Engine revs going up and down after shifting into gear

This is a weird to explain and I'm looking for any advice what is causing the issue.

2018 dbl cab 3.5 4x4. Fuel pump recall done.

This has happened 3 times? Last night I started up the truck and let her warm up a couple mins and shifted into drive and as I did the revs started jumping from 600-1100 without me touching the gas pedal and the truck was lurching ahead on the higher revs and stopping on the low revs. This went on for 20-30 seconds and then everything was normal for the rest of the drive. Any ideas what is happening. Anyone had something similar happen?

 

Maybe it is hunting for a better gear?

 

What was the temp outside? The cold start maps are dependent on both the Park (stopped) and Drive (moving) conditions and can vary with your coolant temperature. Basically, if the coolant temp needle is resting on the cold mark, you can expect high revs and rev changes. It annoys the hell out of me, esp when it get over 1k.

 

It was cold out. I have routinely shifted into drive or reverse on a cold engine and the revs usually drop from maybe 1200 to 1000 or so and off I go. These times I mentioned, when I shift into drive or reverse the revs are dipping down and then rising without any gas pedal depression. Almost like it's losing power or something. I will just have to warm her up a bit more before I drive her I guess...‍♂️

 

Since it is different from normal, it might be good to look things over like intake connections, air filter condition, etc.? The Crank Position Sensor comes to mind also.

In my experience, warming up takes a very long time on modern engines. Starting and driving off gently has the temp gauge moving within a minute or two.

 

My truck has done this forever on occasion. My truck is a mt but it’s similar when it’s cold and initially under load. Once it’s up to temp it’s fine.

 

My 2020 auto has the "cold idle surge" since day one..Nov 2019. It did improve slightly when I had the latest ecu update done in Nov 2020.

 

My two Tacoma’s have never behaved like that, but I’m experienced similar code start behavior on other vehicles over the years.

When my Subaru got old it developed a super high idle at start that required me to depress the clutch pedal or apply the brakes to maintain a reasonable speed. It go back to normal after a minute or two.

Way back in the day, giving the engine a quick rev would settle down the idle. Modern engines are more sophisticated than that.

 

I’ve had this happen early on in my truck’s life (stock, 2018). The problem disappeared with the 1.05 tune and has not returned.

 

This sounds exacly like what my truck has been doing occasionally this winter. OP do you have a tune at all? @tonered I have been meaning to get in touch and see if this was anything you've heard of with the vehicles you flashed.

 

Hey, Matt.

On my side, no one has mentioned it. We could certainly do a reflash to see if that helps.


While sitting still, it seems that the later TSBs from Toyota will bump the revs with steering input or brakes. I have that, where if I am at a light not long after a cold start, the revs will bump up while on the brakes and drop to normal idle when off the brakes. It seems to be activated purely by moving the pedal enough to make the brake lights come on. Certainly not actual engine load dependent.

 

My 2020 will raise, and drop the idle speed when the engine hasn't come up to temp yet, or when the you activate the blower fan at any time. When the fan is switched off, all is normal. My 2001 tundra did the same.

 

That sounds different than mine. When mine does it it goes like this:

Cold start in park, smooth consistent idle. Put it in drive (but still holding the brakes and not moving) and it will instantly start pulsing up then down on like 1 second intervals. It will do this for a handful of cycles then settle in. But it's aggressive enough that the truck will even lurch forward a bit sometimes if you aren't solid on the brakes. The reason I wondered about the tune is I never noticed it before this winter, and this is the first winter post tune. But the tune also included the lastest factory ECU update so could be that too. Or other things I'm sure.

 

you gotta do the idle relearn procedure when you get a new tune or reset the learned values. Start the truck, turn hvac system off, and let idle for 5 minutes.

 

I seem to remember that happening on other, non-Toyota cars that I have had.

I know that the idle settings are not edited in either the vF or YW tunes, although, I have edited them for my own use. We can certainly try testing stock or a reflash. Lemme know.

 

That is standard ops for me and did that when I flashed his Taco.

 

I notice if I remote start my 17 and hop in and drive shortly after the restart, the RPM's will bounce around oddly for 10 to 15 seconds

 

Thanks for making this post op. I’ve experienced what I think “cold idle surge” best describes for a while, but it’s the worst below 20F when I don’t let the engine warm up enough. I’ve been wondering if it was my tune or something to do with the fuel system more and more recently, but the replies to your post have given me some more things to trouble shoot.

Tuned on kdmax something
HVAC is always on
RPMs only jump up/down while in gear after a cold start with brief warm up. This happens regardless of outside temp. Worst in the winter but happened last summer when it was Alaska “hot” too.
If I let off the brake it will continue to surge and lurch forward.
Giving it gas in N or D will make it idle normally.

I’ve cleaned the MAF and throttle body.

Recently when I start it in the morning the engine hesitates, like it will turn over and then idle really low (like it’s struggling) before idling up to normal start up speed. A week or two ago, I accidentally shut the truck off like 45 seconds after a cold start and when I went to start it again it wouldn’t turn over without me pumping the gas.
It’s been bugging me so I added a bottle of Lucas fuel injector cleaner to a 1/4 of gas then filled up with 91.
Starts up at normal idle now, and I’m going to try an immediate re-start today under similar conditions.

If things are still borked I’ll experiment with my hvac off (idle relearn) or talk to my tuner if all else fails

 

The more people I see jump in with a similar issue the more I'm thinking it's just a stock idle map problem.

 

My truck has been doing the exact same as yours. Weak start and surging rpm when cold.

ETA- stock truck and battery. 66k miles and I haven’t done the 60k maintenance on it yet.

When starting, it”ll “flutter” few a seconds, and then roar back to the normal start engine surge. It’s been doing this since Dec of last year. Restarting after it’s warm/hot is normal.