Running terible well i have lots of symptoms and this is the order in witch they ocured lack of power ( top gear pedal floored at 45 kmph up a 5% grade hill ) exhaust leak under hood ( looks to be exhaust manifold gasket ) hard starting ( turn key and it starts give it fuel and it quits cold or hot ) no choke ( no choke warm or cold whatsoever ) fuel consumption (1/4 tank per 10km around 75L tank ) reluctant to shift up ( pedal floored very high rpm then it shifts to 2nd ) wont shut off ( you shut the key off engine continues to barly run then huge backfire and then it stops ) idles high sounds terible ( while driving there is a terible poping sound ) constantly backfires i know its a big list but every one else has no clue and i am stumped myself i have an 86 5.7 small block 350 v8 Gmc crew with a turbo 400 3 speed auto 2wd no a/c

On your vehicle there is a shifter interlock system ,it's a safety feature . Doesn't allow shifter to be put into gear if your foot isn't on the brake pedal .
Visual Inspection Chart Mechanical Electrical

• Transmission shift cable
• Manual control lever
• Transmission control module out of adjustment (6-speed transaxle)

• Fuse
• Connections
• Wiring harness
• Brake pedal position (BPP) switch
• Shift lock actuator
• Transmission control (TC) switch (MKZ)

Diagnostic Trouble Code (DTC) Chart
DTC Component Description Condition Symptom Action B2572 Brake Shift Interlock Brake Shift Interlock Output Circuit Failure The associated circuitry connected to the smart junction box (SJB) or fuse, or the SJB itself may have an issue causing a brake shift interlock concern. Brake shift interlock is inoperative or does not operate correctly. Go To Pinpoint Test A . Symptom Chart
SYMPTOM CHART Condition Possible Sources Action

• Shift interlock system does not release/lock correctly

• Circuitry open/shorted
• Fuse(s)
• Stoplight switch

• Go To Pinpoint Test A .

• Shift interlock system does not release/lock correctly

• Shift lock actuator

• INSTALL a new selector lever assembly. REFER to Selector Lever in this section.

PINPOINT TEST A: THE SHIFT INTERLOCK SYSTEM DOES NOT RELEASE/LOCK CORRECTLY Test Step Result / Action to Take A1 TEST THE BRAKE LIGHTS

• Apply the brake pedal and view the brake lights.
• Do the brake lights illuminate?

Yes
GO to A2 .

No
REFER to Section 417-01 . A2 TEST SHIFT INTERLOCK ACTUATOR POWER CIRCUIT

• Disconnect: Floor Shifter Harness Connector C3245.
• Key in ON position.
• Vehicles equipped with a 3.0L or a 2.3L engine, measure the voltage between floor shifter harness connector C3245-1, vehicle harness side and ground, while applying the brake pedal.
  
• Vehicles equipped with a 3.5L engine, measure the voltage between floor shifter harness connector C2096-1, vehicle harness side and ground, while applying the brake pedal.
  
• Is the voltage greater than 10 volts?

Yes
GO to A3 .

No
REPAIR the circuit. TEST the system for normal operation. A3 TEST SHIFT INTERLOCK ACTUATOR GROUND CIRCUIT

• Key in OFF position.
• Vehicles equipped with a 3.0L or a 2.3L engine, measure the resistance between floor shifter harness connector C3245-4, vehicle harness side and ground.
  
• Vehicles equipped with a 3.5L engine, measure the resistance between floor shifter harness connector C2096-5, vehicle harness side and ground.
  
• Is the resistance less than 5 ohms?

Yes
INSTALL a new selector lever. REFER to Selector Lever in this section.

No
REPAIR the circuit. TEST the system for normal operation. Don't try to force it , you'll break something !

There are several possible causes for this symptom. Your regulator is integrated to the fuel pump inside the fuel tank. Unless the problem is in the wiring, the pump will probably need replacing. A mechanic can check the wiring for you or you can check yourself with an ohmmeter.

Not likely that the booster is an issue. The booster would not be able to overcome the brake fluid compression.
First open and inspect all brakes for leaks, adjustment, etc. Check all brake lines.
So if no leaks, did the fluid go low in the MC? If so, pad consumption would eat more than a MC reservoir of fluid, and not require MC replacement, but rebleeding and top up of fluid. If the pads are worn, and you replace them, often this will expel air back through the MC.

If you determine the MC is faulty, bench bleed the new one before install, or you will have lots of problems getting air out....

It is possible but the alternator may have went out and the battery is down,

change the temp sensor on the thermostat housing, i had a problem like that on one once it fixed the problem right up.

Hi there,

For an engine to work properly, the fuel air mix must be within certain parameters. Too much fuel uses up the available air before the all the fuel is burned and causes the engine to 'stumble' (a momentary lack of power until the fuel/air ratio has been restored). Flooring the pedal can certainly cause these symptoms.

When this happens, it's lack of air, not gas that causes it. Check your air filter as a possible cause, it may need to be replaced.

I would suggest that your Clutch Pack is in a progressive stage of Failure. These indicators are outlined in your symptoms.
As you will appreciate, each application of the Clutch pedal allows the Clutch Plate [Spinner]to Disengage and Rengage on shift completion, but in a different place on the Flywheel and Clutch Pressure Plate, after each shift, Up or Down the Gears.
This I conclude is why you are getting varying responses, during your driving cycles.
Regards,DT

this is common.
it is caused because NO ON ever changes the cable at 100k miles.
it then wears a groove inside the cable and jams where you cant see.
(got my car dirt cheap cuz no one could figure this out)

the next thing to happen (toss coin) is the fire wall cracks or the clutch pedal spline strips.
full story here,
http://www.kick-fix.com/tranny/clutch/clutch-on-kick.html

now you know the why , so now correct all the damaged caused by a $45 cable.

all parts are at suzuki , every single one.

Your cadaletic converter is clogged.You need to get a new one.

check for clogged catalytic converter