Hi
I am having a lot of trouble with my 1984 Camaro z28 HO 5 speed. I cannot get the car to stop running too rich.

The engine is a 305 which has been recently rebuilt 0.030 over with around 9.5:1 compression and a mild efficiency/low end torque cam from Melling. The stock intake, heads, carb, and distributor are being used. The entire smog system has been removed as well as the egr. The evap canister is connected with all necessary valves. The exhaust manifolds have been replaced with the edelbrock shorty headers/ y pipe set. The catalytic converter is empty and the air pipe leading to it has been blocked. The exhaust backpressure butterfly valve has been removed. Every sensor, gasket, hose, iginition wire, spark plug, etc is brand new. All electrical connections have been checked and also there are zero vacuum leaks.

The carburetor is a rebuilt quadrajet from Holley. This carb is exactly the same as the original carb and has a new m/c solenoid and tps installed. The fuel pump is a new airtex replacement mechanical pump. The car also has a Holley fuel pressure regulator and 0-15psi gauge. The fuel pressure is set at 5.5psi. Lowering the fuel pressure does not help the problem.

The car starts, drives, and shuts down great. The car has lots of power. The idle is a bit rough. When the car is idling at running temp after being driven the idle will sometimes begin "dancing" rythmically between 400 and 700rpm. Revving the engine a bit usually makes this problem go away.

The exhaust smells noticeably fumey/gassy, and after a little driving or idling the oil begins to smell of gas. When driving, the car throws a code 13-oxygen sensor which comes on and goes off. The oxygen sensor was replaced but this problem persisted. When the oxygen sensor was replaced, the old one removed (which was just a few months old) was found to be covered in soot. The old (new) spark plugs were also removed and replaced. When removed they were also covered in soot.

After driving or idling, the bottom of the large vacuum controlled evap canister valve in front of the carburetor collects some gas. When the gas is emptied and the car is driven again, this valve once again has some gas collected within it. The carburetor bowl float height is set according to Holley's recommendations.

When the car is idling in closed loop mode, the dwell reading from the m/c solenoid is 54 degrees. My Haynes book tells me this means the computer is responding to a rich condition by running the m/c solenoid lean 90% of the time which is its maximum. When the car is revved while parked the m/c solenoid dwell reading dips for a split second and then returns to 54 degrees. The voltage from the oxygen sensor while idling is somewhere between 500 and 700 mV.

Most recently, I blew compressed air through the return line from the fuel pump to the tank. Now while driving, the car no longer throws a code 13-no oxygen sensor. Also the idle no longer "dances" while idling at running temp after being driven. All other problems still exist however. The m/c solenoid dwell and oxygen sensor voltages are the same as before.

The idle mixture jets are both set at 1.5 turns. The number of turns from the factory on the original carb was 2.5 turns. Turning these two screws in or out at the front of the carb does not help the problem. The m/c solenoid stop screw within the carburetor is set at 1 1/4 turns. The original number of turns from the original carburetor for this screw was 1 1/8 turns. The numbers I have the carburetor set to are the numbers that Holley recomended.

The initial timing and idle rpm are set to the service manual recommendations which I believe are 8 degrees BTDC and 700rpm. The ignition advance weight springs are original and the computer has not been reprogrammed.

I absolutely cannot figure out what is wrong with this car. I next plan to run the car with the fuel pump return line fed straight into a gas can and observe how the m/c solenoid dwell number and oxygen sensor voltage react. I don't see how this can make a difference however since The fuel pressure is regulated. I just don't have any more ideas.

I will greatly appreciate any help you guys can offer me! Thank you!!

 

My oldest son had the same carb and the same problem. His is an 82, so we removed all smog, unhooked the computer, installed a distributor with vacuum advance and last and most important, got rid of the QJ and bought a 570 cfm Holley Street Avenger carb. End of problems immediately! Well worth the money and effort IMO.

 

How did you remove the first distributor to install the vac advanced one? On the 84 Camaro there is a piece of sheet metal overhanging the distributor. I tried to remove the original distributor but I could not get it past this sheet metal. It seems I would have to remove the entire engine or at least the intake manifold in order to remove the distributor..?

Thanks for any help you can offer me

 

The sheet metal that you are talking about is the lip for the firewall. We just took the cap and rotor off the distributor to get some clearance from the firewall and then took the distributor clamp bolt out and pulled the distributor. We did the same thing on my youngest boy's 86 and replaced it with a vacuum advance distributor. Try taking the distributor apart and I think it will come right out.