Hey folks I am new to the forum and need some help with my 99 Suburban 2WD, Auto, 350 L31.

When I first start the truck in the morning it has a noticeable 1 cylinder repetitive miss. The idle will eventually smooth out after a few minutes but idles low, about 500 RPM.

There doesn't seem to be any miss while accelerating however the engine seems to surge a bit when put under a decent load and doesn't seem to pull as hard as it should.

The temp gauge will run all the way up to 195 when warming up, drop down to 1/4 gauge (160-ish ?) once the stat opens and wont budge, even on a 100F arizona day this truck will not reach operating temp. I have replaced the stat just for kicks and problem still persists.

The truck smells gassy by the pipe and is currently getting about 12 MPG combined. There is only one code and it is for a bad heater circuit on the downstream O2 bank 2. I know o2's can cause all kinds of hell but I thouht only the upstream sensors have any bearing on A/F ratio, lowers are just to calculate cat efficiency, which by the way I don't have. Previous owner removed them and straight piped the section.

So to summarize

500 RPM Idle
Hard miss at cold high idle, rev goes away. Warm idle no miss, just low RPM
Surges under load, lacking power
Sells gassy at the back of truck
Will not warm up.

Thanks in advance.

 

Update ** I pulled all the plugs today and they all look perfect. They are all a nice grey/brown and no build up. I was expecting them to be black. There goes my rich possible CTS theory.

 

Alright well thanks for all the replies folks..