This morning my speedometer went way off, i'm going about 50 and it read 90. My stock oil pressure, and temp gauge were always jumping around or completly off, so i got aftermarket ones. And sometimes my tach goes dead and reads zero. My speedometer was always 5 mph off, but now it's way off.

What is causing this?

I know i have a bad ecm, is that the problem this time?

 

ever think it might be the guage cluster??? you said other things were reading way off, too, right? replace it with a known good one, it only takes about 15 minutes.

 

Weak system voltage and poor grounds will cause the instruments to act up.

How do you know you have a "bad ECM".... what is "bad" in it? Low system voltage and poor grounds will make that act up as well.

 

this isn't really helpful, sorry beforehand but:

i'd take it up to 120ish...and take a picture

 

I know i have a bad ecm because i went to a garage to get the codes read when my ses light kept comming on, and the mechanic said he could not even read it and it wouldnt work at all, and that he tried everything. He said it was bad, and i even smell gas sometimes like it's not burning right inside the engine...and it's not a gas leak because i've had it check for a leak 2 times recently and there's no leak to be found anywhere

I might go look for a gauge cluster that's still in good shape in a junkyard somewhere and give that a try too

 

Already did a while ago, with the needle pointed straight down and burried

 

if your speedo is stock and your car is an 85, then it may be the cable, speedo, transducer or the mech sender in teh tranny. bad grounds or power won't affect the speedo since it is mechanical.

 

85s are independant of the ecm, the speedo can be off by either : bad speedo gears, or the cable/transducer/sender as mentioned above

 

Interesting... my Chiltons shows a "VSS Buffer" connection to the PCM.

 

on those cars, the buffer is in the cluster, basically converts it so the ECM gets a speed reading. Speedo is all mechanical from the tranny to the cluster.

On my 86 Trans Am (Firebirds got electric speedos 4 years before the camaro), the electric sender in the tranny was hooked up to a yellow buffer box and then split to the ECM and to the Speedo.