I have had trouble the last three years passing emmissions with my 91 ta 5.0 tpi I payed an extra 80.00 for a tune up every year to pass. The service engine light always sayed on. always had trouble with idle it was too low at a stop. I changed the ERG valve and the light is gone now but the idle is at 2 grand now. I cant see any vac lines that I missed. Is it possible the idle is high because the tune up they did and can I lower it or does it need to be on a computer to do that

 

It depends on what they did during the tune up.If they got to messing around with the carb settings they could have set the idle to high or you could have a vacum leak go over the engine really good and make sure u dont have a vac leak usually that is the main problem with having high idle.Hope this helps

 

his is a 91 t/a with tpi. any idea what the timing is set at?

 

could be the opening of the TB blades, theres an adjustment screw at the top driver side in the back of the TB. that adjusts the open positon of the blades that determines idle etc. it could also be the IAC valve, maybe they screwed that up or the TPS voltage. i would do over all of them just to be sure, a vacume leak i dont think would cause a higher RPM it causes cr@ppy idle/low irradic idle.