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Discussion Starter · #1 ·
This is getting frustrating. My car has a really bad stumbling problem. It's an 83 280zx na. I replaced all vacumn lines. At one point I disconnected and/or plugged charcoal canister,air regulator,bccd,egr,pcv valve.
Things I have replaced
fuel pump,fuel filter,distributor,airflow meter,injectors, pcv valve, spark plugs, wires, coil, head temp sensor, air regulator, air filter, and cleaned all conections.

After changing all these (which most where in need of replacing anyway) the car is still low on power and now since changing the fuel pump shakes violently until the gas is floored. It doesn't always do it. But if it starts to shake I let off the gas and then give it gas again it will run better. Vacumn is strong at idle (around 21 in/hg).
This is getting very frustrating I just want to get in the car and go. I want to feel strong and steady power.
 

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Discussion Starter · #2 ·
RE: Need Help

You could be suffering from Exhaust back pressure. A 1980 ZX I had before did some of the things you described, although not so violently, it would not hurt to have it checked. Or you can check it yourself depending on weather or not the CAT under the car has flanges, or if it is welded. Mine was flanged, I took off my CAT temporaraly, and just left it open to test, and all of a sudden I had TONS of power, the CAT I had was CLOGGED BAD. Not saying this is your problem, but it would not hurt to check. I replaced a lot of the things you described, and all I had in the end was a GREAT running LOW POWER car, until I changed the CAT. Again I did not get all of the symtoms you are describing, but if it is clogged worse than mine was, it certianly could, and a LOT OF Z and ZX cars I have found to have clogged CATS, stealing power. One other thing that can cause bad behavior close to what you describe is the ground wire comming out of the EFI harness, it grounds the EFI system to the Intake Manifold. Check the ground wire(s) ( some have 2 ), and make sure the connections are clean. Let me know what happens, I would like to know. I suppose the EFI Computer could be out of wack, you can usualy pickup one of those fairly cheep at a junk yard.

Scott Milella
 

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Discussion Starter · #3 ·
<b>RE: Need Help</b>

I removed the cat last year. When I put on headers and a 2.5 inch exhaust. My cat had acouple of screens inside but nothing else. I just rebuilt the engine in january, but it did the same thing before as it is doing now.
I've also cleaned those two ground wires before.

thanks
 

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RE: Need Help

I'm no guru, but have you connected a fuel pressure gauge to the system and monitored the pressure during driving? Does the pressure indicate anything when the stumble occurs? After all you have done I feel kinda stupid suggesting this but I didn't see where you had checked during a drive. Drivabilty problems can sometimes only rear their ugly head under actual circumstances. I thought the guy with the cat thing had his finger on the pulse but geez you got a gremlin deluxe!!

Ken
 

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Discussion Starter · #5 ·
RE: Need Help

How's your timing set? Have you checked it lately? Also, A clogged fuel line could be the prob. Like Ken said, get a fuel pressure gauge on it and take it out for a spin. It won't help you much in the driveway. You can build a pressure gauge yourself for less than $20 and run it up to your windshield. Let me know and I can give you a How-To.

Steve G
 

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Discussion Starter · #6 ·
RE: Need Help

I suppose you could also have a problem with the fuel Dampner, causing irregualr fuel pressure, they are farily inexpensive things to replace, but as the other 2 people indicated the fuel pressure check is a great first place to start, since you said the CAT was replaced and the Wires were cleaned. If your fuel pressure is good, and the dampner is working, The CPU? Can not think of anything else that would cause the eratic problems you are describing.

Scott Milella
 

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Discussion Starter · #7 ·
RE: Check connectors

Have all the plugs to the sensors and injectors been cleaned or replaced? This is a notorious source of gremlins.

Steve G
 

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Discussion Starter · #8 ·
<b>RE: Need Help</b>

I just changed the vacumn advance line from under the throttle body to were the bcdd connects to and now I have more power, but I can still feel the stumbling (but not as bad) Maybe the vacumn advance port under the throttle body is screwed up? I will check the gas line under the car tonight. I know when I got it inspected and new tires put on they crushed the frame right under the passenger side maybe they screwed up the gas line. But then again it ran like that before.

thanks
 

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Discussion Starter · #11 ·
<b>RE: Need Help</b>

One thing I did not see listed was an examination of the inlet side of the fuel pump. If the pickup screen or the inlet tube is plugged, it could account for some of what you are seeing. That shaking of the pump seems like a smoking gun somehow...
 

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Discussion Starter · #12 ·
<b>RE: Need Help</b>

I had the fuel tank opened up before and the pickup screen is clean and there is no blocage in the inlet tube.
 
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