Recently my 90 coupe started cutting out after it got warmed up. I replaced the fuel pump, filter and put in some new after market injectors. The car runs great now but my mileage went from 15 to 9.2. Anybody have any ideas why this could have happened? Thanks for any help!!

 

The possibilities are many! You really need a pressure gauge. Check the rail pressure,if the regulator is stuck or too high,that'll hurt your milage. Were the injectors the same size as stock? Size shouldn't make too much difference,the computer should be able to deal with that. Spray pattern could get into the picture,a lousy mixture would hurt power,causing increased throttle and the o2 sensor might not give a good number if the fuel was not uniformly mixed. I would definitely investigate the pressure issue first!
Ron

 

Hey thanks for the info! I will definitely check it out. Offhand do you know what pressure i should have?

 

I think 35-45,but my memory is not good?
Ron

 

Stock L98's use a 22lb injector, more than that without opening up the engine to breath better (performance enhancements) will be overfueling engine. Have any trouble codes? Does the engine blacksmoke?

 

i had my intake off on my 1990 l98 a few days ago car is totaly stock & it had 19 lb injectors in it .

 

Mine has 22lb in it. When I first built it, I had ordered some injectors and unknowlingly, I put them in without checking them. They were 19 lbs and it ran terrible. The 19 lb injectors are for a 5.0 L98 in the IROC Camaros and also same injectors are used in 5.0 Ford Mustangs.

 

mine runs great now might look into 22 0r 24 when i build my 383

 

I failed to mention that mine has 250,000 mi. on it. The auto trans is probably not helping you in the mileage dept. either. If your power seems low, then I really do think it could be pump or injector problems. This model engine is notorious for fuel pump problems. Mine has needed replaced approx. every 50,000 mi.

 

Are you using Delco pumps? If not, that is probably why you have to keep replacing pumps.