running rough/stalling only in rainy weather

[bkgee]

Hey all - I've got a problem with my 85 4Runner that I have never experienced in 24 years of Toyota trucks. Whats also weird is that a lady friend bought a 1st gen 4Runner last year on my advice, and her truck appears to have the same problem:

In rainy weather (not very frequent in NV), the engine runs very rough, and sounds/feels almost like it is misfiring (not a rhythmic misfire, but rather random, more like fuel cutting out). If let alone it will usually die. I keep it alive with the throttle, and am able to drive around town, and i can reduce or eliminate the condition with a heavy throttle, but as soon as i let up, it gets bad again. although it will also sometimes randomly and intermittently run smooth for a moment, then go back to rough. Next day (today), it will run just fine. 355 day of the year my 4runner spins like a top.

Note, I replaced the fuel filter late last year, so I doubt that's the culprit. I also inspected the fuel pump, looks fine to me, the cage filter is fine. Also replaced the plugs, and the old ones looked normal. Also one time in the rough condition, I pulled plug wires one at a time, which obviously produced misfire, which was quite a distinguished sound and feel from this mysterious condition, so I its not misfiring.

Any ideas? I'd love to fix it, especially since it left my lady friend stranded in death valley last year cool, i thought i'd never use the flamingo.

 

[nat88toy]

had the same problem a few years back after some poking around i found out the throttle body was dirty and moisture was sticking to the inside walls took it off cleaned it and haven't had a problem since same thing has happened to 3 of my friends in there mini trucks did the same to there throttle bodies and it fixed it, one of them also had moisture in there distributer cap ass well

 

[bkgee]

thanks nat, i wonder how moisture is getting into the TB. maybe just moist air condensing in there? i will scrub the TB with CnC TB cleaner ASAP. Actually been considering the late model TB/plenum upgrade, maybe now is the time to do it...

 

[WarDamnEagle]

thanks nat, i wonder how moisture is getting into the TB. maybe just moist air condensing in there? i will scrub the TB with CnC TB cleaner ASAP. Actually been considering the late model TB/plenum upgrade, maybe now is the time to do it...

I picked up a 95 plenum to put on my 85 but haven't done it yet. Document what you do and post it if you go that way. I think I paid less than $100 delivered for the plenum and TB.

Check your distributor as well. I think there is an O-ring seal on the cap; you might try replacing that.

 

[bkgee]

I'll post back whenever I get to this upgrade, but in the mean time I've been provided with this simple writeup, which references Mud's own Pappy Late Model 22re Throttle Body Swap

it also references the high dollar routes offered by DOA Racing and LC Engineering. I am tempted to go with one of these bored and polished setups. LCE includes the gaskets and flow matched injectors for about the same price as DOA. LCE also has the slick mandrel bent intake crossover pipe, separate.

If you follow the link to Pappy's writeups, he did the DOA setup on one truck and the low dollar setup on another truck. I hope he chimes in here as to the difference in performance... (1985 4Runner)

 

[WarDamnEagle]

I asked Pappy that question about a year ago. He said there wasn't much difference. I was going to go with the low dollar approach first. You can always buy the bored throttle body later if you want.

 

[bkgee]

good to know. i think i will approach it the same way, $850 is a far cry from $100! and a port polish kit is less than $50. i think the biggest restriction in the intake is the weird air valve in the filter box anyhow, and theres no way around that - even the K&N FIPK uses that valve IIRC.

 

[raydouble]

Maybe not misfiring, but crossfiring?

How old are the ignition wires?

I have heard of this happening a few times with old plug wires.
Particularly ones that have accidentally gotten coolant on them.

Water inside the cap, a possibility?

 

[bkgee]

the ignition wires are fairly new. i will be checking out the whole spark and air systems tomorrow, will post back if i find anything out of line. but the truck is running fine again, so it may be hard to confirm a diagnosis...

 

[raydouble]

but the truck is running fine again, so it may be hard to confirm a diagnosis...

I hear that....... I had a 22R that I pressure washed the dizzy cap (before I knew what I was doing ) It ran exactly as you described yours to until the water all evaporated.
good luck.

 

[bkgee]

well i cleaned a good deal of gunk out of the TB today, again no way to know if I got the culprit until the next good rain. but the weird thing is that the idle speed bumped up from 750 to 1100 or more. is that to be expected after cleaning a fouled up TB? i screwed the idle back down to 750-800, and it is maxed out clockwise now, no more room to reduce idle. is that unusual? no worries, running good now, just curious..?

 

[HJ-45CrewCab]

My 85 4runner had the exact same symptoms. Turned out the ECU and wiring connectors were getting wet from a leaky windshield. Pull the kick panel cover, stay inside and have someone put a hose on it.

 

[raydouble]

well i cleaned a good deal of gunk out of the TB today, again no way to know if I got the culprit until the next good rain. but the weird thing is that the idle speed bumped up from 750 to 1100 or more. is that to be expected after cleaning a fouled up TB?

Yes, if it is dirty (gunk in the IAC (Idle Air Control))

i screwed the idle back down to 750-800, and it is maxed out clockwise now, no more room to reduce idle. is that unusual? no worries, running good now, just curious..?

May have to pull off the IAC and clean and test, don't think it should be all the way down.

I had to mess with it mine like 3 days in a row to get it to stay proper after cleaning out my throttle body last time.

I would run a hose like 45crewcab said everywhere you would expect water to get when it's raining + some you wouldn't.

 

[bkgee]

yep, good idea, gonna hose it. and yep, i've been messing with it for 3 days too. probably a little hyper sensitive about it, but i do like to hear it tick right.

 

[toyota884runner]

might wanna keep an out for headgasket trouble ahead. mine did this in pouring rain and would die going up hills. my 88 4runner only did it in heavy rain. good luck with it!

 

[bkgee]

i also recently thought about the air intake location, the little hose coming in to the air filter box points straight forward towards the radiator, IIRC. i suppose that it could be sucking in water there. i am gonna take a better look at that, and see if its worth sealing that up and making a better initial intake configuration for the filter box...