78 280z Fuel issues!!!

[turbo 260]

First I would try to figure out if it is fuel or spark related. What kind of plugs are you running? If they aren't NGK, replace them. NGK 5632 is a good common plug for L6s with electronic ignition. Check the cap and rotor. I've worked on a car with a rotor with the back side broken off. it through it out of balance and ran like crap. Make sure to have a good cap and rotor. make sure that your wires are in good condition. If that hasn't fixed the problem, move to fuel. popping out the AFM is a lean condition. That is usually a vaccum leak. With the car running pull the oil cap. The car should die, or at least run very very bad. remember, the entire motor is part of the "vacuum" system. Try pulling the dipstick with the car running. If it doesn't change you have a leak somewhere. Keep us in the loop,

Jim

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Anyone losing thier mind with this sort of thing -See this (keyword:return line)thread:http://www.classiczcars.com/forums/search.php?searchid=489644

Also:On mine I found this also EGR valve system worked per FSM manual checks however further followup reveiled that the EGR diaphram had an almost undetectable vacuum leak that caused much grief, it was found via the propane and small hose method by placing tip just under the EGR housing (hat) that covered the diaphram. F_K ME!

My theory is that with the extra air bypassing the metering and management of the AFM/ECU,the fuel pressure then also had to be raised to compensate or for the motor to run smoothly just forget about gas milage!

[elementalvoid]

First I would try to figure out if it is fuel or spark related. What kind of plugs are you running? If they aren't NGK, replace them. NGK 5632 is a good common plug for L6s with electronic ignition. Check the cap and rotor. I've worked on a car with a rotor with the back side broken off. it through it out of balance and ran like crap. Make sure to have a good cap and rotor. make sure that your wires are in good condition. If that hasn't fixed the problem, move to fuel. popping out the AFM is a lean condition. That is usually a vaccum leak. With the car running pull the oil cap. The car should die, or at least run very very bad. remember, the entire motor is part of the "vacuum" system. Try pulling the dipstick with the car running. If it doesn't change you have a leak somewhere. Keep us in the loop,

Jim

Hey guys, I'm completely new here and just bought a '77 280z. Haven't even done an introduction thread yet.. So thanks in advance for any help you can give me.

I'm having some issues getting the Z to pass emissions. First try was really bad. CO2 was well under limits, but HC was double the limit. I pulled the timing back to ~2 BTDC and that helped a lot. This test was the same on CO2 an only about 50 over on HC. This also made a misfire more evident.

I started digging through things to see what was wrong. Checked the plugs and they were fine. Had to regap one but it was only off by a tiny bit.

Checked that all injectors are firing (sounding).

I started to test the resistance on the plug wires following the service manual procedure (i.e. wires attached to the distributor cap) and found one with no continuity. Turns out that it was not connected to the cap at all!! The boot was the only thing holding it on the cap. It was REALLY oxidized. I cleaned the oxidation off the wire and the cap and reconnected it. Resistance on all wires is well under limits now. ~15-20 kOhms each.

When I went to test the air gap on the pickup I found that the reluctor is damaged. Every other pickup point is broken about half off. Is this a common problem?

So, my question I guess is this.. Will fixing the misfire due to the plug wire not firing correctly (or at all) be enough to pass emissions? I'm not sure how much a difference would be seen by one cylinder not burning correctly.

Also, I tried Jim's test with the oil cap and dipstick. My car runs perfectly fine with the oil cap off as well as the dipstick out. No change in idle at all. Is this definitive proof that there is a vacuum leak? Or just a clue that there might be?

Thanks again for any help you guys can give.

Matt

----- EDIT

I have pictures of the reluctor if needed. I don't have access to get them on my computer at the moment.