I've had this problem for a while. My car smokes (not oil smoke but fuel vapor smoke) on startup in the morning (when cold) and i know thats a problem with the choke. What i don't understand is that after that the idle will vary in everyday driving, from 800 up to 1400 when its warmed up (like i'll stop at one stopsign and it'll idle at 900 and then at the next stopsign idle at 1300). I thought it was a vacuum leak but i hooked up a vacuum pump/gauge to one of the vacuum ports and got a reading of 20 in Hg. Does anyone have an idea whats causing this? Don't know if this has anything to do with it but the computer has thrown some code 15's (coolant sensor), and consequent (?) bad gas mileage as well.

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Red '87Formula Firebird
-mostly stock 5.0L LG4 w/cowl induction setup borrowed from '83 TA and T5 tranny.

My newest Ride:

'85 Silver L98 Corvette w/4+3 manual tranny. not bad for $3500.

 

Yeah, a bad coolant sensor will do that. When that sensor acts up, it doesn't allow the computer to go into "closed loop", and runs in a base timing/fuel curve, Also known as a "Limp Home" mode, which is very rich on the fuel but allows the engine to operate. Also ensures you'll have the engine checked prior to the next emmisions test, or you'll fail big time. BTW, It would also explain the horrible gas milage issue....

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-1983 L69 Camaro Z28 305 H.O. (Bored .030 over,Teflon oil seals,Melling H.V. oil pump,Hyperetic pistons,chrome-moly rings,2040 Crane compu-cam) T-tops, 3:73 Open rear, BW T-5, Rebuilt E4ME 4 Barrel, Duel Snorkle Air Cleaner w/K&N Filter , Rhino Clutch, Crane 2040 Compu-cam, LS1 valve springs, porting, PST front end kit. Now for paint, interior, etc...etc.... Also:
2000 S10 4.3L 4WD LS
1995 Ford Thunderchicken, 4.6 V-8