Exhaust nut missing/ running like crap 1986 vert

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Jul 16, 2021 | 02:53 PM

3D-Aircrew

Thread Starter

Melting Slicks

Joined: Nov 2007

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From: Gainesville FL

Exhaust nut missing/ running like crap 1986 vert

I found that one of the 3 nuts holding the driver's side exhaust pipe fell off. It appears to have the threads rusted off and all that is sticking out is the thinner part of the stud that they have on it to make putting the nut on easier. A new nut won't catch a thread. It doesn't appear to be leaking exhaust from the area but my car has been running like crap.
Symptoms:

Car won't idle until it reaches exactly 119 degrees on the dash.
It's been eating spark plugs which turn black ... this last set has less than 2000 miles on them and I'm already missing on one cylinder.
mileage is only 13.2 on the guage in the city when it used to be ~16 or better. Same exact route everyday.
Occasional code 44 ... every ~ 10 drives.

Thoughts?
Thanks

Jul 16, 2021 | 04:23 PM

s carter

Melting Slicks

Joined: May 2014

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From: New Port Richey FL

Have you ever put an 02 sensor in, it can cause the black plugs poor idle and they Do Ware out and inaccurate.

The exhaust stud 10x150

Jul 16, 2021 | 04:28 PM

3D-Aircrew

Thread Starter

Melting Slicks

Joined: Nov 2007

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From: Gainesville FL

Quote:

Originally Posted by s carter

Have you ever put an 02 sensor in, it can cause the black plugs poor idle and they Do Ware out and inaccurate.

The exhaust stud 10x150

I've done that maybe 10K miles ago but I drive only 3K a year. That's a good point. I'll replace the plugs and fix the stud and see if that makes a difference then I'll check out the O2 sensor.
Thanks!

Jul 16, 2021 | 11:14 PM

jv9999

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From: Lunenburg MA

Are the fuel injectors original? Does the pressure hold when you shut the engine off? Does your oil appear thin or smell like gas?

Jul 20, 2021 | 10:31 AM

3D-Aircrew

Thread Starter

Melting Slicks

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From: Gainesville FL

Quote:

Originally Posted by jv9999

Are the fuel injectors original? Does the pressure hold when you shut the engine off? Does your oil appear thin or smell like gas?

Injector are original and the pressure hold for ~1/2 hour before it bleeds down. No gas in the oil ... I had that happen in the past whe the fuel pressure regulator diaphragm went bad. This is what my plugs look like:

The plugs are lined up as they came out of the engine and the top of the picture is the front of the car.

Jul 20, 2021 | 12:03 PM

3D-Aircrew

Thread Starter

Melting Slicks

Joined: Nov 2007

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From: Gainesville FL

Having a hell of a time getting the messed up exhaust stud out. It is the drivers side where it connects the stock header to the Y-pipe. There is no room to get a pair of vice grips on the stud but I can reach it with a bent nose set of log need nose plyers. I'm having no luck with that thing. Most YT videos show people welding a nut on the exposed part of the stud and using a wrench. I don't have a welder and I don't think there's room anyway. Am I going to have to pull the header? I hope not.

Jul 20, 2021 | 12:43 PM

coupeguy2001

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From: Phoenix AZ

2021 C4 of the Year - Modified Finalist

You have to pull the header.

On left side,
disconnect battery, remove alternator, exh bolts, smog pump hose. It comes off easy sliding it forward and up.
if u already have the plugs out, great.

Jul 20, 2021 | 10:07 PM

coupeguy2001

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From: Phoenix AZ

2021 C4 of the Year - Modified Finalist

Plugs

If you look at # 3plug, it is either not firing or your #3 injector quit working.
i just had an injector quit in my 86, and it had a plug that looked like your #3.
i had swapped caps, coils, wire, and plug.
I had previously cut the cold start injector connector off, and capped the wires.
i used that connector with a 9 volt transistor battery to check the injectors, and on mine, it was #2.
it was the only one not clicking.
with a volt ohm meter, i checked ohms, and zero ohms.
i changed that injector, and runs good.
as for all the rest of your plugs being sooty, i would check the oxygen sensor, but i think either your fuel pressure is too high, or you need to take the air filter off and see if a plastic bag or something is obstructing your intake air.

Last edited by coupeguy2001; Aug 19, 2021 at 06:05 PM.