I have a 1990 300zx tt with 105k miles. It's had routine maintenance done- always. I bought the car early summer. It has stillen exhaust, ecu and intake. I cleaned the intake about midsummer. I'm getting a random misfire while cruising. You can't hear it while ilding or mid> throttle. The original owner(last) said occasionally it would drop a cylinder when started. He said you revved it up once or twice and it would go away. I've had the check engine light come on 2 times while I was in 2nd gear about 5-10 mph@low rpm. It never stayed on long so I couldn't retrieve the code. after that is when the misfire started. It sounds like ignition not fuel. I am wondering if I got the MAF sensor dirty with the intake oil. Could that be a cause? Or are there some common issues I should look into? Wanted to get some advice before I dump a whole tune up on it. Guestimation costs money. Thanks for all/any help.
Modified by SpeedFreak_Josh at 2:46 PM 4/10/2007
Modified by SpeedFreak_Josh at 12:39 PM 5/14/2007
random miss, 90 300zx tt
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SpeedFreak_Josh
- Posts: 65
- Joined: Thu Oct 26, 2006 2:36 pm
- Car: 1990 300zx TT
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SpeedFreak_Josh
- Posts: 65
- Joined: Thu Oct 26, 2006 2:36 pm
- Car: 1990 300zx TT
Re: random miss, 1990 300zx tt (SpeedFreak_Josh)
Update:I just changed the sparkplugs with OEM NGKs. The old ones where a little dark but otherwise in good used condition. The miss is still there. Only when cruising with light throttle.
Check your ignition coil plugs for any corrosion.
The one in question is located around your Upper Radiator hose on the passenger side of the engine bay. The plug is a long plug with wires side by side. It is very common of this plug to corrode over and cause a similar problem to what you are experiencing.
Another thing it could be is a leaky injector. Those injectors are prone to leak internally over time. When the leak, they dump too much fuel all the time, especially when cold, and will basically "flood" the cylinder and cause it not to fire. Then when the engine heats up, the problem may go away because the higher cylinder temps will ignite that fuel and make it appear that the engine is running fine.
Do those checks first.
The one in question is located around your Upper Radiator hose on the passenger side of the engine bay. The plug is a long plug with wires side by side. It is very common of this plug to corrode over and cause a similar problem to what you are experiencing.
Another thing it could be is a leaky injector. Those injectors are prone to leak internally over time. When the leak, they dump too much fuel all the time, especially when cold, and will basically "flood" the cylinder and cause it not to fire. Then when the engine heats up, the problem may go away because the higher cylinder temps will ignite that fuel and make it appear that the engine is running fine.
Do those checks first.
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SpeedFreak_Josh
- Posts: 65
- Joined: Thu Oct 26, 2006 2:36 pm
- Car: 1990 300zx TT
Re: (Ramius83)
I checked all my coil packs when I changed the plugs. None appeared corroded. They actually looked new. Are you talking about the eletrical plug to the coil or the coil socket over the plug itself??
About the injector: It runs fine when cold. Idles fine too. I'm only getting the problem under light throttle at speeds. Most noticeable in 3rd gear around 35mph, or 4th around 50mph.
What is the resistance check for the injectors. I haven't gotten a Hanes for it yet so could someone please give me the layout. Thanks.
About the injector: It runs fine when cold. Idles fine too. I'm only getting the problem under light throttle at speeds. Most noticeable in 3rd gear around 35mph, or 4th around 50mph.
What is the resistance check for the injectors. I haven't gotten a Hanes for it yet so could someone please give me the layout. Thanks.