knocking

i have a 1996 olds bravada 4.3with 89000miles i use pure1 filter with mobile 1 5w30. in the morning i will start it and makes no noise at idel. but whene i pull out and rpms hit about 2600 it makes a knocking sound it almost sounds like a diseal engen. what could it be my 1996 blazer did the exat same thing.i am hoping it is not a rod bearing




mods
hypertech tuner
k@n FIPK)
gibson catback

i have a 1996 olds bravada 4.3with 89000miles i use pure1 filter with mobile 1 5w30. in the morning i will start it and makes no noise at idel. but whene i pull out and rpms hit about 2600 it makes a knocking sound it almost sounds like a diseal engen. what could it be my 1996 blazer did the exat same thing.i am hoping it is not a rod bearing




mods
hypertech tuner
k@n FIPK)
gibson catback

Sounds more like valve tap... Run some seafoam through the system and do a full tune up. Also try running a bottle of octane booster through the fuel system. Also try allowing the motor to run a minute or two before driving....

It does seem like detonation. If the octane booster fixes it then a higher octane fuel may be nessecary if you do not want it to detonate.

im running 94 octane becaues of the hypertech tuner

Try removing the hypertech tune and try it again.

Maybe the knock sensor is not working, you should probably make sure whether it is detonation or a mechanical know first though , it'll help diagnosing.

Sometimes another "listener" can point it out and it seems like you already know what the differnt sounds sounds like. I'm pretty good at being able to tell what a noise is, and your're description of "sound like a diesel" is detonation.

An engine shop that R&R engines from start to finish is good at being able to tell what a particular noise is , when comining the experience and feedback of being able to hear the noise and then immediately see the damamge makes them "good at it"

Try removing the hypertech tune and try it again.

That could be the problem. I've seen the power programmers cause detonation several times. Sometimes switching from the "Performance" setting to the "Towing" Setting will help.

If it clears up with setting removed, the dose of seafoam that rlith suggested, and cleaning the EGR may allow you to put the settings back in.

Sometimes a bound up caliper will also put more load on your engine than normal.

Check for any tire binding due to a brake issue.

Nope went back to stock and still does it I will try to get a recording and repost I will have a lot of time now that I graduated from high school I cant wait to go to Rosedale next fall. Thanks every one for the help