1989 Monter 3.0 rough idle/hesitation ....thoughts?
 

Hello all. I just drove the Montero down to Todos Santos in Baja Sur last week. About 3 hours north, the CheckEngineLight came on, but without symptoms. My EGR TUBE had been patched with JB Weld and that finally melted off, so I replaced it with the spare I brought down with me. The CEL stayed lit. Then a couple of days later, I was driving down to Cabo and while accelerating up a hill, it started to pulse a bit (slight hesitation followed by acceleration). But it still drives fine other than that. On that same drive yesterday, no pulsing. But its running and idling a bit rougher than before. And the exhaust smells worse...

I retrieved the error code with a voltmeter - 42. Haynes suggests Fuel Pump (which is new) and to check Harness and Connector and/or the control relay.

Before I got the code, I took it to a local mechanic. He suggested it was the spark plugs and replaced them (only 4k on them). Still rough...starting to think sensors or ECU.

Anyone have experience here? I'm stumped.....Thank you....