*EDIT*
See post #7 below...it turned out to be a stupidly minor thing causing the problem!
 
 
Hi all.
About 2-3 years ago I installed an Omori 45mm electronic boost gauge in my instrument cluster, the same way that many others have done it.
90% of the time it is great and reads perfectly, but for as long as I can remember there has always been an intermittent issue which I ignored most of the time.
 
- Normally the initial calibration sweep will be fine and the gauge will behave perfectly while driving for a while, but sometimes it will lose calibration while driving, ie. while driving I'll suddenly notice that the gauge is no longer at the correct value (the needle is always too high when this happens). The needle still moves normally after this, just at the wrong spot. Often I don't notice it straight away because I'm not constantly looking at the boost gauge, but it seems to happen most often after high boost (20-24psi).
 
- Once it goes bad it stays bad until turning the key off. Sometimes the calibration sweep will behave incorrectly (correct range but with an offset) when turning the key back on after this. I've never figured out the exact steps to get it back to normal, but it always fixes itself eventually.
 
- After the trackday I noticed that there was a new problem where the initial calibration sweep was especially bad. The sweep would start and stop at inconsistent locations, with a narrower sweep range than normal, and the needle didn't move at a constant rate during the sweep either.
 
It was back to normal and behaving fine today, but I have no doubt that at least one of the above problems will return before too long.
 
So, does anyone have any ideas? Has anyone heard of this problem before?
 
I'll be picking up another Omori 45mm electronic boost gauge (appears to be identical to my current one) from a friend tomorrow, but I don't want to do the swap/re-install before seeing what people have to say here. For all I know, it could end up having the same problem anyway.
 
Thanks guys.

Have you checked all the obvious stuff as in the connections to the gauge and the sensor in the engine bay? Do you have the little in line filter in the vacuum line to the sensor?

I've checked the things that I can see without pulling things apart, but I can't check the connections behind the cluster without taking it out. I don't think it's a connection issue, because the needle never stops moving, it just moves to an incorrect value sometimes.
Yes I have the filter on the hose to the intake manifold.
 
EDIT: I forgot to mention that my tacho has also been reading incorrectly recently...at least I can try to fix both problems with the cluster removed at the same time. Hopefully the tacho problem is just the 2 capacitors on the back of it which are known to fail sometimes.

Could it possibly something as simple as the display needle slipping on the spindle?

Dudeman
Could it possibly something as simple as the display needle slipping on the spindle?

That would match the symptoms I'm seeing.
I'll check that, but I'd be surprised if the needle was that loose.

The gauge has had a relatively easy life, after the latest upgrades and track day the thing has had it's neck throttled.

I removed my instrument cluster tonight, preparing to install another Omori electronic boost gauge that I bought from a friend today, but then I found the (likely) reason for my own Omori electronic boost gauge misbehaving...and it was something annoyingly silly.
 


The thin black disc on the gauge face (with the gauge markings on it) was slightly warped towards the needle between about 15-26psi, and there is a little mark on the gauge face where the needle has been rubbing against it. When I moved the needle by hand I could feel a small but noticeable resistance in that region.
It perfectly matches with the symptons I was seeing, because the gauge only ever misbehaved (suddenly reading too high) after boosting for many seconds. I guess the needle was able to move gradually through the bad area when accelerating on boost, but when letting off the throttle after high boost, the needle would want to drop back as fast as possible, to a vacuum reading, and the stepper motor probably skipped/missed a few steps, leaving the needle at a higher reading than the gauge thinks it's at.

I'll try to fix it before the MR2 club run on Sunday and see how it goes.
 
If the problem is resolved, I'll have another Omori 45mm electronic boost gauge to sell! I'm sure there will be someone who would love to buy the spare one if I don't end up needing it.

How much monies for the other one?

I put a dab of superglue between the boost gauge face and the gauge body and the problem seems to be fixed, I'll know for sure after the MR2 club run tomorrow.
I also replaced the two 10uF capacitors on the tacho and it is now working perfectly again too.

Mrskylighter
How much monies for the other one?

Rico has just called dibs on it.