Coil problem?

I drive a 1992 Chevy Cavalier with close to 170,000 miles on it.
About a month ago I noticed a decrease in gas mileage and the car
started running rough. When I start it is feels kind of rumbly and
there is a smell of gas. As I start driving it is still rumbly as I
accelerate and I smell the gas when I stop.
Then I get on the highway and my acceleration is decreased as I try to
get up to speed. I finally get up to speed let my foot of a little and
the car rattles/rumbles. If I push the accelerator past a certain point
the car stops rumbling and surges. I let off and the rumbling returns.
If I maintain a constant speed the car seems to settle into an almost
normal mood. (The rumbling isn't as noticeable and the rpms settle
around 2500.) The shifting seems to be a little off during accelration
I let off the gas to shift and sometimes it will downshift again and
surge. The rpms during are riding around 3000+ when I do accelerate.
My dad thinks it is the coil. What do you think?

Respond to either email or here, Thanks!

Lots of Dads automatically diagnose problem like this as a coil
failure, but why not tell us what engine you have in the Cavalier.

There are many things that can cause this sort of symptom,
and you really don't want to start throwing parts at the car. It
gets too expensive.

wrote:
> I drive a 1992 Chevy Cavalier with close to 170,000 miles on it.
> About a month ago I noticed a decrease in gas mileage and the car
> started running rough. When I start it is feels kind of rumbly and
> there is a smell of gas. As I start driving it is still rumbly as I
> accelerate and I smell the gas when I stop.
>
> Then I get on the highway and my acceleration is decreased as I try to
> get up to speed. I finally get up to speed let my foot of a little and
> the car rattles/rumbles. If I push the accelerator past a certain point
> the car stops rumbling and surges. I let off and the rumbling returns.
> If I maintain a constant speed the car seems to settle into an almost
> normal mood. (The rumbling isn't as noticeable and the rpms settle
> around 2500.) The shifting seems to be a little off during accelration
> I let off the gas to shift and sometimes it will downshift again and
> surge. The rpms during are riding around 3000+ when I do accelerate.


> My dad thinks it is the coil. What do you think?

I think you have to diagnose what the real problem is. The
possibilities are a lot more broad than your dad's suspicion.

If fuel isn't igniting in the combustion chamber, there could be
various reasons for it, not limited to problems with the coil or even
ignition. Even if it is a spark problem, it could be a bad plug, spark
plug cable, distributor contact, etc.

Ignition problems don't tend to get better at higher RPM. The coil has
to energize and fire more times per second the faster the engine spins.
But you never know, maybe a bad contact somehow behaves itself under
higher RPM. What was the last mileage at which you changed the
spark-plugs? Have you ever inspected and changed the spark plug cables?

Then there is the possibility isn't not a spark problem. Maybe one of
the pistons isn't compressing the fuel-air mixture. Do a compression
test on every cylinder! Compression problems could be less apparent at
higher RPM simply because the piston is coming up faster. Think about a
bicycle pump for a second. It's basically a leaky cylinder with a
piston, right? If you press the pump very rapidly, there is a lot of
resistance and you can achieve compression in spite of the air leaking
out. In your engine, at 3000 RPM, the compression stroke is happening 3
times as fast as at 1000 RPM, so a slow compression leak won't be as
apparent. Also the compression is something that can change with the
engine being warmed up due to the expansion of metals, in particular
piston rings! Compression can also be lost through valves not closing
properly, etc. Imagine if the exhaust valve doesn't close or sit right,
at least through part of the compression stroke. What will that do?
Blow some fuel-air mixture right into the exhaust.

Could be a fuel injector problem too. Maybe a badly clogged
fuel-injector isn't spraying out a fine mist, but squirting out a
liquid stream. Hmm, hard to explain why the problem gets better at
higher RPM though.

wrote:
> Lots of Dads automatically diagnose problem like this as a coil
> failure, but why not tell us what engine you have in the Cavalier.

It's a big, dirty, greasy engine with lots of wires, hoses, wheels and
belts and things, and it's not running too well. Just ask Dad.

What difference does it make. Those general problems that he described
could happen in the V6 or the straight 4.

> There are many things that can cause this sort of symptom,
> and you really don't want to start throwing parts at the car. It
> gets too expensive.

And, to put that into further perspective, doing a quickie web search,
I see people are buying the 1992 Chevy Cavalier 2-door Z24 convertible
with V6 engine for under 1000 bucks. The four bangers go for next to
nothing.

"Kaz Kylheku" > wrote in message

> What difference does it make. Those general problems that he described
> could happen in the V6 or the straight 4.

What difference indeed. All engines are just the same, huh;>)

But, we agree that he needs to diagnose, not just change out parts.

wrote:
>
> I drive a 1992 Chevy Cavalier with close to 170,000 miles on it.
> About a month ago I noticed a decrease in gas mileage and the car
> started running rough. When I start it is feels kind of rumbly and
> there is a smell of gas. As I start driving it is still rumbly as I
> accelerate and I smell the gas when I stop.
> Then I get on the highway and my acceleration is decreased as I try to
> get up to speed. I finally get up to speed let my foot of a little and
> the car rattles/rumbles. If I push the accelerator past a certain point
> the car stops rumbling and surges. I let off and the rumbling returns.
> If I maintain a constant speed the car seems to settle into an almost
> normal mood. (The rumbling isn't as noticeable and the rpms settle
> around 2500.) The shifting seems to be a little off during accelration
> I let off the gas to shift and sometimes it will downshift again and
> surge. The rpms during are riding around 3000+ when I do accelerate.
> My dad thinks it is the coil. What do you think?
>
> Respond to either email or here, Thanks

Your car has 3 coils.
Sounds like bad ignition wires, bad O2 sensors, leaky injectors, and blow fuel
pressure regulator have melted down the cat.

I think checking the fuel pressure regulator was a good idea.
Bill

jlk_2005 wrote:

> We took it to a mechanic and told him we thought it was the catalytic
> converter.... so he took it out.(He isn't a very good mechanic and he
> doesn't make any judgments on his own he just does what you say and
> doesn't check anything so we are looking for a new one) So currently it
> has a pipe replacing it. It didn't make a big difference in the
> condition it drives. I don't have a cat anymore. Anything else?
>

"Bill" > wrote in message
...
> I think checking the fuel pressure regulator was a good idea.
> Bill

So do I. It might be a good idea to check the individual injectors to be
sure
that they are sealed and working as they should.

One last thought... do a compression check. See what condition your valves
are in.