Car: 1997 Camaro SS LT1

After bashing a hole in one of my pistons I took it to a local shop to have the piston replaced. While in the motor I asked them to install egr block plates. I wanted to build a real engine, but at the time I lacked finances. After getting the car back it has a serious idle issue. Idles at 900rpm. When I lightly depress the throttle to increase rpm to 1400 or so the IAC adjusts the rpm back to idle(900) with my foot still on the throttle lightly. When I release the throttle the car stalls because it can't adjust fast enough. I adjusted the minimum air to 900rpm using the idle screw until I could figure this problem out. Idle still fluctuates between 800-1100rpm. I can hear a knocking noise coming from the cyl with the originally damaged piston. Not very loud, but just enough to annoy you. The more rpm the more it knocks. At high rpm the pedal feels like it is vibrating. Since getting the car back I have replaced opti (200 miles ago), TPS sensor, cleaned IAC.

Does anyone have a clue what is going on? I will be getting autotap next week its in the mail now.

 

Are you sure the vacuum line to the EGR was capped off?

 

Vacuum line has been removed/capped. All plug wires are on, new distributor, new tps, clean IAC, tried new MASS AIR at dealer, but that didn't help any, new right bank O2, all injector connections good.

 

Don't think the IAC is going to correct the idle once the throttle is moved from idle position. Don't really see how it could anyway since you now have the throttle plates open and the IAC flow circuit has little effect on the engine speed at that point.

We assume you haven't gotten an SES since you didn't mention it.

You need to scan it for codes first and then data. If say for example you have a KS circuit problem, the PCM will pull timing but will not set the SES. This could give the impression the engine is slowing down when the throttle is cracked.

Oh yeah, one more thing. How can you hear exactly one cylinder making noise and know which one it is?

And if there is a knocking and the KS circuit is working, wouldn't the PCM interpret this as knock and retard the spark resulting in the same effect?

 

On a scantool the KS is pulling out 1.8-2.4 degrees of timing at IDLE. The noise is coming from bank 2, cyl two was the damaged cylinder. I haven't seen scan data while driving.

 

Seems to me, if you had a knocking before some shop worked the engine and you still have the same knock?????? They need to tend to something they didn't fix right the first time NO????? Once the knock is gone, then see if you still have an issue.

BTW why did your piston get a hole in the top of it?