engine lag

[JohnnyP]

I have a 1976 280z. The car fires up right away, but if I give it some gas (within the first few seconds of the car being on) it makes a sort of sputtering noise, like the car is about to die. And when I put it in gear and give it some gas, the car doesn't respond like it should. I guess the easiest way to describe it is it feels like when I press on the accelerator a good amount, the car doesn't go as fast as it should, the car doesn't really get up to speed. Im not sure where exactly to start with problem. Dirty fuel injectors? Bad fuel pump? Clogged fuel lines? I just put a bottle of fuel injector cleaner in the tank this afternoon, and ran it for a while. Hoping to see some result there. If anyone has had a similar experience with a problem like this, your advice would be very appreciated. Just trying to get this Z back on the road. Thanks alot everyone

John

[S30Driver]

If the car was sitting a long time, the fuel system will need a good going thru.

A good place to start would be a compression test. Check all vacuum lines & boots for leaks. Clean all efi electrical connections under the hood (thease FI cars are very sensitive to voltage drops & sensor feedback to the ecu). Check timing & advance is working in distributor. Verify fuel pressure & how clean gas is going into the filter (disconnect line & let it pump some gas into a suitable container.

How many miles on the motor?

Post the results & people here can help you narrow down the problem.

[beandip]

I have a 1976 280z. The car fires up right away, but if I give it some gas (within the first few seconds of the car being on) it makes a sort of sputtering noise, like the car is about to die. And when I put it in gear and give it some gas, the car doesn't respond like it should. I guess the easiest way to describe it is it feels like when I press on the accelerator a good amount, the car doesn't go as fast as it should, the car doesn't really get up to speed. Im not sure where exactly to start with problem. Dirty fuel injectors? Bad fuel pump? Clogged fuel lines? I just put a bottle of fuel injector cleaner in the tank this afternoon, and ran it for a while. Hoping to see some result there. If anyone has had a similar experience with a problem like this, your advice would be very appreciated. Just trying to get this Z back on the road. Thanks alot everyone

John

JP, Are you finding this problem at first start up on a cold engine or one that is at driving temp? If the latter is the case, try this. Remove the Dist cap, disconnect the vacuum hose that runs from the vacuum advance on the side of the Dist, and suck on the hose while looking into the top of the Dist. You should see the advance plate move. if no movement the vacuum advance is bad. If you do see it move put your tongue over the end of the hose to hold vacuum if it leaks down, again a bad vacuum advance. If the part is bad it is a simple repair. A bad vacuum advance pot will cause a stumble coming off idle and when you apply throttle. It's worth a look. Check the hose for cracks also.

Gary

[JohnnyP]

Compression Test Results:

Cyl#1: 155

Cyl#2: 160

Cyl#3: 155

Cyl#4: 160

Cyl#5: 160

Cyl#6: 155

1976 280z FSM compression range: Compression pressure kg/cm2 (psi)/at rpm: 11.5 - 12.5 (164-178)

And beandip, I followed your recommended steps, and when I sucked through the vacuum hose that runs from the vacuum advance on the Dist, and no movement by the advance plate. So That shows that the vacuum advance is bad. Hopefully the only cause of the problem. My guess is the low compression is due to the bad advance plate. I'll be going through The EFI system troubleshoot for "lack of power" tomorrow afternoon. Thanks a ton you guys are awesome!

John

Edited June 18, 2010 by JohnnyP

[Reverend]

I have similar problem! I havent tested the compression but tried to suck that pipe and also nothing moved.

[hotroder]

I would watch your coolant level. I had the same problem with my 76. Very slowly it was using coolant, later i found the head was cracked.

You should probably be able to see this by looking at the spark plugs one of them might be cleaner than the others. #3 cyl was where it was cracked on mine.

but it ran like that for 2 1/2 years before it totally failed.

it ran great when warm.

[JohnnyP]

Does anybody know where I could find a vacuum advance for a 1976 280z? Tried thezstore.com but they dont have it.

[Z Tyler Z]

Compression Test Results:

Cyl#1: 155

Cyl#2: 160

Cyl#3: 155

Cyl#4: 160

Cyl#5: 160

Cyl#6: 155

1976 280z FSM compression range: Compression pressure kg/cm2 (psi)/at rpm: 11.5 - 12.5 (164-178)

And beandip, I followed your recommended steps, and when I sucked through the vacuum hose that runs from the vacuum advance on the Dist, and no movement by the advance plate. So That shows that the vacuum advance is bad. Hopefully the only cause of the problem. My guess is the low compression is due to the bad advance plate. I'll be going through The EFI system troubleshoot for "lack of power" tomorrow afternoon. Thanks a ton you guys are awesome!

John

I have a similar problem as you do, I'm looking forward to hearing what you find when going through the EFI troubleshooting. How your gas mileage been since this was happening?

Edit: Rock Auto has them for a little over $50.

At checkout when it says how did you hear about us type "34251932812537" without the quotes and get 5% off. Small but it can help with shipping.

Edited June 19, 2010 by Z Tyler Z

[Reverend]

Keep us updated on your quest of defeating engine lag! Does Rock Auto have vacuum advance for 72?

[JohnnyP]

I went through the FSM (1976 280z) and went to the Fuel System section and found EFI troubleshooting. I conducted the tests for "lack of power" did the tests, 1-(1), (2), (3), (4), (6), (8) & 2-(1), (2), (3) and everything checked out ok, just as it should. which is good to know…. S30Driver asked earlier, there are 108,713 miles on the motor.

Also, I removed the vacuum advance to test it. I pushed in the plunger (part that screws to the advance plate), plugged the nipple that the hose connect to, and the plunger didn't pop out. I released my thumb from the nipple and than it popped out. Does this mean that the vacuum advance is not broken? And maybe it is the rubber hosing that connects to the vacuum advance? Could that have been why the test I did (suggested by beandip) it led me to believe the vacuum advance was broken?

I think I've narrowed the problem to the rubber hose that connect to the vacuum advance. If thats leaking than it would explain the vacuum advance coming off as faulty. Let me know what you guys think.

Thanks again all

John

[Powerglide]

A malfunctioning vacuum advance will not cause the drivability problem your car is experiencing. A malfunctioning vacuum advance will give poor fuel economy.

You probably have an air leak somewhere in the system.

[JohnnyP]

Problem turned out to be bad hosing. Taped up where I thought the leaks were coming from and the car runs noticeably better!