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'82 ZX N/A: Sluggish performance, tach needle jumping, and RPM surging beyond 5000.


Connor280ZX

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Update: Found a thread on Zdriver where someone seemed to have a very similar problem, and it was his ignition pickup in the dizzy. I replaced that today and no difference. Still cuts out, tach still jumps around. I don't know what's left to replace.wiring is fine, coil has voltage, cap and rotor are fine... Tried two coils btw. Had a spare coil from a '75 280Z, ran even worse with that coil...

Edited by Connor280ZX
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I put a typical alternator capacitor/condenser on the coil negative post once to solve a jumpy tach problem.  It was a GM HEI module with a Z31 coil (yes, the Tony D setup, but since changed to an external GM HEI coil).  Stray RF or voltage spikes, who knows.  The tach started working again.  The tech circuit doesn't require much, in other words it's sensitive, it has a pretty large resistor in-line from the coil post.

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Input circuitry of tach to my knowlege: Tachometer > Negative terminal on coil > ICM > Pickup coil. Ran some more tests, this time on the coil it self. It draws 0.25 ohms, which seemed low since the manf. claims it should output 1.4 ohms. Did a spark test, instead of blue spark, got orange spark which means weak spark. Led me to beleive that my coil was going out after all, so i replaced it and no difference. I am so stumped right now. I've replaced and tested everything electrical that has to do with spark, and the problem persists. BTW, i have to advance the dizzy ALL OF THE WAY to achieve even 9 BTDC. This whole situation is starting to seem supernatural...

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Ohms aren't drawn, they're just there, in the way.  FSM says 0.84 - 1.02 for coil resistance, looks like you're using the 75 coil, not the stock 82 280ZX?  You didn't say what the new coil had either.  Did you measure with the coil connected or disconnected?  If connected, then you were also measuring resistance through all of the other wires connected to - and +.  Parallel circuit.  Disconnect the coil before measuring primary resistance.  

 

What problem are you working on, the jittery tach problem?  Put a condenser on the line, it can't hurt.  Worst case, it's a useless piece of electronica on the circuit.

 

The advance problem is a whole different thing.

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I put the '75 on just for a quick expiriment, i did not test it. Crane PS20 coil is what i tested, and what i used on the car for the past year and a half. I tested it by disconnecting everything, put one cable down the wire outlet, and the other on the positive terminal/pole of the coil. There is already a condenser in the coil harness, looks to be factory (Little silver cylinder with a wire running through it).

 

What im working off of is that everything that is wrong with the car right now is all linked to one part/parts since they all started occuring at the exact same time. Jittery tach, sluggish performance, distributor advance and the heavy misfire all started occuring within maybe 10-20 miles on the ODO of eachother. I am 100% sure that it is all related. I just don't know what the hell is causing it.

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In Post #16 you said the engine was running well, the only remaining problem was the jittery/cutting out tach.  I missed the follow-ups to new problems.

 

Primary resistance is between the coil + and the coil -.  There's a really nice drawing in the FSM, very hard to misinterpret.  Secondary is what you measured and should be very high.  Like  about 10,000 ohms, also shown in the FSM.  So you measured the wrong thing, or reported the wrong spec. (1.4 ohms) but still got a bad number.  

 

I wouldn't assume that all of those things are related to one source.  You need to figure out how to measure the right things first.  No offence.

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In Post #16 you said the engine was running well, the only remaining problem was the jittery/cutting out tach.  I missed the follow-ups to new problems.

 

Primary resistance is between the coil + and the coil -.  There's a really nice drawing in the FSM, very hard to misinterpret.  Secondary is what you measured and should be very high.  Like  about 10,000 ohms, also shown in the FSM.  So you measured the wrong thing, or reported the wrong spec. (1.4 ohms) but still got a bad number.  

 

I wouldn't assume that all of those things are related to one source.  You need to figure out how to measure the right things first.  No offence.

It WAS. A few miles later, and everything else i described started to occur. Going over the FSM now, you're right i did measure that wrong. Some website told me to do it the way i did (Was on my phone so no access to FSM files at the time), but i guess that doesn't matter since the coil(s) don't seem to be the problem as of now... No offense taken.

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Here's the update: Just picked the car up from the shop. The mechanic replaced the ignition coil again, checked the magnetic pickup system in the dizzy, and installed a genuine E12-80. The car runs much better, but the tach is going absolutely nuts now. After 3k rpm, the tach does a FULL sweep, then drops to zero untill engine RPM comes down. What was wierd though is that i notice the tach drop when i pressed the prake pedal, and when i turned on my lights... This makes me think that there's definately some kind of electrical short somewhere. Taking the car back in next Thursday to continue diagnostics.

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  • 4 weeks later...

Alright, car is fixed! So basically, my IGN system required an E12-93, not an 80. Due to the fact that the knockoff ICM's arent made specific to the year of the car, i kept installing the wrong part/s unknowlingly. The module i installed would work on a 1980, but not my 1982. An E12-93 wouldn't work right an the 1980, but would work great on mine. Problem solved, however the tach was still going nuts. Coil was bad as well, so i reinstalled my old PS20 and now the car works perfectly. Yay!

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