1991 T/A check engine light w/ varying idle speed?
 

The problem i have is very odd... I have a 305 TPI (LB9) and this doesn't happen every time i start the car up, but probably once out of every 3-4 starts. The car will start and the check engine light will come on and the idle will go keep varrying about 300-400 rpm on idle. If i try to take off the speedometer will stop working, but if i turn the car off and take the key out and start it back up it will start normally and the check engine and varying idle will be gone, speedo will work, itll run perfectly normal. Any help would be appreciated (im sorta new to this im 17 and im used to working on bikes :D)

Re: 1991 T/A check engine light w/ varying idle speed?
 

Are you able to drive the car? Since your kinda new to this, drive it to an auto parts store or repair shop that can scan the trouble codes for you and help with with a proper diagnosis and subsequent repair.

Good luck and welcome aboard!

BTW, here's a useful thread for future review: http://www.chevythunder.com

Re: 1991 T/A check engine light w/ varying idle speed?
 

Do a search on how to pull codes for the check engine light, (forget going to a auto parts store, it takes a paper clip to do it) do that, and do a search on what it means. Post here initially if it seems confusing.

It's a circuit, component, or input failure, and check engine lights aren't that hard to figure out.

Re: 1991 T/A check engine light w/ varying idle speed?
 

All i get is code 12, it's supposed to flash code 12 3 times and then the trouble codes, but it just keeps flashing code 12 over and over and over again...i don't get it

Re: 1991 T/A check engine light w/ varying idle speed?
 

The simple paper clip trick works for some... It's not fail safe. I once had the exact same problem that you're having, with code 12 only displaying. Scanned it with the propoer diagnostic equipment, TPS faulty. Not saying that's your problem but if you cant get the code to display, seek out someone with the tools to help you pinpoint the problem.

Re: 1991 T/A check engine light w/ varying idle speed?
 

now i have to hold the gas in to even start the car after pulling codes...it will not idle at all...if i let off the gas it instantly dies and it wont start without pressing the gas???