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300CE Engine Trouble Part II

My 300CE is a 1988 with 72,000 (verified) miles. The current situation is as follows:

When cold - or hot, it's difficult to start and get to hold idle. It usually takes some accelerator to get it to stay running at this point. It runs like a top at highway speeds with engine temps in the 90 range. After some driving, it continues to run - even at idle. However, the idle oil pressure is barely at the 1 mark, the idle is a bit rough, and temps start to creep upwards when the car sits with the engine on.

An aside: After driving, if I shut the car off and turn it back on say in a few minutes, the temp gauge indicates a very warm engine (110-115) but that cools down shortly after starting. Not sure if there are some electric cooling fans that are supposed to help with this as the car sits with the engine off or not.

Any suggestions?

Reply to
Applemac_G4
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I suggest you look for a vacuum leak. That's a leak that allows unmetered air to enter the intake manifold and dilute the air / fuel ratio making it difficult for the engine to idle on the too lean mixture. At speed you don't notice the leak as it's a fixed amount, therefore, as the engine's speed increases, the leak as a percentage of the total air / fuel mixture decreases. Idle the engine and listen for a

hissing sound - the leak - particularly from a hose connected to the intake manifold.

As to the second point about the high engine temperature upon hot restart - normal. Any engine sheds its cylinder head heat into the coolant after being shut down. When the engine is restarted this very hot coolant passes the temp sensor (located at the thermostat) enroute to the radiator. It can't be any other way and is completely normal.

The oil pressure is below normal, but still OK, due to the engine's stumbling, too low, idle speed. Fix the problem and the oil pressure will be fine.

Reply to
T.G. Lambach

Ok...other than idling the engine and listening for it, is there another way to look for one?

Reply to
Applemac_G4

Yes but with some danger. Spraying some propane (unlit) into SUSPECTED sites with the engine running will prove or disprove a leak at those spots. If a leak the propane will be drawn into the engine and burned as fuel making the stumbling engine run a bit faster and smoother - as it normally will. BUT this is the step 2 if nothing is found in the hoses etc. and a manifold gasket leak is suspected.

This is DANGEROUS so treat propane or carburetor cleaner with respect and keep your face away for if there's a flash it could take your skin.

Before you go to this step please review the engine's maintenance record.

Are the spark plugs > 15K miles old? If so, install new ones.

Have you added a can of TECHRON to the fuel? If not, do so.

How old are the spark plug wires? If original keep them in mind for replacement - not cheap.

The above will at least exclude these items as possibilities, that's if no obvious vacuum leak is found.

Reply to
T.G. Lambach

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