Wife wanted a burnout! Now the car is sick ( the cough kind, not the cool kind)!!!

[wsutard]

OK, wife and I were out an about. On the way home she wanted a burnout. No problem, good burnout, about 10 seconds, got up to about 6 grand (tad high but shouldn't be an issue for a 340). Coming down the hill to our house I noticed it was backfiring, a lot. Then as I pull into my driveway I notice that the idle, which is normally at 800, is now struggling to keep 500. Rev up to 1500, no issues, let it come back down to idle, struggles to keep 500 and very rough. I let it sit for about an hour. Started it up, same idle issue.

Where do I start to diagnose what is wrong? I am a beginner when it comes to these vehicles so keep that in mind.

 

[mmissile]

Pushrod, rocker arm?

 

[Dennis H]

Push rod,! take it easy. A 10 second burn to 6k should be done on a regular basis. You're lucky to have an enthusiastic girl like her. Let it cool down overnight and do an inspection. Relax. Get xpert advice on the ground there and here. Fluids. Leaks. Noises.

 

[Lionized]

Don't mean to sound like a prick but aren't you having diff issues?
Burnouts are cool but if you suspect any issues...that could lead to worse issues.

 

[wsutard]

Don't mean to sound like a prick but aren't you having diff issues?
Burnouts are cool but if you suspect any issues...that could lead to worse issues.

What a prick! You are right. But I think my diff issues are that the clutch or cone won't allow slippage. Seems like the perfect setup for a burnout!

Anyway, here is a video. Normal idle is 800. The engine doesn't really want to run between 400 and 1000. Get to 1000 and it seems fine. It will hold the 1000 for a few seconds then start to drop. Gets to 800 and then imidiately drops to 400.



For some reason I found the fast idle screw was way backed off as well. Not sure if this has any relevance.

 

[Lionized]

What a prick! You are right. But I think my diff issues are that the clutch or cone won't allow slippage. Seems like the perfect setup for a burnout!

Anyway, here is a video. Normal idle is 800. The engine doesn't really want to run between 400 and 1000. Get to 1000 and it seems fine. It will hold the 1000 for a few seconds then start to drop. Gets to 800 and then imidiately drops to 400.



For some reason I found the fast idle screw was way backed off as well. Not sure if this has any relevance.

Sounds like possibly (hopefully!) a carb issue. Also, check to ensure you have the distributor clamped down tight!
To be safe pull both rocker covers and inspect.

The high idle screw is your adjustment for cold starts/choke engaged. Nothing to do with this issue.

Check it out in the AM.

 

[jimt1971rr]

I would check timing and if that didn't slip, would pull the mixture screws to make sure both sides are clean. run some carb cleaner through them. It hopefully is something simple.

 

[johnny ga]

check timing and then push rods

 

[Derwud]

Failed Muffler Bearing... They hate burnouts!

 

[GetX'd]

Failed Muffler Bearing... They hate burnouts!

Muffler bearings have nothing to do with carb issues/idle......

 

[Lionized]

Muffler bearings have nothing to do with carb issues/idle......

Are you suuuurrreeee!

 

[Dennis H]

Are you suuuurrreeee!

That's the first place I'd look ;). These cars were made to pound on. The more mine gets exercised, the better it runs.

 

[GetX'd]

Are you suuuurrreeee!

I can guarantee it - but it's a very detailed and complicated physics answer.

 

[Derwud]

I would check the output of the headlights in Kelvin and Lumens, that can tell you alot...

 

[WileE]

Check your vacuum hoses, pcv hose, etc.

 

[moper]

A basic inspection of the ignition wires and plugs. A compression test. Maybe pull the valve covers and inspect the valvetrain... It's probably something stupid like a pushrod or rocker or burnt wire.

 

[wsutard]

How would a simple burnout cause any carb changes?

Failed Muffler Bearing... They hate burnouts!

So I can't find this muffler bearing. I have spent about 30 minutes under the car looking. Even disconnected the mufflers but no bearing. You sure a 69 has one?

Wait, found it!

 

[747mopar]

Burnouts = quick revs, not unusual for problems to prevent themselves after a good burnout. I agree with what's been said, check timing, carb settings, pushrods, etc. Don't get to wound up just do your basic tuning checks and have a peek at the rocker assembly.

 

[Darthomas]

Will it keep idling at the low level or just stall out eventually?
If it loads up and stalls, look for something not letting the needle valve close all the way on the carb.
If it keeps on at a low rough idle, check for bent pushrod, bad rocker arm, maybe broken valve spring.
If you have hydraulic lifters, is the oil pressure now low at idle?
If the lifters don't fill fully, that can cause bad idle, could be from a stuck oil overpressure relief valve stuck partly open in the bore.
I'm thinking bent pushrod except that it wouldn't run OK, then slow down after 10 seconds.

 

[kiwigtx]

OK, wife and I were out an about. On the way home she wanted a burnout. No problem, good burnout, about 10 seconds, got up to about 6 grand (tad high but shouldn't be an issue for a 340). Coming down the hill to our house I noticed it was backfiring, a lot. Then as I pull into my driveway I notice that the idle, which is normally at 800, is now struggling to keep 500. Rev up to 1500, no issues, let it come back down to idle, struggles to keep 500 and very rough. I let it sit for about an hour. Started it up, same idle issue.

Where do I start to diagnose what is wrong? I am a beginner when it comes to these vehicles so keep that in mind.

Maybe you're just doin' it wrong?