gtfourdreams

so heres the scoop. its a V6 4x4 4Runner 5speed, its got 230,000 miles on the odo and the timing belt was last changed at about 100, the last clutch at about 200, and nothing else major as far as i know. regular oil, tranny, and coolant changes. but since about summer i've been having a weird problem with my old truck. it only happens when it gets very wet outside, like heavy rain or snow. when i drive it, as soon as i start to cruise at a steady speed, it starts to loose power. then it'll buck like crazy, as if i was mis shifting. the only remedy is to pop the clutch and rev the motor up a bit, then it drives fine for a little bit. then again, it comes back.

now, the mystery is it idles fine, it revs up fine, only happens when the car is cruising in gear. sometimes if it rains really bad, it wont even drive correctly. i changed out the AFM, new spark plugs, new cap rotor combo, all that to no avail. any ideas? maybe water in the tank? bad fuel pump? bad wires? i dont want to replace EVERYTHING! haha

keithguts

Sounds like wires to me. When you put a load on the engine, they may be breaking down.

NaeSLaS

these 3VZ's are notorious for blowing head gaskets.

anything in the exhaust? Steam, smoke, anything?

One of the easiest ways to check for head gasket leakage: pop the radiator cap (when the car is cool, obviously), then start the car. If it starts spurting water, head gasket it probably blown.

Oil in the coolant, coolant in the oil, etc.

Anyway, if it's not the headgasket (which it probably isn't because you mentioned it only happens when it rains), then you might see if you aren't kicking water up into the air inlet, or on the distributor, etc. Make sure all your connections are tight, and make sure all your wheel wells are in and not leaking water into the wiring loom.

TNRabbit

First, you need to see about getting a new timing belt; you've gone over twice the recommended interval for a change (60k) and it's only a matter of time before it grenades on you and costs you an arm & a leg when you have valve dents in the top of your pistons.

Second, you haven't had the ignition system replaced in all that time?!? I would replace the entire ignition system including the rotor/distributor, wires, and spark plugs with OEM Denso or NGK. It's also time for a new Denso or NGK (NOT Bosch) O2 sensor.

If your problem continues, then we can start narrowing down other possibilities. Since it occurs when it's wet, I'd guess an electrical problem.

gtfourdreams

no oil in coolant, no coolant in oil, no coolant or oil burning from tailpipe (other than regular 20yr old stuff)

keep in mind it only happens in heavy rain. no problem when dry, and i drive it all year round, so even in winter when its cold without wet snow, it drives fine. heat comes on strong, ac works well.

ill check those spark plug wires, but i don't think thats the culprit.

Marc

While it's probably a good idea to replace the timing belt the 3VZE is NOT an interference engine. So if the timing belt breaks you'll just coast to a stop.

When it's not wet out get a spray bottle with water in it and spray electical stuff one at a time to see if you can isolate the problem.

I would start with the O2 sensor, maybe some wires are frayed.

gtfourdreams

i know i gotta replace that timing belt. gonna do it this summer. keep in mind, my only other car is an MR2, doesn't do well in MN winters. (plus its too pretty for that season)

the ignition, i haven't completely replaced, but i've done regular work on it. cap and rotor was done, NGK iridium spark plugs are in there (because its too much of a pain to keep changing coppers) so only wires are left.

plus: it always idles perfectly, and always rev's without a hitch. only when CRUISING on the highway or if i try to run from a dead stop. but if i'm in gear over 3000rpm it drives fine as long as im putting LOAD on, not cruising. and it gets worse as it rains harder or for extended periods of time. sometimes, the next night after a hard rainfall, it stays like that until the afternoon after it dries up (i assume).

TNRabbit

Wires break down over time & the resistance increases. Probably not why you're getting your symptom, but still need to be replaced with that many miles on them.

I'm leaning toward a short caused by wetness somewhere in the wiring.

gtfourdreams

just to confirm, the O2 sensor is underneath the car right? i'd have to soak it pretty good then. plus, i donno if its that because the O2 sensor wouldn't get wet overnight if its underneath the car.

gtfourdreams

wiring? as in ignition system or wiring as electrical system? because all the lights work like they shuold and they dont dim or brighten more than normal under load. i don't loose power to anything while driving, other than the lights on the heat control which have been dead for awhile now.

right now im leaning towards, air or fuel problem. maybe water in the tank/lines or intake. but i havent found any holes in the vacuum system or any drips from the gas lines/tank.

JEBSR5

It's very possible to get it wet. It's just in front of the cat converter, right under drivers door. Spray off the wheels can get it wet. Not saying it's your problem, but a quick inspection of the sensor and wiring could disclose bare wires, etc.

When was last time fuel filter changed? Spraying down wires is a good place to start also.

rdharper

This is worth a try.

gtfourdreams

Spark Plug Wires: Borg Warner brand "Premium Nascar set" from Checkers or Bosch Brand "Premium Set" from Autozone? same price. i saw a post about Bosch brand wires somewhere, someone else had problems? seems like people on this board dont like bosch.

And Fuel Filter from Frams. Then, i'll replace the O2 sensor, i think i have an extra 4-wire Bosch or Denso brand somewhere. that should be a good start I suppose.

JEBSR5

Personally, I wouldn't use anything Bosch, especially 02 sensor. I wouldn't use FRAM either.

Yours has a 4 wire?

Try sparkplugs.com for DENSO 02.

Plug wires should be OK if you don't see any arcing, FSM has specs for resistance per foot to test, specs for testing 02 also, but not really convinced 02 test is convincing.

I'd stick with OEM on filters, wires, 02 or any sensor.

It's not the board that don't like Bosch it's you vehicle. Bosch 02's are shorter than OEM which will affect reading to ECM.