'91 Caprice mileage - Chevy Impala SS Forum
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post #1 of 20 (permalink) Old 10-03-2012, 10:03 AM Thread Starter
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'91 Caprice mileage

Hi everyone!

First of all, sorry for my poor english.

Well, i just bought a '91 Chevy Caprice Classic with 305 5.0L Tbi engine. The car bought from a dealer, and the car was started in June (last time). The first start was normally, everything ok, a/c, brakes, abs, etc...
But the consumption is disgraceful, on highway 15MPG, in the city.... less than 10MPG, with normal driving. I think, the average should be over 20MPG, or not?
The old engine oil is still in the car. But on this week i change the oil, filters (oil, air, and fuel), and the spark plugs. But if it isn't help to increase the MPG (i think it isn't help), then what should i do?
I already talked with 2 car mechanic about this. The first said, because of the high mileage (but only 130k miles on it), i cannot increase the mpg. The second said, if the oil and filters change not help, then we should check the all sensors, because of one or more sensors' fault can result more consumption.

Whats your opinion, idea?

Thanks,
Bence
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post #2 of 20 (permalink) Old 10-03-2012, 10:54 AM
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maybe o2's

have you done any type of tune up? spakrs, cap, spark wires ect..ect.

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Go fix your fleet of 91's. I wipes my tushy with TBI.......
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Much like date night with BK, this isn't about what you prefer.
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post #3 of 20 (permalink) Old 10-03-2012, 11:48 AM Thread Starter
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maybe o2's

have you done any type of tune up? spakrs, cap, spark wires ect..ect.
I think the car is stock. I dont know how old is the sparks. I going to replace the oil, spark plugs (maybe the cables also), filters (oil, air, fuel). But the mpg is too low now, or not?
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post #4 of 20 (permalink) Old 10-03-2012, 12:38 PM
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Quote:
Originally Posted by bence.ujszaszi View Post
I think the car is stock. I dont know how old is the sparks. I going to replace the oil, spark plugs (maybe the cables also), filters (oil, air, fuel). But the mpg is too low now, or not?
Yes, lower than what I'd consider normal. My 91 also has the 305 TBI and I get roughly 16 - 17 in CITY. Not sure about strictly highway but I'd suspect low 20's. I've recently given mine a tune up, though, with spark plugs, wires, oil change, fuel filter, distributor cap,...... the whole 9 yards



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post #5 of 20 (permalink) Old 10-03-2012, 01:03 PM
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I averaged about 15 in the city with mixed driving and using a/c. Usually mid 20's on the highway.

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93 Caprice-165k miles- scrapped. ran 18 flat
78 Impala Coupe- Motor is worth more than the car. May run 13's


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post #6 of 20 (permalink) Old 10-03-2012, 02:14 PM
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My commute is about 70/30 hwy/city. Every tankful, I always get 20 - 20.5. Winter months, either longer idle warm ups, gas blend, whatever, it typically loses 1-2mpg.

One thing with mine, not sure if others experience this, I find the plugs pretty shot after 20-25K. Center electrodes always rounded down where it fires. I got it a yearly plug change routine when it was used primarily. Now about at a 2yr cycle. Been like this all it's life. From the 65k when got it, throught the 225K on it now. Even with the new crate engine at 170K. Though it didn't really need it. This is with plain old ac plugs. Been running for the longest the cop spec ones, R43TS though it made no difference to the hotter R45's
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post #7 of 20 (permalink) Old 10-04-2012, 09:32 PM
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Does it run well? Oil and filters are not the cause, it is something else. Is the 'Service Engine Soon' light on?

Since you're overseas, its highly likely someone screwed it up since they're not familair with working on US cars. I'd check the timing, vacuum lines, electrical and ground connections, etc.

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post #8 of 20 (permalink) Old 10-05-2012, 04:56 AM
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When my 91 was stock w/260K, I got 26 MPG hwy, cruising at 75 & using premium fuel. 18 in the city. If I used lower grade fuel it dropped. I was running 3.08 gears.
It all went downhill when I wanted more power.
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post #9 of 20 (permalink) Old 10-05-2012, 05:23 AM Thread Starter
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The car running good. Now i'm wainting for the filters. Which viscosity oil are you prefer?

Today I got the previous owner's phone number. He said that almost all sensors replaced, but it did not help. Or if increase in fuel economy, fuel consumption increased again shortly. He said he has already replaced the ECM, injectors, modules.
We can even cause the error? Maybe something in the exhaust?

I noticed that although the engine can easily reach the "operating" temperature, but the meter on the dashboard going only until the 1/4 (first sign). On every startup the viscous fan runnig so fast, until I'm not driving a little bit with the car (for example until shifting the 3rd gear, or a little driving in the 2nd, a half a mile), or something like so. Maybe its not an error, but the temperature is little bit worry me.






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Originally Posted by cletus284 View Post
Does it run well? Oil and filters are not the cause, it is something else. Is the 'Service Engine Soon' light on?

Since you're overseas, its highly likely someone screwed it up since they're not familair with working on US cars. I'd check the timing, vacuum lines, electrical and ground connections, etc.
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post #10 of 20 (permalink) Old 10-05-2012, 07:09 AM
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1/4 up on the dash is normal for mine too. That's if you have a 192-195 degree thermostat. My scan tool shows 194.0 when it's at that 1/4 mark.
A 180 thermostat had the needle at about 3/16's. Scan tool read about 220 at the 1/2 mark if I recall right.
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