Mpg Needle Acting Weird! - BMW Forum

Privateye · 07-18-2005, 07:19 AM

I have a 87 BMW E30 and recently my MPG needle has been acting weird. It does not correspond to how I drive. When the car is off the needle stays on max mpg rating and when i turn the car on it rises 0 mpg. Whenever I have my foot on the gas pedal the needle would stay on 0 mpg. When I released the pedal it starts rising quickly until it reaches the other the max mpg rating. Any ideas on this strange problem?

nukeduster · 07-18-2005, 11:11 AM

Quote:

Originally posted by Privateye@Jul 18 2005, 04:19 AM
I have a 87 BMW E30 and recently my MPG needle has been acting weird. It does not correspond to how I drive. When the car is off the needle stays on max mpg rating and when i turn the car on it rises 0 mpg. Whenever I have my foot on the gas pedal the needle would stay on 0 mpg. When I released the pedal it starts rising quickly until it reaches the other the max mpg rating. Any ideas on this strange problem?

[snapback]363191[/snapback]

thats how it should work...

when you let off the gas its not injecting any gas and is thusly running at infinite mpg.. when you are stopped.. you are getting 0 mpg. when you are full flooring it, you are probably getting something like 5-8mpg.

Privateye · 07-18-2005, 03:15 PM

No thats not how it works. No matter if I floor the car or drive normally, the meter always shows as 0 mpg and when the car is switched off, the needle goes to "Max" reading level. As long as I have got my foot on the pedal it will always shows 0 mpg. As soon as I take my foot off ottally it slides to the max level.

Paraklas · 07-19-2005, 08:37 AM

Quote:

Originally posted by Privateye@Jul 18 2005, 02:15 PM
No thats not how it works. No matter if I floor the car or drive normally, the meter always shows as 0 mpg and when the car is switched off, the needle goes to "Max" reading level. As long as I have got my foot on the pedal it will always shows 0 mpg. As soon as I take my foot off ottally it slides to the max level.

[snapback]363296[/snapback]

I had the same problem. The needle would not show the proper readings exactly as you describe it. After a few days, the rev. meter stopped working as well and I went to BMW where they replaced a board from the dash. I don't know what board is that but I assume it's the one that handles the readings of mpg, revs, odometer etc. The board also had a small rechargeable battery soldered on it.

nukeduster · 07-19-2005, 10:34 AM

Quote:

Originally posted by Paraklas+Jul 19 2005, 05:37 AM--><div class='quotetop'>QUOTE(Paraklas @ Jul 19 2005, 05:37 AM)</div><div class='quotemain'><!--QuoteBegin-Privateye@Jul 18 2005, 02:15 PM
No thats not how it works. No matter if I floor the car or drive normally, the meter always shows as 0 mpg and when the car is switched off, the needle goes to "Max" reading level. As long as I have got my foot on the pedal it will always shows 0 mpg. As soon as I take my foot off ottally it slides to the max level.

[snapback]363296[/snapback]

I had the same problem. The needle would not show the proper readings exactly as you describe it. After a few days, the rev. meter stopped working as well and I went to BMW where they replaced a board from the dash. I don't know what board is that but I assume it's the one that handles the readings of mpg, revs, odometer etc. The board also had a small rechargeable battery soldered on it.

[snapback]363474[/snapback]

[/b][/quote]

si board

Paraklas · 07-19-2005, 11:30 AM

si board? What does "SI" stands for?

325eXTATIC · 07-20-2005, 02:25 PM

Service Indicator

If you are handy, there is a good chance that you would be able to replace just the rechargeable batter on the SI board. It is IN the dash cluster, and well buried into the cluster itself, but if you are handy, you can do it.
Pull the cluster, find the SI board, and you will see a battery on the SI board, it may very well have a lot of corrosion (but not always) and you can find SI batteries to replace them with at most of your better BMW parts suppliers... pelicanparts.com, bavauto.com, bmpdesign.com.

Do a search on this forum for SI Board Battery, or variations of that, and you should find everything you need!

Hope this helps!!!

Josh W.
'86 325e w/Dinan ECU

Privateye · 07-20-2005, 06:38 PM

I think i am going to have to replace my whole instrument cluster. My petrol needle is also playing up. It shows less fuel than there is. After a while it incrases to show the correct amount. The drops dramatically when i turn the car off for a couple of minutes then turn on again. It eventually goes up after few minutes.