Hey guys, I drive a 2000 Chevy Blazer with 219k miles. 4.3 liter 4x4 4 door.

I can't figure out what these issues are to save me life:

1&2) I have a really rough idle but only when I have the A/C on. When I come to a stop light, my car starts shaking pretty bad if I have the A/C on (cold) but if I turn it off, it's completely fine and idles smoothly. However, when I go to accelerate from stop, it has "choppy" acceleration as if it's struggling. But once it shifts up once or twice, it's fine. It's even worse if I accelerate from a stop WITH the air conditioning on. I am almost in need of an oil change but it did this even the last time I had it changed. I have read around that the shaking may be coming from the IAC valve and that I need to clean it. I'm going to try that soon but I am curious if there are any other suggestions. It's probably due for a tune-up (plugs and cables) and that is on my list, too.

2) I can hear a rattle/high frequency grinding sound that changes frequencies and noise when I am accelerating, which gear I'm in, etc.. I had my muffler replaced (had a hole in it which I thought was the problem) and the heat shield on my Catalytic Converter re-welded (was half hanging off) but the problem is still there. I haven't been able to pin-point where the noise is coming from specifically.


Any help would be great!! Thanks so much.

 

Yes, pull the iac sensor and clean it!!!! also do not cheap out on tune up parts!!!!! acdelco all the way ! Cap,rotor,plugs and wires.....u can use autolite professional wires as a cheaper alternative if u use any other brands u are asking for problems.......... as far as exhaust rattles, well I just pull the heat shields off when they start to rattle

 

I definitely don't plan to cheap out! (except i just got a reman'd alternator because I was tired of the squealing in the pulley) and haha. pretty sure it's not a heat shield though. Definitely sounds like something internal.. but when i clean the iac and replace the other stuff i will definitely update if the problem is still here or not. and as far as the exhaust noise, I still am clueless but will be a little more diligent in trying to be more specific

 

check the cat - thump on it with a rubber mallet ect. if the inside is breaking up it could be the rattle and causing the other problems as well

 

So the exhaust rattle was because my cat heat shield was resting on the cat. Pulled that back with about 7 mm clearance and noise is gone completely. More info on the violent shaking sluggish acceleration from stop: it may also be my tps sensor. If the IAC valve cleaning doesn't help, I'm gonna replace distributor cap and rotary button, then tps sensor. I'll keep updated.