Intermittent Low Idle RPM/Stall, sudden onset.

[LeeMajors]

Hey y'all. I've exhausted my search capabilities here and haven't found a situation quite like mine.

2000 4Runner V6, 2wd. 175000mi.

One time last year, sitting in hot weather I had a brief uneven idle that didn't stall--pulled over, turned off and restarted with no issues...until yesterday.

Same situation, more or less, sitting in hot weather traffic and I noticed my RPMs dropped to around 400. I put it in neutral, goosed it, it settle back at around 700, then dropped back down to 550-600 under load in park but even (which has been norm once the engine is warm since I've owned it).

So I drove it home with no more issues, pulled in the driveway, then sat still with the transmission in D....and it slowly settled down to 400 and stalled.

Fired right back up, put back in drive and the same thing happened.

It has no problem starting afterward. I drove it around after with no significant issues--just when idling for more than a few minutes with the engine warm.

Spark plugs/wires (both NGK) were replaced ~10k mi ago.
PVC valve changed last year also.
Fuel filter is presumably original.
Vacuum hoses don't have any obvious leaks.

I had a MIL beforehand that's been ongoing (P0441), but I checked again and there were no additional trouble codes thrown.

There's no stumbling or hesitation when accelerating. Idle is even without load (P or N).

I'm thinking I'm going to clean the IAC and MAF today most likely, and replace the most worn looking vacuum hoses. If it was a fuel issue I'd suspect it to have issues when not under load, or when accelerating.

Any other things I should look for or consider? I don't want to throw a million parts at it, but cleaning MAF/IAC would probably be a good cheap start, I think.

Thoughts?

 

[nissanh]

I think you have the IAC valve built onto the throttle body. Make sure to remove the throttle body and hold the IAC valve at 12'O clock position when cleaning. This way you can avoid any dirt going into the IAC unit.

 

[LeeMajors]

I think you have the IAC valve built onto the throttle body. Make sure to remove the throttle body and hold the IAC valve at 12'O clock position when cleaning. This way you can avoid any dirt going into the IAC unit.

From what I've read, 01-02 have it built on.

Mine is removable (4 brass screws).

 

[The Count]

Clean the throttle body. No real need to remove the throttle body to clean it, IMO. Just don't spray TB cleaner directly into the TB. Spray it on a shop rag and clean with your fingers in the rag. Continue until it's clean.

I've cleaned throttle bodies like this for 18 years as a mechanic and have NEVER damaged an IAC or other TB related component. Some may call it "short cutting" but it gets the job done, is safe on the TB components, eliminated the chance of messing something else up while R&R'ing a TB assembly, and there is no need to wait on a new TB gasket.

 

[LittleCaesar]

FYI:
P0441 Diagnostic Code - Trouble Code Diagnosis Guide

My friend had a Silverado that threw an EVAP code. Turned out the vacuum switching solenoid was bad. It did cause the truck to cut off a couple of times. After replacing the whole canister and solenoid it ran fine until he flipped it on its side in the marsh.

 

[Aelfwine]

Sorry if I'm hijacking. Is there a way to clean the IAC on 01-02? I'm having a similar low idle issue. I really don't want to replace the TB.

 

[diverscale]

Had the same problem.

Rpm drops and stalled 3 times, very distanced in interval, like more than a month between stalls.

Cleaned the IAC valve really good, let it soak in intake cleaner (not the entire assembly obviously), and made sure it was well lubricated before re-installing. Seem to have fixed the problem. You have to take off the IAC valve from your throttle body.

There is no point in cleaning the throttle body/throttle plate, beside putting a bit of lubricant on the throttle plate pivots, this is not the cause of the problem.

 

[LeeMajors]

So I pulled my TB/IAC today, pulled them apart and the IAC was caked with carbon deposits.

Scrubbed it down with TB cleaner and got it nice and sparkling clean, cleaned the TB and butterfly plate, buttoned everything back up, and it seems to be idling just slightly higher than it was.

Warmed up in park used to be 7-750, now its idling up about 800. In drive it drops to 650-700 instead of the 550.

The heat hasn't kicked in yet today and I haven't driven it all over town yet, but it feels promising.

 

[The Count]

There is no point in cleaning the throttle body/throttle plate, beside putting a bit of lubricant on the throttle plate pivots, this is not the cause of the problem.

Sorry, but this is incorrect, for the most part. Cleaning the throttle body has a significant effect on the idle speed on ALOT of vehicles, assuming it is dirty. GM's LS based motors are currently one of the most common ones. They experience low idle speed, though rarely actually stall. Clean the TB good and it's fixed. On throttle bodied Dodge 5.3L motors the change was usually so significant, you have to disconnect the battery so the computer could "relearn" it's idle speed. I've seen 4 cylinder Corollas that had low idle, almost to the point of stalling, that were fixed by cleaning the TB.

In 18 year of being a mechanic, I have seen WAY more dirty throttle bodies cause issues than I have seen "bad" idle air control valves.

 

[Jhelms]

Sorry if I'm hijacking. Is there a way to clean the IAC on 01-02? I'm having a similar low idle issue. I really don't want to replace the TB.

Does your idle bounce too?

01/02 works quite different. The quick and skinny if you have low idle or bouncy idle on the 01-02.
1. Take off the TB. On top of the throttle body there is a plate with several phillips screws. Take off the plate and clean out the 6 or so holes that lead to the TB with a pick tool. Further clean with carb cleaner.
2. Clean the living heck out of the butterfly and butterfly mating surface. Spray with carb cleaner and use something like scotchbrite to clean the metal up really good. The butterfly should actually be able to rotate a degree or so backwards so that the previously mentioned holes under the top cover can be seen if the butterfly is turned to each side of them (hope this makes sense)
3. Replace your PCV valve with a new OEM only valve. Order the hoses with it as they will be dry and will be very brittle
4. If you so feel inclined, take the stock throttle body gasket that has a D shape hole and use a carbide burr to make it totally round like the old TRD gasket. Takes just a minute or so to do

 

[Jhelms]

Sorry, but this is incorrect, for the most part. Cleaning the throttle body has a significant effect on the idle speed on ALOT of vehicles, assuming it is dirty. GM's LS based motors are currently one of the most common ones. They experience low idle speed, though rarely actually stall. Clean the TB good and it's fixed. On throttle bodied Dodge 5.3L motors the change was usually so significant, you have to disconnect the battery so the computer could "relearn" it's idle speed. I've seen 4 cylinder Corollas that had low idle, almost to the point of stalling, that were fixed by cleaning the TB.

In 18 year of being a mechanic, I have seen WAY more dirty throttle bodies cause issues than I have seen "bad" idle air control valves.

You are correct in most all situations including the 01-02 4runner. However with the earlier models, it is surprising how bad the TB can be and as long as you have a good clean IAC, it will idle fine. But to your point, clean the whole damn thing instead of half-assing it! So yes - excellent advice.

 

[Aelfwine]

Does your idle bounce too?



01/02 works quite different. The quick and skinny if you have low idle or bouncy idle on the 01-02.

1. Take off the TB. On top of the throttle body there is a plate with several phillips screws. Take off the plate and clean out the 6 or so holes that lead to the TB with a pick tool. Further clean with carb cleaner.

2. Clean the living heck out of the butterfly and butterfly mating surface. Spray with carb cleaner and use something like scotchbrite to clean the metal up really good. The butterfly should actually be able to rotate a degree or so backwards so that the previously mentioned holes under the top cover can be seen if the butterfly is turned to each side of them (hope this makes sense)

3. Replace your PCV valve with a new OEM only valve. Order the hoses with it as they will be dry and will be very brittle

4. If you so feel inclined, take the stock throttle body gasket that has a D shape hole and use a carbide burr to make it totally round like the old TRD gasket. Takes just a minute or so to do

Thank you, I will try all of that. Although I've cleaned my TB recently when I installed my SC, the gasket has been modified as well. I haven't replaced my PCV though I've cleaned it out with brake cleaner and it seemed to do what its suppose to. I did have some oil in the plenum and been told its normal, non in the intake tube itself.

What I'm experiencing is not as bad. It happens randomly on hot start, RPM drop to around 500 and sort of bounce up and down. It stalled twice on me within a month. If I rev a few times it evens out.

I've also noticed my VSV clicking rapidly sometimes. I've read somewhere that its suppose to do that but I'm not sure if thats true.

 

[Jhelms]

Thank you, I will try all of that. Although I've cleaned my TB recently when I installed my SC, the gasket has been modified as well. I haven't replaced my PCV though I've cleaned it out with brake cleaner and it seemed to do what its suppose to. I did have some oil in the plenum and been told its normal, non in the intake tube itself.

What I'm experiencing is not as bad. It happens randomly on hot start, RPM drop to around 500 and sort of bounce up and down. It stalled twice on me within a month. If I rev a few times it evens out.

I've also noticed my VSV clicking rapidly sometimes. I've read somewhere that its suppose to do that but I'm not sure if thats true.

I have cured several 01/02 4runners of the same issue above including my own two 4runners by doing the cleaning I suggested. Let me know how it works out for you

 

[LittleCaesar]

Good to hear. Take any pics? Keep us posted.

As per the Count the air intake to get correctly seated on a Dodge Ram 318 can be a real PITA; there is a collar that must be position correctly or all sorts of dirt is sucked in from the engine bay.

 

[The Count]

Another TB that used to always make me laugh was older Ford's that actually had a sticker inside that said not to clean them. It stated that there was a special coating on the inside of the TB to prevent buildup, and that cleaning it would remove it. It obviously didn't work, otherwise it wouldn't need cleaning, lol.

 

[diverscale]

Sorry, but this is incorrect, for the most part. Cleaning the throttle body has a significant effect on the idle speed on ALOT of vehicles, assuming it is dirty. GM's LS based motors are currently one of the most common ones. They experience low idle speed, though rarely actually stall. Clean the TB good and it's fixed. On throttle bodied Dodge 5.3L motors the change was usually so significant, you have to disconnect the battery so the computer could "relearn" it's idle speed. I've seen 4 cylinder Corollas that had low idle, almost to the point of stalling, that were fixed by cleaning the TB.

In 18 year of being a mechanic, I have seen WAY more dirty throttle bodies cause issues than I have seen "bad" idle air control valves.

I was refering to our 3rd gen 4runner, not some old GM's, it is not a dirty TB that will cause a -stall-, but a dirty IAC, it even is a know and relatively common problem. Mine was sludged to the bone.

Also, by cleaning the TB on your corolla, cleaner probably got into the idle conrtoller and cleaned it thus resolving the problem.

 

[The Count]

Also, by cleaning the TB on your corolla, cleaner probably got into the idle conrtoller and cleaned it thus resolving the problem.

No, I don't spray carb cleaner directly into TB's. I spray the cleaner on a shop rag and clean the TB with the rag.