Engine Gurgling/Rough Idle on Startup

[DenaliHD66]

When I start the truck, it starts up okay, then after 5 seconds it goes into a bout of gurgling/running rough for 20 seconds, then it levels off after the RPM's jump 100-200 RPM's then slowly eases back down. Does this with every cold start too. Air intake/system is all cleaned, fuel system, injectors, and fuel filter is new.

To further elaborate, it is kinda like a loping behavior but it is maintaining the same RPM's throughout the rough idle. "blub blub blub blub blub blub blub"

 

[Niklaus]

No CEL? Rough idle is usually associated with a misfire or bad motor mounts or a dirty throttle body which is especially noticeable with the AC on as RPMs drop. Doesn't sound like motor mounts though and can't be the TB if you cleaned it.

 

[kjkim93]

Have you done any work on coolant recently? To me that sounds like a air bubble was caught. Not entirely sure.

 

[IllogicTC]

Just with the cold starts? I wonder if the SAIS may be involved somehow.

 

[DenaliHD66]

Just with the cold starts? I wonder if the SAIS may be involved somehow.

This is the one aspect I don't know much about, but I was under the impression my model year did not have this. Couldn't be an air bubble because its more in the firing of the engine (more akin to a misfire than fluid bubbling up).

Motor mounts would induce more of a rattle as opposed to rough idling, correct?

 

[IllogicTC]

This is the one aspect I don't know much about, but I was under the impression my model year did not have this. Couldn't be an air bubble because its more in the firing of the engine (more akin to a misfire than fluid bubbling up).

Motor mounts would induce more of a rattle as opposed to rough idling, correct?

What year is yours, by the way? And how many miles?

Mounts wouldn't affect the actual idle of the engine itself, no. You'd just feel more of any possible harshness as they wouldn't be properly dampening vibrations anymore.

I'm not entirely convinced it's an air bubble, either. The cooling system for the I6 seems rather straightforward when it comes to both emptying and refilling, there's no bleeder valve or anything.

 

[NJTB]

+1 on the SAIS valve. The 20 seconds of noise gives it away.
Does it do it on warm starts?

 

[DenaliHD66]

+1 on the SAIS valve. The 20 seconds of noise gives it away.
Does it do it on warm starts?

Not really... the truck needs to be off for at least a hour or so. Also, truck is 2004 XL with 128,000 miles. Looks like it doesn't show my ride's specs on here next to my username anymore.

 

[KNBlazer]

When I start the truck, it starts up okay, then after 5 seconds it goes into a bout of gurgling/running rough for 20 seconds, then it levels off after the RPM's jump 100-200 RPM's then slowly eases back down. Does this with every cold start too. Air intake/system is all cleaned, fuel system, injectors, and fuel filter is new.

To further elaborate, it is kinda like a loping behavior but it is maintaining the same RPM's throughout the rough idle. "blub blub blub blub blub blub blub"

No SES light?

 

[DenaliHD66]

Nope no lights. Haven't been able to get it scanned yet either.

 

[cstern71]

When I start the truck, it starts up okay, then after 5 seconds it goes into a bout of gurgling/running rough for 20 seconds, then it levels off after the RPM's jump 100-200 RPM's then slowly eases back down. Does this with every cold start too. Air intake/system is all cleaned, fuel system, injectors, and fuel filter is new.

To further elaborate, it is kinda like a loping behavior but it is maintaining the same RPM's throughout the rough idle. "blub blub blub blub blub blub blub"

I think I have the same issue. Just seems to have started a few weeks ago in the morning. It starts fine, then the RPMs climb a little and I get some gurgling and running rough sounds for probably 10-15 seconds. If I go out back to the exhaust it sounds almost like misfires or sputtering, but after the RPMs drop back to normal it smooths out. I also have my clutch fan engaging during this time. I also have no check engine light. I guess I could see if my ultra gauge has any pending codes.

 

[IllogicTC]

2004 and up I am 99% sure has SAIS installed on every vehicle. 02 had cover plates (I'm sure certain states with strict requirements still had vehicles shipped to them with the SAIS installed) and 03 seemed to mostly have it.

 

[Mounce]

I feel like it's kind of spotty as to what vehicles got it or not. My '04 doesn't have it. I've seen everyone talk about it and how often they mess up, then I was relieved to see that I don't have it.

 

[KNBlazer]

I feel like it's kind of spotty as to what vehicles got it or not. My '04 doesn't have it. I've seen everyone talk about it and how often they mess up, then I was relieved to see that I don't have it.

My 04 EXT doesn't have it either...

 

[Mounce]

Maybe it's an ext thing? Lol either way, I think we're lucky to have one less headache.

 

[DenaliHD66]

My fan clutch is ticking quite loudly as of lately... original one with 128k miles on it. Could it be that its unbalanced or something and this causes the engine to run out of sync until it levels off?

 

[DenaliHD66]

So I've had the engine gurgling/rough idle thing for a few weeks now. So I put a bottle of techron in the gas tank. Next cold startup it ran perfectly FINE. I'll give it another 3 weeks then it'll go back to gurgling. Is my engine really that sensitive?

 

[DenaliHD66]

Well I started it up today, ran really rough on startup, heard a pop/clank noise and then rpms went up to over 2000. Ran like that for a minute or two then slowly leveled off.

 

[dla442]

Look into the cold startup cycle. Is temp readout the same from the dash as the scan tool reading? Perhaps there's a Pressure issue with with fuel at startup..pump/regulator not adequate? Would seem at startup and with a rpm and firing issue would not relate to sais.

 

[KNBlazer]

Replace o2 sensor with an Ac Delco if you haven't already.... I would also try cleaning throttle body again, remember to disconnect battery or remove fuse(s)

 

[gmcman]

i was thinking a leaking or dirty injector, just enough to act like you lost a cylinder but not as bad. I would keep on the fuel injector cleaners and if you have a port on the fuel rail maybe try a commercial cleaner.

 

[DenaliHD66]

O2 sensor is only a year old. Can try tho. Fuel pressure regulator is definitely in need of replacement though

 

[KNBlazer]

O2 sensor is only a year old. Can try tho. Fuel pressure regulator is definitely in need of replacement though

Oh, I would probably leave the o2 sensor on the back burner then.... check your vacuum hoses to make sure they're intact...

 

[DenaliHD66]

i was thinking a leaking or dirty injector, just enough to act like you lost a cylinder but not as bad. I would keep on the fuel injector cleaners and if you have a port on the fuel rail maybe try a commercial cleaner.

How about a dealer-inspired "air induction flush?"