Troubleshooting poor fuel economy

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Troubleshooting poor fuel economy

Postby FunElan » Tue 07.06.2022, 06:48

Hi all,

My Elan has been a blast to drive, but I can't report that it's getting the excellent fuel consumption figures that I've read here. I DO drive the hell out of it sometimes, but even with a solid highway stint, the best I've gotten is 24 mpg (US).

I took an ElanScan reading this weekend to see if I could learn anything. Short drive, with 3 WOT blasts. Eventually I'll have to do a longer one and let the fans come on. Everything looks okay, no faults, but I'm not sure if the IAC position is indicating that I have a slight vacuum leak? Perhaps someone more knowledgeable than me could take a look at my scan.

I was considering replacing the fuel filter, injectors, and O2 sensor anyway to help, but perhaps I should get new vacuum lines as well.

Thanks in advance!
Matt
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Re: Troubleshooting poor fuel economy

Postby chrism » Tue 07.06.2022, 09:40

Hi FunElan. I'm a newbie to ElanScan and no expert but I'm sending my ecu data (The extension ecu is not allowed...) to show that your IAC doesn't seem to settle in the same way as mine does. (Your O2 sensor seems to look fine tho'...)

However I can't really see why his should have such a drastic effect on your fuel economy - unless you spend most of your journey idling :D

As an aside, when I got my '90 SE which seemed to drink fuel at your rate and stank of over-fuelling I discovered that the eprom was 9239, decided that this HAD to change and I'm now running 1499/O2 sensor giving me 10mi/litre which equates to 45.5 m/imp gal :) with a gentle right foot on a longish journey.

US gal is ~83.3%of imp gallon, so your 24mpg is equivalent to our 29mpg - which is still quite low (and I notice that you're running 1499 too) but you do admit to a heavy right foot. I'd have thought that our 35mpg/your 29mpg would be more reasonable if you drive with a heavy right foot.

Imo your 24mpg is still a little too low and I'm looking forward to one of our gurus looking at your data and giving some clues to suggest why.

ps I wish I could have sent my own data to you...but I hope this helps.
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Re: Troubleshooting poor fuel economy

Postby dapinky » Tue 07.06.2022, 09:55

Chris,

Although the forum software doesn't allow for publishing .ecu files - you can zip them, and upload a 'zip file to get round it.....
Dave

Just the one now, but this one's mine! - and it will be finished eventually.....

go on - click this link - you know you want to!
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Re: Troubleshooting poor fuel economy

Postby chrism » Tue 07.06.2022, 11:17

Ah...yes...thanks for that :)
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Re: Troubleshooting poor fuel economy

Postby chrism » Tue 07.06.2022, 11:20

..try this FunElan - courtesy of dapinky...:)
ecu5.zip
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Re: Troubleshooting poor fuel economy

Postby FunElan » Tue 07.06.2022, 22:33

Having trouble opening your file....my computer that I use for ElanScan is ancient! It will load my data fine, but for some reason when I download any other file from the forum, it doesn't seem to display.
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Re: Troubleshooting poor fuel economy

Postby chrism » Wed 08.06.2022, 11:05

FunElan, here's a screenshot showing how my IAC posn seems to 'tail off' whereas yours seems to keep adjusting itself.
Perhaps it has an effect on your mixture and reduces fuel economy, I wonder?


Screenshot (19).jpg
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Re: Troubleshooting poor fuel economy

Postby FunElan » Wed 08.06.2022, 15:16

Thanks for the screengrab Chris, I guess it can’t hurt to pull the IAC and clean it with TB cleaner to see if it matches your curve afterwards.

I’ve sent off an oil sample for analysis, very curious to see if there is any fuel in the oil. If so, I’d guess leaky injector.

Without being able to pinpoint the exact cause of my poor fuel consumption, I usually resort to throwing darts at the board, hoping one of them is a bullseye. Looks like that might have to be the plan here, which. Can’t be bad for a 30 year old/55k car anyway.
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Re: Troubleshooting poor fuel economy

Postby chrism » Wed 08.06.2022, 17:45

...and your air:fuel ratio seems to have loadsa odd blips towards richness too - mine's the black one.

Hope this helps.

Screenshot (20).jpg
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Re: Troubleshooting poor fuel economy

Postby FunElan » Thu 09.06.2022, 06:13

Hmmm that's interesting. My car does have a chip...I wonder if that's contributing
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