Cold Start issue

[Snowman]

Folks - I'm having a cold start issue with my 98 Discovery - It starts up fine but the idle stays high (1000rpm) and runs uneven down the road (surge and drop, surge and drop in power) untill it warms up - Runs smooth on a warm start - Now the Check Engine light has come on - About 1000mi ago I had all O2 sensors replaced - Anyone know whats going on here? - Idle bypass/stepper motor?

 

[Chris-St Louis]

Codes?

 

[Snowman]

The Check Engine light just came on and I haven't stopped by my shop yet to get the codes read - Thought I would fish around for information before I go

 

[MonLand]

Idle bypass/stepper motor?

Yes, that would be my bet. I had similar symptoms on my 1995 D90 (granted, slightly different engine and different engine management system, but same principal).
In my case, as the engine warmed up the idle RPM would go higher. With hot engine, the RPM would be close to 2000RPM.
When moving (let's say 30 mph, in neutral) the engine would jump from 750 rpm to 1500 rpm).
Such an easy fix that I would try there (and don't get OEM, get much cheaper alternative part; Buick or whatever).

 

[GSxTC]

My '94 D1 does this if it gets below 50degrees out. It starts fine, but runs like crap and chugs severely until it warms up, then runs like a champ.

 

[MonLand]

My '94 D1 does this if it gets below 50degrees out. It starts fine, but runs like crap and chugs severely until it warms up, then runs like a champ.

Oxygen sensors? (most specifically the heating element of the O2 sensor)

 

[Snowman]

Just a fallow up for those of you reading - Removed the stepper and cleaned it but it didn't do much - So I took her to my shop to read the codes (misfire in #4) and thay also could hear a slight snaping coming from the coils at the back of the engine - So I had the coil pack, wires and sparkplugs replaced - It did the trick, runs smooth now!

 

[MonLand]

Just a fallow up for those of you reading - Removed the stepper and cleaned it but it didn't do much - So I took her to my shop to read the codes (misfire in #4) and thay also could hear a slight snaping coming from the coils at the back of the engine - So I had the coil pack, wires and sparkplugs replaced - It did the trick, runs smooth now!

Thanks for the follow-up! Never had to replace my coil pack....
But I know that when my ignition wires are dying, the truck runs bad when it's warm (and runs fine when it's cold).