Idle Revs Bouncing Around

Anyone ever had something like this? Don’t know how long it’s been going on but just recognized it.

5.7 at idle, warmed up, bounces between 700-1k RPMS. I revved the truck to 2k, it did it a few more times then stopped. Is that normal?

 

I've seen where during warm up, my temperature gauge will just about indicate normal operating temp. Then I'll notice the temp gauge drop down to about 1/4 1/3 deflection and the idle will go up slightly. I've always attributed this to the thermostat opening up and lower temp coolant from the radiator being circulated past the coolant temp sensor. The t-stat remains closed during warm up and coolant from the radiator isn't included in what is circulated through the engine and the heater core. When the t-stat opens, there's a rush of unwarmed coolant that then enters circulation and the overall temperature initially drops and this may trigger the slight bump in idle. You may already be aware of this, but see if your temp gauge drops like I've observed mine doing.

 

Things I would suggest to check:
clean MAF sensor
check/replace air filter
Check/replace spark plugs, coil packs.

Also, battery going out- low or unstable voltage will do all sorts of strange things to a Tundra

You may also want to get a code reader or stop by an auto parts store and have them check for any codes. Bad O2 sensor can cause idle issues, as well as a vacuum leak somewhere.

And then there is the Tundra air valve issue.

Check those first 3 things I listed and battery. If not resolved check for any codes.

 

Temp stays steady. I was driving the truck all morning. Only noticed bounces in the revs when I was testing out chains and standing near the exhaust. Went to the gauge and it was up and down

Will do MAF and report back. 185k don’t recall it ever being cleaned and trucks been in the family the whole time. Sparks were done a 10k ago or so and filter is KN I just washed and oiled a few weeks back. Appreciate it

 

Was the A/C running for the defroster? That can bump the idle as the compressor cycles on and off. Everything that @frichco228 mentioned are great things too.

 

certainly clean the MAF, the oil from the K&N could be your problem.

 

I think the AC calmed it down honestly
It was stuttering intermittently the entire time, AC off mostly though

Could visibly see dirt in the MAF, cleaned and drying now. Will update later today when I put it back in.

 

Cleaned the MAF sensor. Trucks up to temp for a bit now. Bouncing around far less, steady at 700 or so with slight dips every now and then but far less noticeable, probably due to normal draw. I am gonna get the battery tested just because it’s 24F and I always ran 27F. Only installed it because my dad had it left over. If it’s good then problem solved! Thanks y’all

 

I would be examining long term and short term fuel trims with a scan tool. You could have a small vacuum leak causing problems.

 

Mine does it. I also realized a buddy of mine has the same issue on his, but he's S/C'ed. I'm DAP tuned and had a mechanic look into it. He definitely noticed something weird going on with fuel trims - he said he tried to play around with the ethanol % and the truck wouldn't take his input. As if the tune was denying the modified numbers. He mentioned it would be interesting to see what would happen if the tune was removed or reflashed. I decided it doesn't bother me that much.

 

I've noticed that my truck's idle will be higher mid warm up (temp gauge at about 1/4 deflection) if I have the climate controls set to Auto even with A/C disabled. If I turn off Auto, the idle will decrease. It will also do this if I select the button above the heated mirror/windscreen button that directs all air to the windscreen. My hypothesis is that there is either a small electric heater that provides warm air for the blower to direct to the base of the windscreen, or it's to idle up the engine to warm the coolant in the heater core more quickly. I'm leaning toward the latter, but don't understand why it wouldn't idle up regardless for the purpose of getting cat temps up for emissions. I'm really not worried about it though, to know would simply be of passing interest.

When I short hop my truck and stop to open a gate or something, I notice increased idle. I just figure it's part of the warm up strategy somewhere in the ECU logic. Pretty much just rambling nonsensically at this point...

 

I think that I need to clarify that the increased idle doesn't really bounce, it will just increase for 30-60 seconds and then decrease for a time, and then maybe go up again, but sometimes not.

 

Huh funny you mention having it set to the windscreen. That’s what mine was set at the first time.
It came back today after driving around for a few hours. Going to get battery checked, otherwise I’ll chalk it up to background stuff. Next time I’m at the dealer for routine stuff I’ll mention it (good friends with them)

Bounce might not be the right word. It drops to maybe 600, slowly rises to 7/800, then drops. In like a 3 second rotation

 

If it develops into anything more I will absolutely track. Otherwise gonna let it run for a bit