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Idle and voltage problem
http://forums.ctzcc.com/viewtopic.php?f=4&t=6453		 Page 1 of 2
Author:  georgev77 [ Sun Oct 23, 2011 7:58 pm ]
Post subject:  Idle and voltage problem
I have a 75 280z. The problem is while idling around 800-900 rpm. The motor doesn't idle steady. It jumps up and down when I turn on the head lights, wipers or blinkers. I installed a new alternator and battery still the same problem. Any suggestions ?
Author:  CygnusX1 [ Mon Oct 24, 2011 9:37 pm ]
Post subject: 
Some idle variation should be expected when loads increase on the engine. The older EFI systems like S30's don't have "smart" idle control systems. Another possibility is that the voltage to your injectors is dropping slightly when you turn on accessories, which is normal. However, if it's excessive, I would look at the quality of your wires, connectors, and especially, all the chassis grounds scattered throughout the engine bay, and engine.

Simply disconnecting and connecting them usually works. Even better results come from a good cleaning, and the addition of some dielectric paste.

A common problem area are the fusible links and their spade connectors. Battery cables and their terminations on both ends are also critical.

Good luck. :)
Author:  Paul [ Wed Oct 26, 2011 10:38 am ]
Post subject: 
All the above, especially the Ignition Module. Also check for vacuum leaks as well. Air flow meter also.
Author:  georgev77 [ Wed Oct 26, 2011 7:34 pm ]
Post subject: 
I cleaned some of the grounds but not all yet, been busy with work and home stuff. I used dielectric silicone on all connections cleaned so far. Still the same problem. I'll try to get to cleaning and greasing more engine bay grounds and electrical connections. I also ordered a new old stock voltage regulator. I also want to mention that I removed the hose that connects the air flow meter boot to the valve cover. I installed a breather filter at the valve cover and plugged the hole at the air flow meter boot. I'm not sure if that set up is ok for fuel injection systems. I've seen the same set up on carberated engines like 240 and 260's. I think it looks better but not sure about functionality. I appreciate the info.
Author:  CygnusX1 [ Wed Oct 26, 2011 7:59 pm ]
Post subject: 
No, No, No.... The valve cover CANNOT be vented to atmosphere! It MUST be connected to where it belongs.

The L28 engine is a SEALED system. All air that enters the system MUST come through the AFM. All air that leaves MUST go out the exhaust. Any leaks in the system will make the car run VERY poorly.

Matter of fact, removing the oil cap or the dipstick, should just about stall the car. If not, there is a leak in the system, and the AFM has been adjusted to compensate for the leak. Not good.
Author:  georgev77 [ Wed Oct 26, 2011 10:17 pm ]
Post subject: 
Ok. Thanks for the quick response. No more breather, putting the hose back. So I should be getting the voltage regulator by this weekend. I'll install that and finish checking, cleaning and greasing my connections. Hope that helps.
Author:  Paul [ Thu Oct 27, 2011 6:39 am ]
Post subject: 
You don't want to greese your grounds....metal on metal, then can paint over.
Author:  CygnusX1 [ Thu Oct 27, 2011 7:26 am ]
Post subject: 
Greasing the grounds works well as long as you first clean the contact surfaces to shiny metal first. The grease displaces when you tighten the connection and keeps moisture and O2 from getting into the contact points.
Author:  Paul [ Thu Oct 27, 2011 9:06 am ]
Post subject: 
I would use dielectric greese if doing that. I just sand down the body were it contacts, sand down the ground terminal, add a bigger washer for more surface area, then just paint over.....nice and neat looking. off subject.....Dave,would you believe something fell on that dash and put a blister in it....dope. But the fenders and hood are on and look great, just saying thanks for everything.
Author:  CygnusX1 [ Thu Oct 27, 2011 12:25 pm ]
Post subject: 
Paul, post some photos. :D
Author:  Paul [ Thu Oct 27, 2011 5:23 pm ]
Post subject: 
Will do when finished. :D
Author:  CygnusX1 [ Thu Oct 27, 2011 7:52 pm ]
Post subject: 
George, how's it run with the valve cover hose back in place? Should be a lot better.
Author:  georgev77 [ Tue Nov 01, 2011 10:54 pm ]
Post subject: 
The car is running better. I still have some idle drop but not as much as before. In drive it idles around 850 rpm. With head lights, wipers and blinker on it drops to about 650 but doesn't jump up and down as much as it did before which would cause it to turn off completely. So far I have installed a new battery, alternator, voltage regulator and some ground wire connection cleaning. It has improved but I believe could be better. Thank you for sharing your valuable information.
Author:  georgev77 [ Wed Nov 02, 2011 8:33 pm ]
Post subject: 
Well I took a ride today and was at a stop light and decided to check to see if the problem has improved. I turned the lights, blinker, and wipers on. Not only were people looking at me like I'm crazy but the idle was rough and it was jumping up and down again. I just don't know what else to do. Does it have anything to do with my distributor or fuel injectors.....the fact that they are electronically controlled? I still need help
Author:  Frank T [ Wed Nov 02, 2011 11:11 pm ]
Post subject: 
A "rolling" idle is always either electrical or fuel related, and "fuel" includes vacuum leaks.

"Electrical" includes proper spark advance at the distributor.

When you turn all that stuff on, it imposes a greater load on your alternator, making more resistance for the engine to run against. Regulatory systems should sense this, and automatically modify your spark advance and fuel mixture and flow. I don't personally know how that happens in fuel injector systems (if you had carbs it would be easier for me to discuss).

You might start with a manual examination of your distributor. Pop the cap (and clean & check the terminals while you're in there), and pull the rotor. Check the advance plates to make sure they slide smoothly and easily. The centrifugal weights should be easy to move. Sucking on the vacuum line should make the advance plate move some. Any dirt or rust in there should be removed completely. Your 280 probably has an electronic dizzy, without interruptor points, so there's no need to discuss those.

Vacuum leaks can be hard to trace. The easiest way I know to do that is to spray starting fluid along each vacuum line while the COLD engine is running. If the RPMs jump up, you've sprayed a vacuum leak (the engine sucked the fluid into the cylinders, which made it run faster). I like to stop when the engine gets warm, let it cool off, then resume where I left off.

Keep in mind that some of the accessories you mentioned might (might) have a vacuum line running to them, which must also be checked. One member with a ZX had it stall each time he turned on his A/C ~ one rubber vacuum hose was cracked, which didn't bother the engine until he activated the servo thingy by turning on the A/C. Stuff like that.

Finally, try to turn on each accessory individually, to see if you can identify a single cause (or the greatest cause) for the idle change. That might lead you to inspect a more specific area for an electrical or vacuum problem.

As always, try (and/or change) one thing at a time, always have a fire extinguisher at hand when playing with starting fluid, and don't get your clothes caught in the fan or moving belt. Sounds stupid, until you've seen someone forget one of those.......then you'll tell everyone you know :roll:
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