Need help with shifting problem

[mattmc]

I took my car out on the main street that runs by my house for a short go through the gears to see if there were any problems. Wouldn't you know I had a problem. I'm learning as I go so need some help this this. Here are the symptoms.
from first gear, accelerate to 3.5k, shift to second and accelerate to 3.5k, go to third when I accelerate and hit the 3k mark the car starts to learch and the engine starts to backfire. Downshifting doesn't seem to help much until I pull into my neighborhood and get it back into first. I did have one successful run up to 4th but I was very easy on accelerating that time. Appears accelerating aggressively makes it worse. What should I be checking?

Thanks for the help!
Matt

[tjmotter]

My first thought was that your ignition timing is set too low. With low gearing the engine can make enough power with a retarded advance but as you get into the higher gears, the engine has to work harder and could see backfire if the ignition timing is set too low.

[mattmc]

I have a turner with a few other tunes on it. I'll try those and see what happens.

[mattmc]

I was looking at the injector size and it looks like I have 42lb injectors, they are light green in color. I think the engine had as supercharger on it before I got it and all they did was remove the super charger and put a stock intake on it. does that sound like it could create this type of problem? I guess I need to get stock size injectors 30lb? is that right?

[dsblk93gt]

24lbers are the stock size, I can link up to what they are if needed. It will definitely run like crap with 42lbers and not being tuned for them. I would not drive it like that and change the oil asap. What tuner? SCT or Diablo?

[mattmc]

I have an SCT tuner, getting a new tune should not be a problem. I'm going to check the MAF and get some 24lb injectors and update the tune. On the oil comment, do you think I'm getting gas in oil? thanks for the help.

[CraigS]

I know you haven't run it much but I agree w/ the change oil idea. Too much risk to save the $20 oil will cost. You could even remove the oil filter, pour out the oil and reinstall.

[mattmc]

In case someone stumbles across this thread later. My problem was solved by changing out the fuel injectors to 24lb injectors, I also changed the oil to be safe. took the car out this last weekend and it ran great! Thanks for all the help!