hot start grumble

[dirty-chainrings]

hey all. tried searching for this topic, but only found stuff for 3rd gen and previous (and the sticky for the google 4th gen search is gone?...)

recently i've noticed that in the mornings, the truck starts fine. couple of cranks, it roars up, and stays in the mid 1k rev range

drive around, everything's fine, then go to turn it off. leave it for about an hour, and when i come back to start it up again, it starts in the appropriate amount of time but will hang around 700rpm and shake the truck a noticeable amount. i can hit the gas pedal and it responds accordingly. this usually goes away within 15 sec or so, gas pedal or not.

at first i thought it was bad gas, as they were changing formulas from winter to summer mix. now that i've put a couple of tanks through it i still notice this behavior

i'm looking for places to start. this is what i'm thinking:

• MAF sensor
• throttle body clean
• new spark plugs (they were replaced about a year ago from originals)
• fuel filter (but i don't want to drop the tank)

anything else i should consider? i'm hoping this isn't indicative of the head gasket going, as this REALLY isn't the time to be spending that kinda coin on that.

again, this only consistently happens on warm starts. even then, it doesn't happen all the time, probably 60-90%.

thanks everyone. hope yall staying safe

 

[djpope09]

Check your coolant overflow bottle and see if it's low. The rough start could be coolant getting into one or more cylinders which would mean the head gasket is going bad.

I'm not saying that's your issue, but that's an easy thing to check. If you're low on coolant, top off the radiator and overflow and drive for a few days or more to see if the level drops again. You could also get a camera to see inside the cylinders and see if there's fluid in there.

Have you checked for fault codes to see if there's a misfire on a certain cylinder?

 

[V8Man]

Engine?
Since you mentioned had gaskets, I assume 6 cylinders. Mileage would also help in trouble shooting although everyone's rig is starting to show in years now.
Check everything mentioned, but what you are describing can be from leaking injectors. Fuel building in the cylinders after shutdown. Cleaning the injectors may help along with using top tier fuel.

 

[dirty-chainrings]

Check your coolant overflow bottle and see if it's low. The rough start could be coolant getting into one or more cylinders which would mean the head gasket is going bad.

I'm not saying that's your issue, but that's an easy thing to check. If you're low on coolant, top off the radiator and overflow and drive for a few days or more to see if the level drops again. You could also get a camera to see inside the cylinders and see if there's fluid in there.

Have you checked for fault codes to see if there's a misfire on a certain cylinder?

haven't gotten any lights on the dash, but i haven't plugged in an OBDII to see if anything is on the computer. that's a good place to start

i'll keep an eye on the coolant.

i always thought that the rumble on cold starts is def showing of the coolant leak. is it also during a hot start? it doesn't smoke on startup in either scenario

Engine?
Since you mentioned had gaskets, I assume 6 cylinders. Mileage would also help in trouble shooting although everyone's rig is starting to show in years now.
Check everything mentioned, but what you are describing can be from leaking injectors. Fuel building in the cylinders after shutdown. Cleaning the injectors may help along with using top tier fuel.

yes, a V6 with 197xxx miles. i like (bad phrase) the idea of the injectors leaking. i'm always a little hesitant with things like seafoam. any mild cleaners that would be useful? or would going full bore at it eliminate it as an issue?

 

[dirty-chainrings]

checked fluid. was a little low, so brought it btwn the L and H lines. engine was stone cold

fired it up, every thing was normal. no grumble

plugged in my OBDII connector and ran Torque Pro, no fault codes, no nothing.

i'll try scooping up some injector cleaner and run that next

if that doesn't do something, then i'll start breaking out the cleaners and doing throttle body and MAF. also clean my K&N filter which i did last oil change

i'm still open to suggestions, obviously!

 

[djpope09]

checked fluid. was a little low, so brought it btwn the L and H lines. engine was stone cold

fired it up, every thing was normal. no grumble

plugged in my OBDII connector and ran Torque Pro, no fault codes, no nothing.

i'll try scooping up some injector cleaner and run that next

if that doesn't do something, then i'll start breaking out the cleaners and doing throttle body and MAF. also clean my K&N filter which i did last oil change

i'm still open to suggestions, obviously!

My experience with a leaking headgasket was the engine stumbling only during cold starts. I think you're safe from that being the issue, but you might want to check the level the next couple times you fill up.

Couldn't hurt to clean the TB and MAF. For injector cleaner you could try a bottle of Chevron Techron. Lucas Oil makes one that I've used a few times, but I'm never sure that it's actually doing anything.

Have you thought about getting one of those small cameras that you can stick in the spark plug hole? You might be able to see if any of the cylinders are wet after it's been sitting for an hour.

 

[epicpilgrim]

I'd also check the engine mounts if the whole truck shakes when you have that symptom. May be a couple of things going on at the same time.