2002 Montero Sport Limited AWD with 97K

We replaced teh timing belt about a week ago and it had been running great ever since. Before replacing the timing belt I kept having an very intermittant high idle error. After replacing the timing belt the truck ran very quiet, no problems. Today, when I stopped at a stop light, it started idling rough. In park or neutral, the idle is fine. I was driving all day and no lights, just rough idle. Then, right before I got home, I got the SES light. When I pulled the codes, I got:

Getting error codes:

P0174 (System too lean bank 2)
P0300 (P0300 Random/Multiple Cylinder Misfire Detected)
P0113 (Intake Air Temperature Circuit High Input)
P0107 (Manifold Absolute Pressure/Barometric Pressure Circuit Low Input)

Since I hadn't done it in awhile and since the car has the adaptive memory which clears when the battery is disconnected for awhile, we pulled the K & N air filter and cleaned it, cleaned the mass air flow sensor and throttle body. In doing so, we went to disconnect the battery and noticed the negative cable was a little lose so we will be tightening that.

 

So we cleaned the throttle body, the mass air flow sensor, and the K & N air filter. I reset the codes. When I first started it up, the CEL came on. I drove it around a bit and then read the code again. The only code now is P0300.

The truck is no longer idling rough when in drive at stops.

We just changed out the spark plugs & valve cover gasket on the passenger's side because of an oil leak. We didn't do driver side because there was no oil leaking and we didn't have time.

I guess we will be swapping out the plugs and valve cover gasket this weekend.

 

I'd check for a vacuum leak before I started tearing off the intake plenum again.

 

I figure since we didn't do the driver's side plugs and valve cover gasket, we should do that to eliminate any vaccuum leaks and the misfire problem.

 

So I replaced the plugs, valve cover gasket and spark plug seals today on the driver's side (didn't have time when I did passenger side). Found that center spark plug had oil on it. Wiped it all down and installed new spark plugs with Bosch iridium fusion. Started the truck up and it ran fine. Backed down the driveway, all fine. Went to put it in drive, and SES light came on again. Drove it around town and car appears to run fine. Got back, pulled code and I'm still getting P0300. Possibly oil remnants on plug? I won't have anymore time for a bit to swap out the wires so I guess I'll get to see if it goes away on its own.

 

Did you do that vacuum test?