ISPKI Posted June 8, 2013 Share Posted June 8, 2013 (edited) Hello folks! I just recently finished getting the manifolds and gaskets and sensors and thermostat and what nots back together on my 77 280z. So far so good, the thing starts easily warm or cold now - no more draining the battery trying to start it. My current issue is this: After around 5 minutes of idling after I turn the car on (idle at start is around 1200ish in 80 degree weather) there is a soft click from the engine bay and the idle drops to around 500. Usually when it kicks down from the warm up idle to this extremely low idle, it will just die immediately. It starts right back up but the idle is super low and unstable. It will drive however, and it revs up relatively nicely (stutters slightly when I first stomp the throttle) although it does not feel like it has alot of power. I went through the fuel injection bible and started with the air bypass regulator as that seemed to be most inline with the symptoms. My vehicle does not have EGR. I tested the regulator at the control unit by checking continuity which it has. I also tested it by pinching off the feed line from the throttle body to the regulator once the idle dropped down. This did not change anything so I do not think that is the issue. I have checked many of the vacuum connections, mostly by spraying carb cleaner on them. No leaks anywhere. This leaves valve adjustment and BCDD. When I went to look at the BCDD I noticed that the wire was not connected. Through more research I found that the BCDD wire should be connected to a white/black stripe wire over by the coil. I found that wire plugged into the A/C pump which seemed really odd to me. However, after switching the wire over to the BCDD, nothing changed. Also - I have a fuel gauge hooked up inline. Fuel pressure appears good - sits around 37ish at idle, increases smoothly and quickly when throttle is applied. My next step is going to be testing the circuits listed under step 6 of the bible, unless anyone has any other suggestions. Will post back later if/when I get time to test the system. Edited June 8, 2013 by ISPKI Quote Link to comment Share on other sites More sharing options...
ISPKI Posted June 8, 2013 Author Share Posted June 8, 2013 (edited) Oh also - Here is what I just replaced over the last few weeks: Removed Intake manifold - cleaned inside and out, new vacuum connections sealed with teflon tape. Cleaned injectors, replaced all gaskets for all injectors. cleaned fuel rail replaced all fuel lines on the rail as well as fuel hose clamps replaced water temp sensor replaced thermotime switch replaced thermal transmitter replaced thermostat replaced thermostat housing gaskets replaced intake/exhaust manifold gaskets, studs, spacers, bolts, nuts etc cleaned throttle body and replaced hose clamps replaced throttle body gasket replaced all vacuum hoses and clamps replaced PCV, hose and clamps replaced all the EV1 harness connectors with new connectors - including AFM and TPS connectors replaced valve cover gasket and bolts replaced dizzy cap, rotor. new NGK spark plugs and spark plug cables were also installed and thats about all I can remember Edited June 8, 2013 by ISPKI Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 8, 2013 Share Posted June 8, 2013 Through more research I found that the BCDD wire should be connected to a white/black stripe wire over by the coil. I found that wire plugged into the A/C pump which seemed really odd to me. However, after switching the wire over to the BCDD, nothing changed. Fuel pressure appears good - sits around 37ish at idle, increases smoothly and quickly when throttle is applied. Don't know why your idle would drop from1200 to 500, with a click. But, people get the AC compressor power wire and the BCDD power wire mixed up quite often. They look similar. Try turning your AC on and see if the BCDD clicks. And 37 psi is too high for idle. Sounds like you don't have manifold vacuum to the FPR. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted June 9, 2013 Author Share Posted June 9, 2013 37 is too high? the FSM says 36.3 or something. Do you have any idea what the vacuum pressure should be in the manifold? I could test that next. Something I forgot to mention is that I tried to test to see if there was a vacuum leak by simply pulling a vacuum hose off the manifold. I figured it would make the idle worse, or cause it to surge or something, but it didnt change how the engine was idling at all. Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 9, 2013 Share Posted June 9, 2013 "for idle". The FPR has a hose connected to the intake manifold to drop fuel pressure based on intake vacuum. Typical idle pressure is 26-30 psi. Quote Link to comment Share on other sites More sharing options...
srgunz Posted June 9, 2013 Share Posted June 9, 2013 Likely the TRIG box is bad. Fairly common on these old 280Z's One tell tale sign in poor running once it reaches operating temperature. The box contains two ignitions. One is bad. The emission one that kicks in when warmed up. Quote Link to comment Share on other sites More sharing options...
9rider Posted June 9, 2013 Share Posted June 9, 2013 37 Psi is too high for idle. There is the heater inside air regulator. When engine cold valve open, after that heater element heat up and cause valve close. Thus valve is for air by pass during warm up. You can check throttle switch position if the full throttle contact is touching when it is in idle position. Just my 2 cents. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted June 9, 2013 Author Share Posted June 9, 2013 Likely the TRIG box is bad. Fairly common on these old 280Z's One tell tale sign in poor running once it reaches operating temperature. The box contains two ignitions. One is bad. The emission one that kicks in when warmed up. What is a TRIG box? I cannot seem to find any info on it. Quote Link to comment Share on other sites More sharing options...
Domzs Posted June 10, 2013 Share Posted June 10, 2013 What is a TRIG box? I cannot seem to find any info on it. I think , he's talking about the ignition module . Could be wrong . Quote Link to comment Share on other sites More sharing options...
ISPKI Posted June 10, 2013 Author Share Posted June 10, 2013 Does a 77 280z even have an ignition module? I search and get ignition coils for 280zs, and the ignition module for a zx. Quote Link to comment Share on other sites More sharing options...
srgunz Posted June 10, 2013 Share Posted June 10, 2013 TRIG = Transistor Ignition. Its what all the Datsun mechanics called it at the Dealerships. Quote Link to comment Share on other sites More sharing options...
Domzs Posted June 10, 2013 Share Posted June 10, 2013 Does a 77 280z even have an ignition module? I search and get ignition coils for 280zs, and the ignition module for a zx. Should be mounted at the right kick panel , near the fuse box . Quote Link to comment Share on other sites More sharing options...
ISPKI Posted June 10, 2013 Author Share Posted June 10, 2013 Ah hah. I see it now. Thanks for the education lesson. I will add that to my list of items to check. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted June 14, 2013 Author Share Posted June 14, 2013 Hey guy. I have not had much time to test any of these ideas yet on account of how much rain we have been having. However, I was reading about updating the ignition system on my 77 280z to a newer ignition system and was wondering if I could get a bit of info from you guys that know about the system. I read about swapping a 280zx distributor into the car which seems like a reasonable idea since a rebuilt dizzy is only marginally more $ than a replacement TRIG unit. Correct me if I am wrong, but, just upgrading the distributor will eliminate the ballast resistor and the TRIG unit correct? Since the 280zx dizzy has the ignition unit mounted on it and utilizes the full voltage of the system? I have also read good things about the MSD 6AL ignition module, any suggestions on that? Quote Link to comment Share on other sites More sharing options...
KFD Posted June 18, 2013 Share Posted June 18, 2013 My '77 is having the exact same issues! I am going to test the relay as well and see if this will quell my Z's rough idle and misfire at normal operating temperature. Quote Link to comment Share on other sites More sharing options...
Driver_X Posted June 24, 2013 Share Posted June 24, 2013 I'm having similar symptoms on my recently purchased '77 280Z. Runs reasonably well when first started, but once it gets a bit warm the idle is a bit wobbly. Has changing out the ignition module helped anyone? In addition, it takes it's sweet time getting back down to idle while driving, sometimes as long as 10 seconds....could these two symptoms be related? Quote Link to comment Share on other sites More sharing options...
rcb280z Posted July 6, 2013 Share Posted July 6, 2013 Have you solved your fuel pressure issue yet? You said its running rough after it warms up. Im wondering if you do have too much fuel pressure and after warm up its running too rich. Have you checked your plugs? That will tell you if you are running rich. I would get the fuel pressure fixed before doing anything else. IMO Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 7, 2013 Share Posted July 7, 2013 TRIG = Transistor Ignition. Its what all the Datsun mechanics called it at the Dealerships. Show it to me in Datsun Manuals.... Local slang just misleads people. As an OEM Engineer going to do field training for distributor ship mechanics, the single biggest hurdle is getting field people to refer to things properly so when they call in or technical support everybody is on the same page! What people call it at the distributor in Alabama usually is different than what they called it in Detroit, and different again from what it was in SoCal, or Japan at the Yokohama HQ. I didn't know what a "TRIG Box" was, just more background slang. "TRIG" is written on components as short for "Trigger" meaning the reluctor or ignition Trigger Module in or near the distributor. Not the Transistor Ignition Unit in he right kick panel area! What I don't see is anything other than a passing reference to "warm idle".... Cold it's 1200, it drops to ???, and when you hear a click it drops to 500 or stalls/dies. The obvious thing of the AC drawing it down, or a swap from the BCDD is covered. But what is "Hot Idle"? If its set too low...it stalls under load, under load from the alternator in some cases. Instead of going for the complex: check the basics first. This may be nothing more than a maladjusted hot curb idle...which has degraded over time from not adjusting the valves losing manifold vacuum...driving up idle fuel pressure... Simple things, usually overlooked in a rush to blame electronics which, generally, are rock-solid for decades. What is curb hot idle? What idle vacuum? Before jumping to the third page of the troubleshooting chart, MAKE SURE Page 1 is all correct, FIRST! Quote Link to comment Share on other sites More sharing options...
ISPKI Posted July 7, 2013 Author Share Posted July 7, 2013 Thanks for the Info Tony. I found an interesting lead that I overlooked when I tore down the manifolds and cleaned and reinstalled them with new gaskets. I unthreaded the idle set screw all the way out and the idle popped up to 1100ish. The end of the set screw was caked in carbon that I had to scrape off. I am wondering if the passage that allows the additional air through for idle is clogged? I spoke with a friend of mine who is a mechanic and he said that if that passage were blocked off, then your idle would be lower and you should run rich since that air flow is not regulated by the AFM. Quote Link to comment Share on other sites More sharing options...
ISPKI Posted July 7, 2013 Author Share Posted July 7, 2013 The idle does not gradually drop the way it should. It is high (around 1200ish) when it starts and then plummets down to 450-500ish after a random period of time. The hotter the ambient temp, the less time it takes to drop. With our current temperature outside, it drops after about 20 seconds or so. Is 36~ PSI at idle actually too high? The FSM says that is what it should be... Quote Link to comment Share on other sites More sharing options...
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