Intermittent stall/no start issues...

[Jon Powell]

Ok, so I am no dummy, I am actually pretty good at disagnosing problems on a car, but this one has me stumped...

1977 280Z

New:battery, voltage regulator, starter, spark plugs, wires, dist cap, condenser, rotor

Timed to 10º BTDC, vacuum line attached.

When I first start in the morning, it fires right up, no issues. After about 10 mins, if I try to idle it likes to drop to 500 RPM and not come back. if I go from 0% throttle to anything over about 60% in one quick shot, it will bog HARD and usually die, unless I start pumping the throttle.

If it rains, forget it. I will be lucky if I get her started.

Voltage doesnt drop off, I think its a coolant temp sensor related issue, almost as if the computer thinks the engine is cooler than it is and is adding too much fuel.

If you had any similar problems, let me know.

Thanks!

Jon

[78 280zcar]

You say it is a 77 and you bought new condensor and voltage regulator. Does it have carbs or injection? If it is fuel injection it would probably be the CO set screw in the AFM, just remove the cover on the side closest to the coil and turn it out or in and see where that takes you, you will have to ask someone else if it has been swapped out with carbs!

[sblake01]

The 'CO set screw' just the mixture adjustment. I usually check that adjustment just before a smog check and set it to spec with my exhaust analyzer. If that adjustment is off, the car will run rich or lean but it wouldn't do what Jon describes. I would first check the temp sensor, both the connection and the sensor itself. The rain thing has me stumped, however. I've never experienced that with either of my efi cars.

[DeesZ]

I had a similar problem a while back, only to find that my 'new' dist cap was defective with a slight crack, and it developed a "halo" of junk around the inside as if it had been spit off by the rotor (actually I guess it really was spit off by the rotor). It started in damp weather much better after I hit the inside area with WD-40 and wiped out all of the junk. Of course due to the crack I replaced it in relatively short order.

[78 280zcar]

Sblake, do you remember when I was telling you about how my idle was dropping to 500 and then back up to 850rpm when letting off of the gas. Well it turns out that it was the AFM set screw that was way off and turning it out (lean) was what fixed it, so I thought it might help with this mans problem. A guy that just joined this site about 2 weeks ago told me about it, (jimlhred240z). I just dont have access to an exhaust analyzer!

[sblake01]

Oh, it's a great thing to have. The one I have only measures CO but that's the key to everything else. If your CO is within spec, then everything else seems to follow. I have used it to set the CO prior to an emissions check and I haven't had a car fail since I started using it.

[Jon Powell]

Well, believe it or not, the car "fixed" itself. 2 days after posting that message, the car stopped stalling......rain or no rain. It is still rough to start everynow & then, but it appears to be fine. The car sat from Friday night through this morning and fired right up with a second or 2 of cranking and was good all the way to work. I think whatever the issue was had to do with rain.......open wiring shorting out or something stupid.

[Jon Powell]

It didnt fix itself

It decided to NOT START again on Monday night after a full day of rain.

The coil had come loose from the bracket and was shorting tot he strut tower when water filled the miniscule gap....easy fix, stupid problem.

Thanks guys!