Severe Gas Mileage Drop Problem
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Junior Member
Joined: Nov 2024
Posts: 9
Well I'm only at 863′ above sea level here so who knows. I'm just happy I've started narrowing it down. Well I guess if I'm reading this right that could definitely be an issue if the Barometric pressure of the area is 29inHg
Last edited by Mb0208; Nov 28, 2024 at 01:02 PM.
Senior Member
Joined: Jun 2020
Posts: 307
From: Newport News, VA
Check what the MAP is reading with the engine off. It should be approximately barometric pressure (about 29 inHg as you noted). Your reading of 9 inHg means about 20 inches of vacuum, which in the 'old days' was a very good vacuum reading at idle.
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Junior Member
Joined: Nov 2024
Posts: 9
Yeap with the engine off the MAP is fine sitting at 29
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Joined: Jul 2024
Posts: 86
From: Louisville, KY
Are you using the stock plugs called for in the owner's manual?
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I know you say the vehicle runs well but the gas mileage is down. Per Rube's statement, I'm sure we were at least two heat ranges off on the BMW. You may be one. As a further example, the Saturn S series is very picky in general about spark plugs and runs best on only the cheap copper plugs. Not iridium not Platinum.
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I know you say the vehicle runs well but the gas mileage is down. Per Rube's statement, I'm sure we were at least two heat ranges off on the BMW. You may be one. As a further example, the Saturn S series is very picky in general about spark plugs and runs best on only the cheap copper plugs. Not iridium not Platinum.
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Any more details on why S-series wants the copper plugs?
I am doing mine soon (97 SL1) ... i wanted to see what the manufacture originally recommended for replacements and found this information.
This 41628 ACDELCO spark plug is available on RockAuto, but is not listed as a part under the 1997 SL1... RockAuto does this sometimes...
I believe this is the correct part...
Anyways I wanted to ask you about why S-Series don't do well with the iridium and platinum plugs.
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Joined: Jul 2024
Posts: 86
From: Louisville, KY
I have the ZURICH 11s. That's a fine reader my friend. It looks like you can read live data. Your fuel trims look good. That can sometimes clue you in on MPG issues, but it looks like that's not a problem on your vehicle.
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Junior Member
Joined: Nov 2024
Posts: 9
Well, I replaced the timing belt, pulleys, water pump, and thermostat today. And the timing was perfect so those are all completely ruled out now. Now I just need to wait for my car to run another full cycle to see any EVAP stuff
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