72zcar Posted November 17, 2003 Share Posted November 17, 2003 Bought (my 5th) z for my wife, its a 77 280z with FI. The problem is when the car is driven and the rpm rises above 1500 i can take my foot off the gas and throw it in neutral and the rmps continue to rise to 2000-2500. It does this every time. Between shifts its stays at 2000+... when i come to a stop it stay up at 2000+ for about 10+ seconds then suddenly comes down to the proper idle 0f 800. I can not get it to do this when the car is not moving from under the hood or by pressing the gas from inside the car when the car is not moving. I have lubed the linkage, installed a stiffer spring. tightened all the hoses and tubes. The very strange part is that it only happens when the car is moving...hmmm Any ideas? Thanks, Bob Quote Link to comment Share on other sites More sharing options...
datsunlover Posted November 18, 2003 Share Posted November 18, 2003 There may be a little cylinder type thing (dash pot?) mounted on/around the throttle body, with a vacum hose running out of one side. The other side of it will contact the throttle arm. Try disconecting it (and plug it with something) and see if the idle still jumps around when you drive it. Mine has been disconected (by previous owner) for the same problem you are discribing.. he said it was fine after it was disconected. Quote Link to comment Share on other sites More sharing options...
72zcar Posted November 18, 2003 Author Share Posted November 18, 2003 i was thinking the same thing so i took it conplety off and same thing happens. thanks for the relpy though. anyone else? Quote Link to comment Share on other sites More sharing options...
datsunlover Posted November 18, 2003 Share Posted November 18, 2003 Could it be something to do with the ignition/timing or the water temp sensor? On my 280, there are two circuits for the ignition (two pickups in the distributor) and depending on the signal from the water temp sensor, it runs on one of the two (advance or redard)... just a thought.. Quote Link to comment Share on other sites More sharing options...
72zcar Posted November 18, 2003 Author Share Posted November 18, 2003 it seems like it is getting more gas for those ten seconds. it pulls at 2000+ just like I had my foot on the gas. Quote Link to comment Share on other sites More sharing options...
72zcar Posted November 18, 2003 Author Share Posted November 18, 2003 anyone Quote Link to comment Share on other sites More sharing options...
Guest shauno_ Posted November 19, 2003 Share Posted November 19, 2003 I would say it's you BCDD unit mounted underneath the throttle body. It bypasses an amount of air to keep your rpm up during decelleration to prevent backfiring and help shifting. I took mine apart to check it and it wasn't properly closing so I plugged up the hole with some epoxy, let it dry and sanded it smooth. I have no fast idle at start up now and my car keeps a constant smooth 800 RPM . It used to stick up around 1800 forever....it was so annoying. I could coast it in neutral and the RPM's would just go up on there own with the car just rolling slowly. If you search for a thread on BCDD ( boost controlled decelleration device ), you'll find a picture of the modification I mentioned. Good Luck. P.S. if it looks dirty, you could just clean it and make sure everything moves freely and then just re-assemble it...if you want to keep stock. Quote Link to comment Share on other sites More sharing options...
72zcar Posted November 19, 2003 Author Share Posted November 19, 2003 ok thanks shauno, I will try that later on today and let you know what happens. Quote Link to comment Share on other sites More sharing options...
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