4.0L itermittant idle problem when cold

looking for help , hopefully the video comes through . Has anyone else experienced this before? I'm having trouble finding the cause. the check engine light is a P0420 code, not sure if the same issue is causing both. the truck has new spark plugs, always OEM changed at Toyotas recommended interval. I cleaned the throttle body and MAF. It only does this when its cold, but not consistently. doesn't always stall, and once it gets through it, it runs like a champ. I'm experiencing no drivability issues at all. dealer says 420 code is cats, not plugged but not doing the job anymore.
https://youtu.be/aOThfjIbK64
https://youtu.be/HhGY__iWaMc

 

Btw I’m not looking for a p0420 diagnosis . Hoped got to get some help with the idle issue . Mentioned the 420 code Incase the issue might be related , and to avoid been told to get the codes checked .

 

Bump again cus I got videos attached . Anyone have this issue? Help please

 

I’ve developed the exact same issue on my 2010 4.0 Tacoma. Idle bounces up and down from normal high idle to normal running temp idle right after cold start in -15 Celsius or colder... it almost stalls but hasn’t yet.

No check engine light on at the time. But I have had an intermittent P0430 cat code in the recent past.

I can keep the revs up manually with the throttle for a minute and then it will function properly. Although when giving it gas it feels like it is missing or stuttering.

Once it is slightly warm it runs fine.

Cleaned the MAF, cleaned the throttle body, replaced the coolant temp sensor, SeaFoam top engine treatment. Still having issue.

Have you been able to diagnose this issue yet?!

 

You may have a couple different issues. The first question is whether the ECU is going into 'closed loop' before the stall occurs. I dont think it is. The engine cold start ECU map is basically static before closed loop (no 02 feedback). So, I would be look the basics...Vacuum leak and MAF. I think those are likely culprits and I am betting MAF. The MIL code you are getting, based on your mileage, is most likely an exhaust leak. A good auto tech looking at real time data channels from your ECU can tell you what the stall issue is.

 

Thanks for the replies that good info I’ll check to see if it’s going into closed loop before the stall and I can’t find any vacuum leaks , I haven’t figured it out yet , been swamped at work and it doesn’t do it if I have the block heater plugged in . It has been -38* Celsius here over night for the past two weeks and even at those temps , if the block heater is plugged in , it starts and stays at a steady idle , and runs great

 

I still have this issue even with my block heater plugged in. Odd how this is a temperature issue, or so it seems.

 

I had the dealer check into the p420 code , they said cats are “. Bad “ as in not plugged , just not doing job , will cause no drivability issue , and to expect bank 2 soon. they didn’t look into stall issue

 

Start by cleaning the throttle body and MAF sensor

 

How many miles on your truck? I dont see how the dealer can say they arent plugged without taking them out and looking at them. A clogged cat could be the root cause of this

 

wierd sounds like same problem caused by two different things , cus mine won’t do it when plugged in . Wonder if mine is the coolant temp sensor ?

 

Idk , it defiantly hasn’t got plugged cats, there’s no power loss at all . It has 297000 kms

 

that was first thing I did

 

I appreciate the help and opinions ! But I’m out for now, just got home from a 12 hr night shift and got one more .

 

I’m going to check my MAF again and completely remove the throttle body for a deep clean. Since I don’t have a constant P0430 code I can’t deem my cat completely plugged either.

Why would the vehicle run as per normal after warming up slightly though?!

 

Check your vacuum hoses for cracks/leaks. Check your A/F sensors.

 

I have that code. I have an OBD scanner and used the torque app and made some graphs all of the O2 sensors. Bank one, which is the passenger side, was all over the place. The driver's side, bank 2, was smooth. It changed, but it was a smooth transition. The passenger side looks something like a heart attack. It was all over the place. I had the motor swapped out shortly before this occurred and it eventually was found to be the gasket connecting the passenger side exhaust to the y-pipe. I would look there 4 a dark spot as that is what I found. Or put something up there around the joints to see if there is any exhaust leaking by.
You have to disconnect the y-pipe on both sides to replace either one and those two gaskets were much cheaper than a cat.
Good luck.

 

Removed throttle body, cleaned it completely. Re-cleaned MAF sensor. Can’t find any Vacuum leaks. Still having issue.

Could possibly be ECU issue?

 

This was my cause of my P0420 code and what it looked like on the torque app.
In the graph, O2 1x2 is the second sensor on the passenger side exhaust. It's all over the place compared to the drivers side, (2x2). All because one of those gaskets was leaking.

 

i got the dashcommand app , ill look into this , thanks , i wasnt actually sure what the graph should look like . im gonna change the exhaust gaskets when the weather gets warmer here , no heat in my shop yet lol.