93 sev6, idling rough in gear

[Bennydaheeb]

So I bought this cheap, in good condition with blown head gasket. Replaced head gasket, had head seviced at local shop. Ran ok, but rough, underpowered. Let sit a couple of months, would not start. Fuel pump relay good, fuel pump getting power and fuel guage not working. Replaced fuel pump, will idle ok with occasional miss but when put in any gear other than p or n, it idle drops to 300rpm or so and stutters and tries to stall. Smells like it is rich, and plugs show slight fouling but not the worst I've seen by far. Any ideas? I'm a motorcycle mechanic, and after a bit cars start to baffle me.

[SpecialWarr]

There is an idle-relearn procedure in the FSM available to download for free on this forum, start there! As for what the problem is I have: the Idle Air Control Valve threaded out too far causing fouling, a Mass Air sensor that has a weak ground ( that one has been covered on here many times) or a dirty intake / plugged PCV valve / missing vacuum line on the fuel regulator ( at the back of the intake next to the firewall).... I'm not in any way a mechanic but I do own a now-running Pathfinder thanks to some of the other folks on this forum!

[Precise1]

Also in the FSM (that can be downloaded from the pinned thread in the Garage Section) is a list of fault codes you can read from the ECU which might give you an indication of where to start. Even the automatic transmission has diagnostics, so I recommend checking all that first.

There is a good write up on checking the ECU in the Garage/How To section, and the earliest FSM is for 1994; don't worry, 95% of it applies to 90-93 as well, the only real differences are dash, trim, etc.

 

B