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1981 280ZX turbo is stumbling when hot...


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I commute about 50 miles to work each way. After driving my turbo 280zx home one day, I made

a pit stop to our local supermart and stayed there for about 8-10 minutes. When I got back

to my car and started it, it started but stumbled like it wouldn't idle correctly. It

then died after about 5 seconds.

 

I re-started the car and it stumbled again. This time, I gave it a little gas and it

seems to worsen the stumbling and rough idling. I then put it in Reverse (it's an automatic)

and it runs rough but I get it to go somewhat. I then put it in Drive and step on the gas

and suddenly... it's idling and running okay! I drive home and park the car and

then try to re-start again to see if it will stumble again and it didn't! Car ran fine!

 

Next morning, on a cold start, it starts just fine. I drive to work another 50 miles,

went to the bank to get some cash, restart again, and now it's stumbling again! Got to work

and no starting problems after the initial stumble just like above.

 

Any ideas please? I must add that I have the infamous exhaust leak due to the

broken end bolt by the firewall.

 

Please help.

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Most warm start issues for the 280zxt's seem to be caused by the power transistor. It seems be affected by heat over the years. The power transister is attachd to the distributor. I've heard that hitting it with some type of cooling spray when it's acting up is the way to determine if your's is bad. I believe radio shack has some type of aersol spray that will freeze stuff. A replacement can be difficult to find. I can't remember the sources that were listed. SUggest you do a search in the archives.

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I don't know about the transistor, but I know my 81ZX does the same thing. It's leaking injectors that are causing mine to do it. When you leave it for anything under a hour it leaks enough fuel in the cylinders to flood it and cause the stumbling. A quick restart after shutdown doesn't give it enough time to leak too much fuel into the cylinders therefore doesn't cause the stumbling. It can also be caused by a bad cold start injector or thermotime sensor.

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I think I know what it MIGHT be. Seeing as you have an 81, don't you have the same distributor as the N/A ZX? If you do, then I think I know your problem. It is in fact inside your distributor, but it's possible it's not the transistor box. It could be the breaker plate assembly. That is the mechanism that controlls vacum advace. There is a small plastic plate that holds three ball-bearings in place that lets the plate rotate, with the relutor (or stator, I forget which term means what, it's the jagged pointy thing under the rotor that's on the outside) moving on top of it. If that mechanism is sticky, since you parked it at full vacum, the plate can get stuck. Once you apply vacum to it one or twice by reving it, the plate gets unstuck and works fine.

 

My breaker plate does the exact same thing since I rebuilt the distributor and found the breaker plate wasn't doing anything, I was stuck without vacume advance. I even passed smog once with it like that! I replaced my entire assembly with four or five washers I machined down to the perfect size, lubricated with liberal amounts of lithium grease. The mechanism still sticks if I park it HOT, without idling down first, and try to start it again within 10-15 mins, but other than that, it works great.

 

Disclaimer: Just because this happened to me, dosen't mean it's happening to you. It's possible you have loose wires, the transistor unit is going out, or something else. But this sounds EXACTLY what what my car does. Give it a few good revs, and it work's absolutely perfect again.

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Thanx guys...

 

I will give it a good tune-up this weekend and inspect and clean up everything I can including all those you've mentioned.

 

Anybody else with ideas, please keep posting to this thread. I'm sure all of us as a whole would like know what the ultimate cause of this is.

 

Thanx again!

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might be you were actually experiencing the problem that sometimes occur where fuel is vaporizing in the rail due to high heat. Is your injector cooling fan working??? the guy with the vacuum advance thing is off because the 81 distributor is only that. no wires, no vacuum hoses it just sends spark to the correct plug.

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Well... looks like the gremlin has disappeared. This is after I changed the air filter (and took off the restrictive ducts on both sides). I experimented both going to an coming from work. I park the car, let it sit for 5-10 minutes and restart... NO PROB.

 

I really think my lack of diligent maintainance contributed to all the miles I travel each day. Found that a LOT of leaves were in the air filter surround and clearing them up may have solved my problem.

 

I will be more attentive to all the things needing maintainance.

 

Thanx y'all for the inputs (keep them coming, tho')...

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That would it it all right. Changing the fuel filter can't hurt either, it's often overlooked.

 

When I got my Z, the air filter had a DENT in it. The metal on one side was pushed way down. The housing was fine, so who knows how it happened. I just undented it and drove it that way until the local nissan dealership sent me a flyer with a coupon in it for 7.99 for any air filter. I was really happy to have the coupon when I ordered it at the parts counter, and the guy behind the desk couldn't figure out why, talking about how that's not much of a discount, until he saw the normal price - $33 and something cents. All he said was "Wow, you made out like a bandit."

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