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engine smokes and low power; just bought 1993 convertible 1L auto
Topic Started: Apr 14 2012, 11:52 PM (1,250 Views)
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pat Mcvay
Apr 15 2012, 10:59 PM
What is the alphabet oil you mentioned?
http://geometroforum.com/topic/4141719/1/
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pat Mcvay
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throttle body gotcha. I bought a Chilton's today so I can find it.
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Facetious Educated Donkey

Chiltons will be good to start out with but you will want a service manual at some point if you want to keep the car and do more extensive work. eBay search: 1993 gray repair manual

So, yes (as Coche Blanco says), run the old gas out of it and keep adding low octane fuel. Even ethanol would be good for helping get any water out of the system. Non-ethanol will give you better gas mileage, usually.

Seafoam in the oil should turn it black with carbon pretty soon. :) Great additive just before oil changes.

The throttle body and hoses:
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pat Mcvay
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research online says that hot compression should be higher than cold as I tested. So all 3 cylinders should be above 156 min dry. All 3 cylinders are also similar which is good. Is the difference between dry and wet results greater than what you would expect to see?
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pat Mcvay
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Why do you recomend low octane. I put midgrade in to hopefully improve performance. Ran tank almost dry prior to filling and filled her up all the way with midgrade. will add another dose of seafoam to gas.

Will recheck compression hot tonight and add Marvel into cylinders/spark plug holes tonight if I have time. How much Marvel to add to each spark plug hole? Will also try to Seafoam directly into vacuum.
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Facetious Educated Donkey

Octane's purpose is to slow combustion in high compression engines.

Take a look at http://en.wikipedia.org/wiki/Octane_rating. It has been cleaned up since I last saw it. Here are some statements:

"Self-ignition leads to inefficiencies (or even engine damage) if it occurs during compression prior to the desired position of the piston in the cylinder as appropriate for valve and ignition timing. The problem of premature ignition is referred to as pre-ignition and also as engine knock, which is a sound that is made when the fuel ignites too early in the compression stroke.
Severe knock causes severe engine damage, such as broken connecting rods, melted pistons, melted or broken valves and other components. The octane rating is a measure of how likely a gasoline or liquid petroleum fuel is to self ignite. The higher the number, the less likely an engine is to pre-ignite and suffer damage."

"Higher octane ratings correlate to higher activation energies: This being the amount of applied energy required to initiate combustion."

"Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power."

""Premium" grade is fuel of higher octane, and the minimum grade sold is fuel of lower octane. Purchasing 91 octane fuel (where offered) simply means that more fuel of higher octane is blended with commensurately less fuel of lower octane, than when purchasing a lower grade. The detergents and other additives in the fuel are often, but not always, identical."

IMHO, our engines will not knock on 87 octane and certainly not on 91-92 but it is not necessary since the low compression will not pre-ignite the fuel.

And if you want to discuss "the energy density of the fuel being burnt" then regular gasoline has a BTU rating around 112,000 to 125,000 and ethanol just 76,100 BTUs. http://www.hho4free.com/gasoline_vs_ethanol.htm
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bogs
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pat Mcvay
Apr 16 2012, 09:40 AM
Why do you recomend low octane. I put midgrade in to hopefully improve performance.
Because Octane rating has nothing to do with performance, octane rating specifically measures the fuels resistance to predetonation (simplified explanation). Unless you have some high compression engine under the hood, or have advanced your timing abnormally, your car does not require anything above regular octane gasoline.

**edit
Heh, BB beat me to the punch, but yeah :)
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pat Mcvay
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Sorry for the delay. I broke an alternator belt and had to replace it. Will try to do hot compression tonight and post results.
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pat Mcvay
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Alternator belt replaced. started hot compression test. first cylinder 160 dry and second cylinder 166 dry gage broke while testing third cylinder. I assume pressure was above 166 seen by second cylinder but can't say for sure. I do not think that I have any low compression cylinders.

The engine does seem to run better the more that I run it. It was also much easier to start hot today. Biggest complaint is low power and the smoking. Is some of the smoke caused by the SeaFoam in the gas? Muffler is completely shot and probably provides no back pressure. Could this be a contributor to low power and smoking?

I am starting to wonder if the gray/blue smoke is unburnt gas rather than oil. No oil or liquid coming from tailpipe and no black carbon particles that I can see.Engine may be running to rich? Is there an easy way to test or adjust this?
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Seafoam will not contribute to the smoke unless you dumped a whole can in and even then probably not. It hasn't in my cars at least.
If the muffler is shot then there's a good chance the Catalytic converter is also. A clogged Cat. will cause a loss of power.
Take a look at Testing for clogged Cat. You can also/or disconnect and tie off the pipe from the exhaust manifold to the cat (2 bolts w/springs) and see if it runs better. Very loud but better.

I have even less back pressure with a header, flow-through Cat. and glasspack. :D

Gray/blue smoke is oil. Black is gasoline, white is coolant/water.

I don't have a link to an easy way to tell if it's running rich except to check the plugs and watch your mpg numbers.

Without going back over the thread, if you are using oil then top off a few times with Marvel Mystery Oil. Even up to 1/2 quart is OK in the crank case. It will help with any stuck rings and may reduce smoke. If the smoke is in the morning it's likely valve seals. Any oil in the air cleaner is a bad PCV valve.

Hope that helps.
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