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1986 300ZX Random Misfire
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solaire
New User
Jul 9, 2012, 1:57 PM
Post #1 of 5
(3311 views)
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1986 300ZX Random Misfire
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1986
Nissan
300zx GLL
3.3L V6
130k miles
I am getting a random misfire that I can't find the cause of. It seems to start around 2500 rpm and happens randomly throughout the entire range above 2500 rpm.
I have tried replacing the spark plugs, also tried lowering the gap a bit. This seemed to help but not fix things.
Removed and inspected the plug wires, they are about 1 year old, appear to be fine. Haven't done a resistance test on them because I don't have a multimeter.
Cleaned the contacts in the distributor cap and the rotor button with a wire brush.
Replaced Crank Angle Sensor with a spare from an extra engine, engine ran the exact same with the "new" one.
Cleaned the plugs on the ECCS, AFM, Distributor, Coil with electrical contact cleaner.
Tried a spare coil I had laying around, engine ran the same with that as well.
It also has new fuel injectors in it from Advance Auto, but the problem started before the fuel injectors were replaced. They were replaced because they were leaking fuel out of their casing.
It seems more prone to misfire when increasing rpm, if it is held at a steady rpm it won't misfire where it otherwise would when revving.
What should I try next?
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 9, 2012, 2:04 PM
Post #2 of 5
(3296 views)
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Re: 1986 300ZX Random Misfire
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Those cars were notorious for problems within the wiring harness, most effecting the fuel injectors.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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solaire
New User
Jul 9, 2012, 3:26 PM
Post #3 of 5
(3278 views)
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Re: 1986 300ZX Random Misfire
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Un-plugged one injector at a time and revved the engine and the miss was still there each time, so it doesn't seem to be one particular cylinder that's causing the problem. Could all the injectors be stopping at once, or all the spark? When it misses it drops a couple hundred rpm before it recovers, sort of like when you hit the rev limiter except it's at a random rpm.
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nickwarner
Veteran
/ Moderator
Jul 9, 2012, 8:30 PM
Post #4 of 5
(3256 views)
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Re: 1986 300ZX Random Misfire
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wiggle test it. With the engine running grab harness and shake the crap out of it. If you hear it stumble you found what HT is telling you to look for. At rest it will test fine but not when its vibrating.
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solaire
New User
Jul 10, 2012, 9:50 AM
Post #5 of 5
(3240 views)
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Re: 1986 300ZX Random Misfire
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Alright I'll give that a try.
I went through and wiggled every plug including the ECU plugs with the engine idling and it continued to idle normally without any missing I also wiggled all of the hoses, relays and fusible links in the engine bay.
(This post was edited by solaire on Jul 10, 2012, 12:52 PM)
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