Random Engine/Transmission Issue

[Anderson]

I was driving out today (I did about a 300-mile round-trip up to Charlottesville and back, largely to exchange some food one friend had made for some fresh fruits and veggies from another).  As I was approaching Richmond (on my way out), I randomly seemed to lose power: I started decelerating (despite pressing down further on the accelerator to try and restore my speed); fortunately there was almost no traffic on the highway, so I was able to get over from the center lane to the shoulder in an orderly manner.  I put the car in park, turned the engine off...and then on a lark, I restarted the engine and everything fired up normally.  The rest of the trip was functionally without incident.

I can't even really begin to guess what happened, except that perhaps the car somehow got bumped into neutral.  The engine didn't turn off (I still had power, radio, etc. during the slowdown) but it was like I was coasting.  Again, I completed the remaining 225 miles of the trip without further incident.

[The Tassie Devil(le)]

I had a similar problem and it turned out to be that the internals of the Muffler rusted out, and a piece flipped up and blocked the tail pipe, thus stopping the engine, but when slowing down, the piece dropped down, allowing full flow, till it happened again.

The Muffler in question had a double skin, and looked okay on the outside, but the loose piece was found when it was opened up.

Bruce.

[chrisntam]

What car were you driving?

[Anderson]

What car were you driving?

...this is what happens when I post while tired ;-)

My 1970 Eldorado.

[TJ Hopland]

I like Bruce's theory.  A major exhaust restriction will leave you with a smooth running engine that won't make any power. 

I would also want to keep an eye on the transmission and fluid.  You could be low or maybe there is something odd going on like the filter has come loose so its letting air in when the pan level gets low due to most of the fluid being elsewhere in the transmission.     

[klinebau]

Sounds a lot like carburetor icing.

[Scot Minesinger]

I have not suffered this problem, but have suffered partially blocked exhaust due to internal failure of what looked to be good (still sea the galvanized steel in silver, minimal exterior rust) resonator.  The other symptom of a blocked exhaust will be overheating at higher speed.  You don't have a temperature gauge but you can add one temporarily if needed.  The other issue could be the condenser under dist cap if has not been converted to electronic ignition.

[Anderson]

Sounds a lot like carburetor icing.

Could you elaborate upon this?  The weather was warm, so something "icing" seems counter-intuitive to me.

[35-709]

Basically --- warm, moist air sucked into the carburetor at a high velocity gets super-cooled rapidly.  The colder air cannot hold the moisture, the moisture drops out onto the carb. surface (also cooled) and forms ice on the super-cooled carb. surface.  Neophyte pilots flying carbureted (sp?) engines are instructed in this phenomenon very early on in their flight training and how to prevent it with the application of "carburetor heat".  Automobile engine carburetors are set up differently and carb icing is a very rare occurrence.

[Jeff Rosansky CLC #28373]

Could you elaborate upon this?  The weather was warm, so something "icing" seems counter-intuitive to me.

It is real. As the pressure is lower in the carb the air can cool 50-60 or so degrees. I have had carb ice in the mid 80's on a humid day in the plane. However airplanes typically have the carb down low. It isn't that prevalent in a car because the carb is on top. If on say a real humid 70 degree day, you start it for just a few seconds and shut it off  you can see the condensation form on the outside.  What you can't see is ice starting to block the venturies. Kinda neat to see but hard to catch. You can try to see the temp difference with a temp gun.
Jeff

[klinebau]

Could you elaborate upon this?  The weather was warm, so something "icing" seems counter-intuitive to me.

I think icing is possible particularly if the exhaust ports to the carburetor have been blocked off.  Icing can happen when the temp is in the 40s and 50s and there is high humidity.  What happens is the venturies get restricted with ice and cause the engine to run rich.  The engine shuts off and you pull over to the side of the road.  With no air flowing through the venturies, the residual engine heat melts the ice.  You then attempt to restart the car and it appears that nothing is wrong.

This is just one other possibility to consider.

[5390john]

Might want to consider the ignition coil. I have seen several cases where an engine would be running just fine and then stop for no reason. The usual suspect is the fuel system, either vapor lock, flooding, or icing up. Turned out the ignition coil was the culprit, because when a worn coil gets hot it may cease to function properly. When the engine stops, everything cools down and the coil starts to function properly again.
Found this out the hard way years ago, when I mistakenly replaced the coil on my boat with a non-marine rated one. Had this problem repeatedly and could not figure it out. Turns out the engine compartment on a boat gets a lot hotter than in a car, so the coil would temporarily fail. I replaced the coil in the boat with a marine rated one and the problem vanished. The difference between a marine coil and an auto coil is the heat that the marine one can handle.
Hope this might help.
John Adams

[z3skybolt]

For what it is worth, and since aircraft have been mentioned here I guess that it is safe to mention the 1982 Grand Marquis that I inherited.  The carb. would ice up often under the above described condition.  I had driven cars with carbs. for 40 years prior and never before or since had such  an experience.

Rare? Yes. But if something can happen it will.

Bob R.

[Anderson]

The carburetor problem doesn't *quite* seem to fit since the engine was running.  I'm going to take the presumption of an "exhaust gremlin" since (1) my pull-over lasted like a minute, if that; and (2) it didn't repeat again in the 10-15 minutes before I stopped at a gas station or again during the drive.  But even if it's a carb issue, it sounds like it's a rather rare hiccup...but I'll raise it with a mechanic here all the same.

[Anderson]

So, the car's going into the shop next week (Tuesday, to be specific).  I can add a sense of the engine not quite running right to my list of issues...at highway speed (60 or so) she seems to be "working" a bit more than normal and I have an odd feeling of her running a little hot (the air temperature seems to be warming up faster than it was a week ago...remember, I just have a blower...and I don't think it is "just" a change in the weather).  The sound from the motor has a bit more of a "whirr" than a "rumble" (versus what I was hearing until a few days ago).  So something is definitely rotten in the state of Denmark.

I'm open to the possibility that a partial culprit on this is an overly-light oil being used when I got a change back in December (I want to say that 5W30 was put in).  I'm approaching 3000 miles, so I'd be gunning for an oil change in the next few weeks regardless.  But something still feels a bit "off" and it isn't just the ineffable sense that I'm having to put my foot down a bit harder.

[Gene Beaird]

Like Mr. Adams, I'd make sure the fuel system is up to snuff.  Had an old RX7 that had rust issues in the gas tank.  Small bits would flake off internally during use, and those flakes would get caught on the fuel filter pre-screen.  I say 'flakes', but am refering to really small flecks of rust, big enough to get caught in the pre-screen in line right at the fulter inlet. 

The symptom of this clogging was the car would gradually loose power at speed.  Performance would get worse if I tried to accelerate.  I could nurse the car home, but sometimes my speed on the highway would slow to as low as about 45 MPH.  You can imagine the folks behind me on the tollway!!   

The problem was temporarily-fixed by pulling the inlet hose to the fuel filter, pulling that screen and blowing it out with some carb cleaner.  The permanent fix would be a coated or replaced gas tank, but we sold the car before getting to that point. 

So if you haven't replaced the fuel filter in a while, that might be a thing to consider.  Also, if the gas is old, you may want to consider replacing it.  The compounds in gasoline that provide the power when burned in the engine can 'boil off' with time, making the gasoline less and less powerful.  Depending on where you live, most commercially-available gasoline contains alcohol which is hydrophyllic, so it will absorb a lot of water over time.  It can pull the moisture out of the air that gets cycled into the gas tank as the tank 'breathes' with the daily change in ambient temperature.  Performance will suffer.  Old gas can burn, and real old gas can allow you to start the engine, but there will be no power when you put the car into gear and attempt to accelerate from a stop. 

The coil is another viable consideration.  You could be getting to a point that the coil is just starting to fail. 

[Anderson]

I can eliminate the chance of "old fuel".  The car's been driven almost daily, and I've taken the tank down respectably close to empty on a few occasions (I've had a few fuel-ups over 20 gallons) and put about 3000 miles on the car since December.  The tank went down to nearly fumes earlier this week.  The car is driven on about 90-95% of days (between 10 miles on the low end and 250 on the extreme high end, but usually in the 20-50 range).

With that being said, the fuel system angle (gas tank or otherwise) is something I'll look into, especially since (on speculation) the fuel system issues might be causing the engine issue I mentioned (and since the latest bout of "acting up" came on the heels of an aggressive acceleration).