Rep Power: 0

03 civic EX 1.7 126k miles. Idle is rough. Even rougher when the AC is on. Sometimes the idle drops so much with the AC that it almost dies. Lacking power while driving but engine is smooth at higher rpms. I have an Autel scanner. Only codes were evap vent which occasionally comes on, even after replacing all evap parts, and downstream O2 sensor. Replaced sensor and that code went away. Bi-directional testing failed iac, egr, vtec. Vtec actuates if I jump power to it but doesn't when commanding with the scanner. Vtec seal and screen Replaced less than a year ago. Replaced tps and iac. It got better for a day and got worse. Had a air leak code. EGR was sucking air. Replaced and got better for a day. Timing belt was overdue so Replaced belt, tensioner, crank sensor, cam sensor, cam seals, valve cover gasket, plugs. Adjusted valves. They needed very little adjustment. Smoked the intake and evap and they're both sealed. Alternator was replaced prior to ask this because it failed. Fuel Pump was replaced prior to all this for a leak. Fuel pressure is 45psi at idle and revved up. Idles is now inconsistent. Sometimes as high as 1100 rpms. Rpms are about 100 different from gauge to scanner. One time, at idle, the rpms went up around 6-7 and back to idle but engine never changed. All grounds have been clean and ohm'ed, theyre good. I'm trying to source a salvage ECU to test but I'm not sure where to go on this car. Any help is greatly appreciated.

 
Rep Power: 367

typically, when ECU is fried, the alternator bolts are loose and did the frying. Scanner will not be able to read ECU either. If you can still connect to ECU, not likely.

 
Rep Power: 0

The alternator mounting bolts? I can still connect with it. Some of the bidirectional testing abilities arent working

 
Rep Power: 367

That could indicate ecu issues, yes,,,

 
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What alternator bolts would come loose causing an issue? The last alternator had intermittent issues since it was put on.

 
Rep Power: 367

just check if they are loose. famous issue in the 7th gen cars.

 
Rep Power: 0

Alternator was put on close to 6 years ago. It had intermittent issues. Finally went out. Bolts were tight if I remember correctly. New one went one a month or 2 ago. I just did the timing belt so it came off again. Bolts were tight. Bolts are tight now. Maybe the previous failing alternator caused an issue with the pcm?

 
Rep Power: 367

since you have an ECU on the way, that should answer the question