I have a 92 4runner with 215k on the clock. it's a V6 5 speed and has always ran great with the exception of oil leaking from the crank covers onto the headers.

Two weeks ago I replaced the driver side since that was easy and fixed the leak from that end and this weekend I replaced the passenger side which required me removing the intake plumum. I was able to stop the oil leak but after putting back all of the vacuum lines and bolting everything back according to spec the car started right up but it sounded like it had a miss. as it idles it got progressively worse and dropped lower into the RPM band and started to stall out. i though she just needs to be driven around the block a little so i went for an easy drive. it drove okay, never stalled, just rough idel and a little bucking at lower rpm band. After coming back from my 3 mile drive the idle is still rough and car kept stalling.

Now keep in mind i checked for all vacumm leaks. the werid thing is when i unplugged the throttle position sensor, it was idel really rough but it wouldn't stall out. as soon as i plugged in the throttle position sensor, it stalled out within 10 seconds.

could this be a bad throttle positioning sensor?
thanks for any advise!

 

Are you getting a CEL? If it runs better with it unplugged, it's most likely the TPS. Did it move or go out of spec you think when you took the intake plenum off?

 

Have you done any tune-ups or adjust the idle speed or timing prior to fixing the leaking covers?
If so, your adjustments probably were hiding a vacuum leak caused by the leaking covers and fixing those has plugged the leak, making your adjustments unnecessary. Try doing a basic tune-up, setting the timing and idle speed once the engine is warmed up and see how that goes.

 

thanks for the response guys but to answer your question, it doesn't have a CEL. i might not too convinced that it's the TPS going bad since I did not disassemble TPS and took the entire plumbum with the throttle body attached. i was being very careful so i couldn't have damaged anything.

so about two years ago i had a shop do a tune up and they bumped up the idel speed a little to make sure i don't have issues starting up. since then i have replaced several things but never messed with the timing or the idel speed. by the way, how do you adjust the idel? i turned about a half dozen screwes and none seemed to control the idel...

more on the vacum leak, any recommendations on where i should start for troubleshooting?
thanks

 

There should be a large screw, about 1/2" diameter, on top of the throttle body. That's the idle speed adjustment- turn it in to lower the idle speed, out to raise it. If turning that doesn't affect the idle speed, then something else is up, possibly the o-ring on the screw is worn or...

We need some of the V6 peeps to jump in here.

 

I just did the same exact thing to my 93. The valve covers were leaking so bad, it created a nasty vacuum leak, causing me to run lean, and have the rough idle.. I also bumped the idle speed to keep it from stalling out, and running rough. When I replaced the valve cover gaskets, I had the same problem you just described... all I had to do, was turn down the idle screw a bit, and she now purrs. If that dont fix your problem... I'd suspect a vacuum leak... prolly the intake tube, I had mine off, and checked it over real well, and saw no cracks, but when I put it back on, it some how cracked....thats how 20 yr old rubber works.

 

^^^ if that's all it is, you are my hero!

anyone got a picture of the exact screw?

thanks

 

From: https://www.yotatech.com/forums/f116...cation-110754/

 

when you had the valve cover leak, you bumped up your idle speed to smooth it out right? the part i'm confused about is right after I fixed the leak, the car idled okay (same as before 1000 rpm) but sounded like it had a miss. However after my drive around the block, the idle started to drop down to 500 and eventually stalled out.

 

did u use any rtv or anything on the covers? Sounds to me like you got a vacuum leak.

 

^^^ i used some liquid gasket to make sure it's a good seal. I have done it a few other times with my subarus and haven't had any issues.

went back today to turn up the throttle a little and it's running better however it still sounds like it has a miss and when driven around it's got some power loss. now my question, does a vacuum leak causing misfires? i was going to pull the plugs tomorrow and replace them with new ones just to see.

 

Your Timing may be off...

 

^^^ The truck ran fine before i changed the valve covers and without modifying anything else, how can the timing be thrown off?

 

Yes a vacuum leak can cause misfires, it's un-metered air escaping and not being calculated by the AFM. It's strongly recommended to either use the black gasket sealer or FIPK. You should only be dabbing it on a couple spots on the mating surface of the head and valve cover as show in the link below.
https://www.yotatech.com/547026-post33.html

Also, did you follow the correct torque specs?
https://www.yotatech.com/547028-post34.html

Here is a thread all about the valve cover gasket change and how to do one properly if you want to take a gander if you feel like you may have missed something (whether it be vac lines or whatever).
https://www.yotatech.com/forums/f2/v...acement-52695/

 

I did pretty much the same thing only i lifted the intake plumnum to the driver side. i will double check the hose again tonight.

thanks for all of the info so far!

 

come to think of it. the hose that goes from the top of the valve cover to the intake plumum might be a little lose since i used a different hose than stock. the stock S shaped hose broke into three different pieces. could a small leak from the crank case into the plumum cause my headaches right now?

 

Do you a a MAP torch? TNRabbit always posts that if you use an UNLIT MAP torch and go around all the hoses/vacuum areas if your idle increases suddenly you have pin pointed the leak. You can also do the same with carb cleaner/B12, but since those cans are a bit pricy may just be cheaper to wave around that unlit torch.

Which hose btw? The PCV? Or the one to the PAIR system?

 

I think i solve the issue. while taking off the intake manifold there were 7 small vacuum tubes that were disconnected and when put back on they were in the wrong order. I messed around with them until the truck ran good but i'm not sure if it's in the correct order or now. Can someone please help me by figure out which tube goes where? each tube has a number written on the tube and the closest thing i can find on my service manual was this: http://www.ncttora.com/fsm/1993/engine/74layoutan.pdf

which doesn't tell you exactly where goes where, can someone be so kind and post a pic?

thanks

 

https://www.yotatech.com/forums/f2/v...95/index2.html

 

i was able to find that thread which i noticed i had the wrong order of vacuum tubes. can anyone help me figure out what each of the labeling is?