Help! White smoke from air cleaner!

[Antz81]

Having just fixed some fault codes with the ecm (13,23,34), the vette was running much better. Was a bit harder to start when cold but easier to start when warm. Was also idling fast due to better a/f mixture. OK, that was an easy fix, just adjusted the idle speed screw once warmed up. next for the cold starting problem, as the fast idle speed was non-existent figured this would be a good place to start. so adjusted this up to the correct speed, and watched while she warmed up. I began to notice some white smoke coming from the rear of the engine bay, and immediately shut off the engine. The engine tried to stay running for a little while but died after a few more seconds and clouds of white smoke came out of the air cleaner (intake ducts not currently fitted).
My first thought was white smoke = coolant, so possibly a head gasket. But other than the smoke and wanting to run on everything seems normal.
Wanted to check what she was sounding like after this (to listen for any odd noises mostly) let her cool down again and restarted from cold. This went much better (fired first time without any issues) and sounded completely normal but still the same problem presents itself. Checked for any ecm codes but got only the normal 12.

Am i on the right track with the head gasket? any other ideas on what it could be?

 

[bill81vette]

If you think its a head gasket,do a pressure test on the cooling system.
are you loosing coolant???

 

[Antz81]

If you think its a head gasket,do a pressure test on the cooling system.
are you loosing coolant???

I don't seem to be loosing any coolant.
Not so sure it is the gasket as everything else is normal, but i guess a pressure test wouldn't hurt.

 

[Peer81]

Was the engine fully warmed up?
I get it that coolant can cause white smoke from exhaust or oil in coolant by cracked head or back headgasket but white smoke at rear of engine?

Could it be a bad exhaust gasket at the cilinderhead? When you have some white smoke out of the carb after the engine has run a few sec in its own is a different thing.

Greetings Peter

 

[Antz81]

Hi Peter,
Engine was still warming up, coolant temp gauge was just stating to move away from 100°F.
The other thing that makes me think it may not be a head gasket is the smoke at the back was on a different side each time.

 

[Vettehead Mikey]

A bad head gasket rarely/never allows an external leak of coolant. It usually enters the combustion chamber and reappears in the exhaust pipes as steam. Is it possible that you spilled some engine oil on the exhaust?

 

[Antz81]

A bad head gasket rarely/never allows an external leak of coolant. It usually enters the combustion chamber and reappears in the exhaust pipes as steam. Is it possible that you spilled some engine oil on the exhaust?

Wasn't doing anything with the oil, so i wouldn't think that is it. Unless there is a leak onto the exhaust.

 

[Antz81]

Just had another thought, could some of the vac hoses have been put on in the wrong places cause this? haven't given them a good look but do still think some are in the wrong places including the ones for the pcv.

 

[Jon S]

Having just fixed some fault codes with the ecm (13,23,34), the vette was running much better. Was a bit harder to start when cold but easier to start when warm. Was also idling fast due to better a/f mixture. OK, that was an easy fix, just adjusted the idle speed screw once warmed up. next for the cold starting problem, as the fast idle speed was non-existent figured this would be a good place to start. so adjusted this up to the correct speed, and watched while she warmed up. I began to notice some white smoke coming from the rear of the engine bay, and immediately shut off the engine. The engine tried to stay running for a little while but died after a few more seconds and clouds of white smoke came out of the air cleaner (intake ducts not currently fitted).
My first thought was white smoke = coolant, so possibly a head gasket. But other than the smoke and wanting to run on everything seems normal.
Wanted to check what she was sounding like after this (to listen for any odd noises mostly) let her cool down again and restarted from cold. This went much better (fired first time without any issues) and sounded completely normal but still the same problem presents itself. Checked for any ecm codes but got only the normal 12.

Am i on the right track with the head gasket? any other ideas on what it could be?

A few things seem strange. If your car is stock with ECM and OBD system, that controls the idle speed, not the screw you adjusted. The ECM will see you sped up the idle and lower it. As to the engine running after you turned it off, sounds like your timing is advanced too much. Again, the ECM should be controlling this beyond base set up. I too doubt it's coolant.

Jon

 

[Antz81]

Problems fixed

Swapped a couple of vacuum hoses so they were going to the right places, and replaced to missing one from the PCV valve to the manifold. (Bubba had obviously removed this for some stupid reason) That stopped the white smoke from the air cleaner, the run on problem and reduced the smoke from behind the engine. Also changed the oil and filter.
Was the able to track the remaining white smoke to an exhaust leak where i had the bung for the oxygen sensor installed. the smoke was white as one cylinder was missing due to a damage lead for the spark plug.

 

[Wajulia]

A few things seem strange. If your car is stock with ECM and OBD system, that controls the idle speed, not the screw you adjusted. The ECM will see you sped up the idle and lower it. As to the engine running after you turned it off, sounds like your timing is advanced too much. Again, the ECM should be controlling this beyond base set up. I too doubt it's coolant.

Jon

As far as I know, the 81 ECM only controls the idle mixture. NOT the idle speed. That is still controlled by the idle speed screw

 

[Peer81]

Correct. Idle speed is still controlled by a screw. Later model monte carlos and caprise have isc.

Greetings Peter