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Discussion Starter #1
i am looking for help on where to start with my Z. It is an 86 turbo, with about 85,000 miles. Lately it has been hard to start. taking a few tries before it will start. I had it out yesterday for a drive and it was missing and hesitating very badly under normal driving conditions, and would work better with higher revs. i thought that I might not make it home! I noticed it was worse after the car warmed up a little. I also noticed while stopped at traffic lights, the car would shake while sitting still. Any thoughts on where to start, and what the problem might be, would be greatly appreciated.
 

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How long has it been since it ran well? I wonder, is this one thing or multiple things.


Things to check:
vacuum leaks - these cause a lot of low RPM problems
spark - Are all the plugs firing reliably?
Fuel injection - Are all the injectors firing? Check the fuel pressure against the FSM
Run the ECU self diagnostic


It is a laundry list. Perhaps someone else can pinpoint something.
 

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Discussion Starter #4
Thanks for your help. I will start checking your suggestions, and update as i go along. To start I changed the fuel filter and changed the coil with a spare I have, both had no effect. It seems the car starts to act badly after it warms up.
 

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Discussion Starter #5
Thanks, The air filter is a cone type, and is definitely in need of a good cleaning. I will clean it and and see if it helps.
 

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Discussion Starter #7
I checked the ECU this evening for codes. There are two, 24 and 31. I believe 24 has to do with the neutral safety switch. And I know that the one in my car is not working. And the second code number 31 as a whole list of possible loads listed. I do know that the rear wiper fuse blew last year. And the only way I knew that was because the digital dash was not working and thanks to online help I looked up the fuse for the rear wiper and replace it and the digital dash start to work again. So other than that there are no other codes.
 

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Discussion Starter #9
vacuum question..or two

I also definitely have a vacuum leak that goes from the cannister through the firewall, and then somewhere up under the dash. I think it is for the AC. That would explain why the AC does not work. The AC was overhauled about 5 years ago, but the compressor does not kick in when i try to use AC. Also, I can hear a hissing type sound that seems to be coming from the fuel pressure regulator, or at least near it. Is that normal?
 

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Your 86 turbo should have a vacuum pump down under the front on the right side. On mine when you turn the key on it will run a few seconds. If there is no leaks it will stop. I find this is a good easy way know if you have a
leak free system.
 

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Turn the air conditioner on/off while you're doing the self-diagnosis. That should clear 31. Shift from neutral to other gears and back to neutral. That should clear 24.
 

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The vacuum line that runs from the engine bay into the cabin is to supply vacuum to all the actuators in the dash. These are what open the various doors for different vents, air mix, cabin/outside air.
 

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I also definitely have a vacuum leak that goes from the cannister through the firewall, and then somewhere up under the dash. I think it is for the AC. That would explain why the AC does not work. The AC was overhauled about 5 years ago, but the compressor does not kick in when i try to use AC. Also, I can hear a hissing type sound that seems to be coming from the fuel pressure regulator, or at least near it. Is that normal?
You should find where the leaking AC vacuum attaches to the intake and cap the intake connection to stop the leak.

The fuel pressure regulator (FPR) should not be making any noise. Detach the vacuum line from the top of the FPR see if you can find the hissing noise source.

The vacuum line attached to the top of the Fuel Pressure Regulator runs over to the Fuel Pressure Solenoid (FPS), drivers side of engine compartment, and then another vacuum line runs from the FPS back to the intake manifold. If there is a leak in any of this, the fuel pressure will be to high and cause the engine to run rich at idle. All of this can be bypassed with a short 6" piece of vacuum line from the FPR to a port on the front of the intake plenum as a test.
 

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Discussion Starter #15
I will check everything you mentioned and find the leak. After changing the fuel filter, distributor cap and rotor, the car worked somewhat better. I changed the plugs yesterday and it solved the missing. The car now works great. Now I need to find the vacuum leak
 
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