I have a 95 Lexus sc400 I just replaced the ecm, it sat 8 months, now check engine light is on and it surge idles from 1200-1800 rpms. When I pinch the vacuum behind MAF it idled down and stops surging, I cleaned idle control and egr, I cracked the fuel cap and fuel was at the cap. I've checked all vacuum lines by missing brake clean I have no leaks I have noticed. Any ideas?

 

By what you described I would say you have unmetered air going through the pcv system. I would one, put in a new pcv valve. just because it rattles doesn't mean it is good. One with a worn or broken spring rattles. Two I would make sure all the pcv lines are on and not cracked. Make sure the oil cap is on a sealed. Make sure the oil dipstick is in and tight.

 

Thank you, I'll get that tonight and try again in the morning. I haven't messed with non carburetor vehicles much. I really appreciate it, I'll try it and reply with the outcome

 

You should move this to the 1st gen sc section too.

 

New to this, how do I do that?

 

On CL, only moderators or the staff can actually move posts, but you can copy and paste your original question and start a new thread in that forum.

I agree with Coleroad on the pcv system. I'd also check and see if the idle air-control valve (IAC) needs cleaning, which can be done with aerosol throttle-cleaner or engine top-cleaner.........sometimes they get a carbon buildup or fuel deposits. And, if the car had sat for eight months as you described, and the battery died, some (?) idle-fluctuaton may occur here and there as the engine's computers reset themselves...or with a brand new one.

 

Cleaned the IAC already