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More questions, '86 Cutlass Supreme


mako's Avatar
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07-15-02, 12:19 PM   #1  
More questions, '86 Cutlass Supreme

86 Supreme, 307, 100,600 miles. Automatic.

This car runs and idles as smooth as cream, cold or hot. But I have noticed a lot of racket upon light acceleration (as if about to pass someone). Clatter. In the past, I just ran 93 octane in my clattery GM's and the clatter went away. But considering the cost of 93 I'm not going that route.

New plugs, wires, ignition rotor and cap, new oil and filter, new fuel and filter (just refilled the tank from empty, still clatter). Aweful gas mileage. I expected 15 MPG but am seeing about 12-13 MPG. Seems to me that for such a slow car that the mileage would be a bit better. Maybe this is related to the clatter.

Usually this is a timing thing, so I'll have to have that checked (my old timing light is broken and I don't even know how to use it, lol, was my pops- I dunno why I keep it).


Other than timing, it is possible that the plugs are the wrong size, as I've read. I bought the Delco's from Advance, and they looked it up on the 'puter. When I took the plugs to a friend of mine to install (due to time/patience restraints) he said I had the wrong size, so he went to Advance and swapped to the "correct" size. He assured me that he gapped them right, too. So I'll take his word but I dunno.......

Are there any quick checks I can do to this without any special tools before I truck it over to the shop?

Mako

 
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07-15-02, 01:17 PM   #2  
Joe_F
Depending on your driving, 15 is about right on one of those. It's a heavy full frame car. If you buy it being concerned for fuel mileage, pitch it now. It's no Geo Metro for fuel mileage. Thank God, the Cutlass is 10 times safer .

Check your timing. I suspect play in the timing chain at this mileage, so a timing chain job and water pump should be on your "to do" list in the future. I've had to do a water pump on every 307 I've owned .

You might change the EGR valve...or least clean it. That sometimes has an effect on things.

Plugs: Very simple endeavor. Just look at the sticker on the fan shroud or the owner's manual. It will state the Delco # for the plugs.

The correct Delco plug # should be FR3LS6 for this application. In 1985, the 307 got roller rockers on some engines. With this came a change in spark plugs. My 84 Olds 307 uses the old time R46SX plugs.

Make sure you have the right plugs. The gap should be .060"

 
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07-16-02, 04:51 AM   #3  
Thanks!!
I expected 15 mpg but is seems worse than that. My truck got about 15 (with my lead foot on that manual tranny) so I'm used to it. Safety was reason #2 I bought this car. Army tank caliber.

BTW, I mentioned the vibration on the road? New shocks all around cured that. Oddly, I previously had a stranged knocking sound coming from near the radio/heater console, as if something was loose and thumping inside the dash board. When I had the shocks replace, the thumping stopped totally, even on extremely bumpy roads. Before the shocks, it did it even on the highway flats. Odd, but I'm not complaining!!

 
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07-16-02, 09:11 AM   #4  
Joe_F
One of the first things I do when I inherit a car or get a used one is go to Sears and pick up four of their premium (used to be made by Gabriel) shocks for 15 bucks each and install them.

Usually makes a world of difference . One thing you'll like on this Oldsmobile is that the parts are dirt cheap being that they are typical GM and parts are common across a lot of platforms .

 
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