1989 Dodge B250 van, 318 cu.in. auto.
I have noticed a big drop in power in the past few months, but it all
came to a head this past week. Here's the scenerio: Driving down
the Interstate, cruise on, about 65 mph, when the engine suddenly gave
a whoosh sound, lost power, started missing, and black smoke pouring
out the exhaust. I managed to limp off at the next exit at about 30
miles per hour, found a garage and get it looked at. The engine
analyser showed 'bad O2 sensor', so had it replaced. The mechanic at
the time mentioned if this didn't fix it then maybe the cat. converter
was bad, as small dust and particles fell out when he removed the O2
sensor. I continued down the road, everything fine. Next trip out,
the same thing, the whoosh sound, missing, smoke, etc. This time, I
limped into a garage and explained the history of the problem and
asked if there was any way the cat. converter could be cut out, and a
straight pipe put in its place. This was done to temp. get me home,
as they had no cat. converters or ability to get one. The smog line
from the engine was also cut, and tack wleded to the side of the new
straight pipe. Anyway, the cat. converter was in bad shape, once
removed. The 'pack' has been 'worn' away at the inlet end, rounded
down, lots of dust and small particles in the shell of the thing, plus
the 'pack' had come loose and was floating around in there. Started
the engine, lots of black smoke and particles came out, then cleared
up after about 5 miles driving. The change in the power and engine
'feel' was amazing. Much more peppy, etc. Also, the last tank of gas
that I burned, filled up just after the cat. removal, got me 9.2 mpg,
instead of the normal 15.3 that I had been getting. All in all, the
engine runs like a new one again. After I got home, I replaced the
muffler, it was mushroomed and full of the same dust and particles. I
recovered even more smooth running and power.
Now, my concerns and questions:
This engine was obviously, to me, suffering from several months of
restricted exhaust flow, back pressure and the resulting buildup of
deposits inside the engine. The only difference I can find now is the
valve chatter is somewhat louder when the engine is under a good load,
climbing a hill, etc. From the drivers seat, I can't hear any normal
idling chatter, but with the doghouse off, it is really noisy at idle,
with some valve chatter. I plan to change the plugs, check the timing
and distributor. I don't plan to put the cat. converter back, unless
it requires it for the engine working properly.
What is the likely long term result of running this engine for say 500
miles in this condition of restricted exhaust outlet?
What is the chances that there is a lot of deposit buildup inside it?
What is the best way to clean these deposits out, if they are there?
What about the chatter under heavy load? Can not having the cat.
converter in the exhaust system have changed the engine to the extent
that I need a gas booster or to go to a higher octane level gas?
Any help or thoughts will be appreciated.