Gearing down with blue smoke and back firing

[Redwing]

Hi all,

Something has shown up since getting the new muffler installed.   I have noticed that after gearing down preparing to turn that (backfiring) putt putts happen.  Then when turned and accelerating again there is a large amount of blue exhaust sometimes with a small backfire.

1.)  The backfire is coming from rear of car.  Did not backfire before muffler addition.  When gearing down, if I rev the engine some, little putt putts happen.

2.)  Don't  know if the gearing down makes it worse.  I think it does.  I had not noticed it before the new muffler, which makes it louder natch.  So noticeable.

3.)  I'll  have to check oil usage, have not done so since it was changed very recently.

4.)  Don't  know if it is the same exhaust no matter which way turning.  I'm  more aware of it, being more visable, when turning right.  I'll pay more attention next time out.

5.)  A year ago RB turned up 100,000 miles.  I can only guess that was her 2nd go around.  I have no way of knowing what her actual mileage is.

6.)  It is a backfire, not just a stumble.

These answers are in response to questions sent to me by Mark.  Please do ask if you need more information.

By the way.  I live in a very small town, and have been told twice now, that there is another red Z  that looks like my RedBird  travelling the streets here.  I'm  on a quest to find it and talk with the owner.  If I do, expect photos of the 2 of them!  That's  exciting!

Thanks for your input, as always it's the greatest.

Jai

[Mark Maras]

 Sounds like RedBird has a doppelganger. Clarify one thing for me. Jai, Is there an engine stumble along with a small backfire or is it a backfire only? Jalex in Panama brought up a similar issue when he changed his exhaust. I'm wondering if the small backfire was always there, just not noticeable because of the previous quiet  exhaust.

[EuroDat]

Hi Jai,

From your description, the first thing that comes to mind is valve stem seals. They are little rubber seals around the valve stems that limit the amount of oil passing through to the valve guide to a minimum. If the become old, they harden and break and allow oil to run down the stem and throught the valve guide to the inlet valve. The inlet valve is mostly under vacuum and causes the blue smoke problem after a period of coasting and the acceleration.

A simple test would be to coast down a hill with no throttle and at the bottom of the hill a short burst of full throttle or hard acceleration. You should see a plume of grey blue smoke. That is a good indication.

Why the test: When coasting, high vacuum pulls in more oil then normal, but a closed throttle doen't give it enough fuel air to burn the oil. When you give it full throttle, the fuel air mixture then burns the oil creating excessive smoke for some seconds.

A compression test will tell you more about the overall condition of the engine.

A bit hard to say if the putt putt sound was there before or not, since the muffler was changed, makes that hard to say with any certainty. And you mention the exhaust sound is more noticable with the new muffler.

The smoke issue could be all some time, but it has now come to your attention due to the sounds from the new muffler.

Goodluck with finding a solution Jai.

Regadds

Chas

[siteunseen]

Does it smoke on the first start up of the day?  That's a sign of leaky valve seals too.

[Redwing]

Just now, Mark Maras said:

 Sounds like RedBird has a doppelganger. Clarify one thing for me. Jai, Is there an engine stumble along with a small backfire or is it a backfire only? Jalex in Panama brought up a similar issue when he changed his exhaust. I'm wondering if the small backfire was always there, just not noticeable because of the previous quiet  exhaust.

Mark,

I don't  know what an engine stumble is.  Would you please describe it for me?  

Also doppleganger... means several different problems?  Sorry, I just do not know these terms.  ?

Jai

[Mark Maras]

 @RedwingMy description of a stumble is a MOMENTARY loss of power. Normally caused by one or more cylinders BRIEFLY misfiring. You can feel it as well as hear it. If it's severe enough under heavy acceleration you'll feel yourself pitch slightly forward and then back. An exhaust backfire has no feel to it. It's just noise.Have you noticed RedBird running worse, my suspicion is the backfire is just that, backfire. The new muffler may take some getting used to. As for the smoke, it probably needs valve guide seals. It's possible the smoke has been there all along and gradually getting worse (normal) but you noticed it when the backfire started. What do you think?

[Redwing]

Just now, EuroDat said:

Just now, EuroDat said:

 

A simple test would be to coast down a hill with no throttle and at the bottom of the hill a short burst of full throttle or hard acceleration. You should see a plume of grey blue smoke. That is a good indication.

Chas,

Question on your comment on the simple test.  After downshifting, and coasting on toward the corner, coasting around it, would that be similar to what you said about the coasting down a hill, then hard acceleration, to see a plume of gray blue smoke...  a good thing?

Thanks, 

Jai

[Redwing]

Just now, siteunseen said:

Does it smoke on the first start up of the day?  That's a sign of leaky valve seals too.

I don't  think so.  Will make sure when I go out again.  Which will be Thurs.  I don't go much when the temps are below 20 plus wind chill in the early morning.

Thanks,

Jai

[Mark Maras]

 When Chas says "coast down the hill" he means, in gear using the engine to slow you down. 

[Redwing]

Just now, Mark Maras said:

 @RedwingMy description of a stumble is a MOMENTARY loss of power. Normally caused by one or more cylinders BRIEFLY misfiring. You can feel it as well as hear it. If it's severe enough under heavy acceleration you'll feel yourself pitch slightly forward and then back. An exhaust backfire has no feel to it. It's just noise.Have you noticed RedBird running worse, my suspicion is the backfire is just that, backfire. The new muffler may take some getting used to. As for the smoke, it probably needs valve guide seals. It's possible the smoke has been there all along and gradually getting worse (normal) but you noticed it when the backfire started. What do you think?

Mark,

No I do not feel any loss of power, and she is running great!    No feel to the backfire.

Yes all could have been brewing, with me not noticing it.   I just started paying attention to the muffler when the new one was put on.   There was almost no sound from the other one, nothing to pay attention to.  

Jai

[Redwing]

Just now, Mark Maras said:

 When Chas says "coast down the hill" he means, in gear using the engine to slow you down. 

Well, that is what I do approaching the corner.  Then heavy acceleration to get going after turning.  Then is when I see the blue - blue/gray smoke.  Which he said a good thing.  Hunh?

[EuroDat]

9 minutes ago, Redwing said:

 

Hi Jai.

Yes, if you have enough revs and no throttle. There should be enough vacuum to pull in oil and not burn it. Then drive further a little harder than normal.

Is it a good sign. The seals are not expensive and people use the ford units with succes. Getting them fitted could be costly or someone close by that is hangy with cars could do it.