1987 Firebird GTA 350 Auto. Heres the deal. At about 2000 - 2300 RPM on the highway or in neutral the car sometimes but more often lately starts to backfire loose power and surge. Its worse on the highway. When this happens I cant get the RPM above 2000. It seems to idle fine. It was real bad yesterday. Then coming off the highway to a stop light, all was fine. I hammered it off the light, no problem. But....If i drive an hold it at 2000 RPM it starts surging and backfiring, then I cant get it above 2000 until I stop. Its doing this bacfire in park as well if I hold the RPM at 2000. Also I am getting no codes of any kind. Any ideas guys?

Thanks

 

try hooking up a timing lite and whatch to see if the strobe cuts out as you slowly bring thew rpm up into the range its acting up...

when I had a similar problem it was the coil...

if thats not it try doing the same while watching a fuel pressure guage... see if its the fuel filter or pump...

 

My guess is that your leaning out. Try what zroc said and throw a gauge on the rail and see what it reads. If possible, put the car under load and see if the pressure maintains or drops.

Matt

 

It's almost certainly ignition related, not the injection. All the injection can do is change the mixture and poor mixture won't cause a backfire. Extremely lean mixtures may cause sort of rough running but the backfire tells you it's the ignition firing a plug off when it shouldn't. I'd start with the distributor cap first and go from there.