Currently - 2 leaks at intake mani or valve covers -High/cold idle at 2100 RPMs & delayed warm start

Edit: I thought this was resolved however it was only slightly improved. Once it was fully cold the next morning, it is gone right back to almost as high as it was before.


Orig post:

Originally had this problem when I installed headers and the vacuum hose in the picture had come off. Once I reconnected that hose it idled normally

after replacing my timing belt I made sure that and all of the vacuum hoses were connected, but I'm having the same idling issues


Any other hoses known to cause this problem? I've looked, but I see nothing. Not getting any codes. I need to start replacing the vacuum hoses due to their age, but the one that caused the problem before seems to be fine with no cracks


I first thought it was the ECU. I recently replaced it with one performance tuned specifically for the headers. But then I remembered once I found that loose hose it idled fine. I just didn't drive it much because almost immediately after the exhaust upgrade I started on the timing belt

 

I assume it matters if these two at the power steering pump are switched. I just swapped them and it seems to be better.

Almost fully cold and it only jumped up to 1700 RPMs but quickly dropped to 1000. and seems to be smoother at idle. Before it would hover at 2100 to 2200 then eventually only drop down to 1500 for several minutes before dropping below 1000

I'll fully confirm once motor is cold maybe in the morning

 

Yes, the power steering air control valve, when blocked, will cause high idle. But I thought it only jumped 20%, your numbers sounded high to me for that.

 

I think it was a combination of that new ECU and those vacuum hoses being swapped.

Now it idles smooth consistently when warm. It's not dropping down to 500 RPMs at times. it doesn't stay at 2100 RPMs it drops down to 1000 pretty quickly and then gradually goes down to about 800 as it always has

so the big problem was those vacuum hoses. It seems that new ecu performance tune exaggerated it.

 

UPDATE:

I thought this was resolved however it was only slightly improved after swapping the two vacuum hoses

On a cold engine crank/start it is running at a very uncharacteristic 2200-2300 RPM's


I saw references to throttle body cleaning in other threads and to the ecu relearning idle in a thread which in turn referenced a post on tundra solutions forum.


The only other symptom is that it also sometimes takes a little longer to do a warm start. You crank it normally and it sounds like it is starting but then the starter keeps running for another second.

Both of these behaviors seem to start after my timing belt change when I had a little spacer create a bump that slightly shook the hood. I didn't catch that the Spicer had fallen out of a timing belt cover, and when I cranked it, it apparently fell and got pinched somewhere under the timing belt covers. I checked, but I could find no damage

 

I believe this was the same as the solution I saw. Not sure if it is legit for our 4.7 1st Gen


Edit: I guess my cut and paste only got about half of the instructions

1. Get car up to operating temp
2. Shut off
3. Turn to on
4. Shut off
5. Turn to on for a few seconds then start
6. Put ebrake and brake on and idle for a few minutes while in drive

 

I just did what was detailed above to reprogram so I guess I'll wait and see

I did notice that although it started and jumped up to 2200 RPMs it dropped a lot more quickly down to what I would consider normal for a cold start at around 1200-1300. But 4 or 5 seconds at 2200 RPMs just isn't right.

 

After cleaning my throttle body, I was having too high idle on cold starts. I then disconnected my battery but that didn't seem to change the idle. Someone on here suggested a throttle relearning procedure that then did the trick. Maybe this will work for you too.

Throttle Relearning procedure:
- Turn the ignition on to ON (not ACC)
- Slowly press the throttle from 0 - 100% over roughly 5 seconds or so, holding 100% for a few seconds
- Slowly release back to 0 over 5 seconds or so
- Rinse and repeat at least 3 times, preferably 5+
- Turn the truck off and let it sit for 30-60 seconds
- Turn the truck on and test out the throttle

 

I did that a few weeks ago. My understanding was that was about throttle response and was told it would help with throttle delays and inconsistencies. It did seem to help that but had no effect on my issue

 

I've already detailed the cold start issue



This issue in this video only happens on a warm start. The high idle is not a problem on a warm start. Both cold and warm start behaviors started about the same time

it doesn't do this every warm start - about half the time. This one was worse than usual:

https://youtu.be/6PZJ9L_hwIM?si=iaOLAN1VkJae4u5z

 

I would inspect all your wiring. Clean tb , sensor. Maf..make sure no wires were burnt by headers. Sounds like you still have a vac leak to me.

 

throttle body was extremely nasty. I'll do another cleaning one day when the engine is fully cool

I did one wipe with the brush before I thought to take a picture so that is the streak on the bottom

Before:





After:





at least a little bit of what's left in the after picture is more of a stain

I thoroughly cleaned that brush about three times and finally just started using rags. And what's on those rags is less than half of what I got out

 

I'll have to go back and look at the throttlebody sensor. Mass airflow has been cleaned and replaced within the last three months.

I agree about the vac leak. And the idle still drops way down when you're doing a low speed turn. I replaced the vacuum hose that connects around the top of the throttle body to the power steering pump (valve?) when I did the timing belt change. The other one is a little loose, but it has a clamp on it. I remember cutting off the end because it did have a split when I was doing the timing belt
I need to replace it Really time to start replacing all hoses and lines over this next year

 

I was about to say with that idle drop on turns, are you sure the PSAC valve is good? And that the houses were actually backwards in that weird high idle condition you had?

RE: Toothbrush, I feel like a broken record for Dawn's Powerwash product by now, but I sprayed it in all my greasy toothbrushes, I keep a stack in a coffee can in the garage. Spray it on, let it dwell for 1-2 mins, then run my thumb back and forth thru the brush, rinse, and it goes from black to white again. Something magical happens when you add rubbing alcohol to Dawn dish liquid, then aerolize it.

 

I was beginning to question that valve myself. I even swapped it back-and-forth again today. Wasn't sure which one was better.

 

You want me to snap some pics of how mine is piped? Sanity check and all?

RockAuto had a closeout on a Dorman replacement PSAC valve and I got it for like $30 so I jumped on it. Appears identical to OEM, even same stampings. I figure I'll eventually need it, better to have it on-hand.

 

That would be great on the pictures

I would think that valve is original. Otherwise they just replaced it when they did some other work on the power steering lines and I didn't catch it, but if so that likely means they replaced it with some cheap third-party product

also replaced the PCV valve earlier this week. Got OEM Toyota online from a Toyota dealership.

 

Heck no, you don't have to convince me - that stuff is amazing.

I didn't even change into my work clothes today but I'm not even worried about the grease and oil I got on my casual khaki shorts cause that stuff will get it right out. Even if you miss a spot and have already washed and dried it can get it out the next time

 

Cold start this morning. Overall slightly improved. It drops down to 1500 much quicker, but that started before I cleaned the throttle body yesterday

https://youtu.be/OtEmcTD93xM?si=xM2p8MfY_sWQvpzS

 

Just finished thoroughly cleaning. It passed the white glove test. Now I should be able to keep it in good shape with routine cleaning







unfortunately that still was not the issue but got some overdue maintenance and cleaning behind me

https://youtu.be/dP3-rYDBbQQ?si=r68MAUFO5-1xgX-X

 

Might as well replace that vent hose while you can still get them.

 

Edit: we do not have an IAC valve. It is controlled by the ECU based on the throttle position sensor (TPS) The video I watched was on a six cylinder


Orig post:

Anyone had issues with their IAC valve?

just watched a few videos and in one of them a good mechanic showed how to remove and test the IAC valve according to the FSM. it seems that IAC valve is supposed to do two different actions depending on if it is cold or warm.

I don't think it's a coincidence that I simultaneously started experiencing one issue when it is cold and a different issue when it is warm. But I still cannot find any posts where someone is having my same problems

I also looked up replacements for the IAC valve. Price range was from 70 to about $400??? That just doesn't seem right

also worth noting. My SAIS has been disabled through the ECU. The long tube headers block the ports for the air tubes so that was a necessity. But it ran fine afterwards. These problems started later

 

Man, got a scare today. Truck wouldn’t start while the oldest and I were finishing a 5mi hike about 45nins south of the house in a remote area. I knew it would start eventually but same ahit as before. Turn the key, click or nothing. Turn it off. Wait, try again, nothing. But this time, Third time turning on the truck, didn’t even turn the key to START, and it starts cranking on its own, cranks for 3 seconds with key in ON position, fails to fire (which usually happens in first 0.25 seconds) and stops cranking. I wait a second, turn to START and it fires right up like normal. No codes. Hooked up OBDII dongle immediately after to check for pending codes, anything unusual… NOTHING. I’m stumped. Clearly this is not the starter. Something fucky going on.

 

that's crazy it was trying to start while just in the on position

and no codes just like with me. damn

 

Sticking relay?

 

Probably still the starter. If my truck tries and fails to start, it will not want to fire on a subsequent start without turning it off and back on. Probably related to the way our fuel pumps behave.

 

Damn sure seems like it eh? Thats next on the agenda, swap the relay. The fact it’s not happening every time makes me skeptical testing the relay would uncover anything. But the fact it threw a cam position sensor code last time also had me scratching. It’s happened only a few times since owning the truck. Once a couple years ago. More recently, like all in the past month, it’s happened 3 times now.

I really need to go over my wiring soon, and see if there’s something the stealership missed when I paid for diagnostics, for them to go over all the harnesses linked to the alternator/power after it shorted and caught fire back in 2018-2019 I was leaving town for work the next day and didn’t have time to do it myself, so I paid them to diag it, then had it towed to the only shop whose rep I trusted to do the work. I know the inside of the alternator got hot enough to glow, but they assured me they found no wiring toasted, nothing melted, no problems. I confirmed the connector wasn’t burnt up (nor the exposed end of the wire leading into it) when I replaced the wrong 100A Denso alternator that “trusted” shop installed with the proper 130A. I haven’t gotten up under the fuse/relay box next to the battery, or looked anywhere on the wiring between there and alternator.

 

Not convinced.

Do y’all’s earlier year trucks have the rapid start (or whatever) function the later years have, where they automatically crank for 3 seconds when you kick the key forward? Even if I tap the key forward for a fraction of a second, it’ll continue cranking on its own for 3 seconds.

 

“Bump start” is what it’s called I believe

 

Thanks, couldn’t remember wtf it’s called.

But yeah, the reason I wasn’t thinking it is starter or starter contacts is b/c it’s almost like either (A) the ECU is delayed in getting the signal that it’s OK to fire off the bump start sequence, like maybe a sensor required to report back during pre-start checks isn’t checking in or giving output or (B) something is causing a delay in the transmission of the start itself, like maybe the relay is failing or sticking. But there’s no obvious issues outside of that, and the clicking is too faint to be solenoid, solenoid fail is typically more of a CLUNK, I’m hearing more of a click (like a relay pole type click).

It’s a weird as hell thing to troubleshoot, and the fact it’s happening, but clears up before I can get to debugging (and half the time auto-starts eventually if I leave the key at ON), it’s damn hard to even try to track it down. It’s why I’m thinking of parts-cannon for the relay first, and if it continues I know that’s not the issue.