[PTSchram]

OK fellas, the Disco is running pretty well, but the idle won't even out, seems to be surging, but I can't tell if it is electrical (thank you Lord Lucas), mechanical (vacuum leak?), or hydraulic (bad injector on one or two cylinders).

I have replaced the coolant temp sensor and the battery, and even cleaned the dreaded K&N air filter. The truck starts up perfectly and almost immediately begins this low RPM surging...

Damned thing runs fine, gets me to/ from work every day (100 miles), the gas mileage seems to be coming aorund too and I'll have new oxygen sensors soon (I don't know why I think I need to replace them, they only have 163K on them and they LOOK fine.

The surging reminds me of a Toyota without a full radiator and the ECU can't tell if it should be in cold mode or hot mode...

Oh yeah, I put a new cap/rotor on it last week at about 44K on the old cap/rotor. Maybe try some new plugs this weekend, the weather is supposed to go positive in temps.

Peace,
Paul

 

[Old Scout]

Is the IAC port clean?

 

[evilfij]

Ditto

 

[PTSchram]

Gee, I only cleaned it 40 or 50K ago. I'll check it, it was on my list, thanx fellas. Maybe it needs to be replaced along with the oxygen sensors. I thought these things last forever...

Paul

 

[J bradley]

Some arm-chair back seat wanna be mechanic pontification

Did you try sucking on the vac advance hose to see if it affects the idle?
I read somewhere , but don't believe, that non-stock cap and rotor can cause stumble, maybe try swapping back the old'uns. If the O2's aren't functioning well the stepper can get filthy fast right ? A slightly loose plug wire will stumble it too...

How well does it run up to 85mph ? ?

 

[PTSchram]

Thanx Brad. It runs fine up to 85, no vibes even! The vacuum advance can should have little to no effect at idle, however, it can be a source of vacuum loss, so I'll add it to the list of things to check.

The cap/rotor I replaced were also aftermarket, so that might not prove anything. Working for a tier one supplier, I discount much of the voodoo about aftermarket parts. We ship parts from this factory in OEM boxes bearing the OEM name, rather than ours.

Plug wires-replaced plugs a few thousand miles ago and carefully reattached.

Don't know about the stepper getting dirty with old oxygen sensors-the sensors aren't lazy enough to throw a code so they may be working fine, I have yet to throw the oscilloscope on them to see what's really happening, but given the mileage, it would be a wise move to replace them anyway.

Keep 'em comin'

Paul