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JDM 280zx has a strange running problem


BluDestiny

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So I got my car all sorted out and now that I'm home my friend has asked for my help.

 

What is happening is that when the car is (normally) warmed up to operating temp. While the car is under load only it will literally just lose all throttle response until it goes back to a normal idle. Like it won't hot a wall, or have problems running, the gas pedal just has no effect and it will drop revs. Its like the car is resetting to idle.

 

The car was over at sunrise Z and art was checking it out, but it has him stumped too. They replaced the tps (with a usdm one) since since the original was toast and it supposedly ran a little better. Art thinks is may be the ecu, like a lose connection inside the unit or something.

 

Now I'm not a fan off all the irreplaceable jdm stuff so i will attempt to swap a jdm ecu and harness in. But to do that the jdm intake manifold and throttle body need to be changed as well.

 

Does anyone have suggestions why this won't work? Like an issue with it connected to certain sensors. I will try to change as many sensors over as i can to get it to run.

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Sunrise tried a usdm ecu and it didn't even crank. Guessing the pin outs are different. My friend has gotten a lead on a used ecu from new Zealand, but for $350 not including shipping.

 

In my opinion swapping over to usdm components can only make trouble shooting and replacing parts easier. Vigges concern is how much it wraps into the main harness, like if I swap in the usdm ecu and harness with the gauges work etc...

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Ok so I took out all the jdm stuff (harness, ecu, intake and trottle body) and tried to start it with the my 81 USDM stuff and that was a no go.

 

So I threw all the JDM stuff back in, after cleaning it, and it worked fine. Drive it around all day. No idea why

 

Well this morning, I started her up and as I pull away from my house it has the same problem, just cuts at a certain rpm and goes to idle.

 

Well I got it back in and took a short vid. You can see me holding the throttle down and it just goes back to idle then "remembers" the throttle is down.

 

 

Does anyone have any idea what is causing this? like I said it was running fine yesterday and I literally drove it for about an hour, didn't take it on the freeway, but ran errands in it.

Edited by BluDestiny
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Well it revs up fine, and to get the car running we had to drop the tank, clean it, blow air through the lines etc... Last time my friend checked it has 30-35 psi using a fuel pressure tester from autozone.

 

The idle screw is ALL THE WAY IN which to my understanding is making it richer(?) with the idle screw out it idles at like 2000rpm. But I can not find a vacuum leak, although there could be one inside the throttle body ( like I said it has 2 throttle valves)

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Yes, when I got the car I had to take the intake and exhaust mani off and we redid everything. Had to recheck it all again. Anyway the problem got progressively worse and it started choking out at 2k instead of 3k. Back to where it was originally.

 

I was trying to convince him to go mega squirt, but he doesn't want to deal with the learning curve so I think he's gonna drop it off at sim tech in Santa clarita. For those of you who know the owner Craig is a great guy, and he's gonna try and do a turnkey setup for about $3000. Yes my friend is a tard. Lol but we will see when it gets done.

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  • 2 weeks later...
  • 2 weeks later...

If I stay steady it won't go past it and will buck and surge perpetually.Give it gas, get past it, and drive on.

The PO had HUGE tires on it, so his highway speed cruise was considerably lower than when I put OEM Size tyres on it.

I bumped my highway cruise speed up to 75+ and haven't looked back.The EFI system I have in the car is a 1976 setup with 176,000 miles on it.

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