Will an exhaust leak at the manifold make a car run like complete crap? I have a leak on my 86 turbo, and it was still running fine with the leak until a couple days ago. Now it cuts our and misses in boost. It also cuts out just during normal driving conditions.

Run the codes. I'd suspect you'll get either the Fuel Temp Sensor or the CHTS.

Fix the exhaust leak too, but that shouldn't cause these types of issues.

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1985 300ZX n/a

See my Z project

Ok thanks. How do I run the codes exactly?

EDIT: Nevermind, I found out how to.



Edited 1 time(s). Last edit was 2008:08:17:17:53:26.

Use the FSM. The download is free, use the search engine.



Edited 1 time(s). Last edit was 2008:08:17:17:53:10.

Ok im still confused.

The fsm says to get the car to above 6mph. Am I supposed to read the codes WHILE the car is moving?

Oh and I started looking for the chts and fuel temp sensor, and nobody has either of those things. Where would I find them?

no, the vehicle needs to be driven above 6mph to test the VSS, once that test is done it removes the code from the list of active codes.

But are you getting codes for the FTS and CHTS? Have you tested the CHTS as described in the FSM? Don't waste your time and money replacing parts unless you know they are not working as they should.

I am not getting any codes at all. There is no check engine light on either. I called Fenton Nissan, and they said the z31 does not have a fuel temp sensor, or a chts. So even if I did need those parts, I would be @#$%&.

Fenton is wrong. The 86 turbo does not have a check engine light. You will get code 44 if you have no codes, did you get code 44?

I did not get a code 44. I guess i must have done one of the steps wrong. I'll try it again and get back to you.

The car usually had around 18 (whatever unit) of vacuum on my boost gauge at idle. And on the highway at 70mph, the vacuum is at 12-10. Since the car has been running like crap it usually is at 15 at idle (with 2 bars lit up on my digital cluster instead of the usual 1 bar), and 5-0 going 70. (a/c is off in all scenarios)

Could that be due to a vacuum leak? I have checked for leaks on all the hoses, but maybe one of the intake manifold gaskets os bad? I hear a hissing sound from the middle of the engine that I dont remember hearing before.



Edited 2 time(s). Last edit was 2008:08:24:15:22:14.

a large vacuum leak will give a lower indicated manifold pressure reading. A boost leak test will allow you to see where all the leaks are. boostpro.net

I agree with red most probably a boost leak/vacuum leak. 15 isn't so bad, i had mine at close to -5 on a boost gauge instead of 18-20 once. From a faulty manifold gasket and turbo rubber grommet pipe seal. It still boosted hard but was pretty inefficient on petrol being that high on a boost gauge at idle.

I just learned something new about my car. when it sits overnight, and I drive it in the morning it drives like a bat outta hell holding steady at 12psi. then when it warms up, it starts missing etc. so that leads me to believe it doesn't have a vacuum or boost leak.



Edited 1 time(s). Last edit was 2008:08:26:21:06:54.

On the contrary, that is even more of an indication that you have a leak - the mixture is rich at cooler temperature, so you would be running "less lean" while your car is still warming up.. When it does warm up you are back to running too lean due to your leak.

Hang on wouldn't it run rich as there is less air to help combust?

a vacuum leak means more are than the ECU thinks, since air is being introduced to the intake after the meter. This would make a lean condition.

If its a boost leak, then you'd be correct except when the vehicle isn't producing any positive intake pressure.

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1985 300ZX n/a

See my Z project

OK, I have an update.

I ran the computer for codes, and got a code 44. Ok, so then I took off the upper intake manifold to see if there any traces of an intake leak. The only thing I found that was out of place was a vacuum hose on the bottom of the throttle body was disconnected. The coupling connecting the tb to the turbo pipe was also hard and cracked, so I replaced that. Then I put everything back together and it still runs like it did before. The only difference is there is no hissing sound from the intake, and I have more vacuum at idle.

Next weekend I will TRY to tackle the exhaust manifold gasket, but I dont know if I will get around to it. Thats the only thing left to do thats wrong with the engine to my knowledge. Along with that I am putting in all new intake manifold gaskets just because it will be easier to do now rather than later.