Fox Bad Engine Knock

[Tim83]

My 1989 GT just started making this dreadful sound today. I was pulling away from a stop light in 1st gear at about 10mph when happened. I had it towed back to my house. I've blown only one engine in my life and it was a 4 cylinder. This does sound similar to that but I cannot be certain. It has engine work done as a previous owner built it as a street/track car and could have beat it to hell for all I know.

You can skip to the 30 second mark of the video for the start up and sound. Any thought you folks have would be appreciated.


View: https://youtu.be/w_4GShd3ooo

 

[General karthief]

Can't till from the vid. Could be anything from a stuck valve to a wrist pin. Does it miss? Yank a valve cover off on the fending side and see if you got a spring broke/valve stuck open. If not your likely pull'n it out to investigate.

 

[RangerJoe]

That doesn't sound like a engine knock to me. sounds like something has come loose on the accessory drive or flywheel end and is hitting.

Joe

 

[General karthief]

That doesn't sound like a engine knock to me. sounds like something has come loose on the accessory drive or flywheel end and is hitting.

Joe

What he said, I always figuare the person posting has at least checked the obvious, that's what's nice about people here, you can post 'my car won't start because someone stole my battery what do I do' and they won't bash you.
Motor noise can drive you bonkers.
These imoji things are cool. That one is so me!

 

[Tim83]

I'm working on trying to figure out what is causing this noise today and I noticed that one of the bolts in the exhaust header is very loose. It's the rearmost bolt connecting the header to the mid pipe. There is a nut on the underside that is still threaded into the bolt but there is plenty of thread showing. Tightening from the top is difficult as I can't get a 3/4 socket around it because the header is so close. I'm going to upload a picture. Could this horrific sound be cause by the header being separated from the mid pipe?

 

[stykthyn]

I'm working on trying to figure out what is causing this noise today and I noticed that one of the bolts in the exhaust header is very loose. It's the rearmost bolt connecting the header to the mid pipe. There is a nut on the underside that is still threaded into the bolt but there is plenty of thread showing. Tightening from the top is difficult as I can't get a 3/4 socket around it because the header is so close. I'm going to upload a picture. Could this horrific sound be cause by the header being separated from the mid pipe?

Doubtful.

 

[CarMichael Angelo]

I'm saying you're screw-u-lated. Definitely NOT a something loose in the flywheel area as the engine runs like holy hell. If that was a bolt that's say sticking out of the back of the flywheel or something, it would still be running, just on a mission to shear off what ever was hanging out.

As bad as it runs, I wouldn't be surprised if there wasn't a rod swinging around banging on junk in the pan.

But I'm an alarmist,.....I always look at worst case scenarios.

 

[stykthyn]

Did you check the balancer like suggested in your other post? If it spun or even backed off a bit it wouldn't be hard to snap your crank and that would have your rods waving like a wacky waving tube guy.

 

[Boosted92LX]

Go find the largest screwdriver you can find. This is the mechanic's stethoscope. Poke it around on the engine while putting your ear to the butt of the screwdriver handle. This will without a doubt help you find the area the noise is coming from. It won't tell you exactly, but when you get close you'll know.

 

[Tim83]

I'm saying you're screw-u-lated. Definitely NOT a something loose in the flywheel area as the engine runs like holy hell. If that was a bolt that's say sticking out of the back of the flywheel or something, it would still be running, just on a mission to shear off what ever was hanging out.

As bad as it runs, I wouldn't be surprised if there wasn't a rod swinging around banging on junk in the pan.

But I'm an alarmist,.....I always look at worst case scenarios.

That was my initial fear. From the help that folks have provided I'm less convinced I blew the engine but still convinced there is a significant problem.

 

[Tim83]

Did you check the balancer like suggested in your other post? If it spun or even backed off a bit it wouldn't be hard to snap your crank and that would have your rods waving like a wacky waving tube guy.

The balancer does not appear to be loose. The belt seems to run smoothly and I do not see any wobbling or extra vibration. What specifically would I be looking for? Or how could I check to see if it's not working properly?

 

[mikestang63]

pull the spark plug wire off each spark plug 1 at a time and ground it.. See if the engine runs worse or the same each time.. That may help you isolate where the problem is.

 

[Tim83]

Go find the largest screwdriver you can find. This is the mechanic's stethoscope. Poke it around on the engine while putting your ear to the butt of the screwdriver handle. This will without a doubt help you find the area the noise is coming from. It won't tell you exactly, but when you get close you'll know.

Someone suggested I pull each spark plug wire individually and start to car to see if it's a specific cylinder knocking around. I've been hesitant to start it up over and over for fear of making things worse. It's also been suggested that I pull the valve covers to look at the lifters but I did not have enough time to do that today.

 

[mikestang63]

sorry to say this but if you busted a rod or other major failure, it's already done man. I'm talking about running it for a few seconds on each cylinder not a minute

 

[Tim83]

pull the spark plug wire off each spark plug 1 at a time and ground it.. See if the engine runs worse or the same each time.. That may help you isolate where the problem is.

When I said someone suggested I pull the wires I did not mean you. You just happened to respond with that right before I posted. I'm going to try this tomorrow and provide an update.

 

[Boosted92LX]

I'm saying you're screw-u-lated. Definitely NOT a something loose in the flywheel area as the engine runs like holy hell. If that was a bolt that's say sticking out of the back of the flywheel or something, it would still be running, just on a mission to shear off what ever was hanging out.

As bad as it runs, I wouldn't be surprised if there wasn't a rod swinging around banging on junk in the pan.

But I'm an alarmist,.....I always look at worst case scenarios.

Allow me to submit that I just helped my son do a clutch, pp and flywheel in my boy's car. The flywheel was from rock auto, and the balance was incorrect, even though the box it came in said 50oz... it was wrong. That car ran like POOP. Low on power, shook it's ass off, died while idling. All because of a bad flywheel. Swapped it out, ran beautifully. If this fella's flywheel is loose it could absolutely run as bad as it appears to, IMHO.

 

[FoxMustangLvr]

There is obviously something wrong and if were me I would NOT start it up again. Remove valve covers and see what you see. If nothing then check clutch/flywheel, etc. If you must turn it over at least do it with a socket wrench by hand on the pulley and you'll be able to hear better with everything being much quieter.

 

[General karthief]

You got a lot of good advice on here, you already started at the front of the engine now just work your way back, the screw driver used like a listening device is good, I use a modified stethoscope but a long skinny funnel works too. If its valve train you'll here it up top, rods down lower on the block, clutch and flywheel in back of motor.
Don't worry too much about running the engine just don't rev it up, it will only take a couple minutes to tell where it come'n from. JMO

 

[General karthief]

There is obviously something wrong and if were me I would NOT start it up again. Remove valve covers and see what you see. If nothing then check clutch/flywheel, etc. If you must turn it over at least do it with a socket wrench by hand on the pulley and you'll be able to hear better with everything being much quieter.

Thats a good idea too.
Now get to work and let us know, we are waiting.

 

[JD1964]

Sure sounds like a rod knock to me. You might be able to figure which cylinder but removing the plug wires at the dist one at a time. If it quiets down noticeably on a particular cylinder, that would be the one. A really bad knock might make some noise either way. But if it quiets down with a particular plug wire off, it almost certainly would confirm a rod knock. If you are running for short periods at idle speed I think the engine will stay together.

How long have you owned this car? Any oil consumption issues?