Baffled 2003 QX4 - idle and choking/stalling issues.

[waynorth]

So, earlier this spring, I started having issues with my idling, in where my 2003 QX4 was cold it would surge up and down, from 750/800 rpms to 1500/1800 rpms and once it warmed up it would stop. It got to the point where even after it was warmed up the rpms would surge up and down. I finely figured out from this site that quite possibly the ECM was fried due to a bad IACV. I sent off my ECM for repair and while I was waiting for it to come back I ordered the following items for replacement - a TPS, IACV, PCV valve, intake manifold gaskets and a intake air temperature sensor. While I was at it, the exhaust was rusted out so I ordered a whole new exhaust as well as new O2 sensors. The exhaust arrived first, so I got busy and installed it first - no problems, went nice and smooth. All the other parts arrived in. I first unhooked the battery, and then took my time installing all the parts over the day, nice and easy. On the second day, installed my repaired ECM, hooked up the battery and completed the relearn and the other gas pedal setups as explained in a post from this site. Car started fine, no surging but a still a high idle(1000-1050rpms) in park. I had set the TPS the day before but I checked it again and it was fine at .41 VDC. I tried the relearn again but it does not take. Idle still high at around 1000rpms. A new problem arises, now when I press the gas pedal the QX4 stalls/chokes itself out and will not rev up at all, then I get a code P0051 on my reader which translates to a O2 sensor heater not working on Bank2 Sensor1(drivers side front O2 sensor). So I go back under the hood and start double checking connectors, checking settings, checking fuses, and everything seems good. I and still getting the P0051 code but I found something weird to me, when I was checking the TPS, I had both connectors off blowing them out with air and forgot to install the bottom (grey) plug back in and when I started the QX4, the idle never changed, it was still high but the engine ran perfect, it would rev up and down, with no choking/stalling issues. As soon as I realized that I had not plugged in the grey connector, I shut off the QX4 and plugged it back in, started it up and back to the same issues of stalling/choking out when trying to rev up the engine. I double check the plug issue twice and got the same result, grey plug in, stalling and choking, grey plug out, engine runs fine.

My questions are as follows, why the high idle still and why when the grey connector on the TPS is left unplugged the QX4 runs great but when plugged it chokes/stalls itself out?

Any help would be greatly appreciated.

Way North

[atraudes]

Sounds like a bad or uncalibrated TPS. What brand did you buy? Did you calibrate it per the FSM when you installed it?

[Buzzman]

Sounds an awful lot like a relearn issue.
After the ECM/IACV crap I went through, I tried and tried to do a relearn as per the FSM, and was never successful.
Took it to my dealer, and the techy did it in five minutes with his scan tool, at no charge.
It's been running great ever since.
Take it to a dealer if you're close to one, and see if you can talk them into doing it for you. It's a five minute procedure.
Good luck.