I have a 89 formula 305 with about 64K miles on and for some reason it has had a miss in it since i purchased it about a year ago. The miss happens when the car is under load or in hard WOT accel. Now i have already replaced the O2 sensor, cap, rotor, plugs, wires, and fuel filter, but nothing has fixed it. I now have a set of SLP 26# injectors that i am about to install, but i am wondering if any of you out there have had a simular problem.

Thanks,
byrdman

 

check your vacuume lines and make sure you dont have a leak

 

I'm not sure about the miss but I don't think you should be putting 26# injectors on a 305. You will be running real rich afterwards.

Would that really cause a miss?

 

 

A vacuum leak would cause a miss at idle or cruise (when vacuum is high), more than when you get on it (vacuum is low.... no suction, so a leak doesn't matter so much).

Injectors are a better bet. If you've already got them, try them. Those particular ones are probably too big, they'll make your car blow out black smoke at WOT and foul plugs real fast; but at least if it smooths out until all that happens, you know that one of the ones that are in it, is probably bad.

 

Have you made any mods to the vehicle? If its bone stock then adding the injectors may just mask what the real issue really is. Do you have the ability to scan and datalog? Also, is all the intake ducting air tight? Like, no open ports or cracks after the MAF?

 

Have you checked or replaced the Coil? Bad coil will cause a misfire at high RPM or heavy loads.

 

I am going to have a chip burned to compensate for the injectors. The only other mod is a cone air filter. I do work for a chevy dealer and have had several techs look at the car but they tell me that they can not find a problem. I have also hooked it put to a scanner but with no results. This can was owned by ,litteraly, a 64year old lady who owned it since it was new, and i think it has just sat around for so long that there are some parts that need replacing.

Thanks ya

 

Good point Chickenman, Id check teh coil and module. A weak ignition will cause a miss like said above.