stony Posted December 21, 2013 Share Posted December 21, 2013 I just got done swapping my motor in my 280 Z. Same motor from one car to the next swap intake manifold exhaust manifold other than that its just a new long block. When I started it up it does not want to idle below 2000 rpm. I'm figuring I have a wire hooked up backwards or something but I can't figure it out. Any help would be appreciated Quote Link to comment Share on other sites More sharing options...
dexter72 Posted December 21, 2013 Share Posted December 21, 2013 Possible large vacuum leak, Try spraying around the intake with carb, starting fluid, or brake cleaner spray. Quote Link to comment Share on other sites More sharing options...
stony Posted December 21, 2013 Author Share Posted December 21, 2013 Thats what I thought. Sprayed entire intake down even sprayed in the intake just to be sure. The only time the rpm rose was when I shot it in the intake. Are there any wires that I could have mixed up to cause this? Quote Link to comment Share on other sites More sharing options...
stony Posted December 21, 2013 Author Share Posted December 21, 2013 BTW this is a 77 280z with efi. i swapped the long-block out and used my intake and exhaust. ran good in old car and my old setup ran good until head-gasket blew. is there a sensor that will cause this issue? Quote Link to comment Share on other sites More sharing options...
Josh280z Posted December 21, 2013 Share Posted December 21, 2013 I hear the PCV valve has the tendency to cause high idle sometimes. Quote Link to comment Share on other sites More sharing options...
stony Posted December 21, 2013 Author Share Posted December 21, 2013 I'm leaning towards i have something that is not hooked up correctly. Car idled fine before the headgasket. all i did was swap the long block with my intake. Quote Link to comment Share on other sites More sharing options...
NewZed Posted December 21, 2013 Share Posted December 21, 2013 Thought this was about the RB26DETT in your sig. If you're using the stock 280Z throttle body and intake, there are many possibilities, from sticking throttle blade to hanging throttle return dash pot to bad BCDD diaphragm to stuck AAR to no power to the AAR (although it would only hold the idle up until the coolant got warm) to cracked PCV hose (including the one from the valve cover) to no dip stick in the dip stick tube, and more. If you're using the stock 77 ECU, there are no sensors that control idle directly. Don't forget that advanced timing will speed idle. 77 had a solenoid valve, controlled by a switch on the transmission, that only let vacuum to the distributor advance when in top gear. If you connected the hoses wrong you might have more advance than planned and a faster idle. Quote Link to comment Share on other sites More sharing options...
stony Posted December 21, 2013 Author Share Posted December 21, 2013 77 long block with 75 intake manifold. The old block didn't have the inserts in the exhaust ports the new long block does. do i need to use the 77 intake? Quote Link to comment Share on other sites More sharing options...
NewZed Posted December 21, 2013 Share Posted December 21, 2013 (edited) I ran a 76 intake and exhaust on a 78 round port head for a couple of years. Shouldn't matter. The exhaust manifold can be an issue but only if you use the round port exhaust on a square port head. It blocks the edges of the ports. But you don't have that problem. If you go through my list you might find something. I've the same problem when I forgot to reconnect the AAR power. Without power to the internal heating element it takes a long time to heat up and close. And the connector is jammed up against the hose so it can look connected when it's really not. Actually, I've had high idle problems from five of the things on that list. Edited December 21, 2013 by NewZed Quote Link to comment Share on other sites More sharing options...
9rider Posted December 23, 2013 Share Posted December 23, 2013 (edited) AFM , or idle screw or , brake hose leak. Wires problems? AFM problem? All that can cause from a swap. I swap couple cars in life to now. Common problems is wire , when you putting new wire in your car . Should have keep the old one even it is rusty. Edited December 23, 2013 by 9rider Quote Link to comment Share on other sites More sharing options...
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