'87 GXL : Recent tune-up 1000 miles ago; cone filter and 2.5 exhaust with catco cat; MSD 6A installed; flexalite fan. Here's the problem : car is at operating temp, cruising along the road and when I'm braking and about to come to a stop, RPM needle drops to 200 rpm until I come to a complete stop. Stopped at a light, car idles fine at 750. Did recent vacuum checks, installed Brown Black wire from boost sensor to coolant filler neck, and checked all grounds : everything good. Still has hesitation at 3800. Also, adjusted tps with no luck. What should I do?

 

Could be a solder problem in ECU, also try cleaning all the injectors.

 

sounds like injector related problems

considering 2ndaries open at 3.8k rpms

 

That was the next thing I was going to do, take the manifolds off and replace gaskets as well as clean the injectors. But even after cleaning the injectors, will that solve my idle problems?

 

what are you idling at, cause secondaries dont come in till i think 3800 rpm.....

 

The RPM drop under braking makes me wonder if your brake booster is somehow causing a vacuum leak when it's activated (and I'm just guessing).

Whatever the cause, I think that's a different problem than your 3800 RPM hesitation.

 

i agree, 3800 hess is usually secondaries...i just dont think that would have anything to do w/ what u stated... check for leaks

 

most likely a bad BAC valve. its on the driver side of the intake manifold, opisite the throttle body, has coolant lines going through it and is blue at one end where the plug for it is. check the fsm for methods of testing it

 

Sorry to take so long to respond. So check BAC and brake booster, got it. Will try ASAP, thanks guys. I will post up pics of my car and engine bay in a couple of days. Tell me what you guys think.