Cold weather stalling

[mamesteco]

Now that the cold weather has hit us here in Ontario, my 96 Disco has started to stall occasionally.
Before the cold weather was here I had a code for upstream O2 sensors, engine light was on. I changed both upstream and cleared the code. Now I have the P1194 downstream code on and engine light. Still occasional stalling, low idle when it is warmed up.
Anyone have an idea what is going on?
Why do I have a downstream code now and didn't have it when I had the upstream code?

 

[joey]

Clean your MAF, TPS and IAC and clear your codes, you should be good after that.

 

[mamesteco]

Any cautions on cleaning?
Can carb cleaner be used on all?
Don't want to trash any.

 

[joey]

Contact cleaner or MAF cleaner.

 

[mamesteco]

Cleaned TPS, IAC(did a check, and it moves with on-off of key) , and MAF and cleared the codes. Now when I start it, it revs at 2200rpm when idle, drops to around 1100rpm with a load. Now What????

 

[joey]

If after a couple of shutdown/restarts if it is still running high rpms, then I would Disconnect the battery for an hour, reconnect and try again.. if issue continues, I would check fuel pressure to make sure it isn't the sign of a bad fuel pump.

 

[mamesteco]

Thanks for your help Joey.
Took it for a couple of good runs.
Disconnected battery for a couple hours, still idled high.
Checked stepper motor again. (I believe that was my problem for the low idle, it was very dirty).
From our searching we found the TPS defaults to 2300 rpm (right about where it was idling) when not working.
Took TPS off and cleaned again.
Idle is down now. Idles down to 1000 rpm when stopping and a couple of seconds later it will idle down to approx. 750 rpm.
Why the hesitation?

 

[mamesteco]

Nope, back to a low idle and stalling!

 

[joey]

just to make sure, I would check the fuel pressure at the rail to see if you don't have a fuel pump starting to go out.

 

[mamesteco]

What is your reasoning for checking the fuel pressure?
I see the fitting on the rail, have never checked this before. Do I need a special fuel pressure gauge to check the pressure.
Can a gauge be permenantly mounted to the fuel rail?