I have a 95 K2500 Pickup with TBI 350 and 4l80e. Every once and a while it breaks up when I jump on it. Mostly in upper RPMs right before a shift. I have an FIPK2 from K&N(previous owner), ported throttle body with shaved throttle shafts(my own work), and the cat is removed and replaced with a few feet of pipe and a flowmaster 40 with dual outlets. I am going to put tailpipes on the muffler tomorrow hoping to quiet it a little bit. I will be puting on a Turbo City TBI spacer soon and I think I need a fuel pressure regulator. I pulled plugs and they were all pretty white at the tips. I'm coming off a carburated motor and to me this says I'm running pretty darn lean. A friend thinks my injectors may need replacing. I am wondering what the specs on injectors are? I heard that stock 350 is 55lbs and 9c1 cop 350s are 65lbs. Is this true? If so would running the 65s be better and would I need a chip change?

 

well I finally located the wire to disconnect EST so I could check my timing and it was quite retarded so I set it to like 1 degree advanced and it seems a lot better and didn't stumble on the quick test drive I did. Still wonder if the bigger injectors would be more power?

 

How much did you port it to? It sounds like its time for larger injectors if its going that lean. Also, check your fuel pressure! It also sounds as though your pump may be going bad and your loosing pressure at high rpms/loads. Advancing the timing will only make things worse for your motor as the already dangerously hot lean mixture will burn even hotter.

BTW, if its going really lean, id park it untill its fixed if i where you. No need to damage the motor. The stupid tbi computer will jsut merrily burn down the engine without even throwing a code in some cases as the O2 output has to be <.2 volts for something like two seconds or more.

 

I don't think its so lean that its dangerous, I ran my K5 about as lean for quite some time, but I'd like to address why it is. When I adjusted my timing it was like 5 degrees retarded so I put it to like 2 advanced. It seems to run better I haven't tried pulling a plug yet. The platinum plugs weren't holding onto crap when I checked one last night so I couldn't tell. I didn't change the throttle bore at the butterflies but I hogged out the rest of the bore pretty well. And I ground the throttle shafts and screws down for better wide open flow. I think I need to get an adjustable regulator and bigger injectors. Will it require a chip change if I do get bigger injectors?

 

i was under the impression that it was running really lean. Well, if you didnt change the bores at the butterflies then the ammount of fuel needed wont change much from stock. Id say if its breaking up at high rpms and going lean id check the fuel pump. Its most likely getting tired and not providing the needed pressure under load. Hook a gauge up and put it somewhere where you can see it from inside the truck and watch the fuel pressure. If teh needle falls off as the engine is put uder load then the pump is garbage and youll need a new one. If you do move to larger injectors, then you will need to get/ burn another chip for the injectors to have the fueling be right. Id check the fuel pressure/fuel pump first before you move onto other things.

 

do you have those bosch platinums? Ive found out that they seem to be pretty hot runnign plugs and they stay realativly clean compaired to other plugs that ive used.

 

yep bosch platinums they definetally stay clean