Hello,
I bought at 1990 Camaro RS 305 TBI the other day and its in pretty good shape, just a few little things I need to fix. One of them is the tach appears to be reading double what the engine is putting out. The motor runs fine, just the tach is off by a factor of 2. Now I know I can buy and interface box and just divide the Tach's signal by 2 and it will work fine, but is there an easier (and cheaper) fix to this problem? The cars an automatic so it doesnt really matter all that much, but Id like at least one of my 3rd gens to have a working tach. (at least this one moves...haha)

 

I've got the same problem on our 1991 RS 305 and on another board i was told to check out the sensor in the dizzy. Make sure its clean and not damaged.

Still haven't got around to it mind! Maybe thats worth a thought. I could be talking complete bs though, i'm pretty new to this automotive stuff!

 

I dont know much about the TBI sensors...is that where the tach sensor is on the distributor? I figured it is, but im used to all this LS1 stuff.

 

From what i was told and what i've read in the manuals the sensor should be located in the dizzy. I have yet to tackle it but if i do in the next couple of weeks i'll get back to you on it.

 

https://www.thirdgen.org/forums/elec...hlight=ANDYZ28

 

Hmm more complicated than I thought...Im doing electricity in Physics now, but nothing too complex when it comes to circut boards and such. But from what I gather I could alter the tach signal right now with an interface box but if it is a bad capacitor then it will just get worse and worse...and probably have linearity iissues.

Everyone in that thread was getting into adjusting the resistances and replacing capacitors on the tach driver, why not just replace the entire tach driver?

 

Im having the same problem with my TBI. It started last year and was only off by a little bit. Now the needle goes all the way to 8k when it shifts at WOT. Its only off by about 400 rpm at warm idle though... Im curious if anyone has found a solution to this because I would really like to keep my stock gauges. I read that whole other thread and got confused in no time!

 

Originally posted by 92CamaroLS1 "Everyone in that thread was getting into adjusting the resistances and replacing capacitors on the tach driver, why not just replace the entire tach driver?"

Because the tach driver is no longer available, we may have to make one.

 

I would be alright with making one, but I'm just not smart enough to figure it out by myself! I hope someone smart can figure this out.