Hi, been lurking on this forums for sometime now and I figure I post something that hasn't been mentioned before or may have been but not brought up again about the 99.9 readout on the MFA.
So we know the earlier Corrados had the MPG calculated through a vacuum hose and the later Corrados was done through the ECU to a purple signal wire. Usually the problem is just a disconnected signal wire or vac hose and plugging it back in solves it.
But there is the other issue that I have been reading and myself been having is everything is plugged in but it still reads out 99.9 in one drive and sometimes it reads out normally. Or for some people it's just stuck at 99.9. Well my Corrado recently has been getting worse with the 99.9 readout and I decided to dig into it a bit.
I have a Vac/Boost gauge tee'd into this line and sometime last year under boost the vac line popped off because I was lazy and didn't zip tie the plastic hose to the gauge. I reconnected it and zip tied it down and never bothered to check it again. Today I went under to clean up the zip ties I could smell motor oil right around the fuse block (not a good combo). So I took a look with a flashlight to see that some relays specifically the load reduction relay had oil on it. Right above the relays is where I have the gauge tee'd into the vac line so thinking back when the one night the line popped off under boost it must have misted some oil around there.
Now I hope that's not telling me my G60 oil seals are leaking heavily but it does tell me there could be oil build up from the life of the car that it could make the MFA vac sensor act abnormally. So I pulled it out *remove battery ground* (I have a 1990 G60 so I had to remove the cluster cover and temp/fuel cluster to remove the MFA vac sensor) and sprayed some electric cleaner in the line inlet and shook it a few times before reinstalling it.
I took it around the block and my MPG readout was working correctly again, it went up as I was driving normally and it went down when I stopped and was idling. Thursday will be the test to see if this fix really works when I drive my Corrado to class.
Sorry for a long post for sometime simple I usually want to be detailed but it confuses people and maybe it's been posted before. I couldn't find it using the search option and with google so I figured why the heck not and post it and see if anyone else that was bored and had this issue give it a try too.
Something to consider is if you've been having this 99.9 readout for a long time, I don't think this may work. But if it's been intermediate lately this fix may work.
tl;dr
Possible 99.9 MFA readout fix:
Vac line is connected
Oil build up (clog) in MFA vac sensor,
Remove and spray some electric cleaner
Fixed :cheers:
May work for others? report back if successful or not.
Edit*
Took it out for a drive today after messing with the ABS. The MPG on the MFA is functioning properly.
