Smoking muffler and lost power

LFogelson · LFogelson's Garage

'82 SC - I was driving on the highway almost home and noticed a loss of power at higher rpms. There is a large hill before my exit and I had to pull to the shoulder because of the power loss and drive 30mph to get off the highway. When off the highway the idle was fine, oil pressure/temp/level all normal. Looked under the hood, no obvious problems except smoking from the muffler. I have been having vacuum issues (see below) so I removed the oil cap and the car began to idle rough - normal. I drove the rest of the way home very slow.

Is this a clogged catalytic converter? But then why was the muffler smoking? I restarted the car cold and it idled and revved normal but I am afraid to drive it. Is there anything else this could be before I start cutting the rusty bolts on the catalytic. May be time for a hollow core.

Also for the last couple of months I have been chasing a problem with the idle rising to 1200rpm when the engine is warm. The warmer the engine the higher the idle. I recently took off the WUR and cleaned it. Didn't seem to make a difference. I have been meaning to get the CO checked.... it usually smells rich during warmup. That is why I have worried about a vacuum leak that worsens (leaning the engine) as it warms up. Is this related to the present problem?

LFogelson · LFogelson's Garage

Any thoughts?

I started the car today and it runs fine cold. As soon as it warms (temp gauge 8 oclock) it starts to stutter. The muffler didn't smoke this time but I ran it for a short time only.

Old posts on the topic seem to relate to fuel starvation... fuel pump, fuel filter, relays. However, this doesn't explain why my muffler became so hot. It burned the paper off the the right lower heater hose. Is there a way to test the catalytic flow without taking it off? The exhaust at the tail pipe is hot and blowing.

cowtown · 08-13-2004, 07:24 AM

Could it be that you're running very lean when the engine's warmed up, resulting in very hot exhaust? Have you checked fuel pressures and mixture? You say you recently R&Red the WUR....

emcon5 · emcon5's Garage

Did you add oil recently?

Tom

Groesbeck Hurricane · 08-13-2004, 07:40 AM

Do you hear any abnormal noise? What does your idle do when you remove the oil filler cap? What is the idle set at when warm? It could just be the WUR going bad but that is not explained by a loss of power. Clogged CAT will cause a loss of power.

Not to alarm, but when I started having smoke coming off the exhaust it was caused by leakage around my broken head studs.

LFogelson · LFogelson's Garage

If the fuel mixture is lean wouldn't it heat the whole engine not just the exhaust?

I have not recently added oil, level is ok?

When I remove the oil filler cap the idle does drop. I think the sound of the exhaust is getting louder as the car warms up. The smoke seemed to be from abnormal heat. Would that happed with a broken head stud?

Also a few months ago I failed my emissions because the CO was too high. I thought maybe then my cat was bad, but was told because my hydrocarbons were low it was probably ok. I was able to pass by leaning the mixture, running the engine hot, and using fuel dryer. I have since changed the plugs and thought I was running better (platinum to copper). However my gas mileage usually averages only 15-16mpg (mixed highway/city).

Groesbeck Hurricane · 08-13-2004, 09:06 AM

I am not an expert, but here is my $.02 until one comes along:

I seem to remember that lean will heat the exhaust gases, but I could be so very far off the base!

Check the oil level with every fill up. Do not miss one. More often the car sits any length of time and the oil leaks.

If I remember correctly, the idle dropping when the oil filler cap comes off is normal. If it stayed the same then you might have a vacuum leak. This is a good sign.

Many bad things can happen with a broken head stud. I was asking ask the oil might be leaking out when the motor is hot and expanding or cold and standing. It will then burn off on the exhaust. Many people drive with broken lower studs. You can easily check them when you next do a valve clearance check. Remove any broken material. I would change them if any were broken, but others drive with some broken ones. One broken one on an inside cylinder might be no issue. Do a search on Head Studs and John Walker's Workshop. Very good information!

I truly don't know about the mixture.

LFogelson · LFogelson's Garage

Oil on the exhaust is a good thought, but I really think the exhaust got "smoking" hot. The rear quarter panel and rear bumper seemed much hotter than usual. Also, I haven't noticed any leaks under the car. My car is very dry... replaced oil return tubes a year ago and almost eliminated drips.

Paulporsche · 08-13-2004, 11:50 AM

What are your engine temps like? Did they go up any after you leaned the mixture? Did you richen the mixture back up after your smog test?
With my car, the engine usually sounds louder, more raspy, with more of a growl, when lean. As it gets richer, the sound is more mellow.

LFogelson · LFogelson's Garage

FIXED

I think it was lean... I did three things. 1) changed the vacuum advance hose to the distributor. 2) Cleaned the distributor cap contacts 3) removed and cleaned the WUR again with tons of carb cleaner