odonnell

Trying to get to the bottom of this issue - 1999 4Runner limited, 3.4l 4WD.

This last weekend I was driving and when making a U-turn at low speed, the car stuttered and jerked twice. It happened so quickly that I wasn't sure if it was the engine, or losing traction on the nearly frozen water on the road. No CEL and it drove fine. It was fully up to temperature and everything else seemed 100% normal, including idle. Sort of wrote it off.

Fast forward to tonight. Pulling into a store, turned into the parking lot (slight uphill ramp) and accelerated and the engine died. Neutral and restarted - no dice. 2nd try got it started, and again, everything was normal once it was running. My instinct said vacuum leak, but the idle was smooth as glass.

Upon driving home, it bucked but didn't die after slowing down and re-accelerating, and then died 2 more times as I navigated the apartment parking lot to my space. After dying and restarting, I smelled that the engine was pig rich - perhaps flooded with fuel (causing the stalling) or simply not getting spark while fuel injection was still active for a second or two. In my experience with tuning EFI systems, a rich condition won't cause bucking, but sluggishness and a low idle. Maybe that's not applicable to the particular EGO feedback system with these cars.

As far as possibly related issues, the car is hard to start at certain temperatures. This seems to be after the car is at full operating temperature, but is then parked for 15-60 minutes. It has always started but I can tell something is off. I wrote this off as an ECU coolant temp sensor, which I've been meaning to replace, based on past run-ins with issues on other EFI cars. May or may not be a correct diagnosis.

Here's what I believe these incidents all have in common:
- low speeds
- happens after a corner
- no CEL or other warnings
- throttle tip-in while car is in 1st gear
- immediate stalling/bucking, not tapered off.
- car runs fine immediately before and immediately after.

As far as possible maintenance items already addressed, in the last year I've replaced the plugs, ignition leads, and fuel filter (not including other non-engine maintenance). In general it's been well maintained and I'm not (knowingly) deferring anything besides the valve cover gaskets, which recently started a slow leak...I'll get to that. Normal oil and air filter changes, etc etc.

Anyone have any suggestions? I'm replacing the coolant temp sensor and PCV as soon as they arrive - ordering tonight. I plan to clean the MAF as well. Besides that, I'll look for obvious vacuum leaks.

thealexdexter

I would clean the idle air valve. And make sure it is functioning properly. It may not be the problem but it's easy enough to do and you can't really hurt anything if you are reasonable careful.


I didn't watch vid, but assume it's proper enough to get you started.

wyoming9

iTrader: (1)

Your MIL does indeed work??

It does come on when the key is turned??

odonnell

Thanks gents.

I'll give cleaning the IAC a shot, can't hurt. But wouldn't that manifest itself as dying while the car is coming to idle?

The MIL/CEL does work - it comes on when the car is cranking and in other situations where it's normally supposed to.

After thinking more about it, does this case sound inline with a failing crank or cam position sensor, or maybe ignition switch? I hate to throw parts at it, but I'm not sure how these rigs respond when to certain failures, when the issue is sporadic and I can't get any codes.

wyoming9

iTrader: (1)

If your having a fuel issue either filter or pump because of Mechanical or Electrical failure.

It does not trip the mill

If your having IAC issues it most often gives you a P0505 code

Same with a Cam or Crank Sensor it will trip a code and Shut the engine off

You might also want to check your battery connections every thing clean and tight ??

Ground connections can cause this as well this is where having a volt meter is nice any problems you notice.

Good luck Intermittent problems can be interesting

odonnell

Update to the thread. I replaced the EFI temperature sensor, TPS, and PCV (the latter was just because I had never done it and it's cheap). It's been almost 2 weeks and the car hasn't had any issues

There is still a sign of poor running when the engine is started warm (sitting for ~45 mins). It starts on the first try, but is a little reluctant to catch crisply...it sort of sputters into life but then runs and idles fine. Within the first 30 mins after being shut down it restarts fine, and cold starts are fine. Are there are any sensors that could cause this? I replaced the coolant sensor, which generally provides the primary input for cranking enrichment depending on engine temp. Scratching my head a little.

TacoLimited-99

my 99 would never set a code when the IAC was sticking

wyoming9

iTrader: (1)

Funny my 98 4Runner would every time if the idle was not in the normal range according to the temp sensor .

aowRS

The 4Runner is still recovering from when it towed that crispy 951 home (I'm AOW162435 on Rennlist).






Andreas

odonnell

HAH! Glad to see another P car guy on here! Indeed, she's probably a little jealous as I use her to support my other mistresses.

To update the thread, still zero issues. I'm confident that the coolant temp sensor was indeed the culprit, as it's running better than ever. Today I ordered new valve cover gaskets, IAC seal, throttle body seal, intake plenum seals, intake couplers, a new headlight (cracked one) and a handful of other parts. I also have new Tundra calipers/rotors/pads in hand and will install shortly. Feels good to get this rig nice and proper.