So a year ago I bought 79 280zx, I did everything to it from cleaning out the entire fuel system, cleaning the afm, valve adjustments, trying to clean the throttle body, I blew air through injectors and the fuel rail, sealed the tps after cleaning it, changed spark plugs and wires, ran fuel cleaner through it, and changed the plugged pcv tube, changed one injector to get rid of a misfire which it succeeded at doing, checked for vaccum leaks, corrected timing. It also would sometimes start up and the idle would go up and down and after driving for a bit it would stop the bad idle and it rarely stalled but started stalling more and more at only the first stop light times the idle was bad and also sometime later into owning it, it started randomly somtimes dropping rpms on the freeway, the idle didnt really matter on it being winter or summer, but the rpm dropping was when it got warmer. Oh and its straight piped and cold air intaked. Recently I got a 83 280zx after rear ending someone with the previous one and without doing much to it, it had way more power already the first time I drove it. Any one have any other ideas as to why it was this way? I've looked everywhere for a while as to why. If I can figure this out it would be a really big accomplishment.

 

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Oh and the air bypass valve would make really loud high pitched vibrating noise every once and a while, that cause me to find a vacuum leak but it still had all the other issues

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20 minutes ago, thetech101 said:

. Recently I got a 83 280zx after rear ending someone with the previous one and without doing much to it, it had way more power already the first time I drove it. Any one have any other ideas as to why it was this way? I've looked everywhere for a while as to why. If I can figure this out it would be a really big accomplishment.

You don't have the 79 anymore?

 The 83 engine is probably in better shape, and set up and tuned the way that Nissan intended.

 

You don't have the 79 anymore?
 The 83 engine is probably in better shape, and set up and tuned the way that Nissan intended.
 

The 83 has 200,000 miles so I doubt it's in better shape. I still have the 79 but it has an issue I'm hoping someone here knows about, cause I can't find it

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19 minutes ago, thetech101 said:

The 83 has 200,000 miles so I doubt it's in better shape. I still have the 79 but it has an issue I'm hoping someone here knows about, cause I can't find it
 

How many miles does the 79 have?

The key to success with these problems is generating and using good numbers, and good descriptions of the problems, and the actions taken.  Like you gave mileage for the 83 but not for the 79.  Without both, there's no comparison to make.  The 79 might have 400,000 miles.

You haven't really described a problem with the 79 either besides the idle RPM dropping.  And apparently it feels less powerful than the 83.  but you don't have any thing to compare, like 0-60 times, or dyno results, or burnouts, or really anything.

Sometimes the straight pipe engines are so painfully noisy that they feel less powerful.  All of the straight pipe straight six cars I've ridden, since high school to today, have sounded like tractors.

Just saying, there's not much to work with here.

I'd assume it have either 200,000 or 300,000 bit it's hard to tell based on only going to 90,000 on the gauge. And the 83 is almost as loud with a bad muffler, it's just the 79 never squatted like a z is supposed to and never really have power in any gears other than first and second. I can also verify it's faster due to finally beating my friend who was in Chevy Tahoe, the fact the last one couldn't beat a Chevy Tahoe was shameful

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Good luck.  There are many possible reasons one beats a Tahoe and one doesn't.  Rear gear ratio, for example.  And the 280Z's aren't supposed to squat.  The 280ZX has a different type of rear suspension.

You're way back on the simple side of "fast".  No offense.  Tuning a car for a certain purpose, like beating a Tahoe, requires attention to many small details.  Study up on the basics and you'll figure it out.  It's not going to be one thing, like a "cold" air intake.

I'm just gonna wait for someone idk how to explain to you that it doesn't need to be fast but to have normal power and not way less than normal

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Someone else*

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Have you replaced the air bypass yet? Also have you cleaned the contacts going to the ECU? Grounds are also important to be good and clean. Also clean the TPS connection as well. 

I know it's hard as I think one thing and tend to type another, but be very specific on your question. 

Edited August 19, 20177 yr by JSM

Oh ya I also replaced all connectors on engine, so many things I done to it, it's hard to remember. And will the air bypass cause it to be sluggish powerless

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If it's stuck open for some reason.