engine cutting out

[mom'sZ]

I have a 77 280z with the stock engine (L-28) and stock fuel injection. I pull out of a parking lot tonight, got rolling in first, shifted into second (normally, not hard) then pressed the pedal to the floor and wound the car all the way to 5500 or 6000 RPMs. I shifted into third, then forth and was cruising along about 50 mph when I noticed the engine seemed to be cutting in and out. I let off a bit then stepped down again and sure enough, it seemed to be cutting in and out, kind of jerking. It got worse and I worried I won't make it home. I made it, but it continued to do it the rest of the ride home. It seemed a lot like a time I got the throttle position sensor wet, but it did not get wet. When I got home, I checked for anything obvious but couldn't find anything. I took it for a ride and it seemed to still do it, but as I drove around it did it less. If I accelled real hard, I could get it to do it again.

This is a well maintained car and has new wires, cap, rotor ect. Fuel filter is new and pressure gauge shows no drop. It seems like it cuts all cylinders, not just one or two. Like the engine cuts completely in and out, not dropping cylinders.

Any ideas?

[roger.svoboda]

May be totally off but my 81 turbo did very similar. Diagnosed it down to the a/c compressor by rigging a switch to the compressor clutch. when it started if I deenergized the clutch the jerking and bucking would stop. As you are in florida it might seem that you have and were using your a/c. Easy way to tell is if it starts again pull the wire off the compressor clutch and then drive on. If problem is gone that may be your problem. I live in the NW so never got it repaired and have since sold the car.

[Pop N Wood]

That could be anything. A loose or dirty connector, wire shorting to ground, dirty fuel filter, failing fuel pump, low on gas.

 

Not a fun problem to diagnois.

[VinhZXT]

First thing to check is your plugs. if they look good then check the inside of your gas tank. I have a hunch that it has some rusts in there and clog the fuel line. GL

[HizAndHerz]

An AFM boot with a hidden tear between the folds will do that. Often they will only leak a significant amount of air when you stomp on the gas. Very common problem!

 

Look for other sources of vacuum leaks, but most will cause the engine to idle poorly. A bad diaphram in the brake booster might also cause intermittant vacuum leaks.

 

Also, this might be an ignition problem. Sometimes, a flaky ignition module will drop out at high RPMs. The reg and green VR sensor wires in the distributor sometimes go bad since they get flexed when accelerating due to mechanical and vacuum advance kicking in. Check rotor, cap and ignition wires.

[naviathan]

As has been stated, check the plugs. This sounds like you're running extremely rich at WOT and as it works out the extra fuel the problem lessens until you stomp on it again.

[mom'sZ]

I think it was the ignition module. (good guess hizandherz) here's why. All the items suggested are virtually brand new. This car is maintained to the hillt. Plugs rotor cap, weeks old. Wires, magnacor maybe two months. Fuel filter, injectors new. But the ignition module is the original 30 year old part.

I remember someone mentioning they start to cut out when they get hot. Then work fine once they cool off. That seemed to be how this worked. When I got home I checked under the hood for anything obyious, then drove it around. It continued to do it pretty bad. The more I drove around at low RPMs, the less it would do it. I let the car sit for an hour or so and it totally stopped happening.

I plan on replacing it with an aftermarket unit. I will retest this one just to be sure that is the issue before I change it out and let you guys know what I find. Thanks for the help

[TBK]

check your fuseable links first!!! My 77 did same thing, hard excel was the worse! a loose or bad connection will cause this or burnt link! look for melted block thats the first indicator, then try to slightly crip the ends tighter and reinstall them!