2002 Lancer – Rough idle and getting worse

I’ve got a (U.S.A.) 2002 OZ Rally Lancer that’s got 218K miles on it with several problems I’m trying to chase down. It’s got two codes on it that it’s had for quite a while but they’ve never affected the idle or performance before – P0402 and P0421 for the EGR and first catalytic converter. Mileage for combined city and highway for years has been reaching up to 32MPG until recently when a miss that usually occurred once shortly after the engine reaches full temperature has now become much more frequent. Also I’ve been experiencing very rough acceleration from a standing start even though I’ve cleaned out the throttle body (and there was a bunch of gunk in there). I usually manage that problem by gently accelerating till the butterfly valve in the throttle body is more open then I’m usually OK. A while back I did replace the O2 sensor on the first catalytic converter but I’ve not been able to dislodge the 2nd to replace it. Tried the special tool from AutoZone and then Channel Locks but had to quit before I tore a hole in the cat’s exhaust tube.

I’ve wondered about the Idle Control Valve. I pulled the original out and tried to clean it, couldn’t take it apart like the guy on YouTube because the stem was too far in so I couldn’t take the brown, twist lock cover off. This, apparently,seized the original one completely so I went and got another from the local junk yard. That one (from an 05 Lancer but physically identical) would actually retract about 1/16″ when you turned the ignition switch to “On” and did help a little with the idle problem originally but not now. How do you tell if that valve is actually working or not?

Today I discovered the purge solenoid valve for the vapor canister next to the EGR solenoid just below the intake manifold was the source of a regular clicking noise once the engine reached operating temperature. When I pulled the wires off of it the clicking stopped. Is this click normal? I don’t recall it doing this from times past. Could it be broken internally?

The actual EGR valve does work. I can put a little suction on it and it will all but shut down the engine if I keep it open a little. I’ve also replace its solenoid valve but I’ve never been able to detect any application of vacuum to the EGR valve while driving once operating temperature was reached. I put a T in the vacuum line to the EGR valve and ran a line from that to a gauge that I taped to the windshield. No vacuum was ever indicated once normal temperature was reached. I checked for kinks, too.

I also pulled the signal connections for each fuel injector on each cylinder to see if there was an RPM drop and there was. I think this produced an additional code I’d not seen before in the form of a misfire notice but only for one cylinder. I’ve cleared the codes to see if that one comes back. The others will I know for sure.

I have gone through and checked the plugs, cleaned and regapped them. The oil is still good as well as the air filter. The MAF sensor I cleaned a few months ago with the special MAF sensor cleaner. I’m pretty much at a loss as to where to go from here unless it’s that second O2 sensor that’s throwing everything off. The engine works very well up until it reaches operating temperature and then goes to pot, it seems. At 218K miles I’m worried about the timing belt who’s idler squeals like crazy quite often but that’s a huge amount of work or a $630 bill from my trusted mechanic in town. His time is certainly worth the money but I gotta have the money first!