Surging on start-up

[AFSP1211]

Well I think I know what the problem is but just want a lil more confirmation. It is hella cold here so I know that contributes to it along with throwing O2 sensor codes but could there be an underlying problem?
On start-up my truck surges really bad at idle, from almost dying up to about 1200rpms. It does it until it gets to operatinig temp then it runs normal but it seems like it doesn't want to fall below 1k rpms while coasting and not under throttle. Could it be only the O2 sensors that are causing this?

[RedHeartbeat]

The 02 sensors are not used in cold engine startup and idle. It takes a couple minutes before the 02 readings are used in closed loop. That is when your engine probably starts idling correctly. Try putting the stock tune back in the PCM.

[txarkitekt]

It may have something to do with adjusting MAF tables and/or IATs at idle?

[Madd Maxx]

The cold idle surging you're describing is indicative of a vacuum leak.

Since it goes away when warmed up, I would look at the intake gaskets.

[Beatdown Z]

My brothers work truck does the same thing on these 45* and colder mornings. So the other day he fired it up and while it was surging i unplugged the maf sensor and the idle smoothed out. that might be a sign of a bad maf, right?

[farmtruc]

Surging is usually a vac leak or a lean condition, the only way to find a vac leak is with a smoke machine, you'll be surprised how many leaks your system has.
If it's a lean condition, well, that could be dirty injectors, filter, low fuel pressure.
Or a false lean condition is because of a vac leak.
The o2's are probably good since the truck acts better when it's warm.


By unplugging the maf, you're forcing the pcm into speed density mode. When in SD mode, the truck is running solely on the feedback of the map sensor.
The map sensor isn't affected by vac leaks as much as the maf is, so by unplugging the maf, you could be determining if there is a vac leak, not necessarily a bad maf. Try cleaing the maf with MAF Cleaner once in a while to ensure the small stuff in there stays clean and reads correctly.

[AFSP1211]

K, I'll check it out when I get off today if the temp's not in the Negs. Thanks guys.

[Beatdown Z]

any update?

[AFSP1211]

Nah, It's still doing it, but it's warmed up a lil so it's not as bad. I'm just pissed with it and want a LS2 already. I'm thinkin of just drivin this thing hard till it goes POOF

[Beatdown Z]

Just wanted to say that the fix is new intake gaskets. Preferably the updated blue ones.