Alright, thought I was at the end of my issues when I replaced the MAF, TPS & Air Temp Sensor, but not so much! Yesterday while on the last leg of a 350 mile trip, I stopped for dinner & when I came out the truck the truck started as usual, but then the idle started fluctuating between 1000 & 250 RPMs erratically. When I stepped on & held the gas at the same place, it would idle evenly but as soon as I would leave off the gas, it would start to idle erratically again; but never stalled. I took a chance & got back on the interstate. For the first mile or so, it acted like it wanted to stall, but never did & then ran fine. Stopped about 50 miles later, and it idled perfectly and I shut the truck off. When I restarted the Disco, the idle went to about 750 RPM, and dropped to about 250 RPM and then went back to a normal idle & ran fine. When I got home last night I turned the Disco off, and restarted it, and the idle went to about 750 RPM & dropped to 250 RPM before evening out. This morning, I started it, and again with the erratic idle. I left it running and checked the fuel pressure at the rail; steady @ 38psi, and watched the TSP reading on my UG which remained steady at 12.2 the entire time while the RPMs but the idle was bouncing between 750 - 250 RPMs. I know I have a dead spot if I step on the gas a bit hard when pulling into traffic from a stop sign that I can overcome if I ease into the pedal, but if the TPS is reading steady, and the fuel pressure is steady, what in the heck is causing this new level of idle Hades??

 

Have you tried unplugging vss, did you reset ecm after changing the IACV?

Look at wiring on the crank sensor be sure it is not toast

Pull one plug wire at a time from plugs while running look for good constant blue arc

Just throwing out ideas

 

Nope, I didn't reset the ECM after replacing the IACV. Haven't been near a dealer to do that. Haven't looked at the crank shaft position sensor wiring as I didn't think the issue could be that, but I will.


Not that I'm reaching at straws or anything, but I was just sitting here wondering if there was a plastic safety coating from the shipper on that IACV I might have forgotten to take off... Yep, I'm reaching for straws

 

You did put gasket on IACV right? You may want to find a shop to reset ecm values dealers are $

 

I did put the gasket on. Curious if Lucky8 can do something like re-flash the ECU. They would be about the closest place I can think of. After all of the weirdness yesterday & this morning, This possessed piece of engineering (in lieu of expletive) started & ran great all afternoon with no issues.

 

Codes? Think mine did this some also before I was reset

 

Just that pesky 1179 code. Yep, I'm thinking I need to have the ECM reset. Did you take yours to a shop to have it done, or send it off?

 

Drove 2 hours to a shop ,dealer screwed me on the reset previously

 

That's about how long it takes to get from here to Buffalo. Going to call Lucky8 in the morning to see if they can do it & what they charge.

 

guy felt sorry I had to drive so far $20, cost a tank of fuel though, still cheaper then the dealer