Troubleshooting poor fuel economy

[FunElan]

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

[chrism]

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

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.

[dapinky]

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.....

[chrism]

Ah...yes...thanks for that

[chrism]

..try this FunElan - courtesy of dapinky...

ecu5.zip

[FunElan]

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.

[chrism]

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

[FunElan]

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.

[chrism]

...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

[FunElan]

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