Topic: 3.0 4runner runs rough at idle

[superyota]

i have a 90 4runner with a 3.0.  motor was bad when i got it, swapped in another engine.  at idle, it sounds like it has a cam, lopes around.  i jumped the terminals in the diagnostic port to check the timing, and it was jumping around from 9-12 or so.  also with the terminals jumpered or not, the timing didn't change at all, it stayed exactly the same also, i'm getting a code 12-engine revolution signal missing, and a code 41- throttle position circuit fault?  i don't even know where to start.   any ideas?

[axled89]

hey man!   when i put mine in a couple of months back . it did the same thing and it had a big vacuum leak. it idal like that and smelt like raw fuel. and codes bouncing off the walls. so check that  out.

[superyota [OP]]

i tried spraying starting fluid all around and got nothing.  its getting really frustrating.  i need to figure it out so i can get it smogged and driving

[axled89]

any codes poping up?   or smell like raw fuel? any thing but that?

[superyota [OP]]

code 12 and 41, throttle position sesnor fault, and engine revolution signal missing.  but i just checked it today and now it just flashes non stop.  maybe it is a vacuum leak making it go crazy.  i'll spend more time checking it out.  thanks for the info.

[superyota [OP]]

yes, it smells like raw fuel too.

[axled89]

hey man!    when i did mine 3.0 took one out and put a new one in a year later.    did you change the intake's
or did you drop in the hole thing?     2. did you clear the codes since you put the new motor in.
   might take awhile but reply and i will get back to you.

[superyota [OP]]

swapped the whole thing out, new motor came with the intake already mounted.  the battery was disconnected for a while, would that clear the codes?  i pulled the fuses under the hood one by one yesterday afternoon and after i put them back in was when the check light just started flashing non stop.  does that mean its cleared?  thanks for the info, greatly appreciated.

edwin

[axled89]

no it doesn't.  do you have a manual Chilton's.  it Will tell you how.   if not i can find out tomorrow i don't remember right now.  man i had all sorts of codes when i put mine back in.

[superyota [OP]]

had something interesting happen... i pulled the cover off the mass air flow and when i turn the needle inside to where it is giving it a bit more fuel, the rough idle goes away.  should i adjust it to where there is less tension on the needle or is that going to cause other problems or just cover up what is really wrong?  i chased all the vacuum lines and they are connected right, checked them for cracks, sprayed starting fluid everywhere, and even tried hosing the motor down while it was running to see if i could find some kind of a vacuum leak and nothing shows.  i'm almost starting to think the motor i put in might have a bigger cam than stock, i'm really hoping i'm wrong.  any ideas on anything else i can check? 

[superyota [OP]]

what do you guys think the chance is it would pass smog like this? 

[axled89]

there might be a search thing on messin with that air flow sensor.

[BLACKDOG]

check the resistance on your AFM and your TPS.  A chilton's or haynes manual will tell you how. 

As for your codes, do you still have the diagnostic port jumped?  If you've cleared the codes (pulling the EFI fuse for 5 minutes or so, or disconnecting the battery), and the diagnostic port still has the jumper wire in, you'll get a steady flash every second. 

[axled89]

thanx blackdog i couln't find the damn book.   i guess that's a good sign that my rig is sound and not breaking
down all the time. or that it is going to soon. ha ha lol lol.

[superyota [OP]]

well, i know its notg the right way of doing it, but i adjusted the mass air flow meter tonight and its running great now.  not sure why more fuel makes it go away, but until i figure it it, this will be a temp. fix.  is it possible for the fuel pump to have to low of pressure at idle?  it seems to run good off idle.  i'll keep posted on what i find.

[axled89]

hey man!   mine still runs good but smells alittle rich.