Do I Have a Misfire Problem?

[Tyler_S]

I've done a lot of searching, but I've yet to come up with any answers.

I'm not sure if I have a misfire problem or not, but either way, I'm getting some screwy symptoms of something in my car.

1. Yellow-y build up under oil cap.

Every short trip I go on, I look under the oil cap and I see a yellow film. It never stays, but I've never seen it before. I'm definately not leaking coolant.

2. I get a smell of gas from the exhaust.

It's not too strong when the engine is running, but after I turn off the engine and walk to the rear of the car, I can smell gas.

3. The car feels sluggish.

But not overly so... the engine starts fine, but my car has felt a bit sluggish as of late. Though the engine does not sound any different than it did before.


So what's going on?

I recently changed my oil to synthetic for the winter, and that is the only change I can think of to my car that may have done anything.

Any ideas?

[Peyman]

is it possible you have a clogged cat?

[Tyler_S]

is it possible you have a clogged cat?

Would that cause a smell?

I've read that the yellow film under the oil cap is normal in some cars, where a coolant leak isn't present.

[Blackhawk]

The film is just oil vapor that condensed onto the cap, caused by short trip driving, perfectly normal, just take it on long (10-15 min) drives once in a while.

You don't mention any codes, which would show up if there is anything more than just a very minor misfire, and it would flash if it could damage the cat. What are you getting in terms of gas milage? Has it gone down from before the symptoms showed up?

[Peyman]

a clogged cat would cause sluggish performance... and it would also smell bad too

[rixGAphx]

'95, 3-yrs old, mebbe 150k miles?

The gunk on the underside of the cap is actually a combination of water vapor and oil vapor, both collecting on the cold cap at the same time and 'kind of' mixing.
Now that the weather has turned crisp, you'll see it more often.

When the engine finally warms up and the cap itself gets warm, then the vapors stop condensing.
But once they combined into that goo, they will never 'burn-off'.

Don't worry about, it's been happening to every engine since the Model T.
* * *

The catalytic converter was warrantied by GM in the US for 8 yrs/80k miles.
If that's your original cat, at 150k its gone twice its expected life.
Get a new one and lay the old to rest.
It will pay for itself improved performance.

How long has it been since the plugs, wires, and O2 sensors were replaced??
If all of these are at 50k+ miles, then a combination of their bad performance could be overwhelming an otherwise still-good cat.

Standing by,
-Rick

[Tyler_S]

Thanks guys.

The plugs and wires were replaced with the LIM gasket about a year ago. The CAT is original.

I don't know of any codes because I don't have a code reader, but no warning lights have come on, though I don't think the PCM would even monitor that kind of thing.

My gas milage seems OK, but the last long trip I took it on was almost a month ago, so I can't really guage it.

The only work I've done on this car in the last month was to replace the block heater, and I don't think that would be related to any problems I'm having.

[rixGAphx]

Cats fail in a couple ways:
1. The platinum and rhodium (whatever the hell THAT is) that make them work get totally used-up, or coated with soot, wo they just stop cleaning the exhaust.
But exhaust still flows thru the honey-comb structure just fine.
Then you smell the raw exhaust, like I remember as a kid with belching carb'd non-cat V8's.

2. The honecomb structure itself fails or collapes or gets clogged, so the exhaust gases can't flow easily thru the cat.
Excess backpressure robs the engine of horse power, and the engine feels sluggish.
BUT, there still may be enough platinum and rhodium on exposed surfaces of the honecomb to clean a mildly-dirty engine, so you *might* not smell anything unusual.

I'll bet you have BOTH of the above conditions.
Replace the cat, or at least test it for blockage: Drill a 3/16" hole in the side of the exhaust pipe, about 3 inches in front (toward the engine) of the cat.
If the exhaust flows more freely and the engine idle improves noticably, then that proves blockage.
Close the hole with a stainless steel self-tapping sheetmetal screw. Drilling in the side of the pipe prevents condensation water from rusting thru the bottom of the pipe at this hole location.
* * *

You've NEVER replaced the O2 sensor???
:banghead:
Replace this VITAL device ASAP!!!!
The PCM absolutely depends on accurate data from the O2 sensor to set the fuel injection.
Yours has failed, and it is making your air/fuel mixture (and exhaust) so rich that it will soon KILL the cat if it hasn't already.

Your performance and milage will SKYROCKET (~20% better milage, mebbe +5pmg) once you replace this $50 part.
At today's gas prices ($2.75?), you will recoup that cost in:
* 20mpg--->25mpg = 1 gallon saved per 4 gallons consumed = $2.75 saving/80 miles=
* 50/2.75 = 18 (80 miles) = 1440 miles = ~ 7 weeks at 200 miles/week

Do yourself and the car and the environment a favor, and replace that device now.
Takes 15 minutes to DIY, using the special $10 'universal' O2 socket.

Hope this helps,
-Rick

[Tyler_S]

I'm pretty sure the O2 sensor has been replaced more than once since I've owned the car, as that was one of my first SES lights that came up. :D

I'll have the CAT checked out, and I'll probably get one from Autozone for cheap.

Should I get a high flow cat while I'm at it?

[HeyDace]

"2. I get a smell of gas from the exhaust.

It's not too strong when the engine is running, but after I turn off the engine and walk to the rear of the car, I can smell gas."

A smell of fuel or even the rotten egg smell does not mean a bad cat. Your problem may be in fuel delivery. A leaking fuel supply line or a failing pump. A leaking line will decrease fuel pressure and volume, more so with an old pump which has decreased its performance over time.

[gobraves00]

rix, do you know where i can get pics of a how to on replacing oxygen sensors in a 97, im at 165,000 and i dont think they have ever been changed, and i get shiotttttty gas mileage