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My 1992 caprice is having a hard time passing California smog check before I took it in I had replaced spark plugs and wires oxygen sensor throttle position sensor coolant temp sensor map sensor air idle control valve and it failed there was a check lite on it only comes on now when I run it hard or on highway after car has been running it seams like its guna Die but sometimes will spudder and almost die but will kick in after a few seconds then I had timing checked it’s dead on 0 zero so I’m at a lose her can you help the converter looks and seams ok that’s like the only thing I haven’t replaced
Hi @daytons , Check if there are any codes showing in the OBDI port which may give an idea of what is happening in the engine. As far as I can find out your model has an OBDI system. (also known simply as OBD) As best that I can find out OBDII came out in 1995 for your make and model, you may wish to verify this however. Here’s a link that may be of some help on how to do this. If it works and there is a code showing search online for what the code means for your year model vehicle.
Check the EGR valve and make sure it isn’t stuck open or closed, it can cause a engine light at highway speeds sometimes my 90 does the same thing
