Hi, all. I recently acquired a 1998 4Runner with the 3.4l and ~220k on it. I love the truck, but it's got an intermittent issue that I thought had disappeared, but reappeared today at the most inconvenient possible time (busy interstate ramp) and was the worst manifestation yet.

The 4runner is dying suddenly. By suddenly, I mean that there are no preceding symptoms, it basically just shuts off instantly - no sputtering or gradual loss of power. Goes from running normally to dead in an instant. No CEL, and had the codes pulled anyway and nothing showed. It seems to always happen "at idle". I've been driving it each time, but it happens when I'm slowing down/braking and the engine falls to idle speed. The sudden-ness of it stands out it me - the RPMS basically just fall flat, without a hiccup, to "dead".

It will have trouble starting unless I hold down the gas pedal, and eventually be fine. The worst bout of this was today where I had to drive to work doing the 2-foot brake pedal/shift from neutral to drive shuffle. The previous two times it didn't take much to get it running again, no 2-foot shuffle needed (but I was on a street this time and couldn't let it sit for a minute).

I've had the alternator checked and replaced the battery with a redtop and it's happened twice since.

From what I gather, it could be the following:

PCV
TPS
IACV
Diry TB
MAF

Since I'm poor and work through all of the available daylight, are there any clues that could help me narrow it down?

Edit: Forgot to note that other than this, it runs smoothly - basically perfectly.

based on your thoughts, i'd say get some seafoam and some sensor cleaner and get your hands dirty for a day and see how that goes, it could be any of the things you listed , a simple cleaning may do wonders, and will at least take care of some maintenance to protect some of those things you listed that aren't failing, it's simple work and your cheapest option right now....
depending on how handy you are with a multi-meter, you could possibly narrow this down quit a bit....there are various threads for testing methods on the pieces you listed.

really though try cleaning the sensors first before replacing...from what your saying i'd think ....IAC is the culprit

It sounds undoubtedly like an IAC issue.

Unfortunately standard searches for IAC won't turn up any results because the keyword has < 4 chars. You need at least 4 chars in a search.

Use the search method linked in my Signature.

I dealt with an IAC issue for years. It is no big deal; it throws no codes and drives normally. The only issues are when stopped at idle and even then it usually happens within first 5 mins of engine running.

Don't seafoam your engine without reading about it. It is a shady process that may not fix your problem.
Also be careful not to mess with your MAF. They are sensitive and can be broken by "cleaning"; actually there is a special film that must not be touched on your MAF.

not going to get into a seafoam debate...lol...but i'd think you or i would be quite capable of cleaning our MAF's....some people not so much...i'll give you that, i should be more careful telling people fixes
the OP did say cheap though....

Thanks, guys. I was thinking IAC, too. I picked up some carb cleaner on the way home from work last night. I had some MAF cleaner sitting around from cleaning it on my wife's vehicle.

Just didn't want to chase through all the sensors if more evidence could help narrow it down.

I'm capable of doing any of the labor. Haven't worked on the 4runner much obviously but have effectively taken other cars completely apart/rebuilt motors (when I had a garage).

I'll give the MAF, TB, and IAC a good cleaning this weekend. Since it seems like MAF is not likely, I'll just hit it with the MAF cleaner and let it dry and reinstall.

I'm new here as I just picked up a '97 SR5.
I'll introduce myself and get some pics up soon.

I was driving home from work yesterday and had a similar problem. I've only had the truck for 2 days and I decided to "wind it out" for the first time. I got it up to just over 70 mph (clear road ahead, no traffic) which was fast enough for me. After that I let off the gas, and allowed it to slow down as I came up on a red light, slowed to a stop, nothing dramatic. Shortly after stopping at the light, I realize that the engine stalled. No sputtering, no shaking, just shut off.
Same as in the OP, I had to left foot brake to keep the idle up to prevent it from stalling out.
Luckily I wasn't more than a half mile from home, so I limped it back to the house where it exhibited the same symptoms. I had to keep my foot on the gas to keep it running. as soon as I would let off, it would stall. Otherwise it was running smooth, no choking, sputtering, stumbling, nothing unusual.

I decided to let it sit for a while (because I didn't know what else to do) after about 30 minutes, I went out and it started right up, idled high for about 10 seconds and kicked down to the warm idle with no problems.

I came upon this thread searching for a solution. What is the IAC? and how do I go about cleaning it?

Thanks,

Mike

I say clean your MAF, IACV, and throttle body. If the symptoms procede then you might have to check your fuel supply system. Napa has a good MAF and throttle body cleaner (foaming) spray it on and leave it till it dries. Seafoam is a good product just not for what could be causing your current issue.

Whatever you do, don't use carb cleaner. Pick up some throttle plate cleaner, its petroleum based and won't damage anything. I ruined an IAC by using carb cleaner.

not that this is your problem, but my 5speed does this occasionally. particularly after its been running for maybe 20-30 minutes..i stop for a few minutes (getting my starbucks) and then crank it up.

because i'm always listening to music i failed to notice the RPMs had dipped well below 1000. that was the issue. for some reason after it initially warms up, after stopping and restarting it idles so low that it simply dies sometimes. embarrassing since often i kill it when letting off the clutch because i'm so conditioned to how much gas/clutch pedal pressure to use and if its idling low this will kill me at a red light. i just wave and make a goofy face like "YEAH I DONT KNOW HOW THAT SILLY CLUTCH WORKS"

the solution for me is to ignore it. if the music isn't on i will notice that its idling lower than normal and give it more gas to keep it from stalling out, particularly when releasing the clutch.

i've had this vehicle for 6+ years now and have always had this issue but i don't really even consider it a problem since it usually only happens once every few days or maybe even once every couple weeks.

You can clean the IAC valve. Which I have done many times. But still, on occasions, my engine would stall like how you described. And a pain in the ass surprise. The best thing to do is just to replace it. If I remember correctly, you can get it OEM for about $200. It's not cheap, but it'll remedy the problem.

Wish I had read this information before I used carb cleaner I am now getting CEL 0120,0121 and similar idle issues. Could have bought sliders with that money.

Did you ever resolve this issue? I have same year rig with 260k miles with the same symptoms.

We acquired a nice 2wd 4Runner with 235K. Super clean chassis, no valve/head oil leaks, clean radiator & coolant. Zero issues on a 10 minute test drive and 45 minute drive home... except... rounding a right hand corner at a traffic light, total stall, just as the OP describes. ZERO RPM on gauge, warning lights, immediate loss of power; steering and braking affected. Required effort to steer and stop.

Vehicle restarted after a few cranks, ran well, but idled 1500 RPM during stops after that... off the highway, down the road and into the driveway.

Shut down, eased to a stop. Started up... normal idle, indicated ~750 RPM. Drove it around the farm, no issues.

I chalked up the stall to condensation in the fuel system, a/or ECU re-learn due to jump start.

After talking to a mechanic bud and viewing some YouTubes... sounds like a thorough cleaning of the throttle body, IAC, (MAF) will help... along with checking/replacing all attached vacuum lines, will solve the symptoms and possibly rectify the issue.

May also need an idle adjustment, and check/lube of idle mechanism, cables, springs, etc. Anything that does not easily move, or is brittle beyond use. Back when automobiles were actuated via levers and cables and sinew and grey matter.