dragondwc777

First off I have been adjusting the variable resistor and the BAC for idle... I set the coupler when doing this. I adjust it to 750 rpm. Then remove the coupler. But when I rev it up idle seems to land somewhere between 600 and 1500 every time. Any ideas on why? Also when I pump the brakes it misses at idle and wants to die but doesnt. Another problem with idle maybe?

1FastT2

iTrader: (1)

That kinda sounds like you have a vacuum leak somewhere.

Poindexter10thae

iTrader: (2)

I concur with 1fastt2, definitely sounds like a vacuum leak

mrb63083

iTrader: (4)

Check your hose going from the boost sensor to the Air control valve, mine came loose one night and did the same thing you're talking about. I just put the hose back on the Air control valve and it did the job.

akageals

You could have a leaking brake booster. That would account for the vac. leak when the brakes are used. I think I have a leaking booster. I hear a "farting" sound from behind the dash on the drivers side whenever I step on or let off the brake pedal.

Todd

Aaron Cake

iTrader: (1)

Actually, the problem either sounds like a vacuum leak, or a bad/sticky BAC valve. Or a combination of both.

Doubtful there is a problem with the brake booster or ACV.

turbotwista

can a vac leak make your car hunt for idle? Mine has been doing this since I bought it I adjusted the tps to death and checked the bac. Now I can choke it down with the bac to 1000rpm but it wants to stall and backfires like crazy. Any ideas?

dragondwc777

I readjusted both the BAC and the variable resistor again today with a better set coupler. It seems to be alot better but it is still hunting for idle as well now between 700 and 1000 rpm. When I pump the brakes it drops to about 300 rpm. I have checked fo vac leaks no luck yet. Will try all suggestions. Thnx for all the info guys

akageals

The BAC should only be affecting idle when some load is placed on the engine (A/C, electrical load, etc.). My car idles just fine with the BAC unplugged except with the A/C on. The idle would hunt between 300 and 900 with the A/C on and the BAC disconnected. Here's what I did to get my '87TII to idle properly when I bought it.

1.) Turn the BAC bypass screw (the adjusting screw) all the way out (as high as possible).

2.) Use the throttle stop screw to set the idle at about 1200 RPM.

3.) Turn the BAC adjusting screw in to set the idle where you want (750-800 RPM usually).

Make sure that the thermowax is completely disengaged (engine is fully hot).

Jumper initial set connector during the procedure.

Be sure to adjust the TPS before starting and after finishing.

My car had been misadjusted by someone who did not know what they were doing. The BAC bypass screw would not raise the idle speed enough to get it to idle properly. The above procedure worked great. My car idles perfectly now, hot or cold, load or no load.

Todd