07-23-10, 12:15 AM
On my 94 STS, I did a couple of WOT's. When I pulled into driveway, my check engine light came on, code P136. Car had a real rough low idle. Before the WOT's, the idle was smooth. Would a bad EGR cause a bad idle? I know the EGR is mounted on the water crossover. If I decide to change the EGR valve, will antifreeze come out? Do I need to drain the antifreeze before changing this EGR valve? Do these EGR's go bad? I unplugged the electrical connection from the EGR and now the car has a smoother idle, however I of course still have that P136 current code.
07-23-10, 09:49 AM
The EGR (Exhaust Gas Recirculation) valve bleeds a metered, changing, amount of gas back into the intake manifold to slow down combustion and therefore cool the exhaust gas discharge, limiting NO. The EGR is NOT wet. You probably blew carbon chips and crap into the orifice and tapered pintle, so it's hung open at idle and giving a false air/fuel mixture. Either remove and clean it thoroughly, or with a stroke of luck, a couple more real WOT's might blow it clean. There is no magic potion or snake oil that will clean an EGR: it's knuckle-busting time.
The crossover was merely a good place to add a casting for the EGR mount and gas passages.
Would a bad EGR cause a bad idle?
Yes, if it is not completely closed. Stuck open it will cause a stall.
Do these EGR's go bad?
Rarely. Do as Sub said and clean it. There is a tutorial in the Tech Tips section