My 1989 Formula Convertible is sick. The car has a 305 TPI, a 5-speed and dual cats. It starts fine, but usually idles a bit rough. It also feels a weak, has a stumble at steady throttle and spits black soot out of its tailpipe. The car is essentially stock and has 62,000 miles on it. It obviously sits more than I drive it. Have my injectors gotten old? Any help would be greatly appreciated.

 

the black stuff normally means you got a rich condition. my car did the same thing when my injectors went out. check the ohm reading on your injectors then look for the normal things toi go wrong likr plugs wires and if it sits a lot you might have shitty gas

 

Checking the injector solenoid resistance won't hurt, and if one or more are significantly low resistance, it may be causing the remainder to go static (always on). However, solenoid coil resistance won't tell you anything about injector flow and performance. One or more might be streaming, leaking, or sticking.

Perform a running and standing fuel pressure test to see if there is a leakage problem, then perform an injector power balance test to help determine which injector(s) might be a problem.

I first pulled my injectors at 18,000 miles because of flow problems, and again at 22,000 miles, so mileage may not be a good indicator.

 

no matter what anyone tells you here, you have 20.5lb injectors stock, not 19lb. your dual cat car is special. do not put 19 lb injectors in your car, it won't run above 4000 rpm's.

 

Blocker: If you have black soot coming out of the tail pipe, I would think that you are burning oil in the combustion chambers. However, do a complete turnup (spark plugs, TPS & IAC addjustment) and check the injectors as talked about above. There are several tech articles on the home page here that you should read to tune up your engine.

the blur: What the heck are you talking about????? Whether the injectors are 19s or whatever you say, the engine should have no trouble whats so ever running above 4,000RPM if its tuned correctly. The ECM can correct the fueling about plus/minus 15%.

 

except when you go WOT, and it starts leaning out above 4000 rpm because the incorrect injectors are in there. considering your running with the factory tune.