Another rough idle, but different scenario
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Joined: Mar 2010
Posts: 129
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Car: 1991 Firebird Formula
Engine: 305 TPI
Another rough idle, but different scenario
The car is a 1991 305 TPI Firebird. New injectors and new fuel pump.
If the car has been sitting many hours, it will start and run fine. On a restart, sometimes it takes 2-3 restarts, the idle is high at about 2K in park or neutral, put it in gear and it slams hard and drops to about .5 and surges, wanting to die. Sometimes if I let it sit and go back and forth from park to reverse, after about 5 minutes it clears up ad goes back to normal.
The check engine light never comes on during any of this.
Thanks!
If the car has been sitting many hours, it will start and run fine. On a restart, sometimes it takes 2-3 restarts, the idle is high at about 2K in park or neutral, put it in gear and it slams hard and drops to about .5 and surges, wanting to die. Sometimes if I let it sit and go back and forth from park to reverse, after about 5 minutes it clears up ad goes back to normal.
The check engine light never comes on during any of this.
Thanks!
Joined: May 2009
Posts: 4,915
Likes: 40
From: Far West
Car: 1986 Camaro Z28 IROC-Z
Engine: 350 Tuned Port Injection, for now.
Transmission: 700R4
Axle/Gears: Posi - 3.23
Re: Another rough idle, but different scenario
Could be the Idle Control Valve not regulating the proper air flow. Try tuning the TPI system. Here are two good web sites that I recommend for tuning your system #1 http://mpikas.blogspot.com/2008/08/t...june-2000.html and #2 http://www.highperformancepontiac.co...gta/index.html . I have the same issue too. As for the hard starts, you may want to upgrade your dizzy as in getting performance parts or just replacing the whole unit (dizzy). In most cases, this will fix the hard starts. Maby replacing the spark plugs may help too. As for when you shift from park to drive or reverse, the engine may be at high revs, thus giving you the hard engagement. I once heard that the torque converter could be a culprit too, but dont quote me on that. Good luck and let me know what happens.
Thread Starter
Member
Joined: Mar 2010
Posts: 129
Likes: 0
Car: 1991 Firebird Formula
Engine: 305 TPI
Re: Another rough idle, but different scenario
Thanks for those links. Those will be useful no matter what.
The thing I can't wrap head around is the vacuum problem. Here is why. The car starts runs perfect on a cold start and I can drive cross country on that start. It is on a warm (not even hot) restart that the trouble emerges. And not even every time on that warm restart. Sometimes it has to be on the 2nd or 3rd warm restart.
Yesterday I induced the surging idle by taking it out and pulling over and restarting until the problem came back. When it started doing it I just let the car try to sort itself out rather than pushing harder on the gas. It seemed to get better through the trip and was only surging a little by the time I got home, but it it was still surging none the less.
The thing I can't wrap head around is the vacuum problem. Here is why. The car starts runs perfect on a cold start and I can drive cross country on that start. It is on a warm (not even hot) restart that the trouble emerges. And not even every time on that warm restart. Sometimes it has to be on the 2nd or 3rd warm restart.
Yesterday I induced the surging idle by taking it out and pulling over and restarting until the problem came back. When it started doing it I just let the car try to sort itself out rather than pushing harder on the gas. It seemed to get better through the trip and was only surging a little by the time I got home, but it it was still surging none the less.
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