Sensors. I assume you have set the timing with a timing light?
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post #8 of 9 (permalink) Old 10-12-2019, 08:54 AM
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it would be a good idea to do actual driving just to confirm you have a problem still.
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post #9 of 9 (permalink) Old 10-14-2019, 05:06 PM Thread Starter
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Fuel pressure is at 32 using an aeromotive FPR. I wont be able to diagnose problem until I have my down pipe welded and connected to my cat. I think the problem with the surging might have to do with my throttle position sensor. It was tilted up after installing fuel rail. I took previous pictures of this sensor before all these modifications and it was tilted down originally, and it ran really well before that. I haven't been able to test this out yet though. I haven't set timing since i don't have that light.
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