I have a 99 accord with the 4 cylinder that is has some problems recently. I just had a new radiator put and head gasket put in and now it is stalling a little at 4000 rpms. It doesn't die but it just can't get passed 4000. It only does it after I've been driving for about 45 minutes or so and once it does it there seems to be less power at lower rpms also. I also just ran some injector cleaner through it too thinking that it might be a fuel system problem but that didn't help. Does anyone know what it might be?

do you have a check engine light?
sounds like you're in limp mode.

Ya the check engine light is on. What is limp mode and how do I fix it?

limp mode is when your ecu protects your engine from over-revving while broken.
go to autozone, diagnose your cel then get it fixed. then you should be able to redline again.

Thread moved to Problems and Solutions.

If you had head gasket put in, then the cylinder head had to come off the block, it's likely the timing belt was not reinstalled exactly right, ie the camshaft gear maybe off a tooth relative to the crankshaft pully, which can easily explain the loss of power condition you are describing.

Thanks for the help

Ok I just went to Autozone and had it tested and it said that it is a VTEC system malfunction. The oil level is fine. What else could it be?

Check the electrical connection to the VTEC solenoid to see if power is getting there, you likely can't monitor this while the car is stationary (there maybe a way but I don't know it without a shop manual).

You could (as I did years ago with my Integra) stick a couple of pieces of wire into the connector and bring the wire into the cabin to hook up to a small pieze transducer, it will buzz when the electrical signal reaches the VTEC solenoid.

The VTEC solenoid also has a fine wire-mesh screen to filter out crud, take the valve out and see if there are any crud, clean it if there is then try again.

Or maybe it's as simple as the guy who did the head gasket work forgot to plug the VTEC solenoid connector back on, or it got loosened, or it fell off.

Where is the VTEC solenoid?