Pontiac Repair: 1986 fiero gt 2.8, 1986 fiero gt, octane fuel

Question
My fiero has been stored for about 3 years I drove it maybe 1000 km's each summer using high octane and fuel injection cleaners in the gas to keep the gas lines and injectors from gumming up. this year I have been driving it a lot more and recently it has been idling at 1500 - 2000 rpm when warmed up. also when i am driving about 80 kmph it started backfiring. I turned on the ac switch and the fan in the car to cool the engine and it runs fine. any ideas?

Answer
Hi Brian:
First off those are nice cars if they are kept in good shape! well your issue could be a lot of things. It could be an ignition problem like moisture inside the distributor cap for the backfire issue. The idle concern could be a lot of things. first and foremost I would check the throttle body to make sure it's not choked up with carbon. the second thing I would check is to make sure the ER valve is not stuck open at all. you can push up on the diaphragm and see it it fully seats back down and the idle should change when you push up on it and then smooth back down again. You could have a vacuum leak causing an issue with the high idle or hunting idle. Also if just before this started to act up if the battery went dead the ECM may be dumb and needs to relearn the idle. try this clean the throttle body first disconnect the battery for a few minutes and then reconnect it and start the car turn off the A/C and if it's an automatic trans car and the parking brake works set the brake and put the car in gear and let it idle for about 10 minutes stay in the car and if it want to take off then use the regular service brake. if the parking brake holds the car do not apply the service brake because this take away from the engines manifold vacuum. after it runs 10 minutes shut it off wait 30 seconds and start it up and let it run again in drive for another 5 minutes and see what happens. it could be a lot of other things but those are the basics. As for fuel use only 87 octane fuel or what ever the owners manual states to use if you use higher than they say then #1 your wasting your money and you are going to get poorer fuel economy. Also do not use injector cleaner on a regular basis it will damage the injectors on this car. Good luck :)