Hi all,

here are my symptoms...maybe gasket leak?

rattling at cold start up that goes away in a couple seconds...right as choke kicks in.
popcorn under light throttle - full throttle fine...
stumble under initial take off...half throttle.....( only happens sometimes )
tried to start the car yesterda after driving for about 20 minutes...wouldnt start...unless it was floored first.
While driving , half throttle and full throttle are fine...partial throttle has the popcorn sound.
The car feels strong...transmissiion feels strong.
Having said that...I am getting a bogging after fully warmed up engine...between 2 and Drive ( auto )
almost like it goes into gear too early and the load is on the engine causing popcorn.
It doesnt do this when the car is cold and still warming up.....it doesnt do this when I get on it good.
I had an oxygen sensor warning and replaced that...no more codes.
Ive looked inside the carb and it seems to be pumping good amounts of fuel.
What the heck is going on.
When the car warms up in the morning everyhting is very smooth idle wise....the engine sounds, feels very smooth. ..... and for the most part the idle is smooth always....

Could my computer be bad.?
How do I diagnose an exhaust gasket leak...?
would a gasket leak make a nopise ALL the time?
I dont burn any oil or coolant...exhaust color is normal....only oil loss is from the leaking valve
cover gasket on the passenger side :)

I have a feeling that it isnt anything major.... and that is EXACTLY what is frustrating me.:(

I know this is alot...I just dont know where to start...any ideas?

Thanks
Kevin

 

Just a suggestion... post the year/engine etc in the body of your post... many people (myself included) must turn off pictures etc due to slow dialup connections, and we can't see signatures... just the text of the post. If I could not turn all that funky stuff off, I would not even be here....it would be an impossible situation to deal with.

 

Check your spark plug wires.

Under part throttle the spark advance results in the spark having to jump a larger gap in the distributor cap. That, coupled with having to jump a gap that's burned into one or more wires may be causing misfiring or cross-firing (spark jumping to another wire).

I fought a problem like this many years ago. Spark plug wires do go bad.

-Noel

 

Tom,

its at the bottom of the post...but here goes

1981
stock
Auto Transmission - rebuilt less than a year ago.
L81 Engine :)...no mods
Dynomax Mufflers
tune up less than a year ago...new cap,rotor,plugs
new oygen sensor recently
new fuel pump..problem existed the same before AND after installation.
new water pump...bythe way car is running at around 200 degrees.

Kevin

 

I agree with Noel. It's either sparkplug wires or vacuum advance. If new plug wires don't solve it you can either retard the total timing a little or get an adjustable vacuum advance canister and back it off with that.

 

Kevin... here is all that I see from the original post... the tech stuff that you added does not show up for me in the original post... FYI, Tom


Hi all,

here are my symptoms...maybe gasket leak?

rattling at cold start up that goes away in a couple seconds...right as choke kicks in.
popcorn under light throttle - full throttle fine...
stumble under initial take off...half throttle.....( only happens sometimes )
tried to start the car yesterda after driving for about 20 minutes...wouldnt start...unless it
was floored first.
While driving , half throttle and full throttle are fine...partial throttle has the popcorn sound.
The car feels strong...transmissiion feels strong.
Having said that...I am getting a bogging after fully warmed up engine...between 2 and Drive
( auto )
almost like it goes into gear too early and the load is on the engine causing popcorn.
It doesnt do this when the car is cold and still warming up.....it doesnt do this when I get on
it good.
I had an oxygen sensor warning and replaced that...no more codes.
Ive looked inside the carb and it seems to be pumping good amounts of fuel.
What the heck is going on.
When the car warms up in the morning everyhting is very smooth idle wise....the engine
sounds, feels very smooth. ..... and for the most part the idle is smooth always....

Could my computer be bad.?
How do I diagnose an exhaust gasket leak...?
would a gasket leak make a nopise ALL the time?
I dont burn any oil or coolant...exhaust color is normal....only oil loss is from the leaking valve
cover gasket on the passenger side

I have a feeling that it isnt anything major.... and that is EXACTLY what is frustrating me.

I know this is alot...I just dont know where to start...any ideas?

Thanks
Kevin

FYI- Spark Plug wires will cross fire & mis-fire more under load (full throttle) than they will under a light load. My typical test for bad wires, assuming no access to a scope, is to mist the wires with water and put it in drive, foot on the brake, and throttle it up, in the dark. This is when you will see the most activity (arcing).

The rattle may be the heat riser valve on the passenger side exhaust manifold... vacuum controlled, temp sensor dependent.

The systems on your engine rely on several temp controlled vacuum switches. If they are broke, or if a nipple is cracked where you cannot see it, there will be problems such as yours. Also, look for rotten or cracked vacuum lines.

 

Quote: "It's either sparkplug wires or vacuum advance"

Note that it can't be vacuum advance, since stock '81s do NOT have vacuum advance, because the spark advance is controled by the ECM/computer.

I agree that it's a great suggestion to check all of the temp/vacuum switches and related vacuum hoses which they are attached to. A vacuum leak can result in intermittant problems. Also agree good idea to check/replace spark plug wires.

 

Tom - Thanks - I will try the "misting" idea first and see what I can see.

The plug wires are about 4 years old...maybe they are bad.
I HOPE that is all that it is :)...when I got the tune up last year...it ran great.

Ive already replaced the vacuum canister and alot of the hoses under the hood.
could be something up in there though.
I do notice a little stumble when Im in the garage after coming home and I lower the headlights.
So that is surely an indication of a leak somewhere..maybe the actuators?

Thanks all very much....cross your fingers...:D

So I guess none of this sounds like an exhaust gasket leak , huh.?
Is the heat riser going to affect performance?


Kevin

 

Another guy r cooper had problems similar to yours only his would stall when turn headlight on when idling.Turned out his puter was bad.

 

all smiles -

dont say that ! :)

my computer is just fine, thank you very much ! :D

Kevin

 

I've had similar problems like this and it turned out to be a little water in the gas from condensation in the winter if you don't keep it pretty full. Just a suggestion, good luck

 

I have sen HEI modules good bad like this. Usually as heat gets up to temp in the distributor the units starts for fail by causeing bogging etc...

 

Chuck - I drive the car all year around here...pretty much...so I dont think it would be that. Thanks though

Dave - the module was replaced, I think , about 2 years ago - maybe less.
Worth looking at , I still have the old one...dont think it was bad.

Thanks
Kevin