3.4 High idle (1 Viewer)

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Hi all,

After reading a ton on this I am still no expert. Wondering if some of you can chime in, figured I'd make use of my time at work while 4runner is a good distance away waiting for me to attempt to solve this over the weekend.

Important info: 87 4runner, 2003 3.4L swap, K&N filter charger/no stock air filter/box, no EVAP at all, aluminum radiator, dual fan setup, dead temp gauges on left side of cluster [both], number style gauges underneath stereo.

So, I've got the high idle issues that we've all heard and read about. I've already MAF'd the hole in front of the butterfly vlave on the throttle body and PB blasted the rod. The thorttle body had already been out and sprayed obsessively with throttle body cleaner. I've also removed the MAF and sprayed the snot out of that with MAF sensor.

From reading, I'm going to eliminate vaccum leaks, and IAC valve as culprits. Assuming at this point that maybe the butterfly is hanging up and allowing air to pass, and I'll need to space out the rod with a washer.

However, before I remove the t-body to confirm and diagnose the buttefly valve culpability, I wanted to ask:

Is there any possibility that the dead temp gauges are affecting this [coolant sensor to ECM]? Or should I already know the answer - lack of EVAP system?

I'll also try to meter the TPS, and IAC prior to removing t-body, but thats not my area of expertise, so I plan to learn that first.

Anyway, feel free to add in anything I didn't mention or discover for paths to resolution please, 6.9mpg is not fun this week.

Thank you all,

Aaron
 
So, this completely buggered me for 2 weeks.

Before checking IAC as guided above I had found a youtube video about pulling on the linkage. I had already been able to lower idle by pressing linkage in correct direction. After pulling it towards front of vehicle I was certain I needed the washer fix. Well, the washer didn't help.

So then I did the duct tape over IAC hole in carb. That lowered idle from 1700-1400, leading me to believe it was still a binding issue.

With that and not fully understanding IACs yet, I luckily had 2 more tbodies on hand. Threw one on and now had 2500rpms, obviously much more unpleasant.

After fumbling around with a multimeter, confirming the IAC white wire was good, I wasn't getting equal readings on the other two. Also confirmed that the pinouts in my ECU [with no lasting part number on it nowadays], matched the wiring colors i found online and in the harness leading to the IAC.

So, I took off the 2nd tbody and corrected the idle set screw and cleaned all 3 IACS delicately because I thought i was possible to break them. But, after figuring out how the IACS worked, I cleaned them again. Found the original to not have much "spring back" to it. Chose to swap on one that seemed to function better.

I believe I had multiple issues going on - 1st tbody wasn't closing enough and had a less than optimal functioning IAC. 2nd tbody had incorrect idle set screw and sticky IAC as well.

Now I'm idling at 650 after warming up. :clap:

One tip I would like to share: needle nose channel lock is your friend on the IAC screws!

Good news: saved $230 for a new IAC, and/or $800 for new tbody and learned a ton about this era truck
Bad news: I now can't get my unlocked front driver door open, from the inside or outside :frown:

Thanks for the help guys, and also Foxfab with the intricacies,

Aaron
 
So, this completely buggered me for 2 weeks.

Before checking IAC as guided above I had found a youtube video about pulling on the linkage. I had already been able to lower idle by pressing linkage in correct direction. After pulling it towards front of vehicle I was certain I needed the washer fix. Well, the washer didn't help.

So then I did the duct tape over IAC hole in carb. That lowered idle from 1700-1400, leading me to believe it was still a binding issue.

With that and not fully understanding IACs yet, I luckily had 2 more tbodies on hand. Threw one on and now had 2500rpms, obviously much more unpleasant.

After fumbling around with a multimeter, confirming the IAC white wire was good, I wasn't getting equal readings on the other two. Also confirmed that the pinouts in my ECU [with no lasting part number on it nowadays], matched the wiring colors i found online and in the harness leading to the IAC.

So, I took off the 2nd tbody and corrected the idle set screw and cleaned all 3 IACS delicately because I thought i was possible to break them. But, after figuring out how the IACS worked, I cleaned them again. Found the original to not have much "spring back" to it. Chose to swap on one that seemed to function better.

I believe I had multiple issues going on - 1st tbody wasn't closing enough and had a less than optimal functioning IAC. 2nd tbody had incorrect idle set screw and sticky IAC as well.

Now I'm idling at 650 after warming up. :clap:

One tip I would like to share: needle nose channel lock is your friend on the IAC screws!

Good news: saved $230 for a new IAC, and/or $800 for new tbody and learned a ton about this era truck
Bad news: I now can't get my unlocked front driver door open, from the inside or outside :frown:

Thanks for the help guys, and also Foxfab with the intricacies,

Aaron

Thanks for coming back and sharing your solution to the problem!! Glad it's all working now!
 
Shortly after my last post on this, my high idle came back. So i ordered a new IAC. after being shipped a $280 thermostat and going through the return/replace process for a month I put the new IAC in this weekend and my idle is down enough for me. Well earmed up running at 180F I'm at 950 rpm. not the 650 i previously had but way better than the 1700 i was stuck in traffic with and wheeling with one weekend.

Curious if any one knows if the IACs can be brought back. I went through 3 used ones, doing the MAF cleaner bit and removing all black gunk. I'm guessing that the spring tension in that [air damper?] has failed over 30 years and that we can't actually get in there to replace it/fix it/bring it back to life? just checking before I throw all 3 of them away.
 
Shortly after my last post on this, my high idle came back. So i ordered a new IAC. after being shipped a $280 thermostat and going through the return/replace process for a month I put the new IAC in this weekend and my idle is down enough for me. Well earmed up running at 180F I'm at 950 rpm. not the 650 i previously had but way better than the 1700 i was stuck in traffic with and wheeling with one weekend.

Curious if any one knows if the IACs can be brought back. I went through 3 used ones, doing the MAF cleaner bit and removing all black gunk. I'm guessing that the spring tension in that [air damper?] has failed over 30 years and that we can't actually get in there to replace it/fix it/bring it back to life? just checking before I throw all 3 of them away.

I've never heard of anyone repairing the internals of them before. Usually all you can do is just clean them, cross your fingers and hope for the best. I would almost guarantee that any of the parts you would need to refurbish one are not available.
 
High idle on my LC 100 series was solved by replaing the coolant temp sensor. If it is faulty, it will send an incorrect signal to ECU which then keeps the idle rpm high by keeping the IAC valve open.
 
aaannnddd the saga continues.

after a month of living with slightly high idle and dong 6o-mile 1 way trips 2X per week - , yesterday I warmed her up then did 20 highway miles. parked for 2 hours. on restart 2 hours later had a slow draggy start, let it warm back up and went to get a coffee 3 miles away. After coffee, back in the truck and upon turning key heard a kind of clunk noise and straight to 2200rpm, while temp gauge was already warm. Engaging clutch lowers the rpms, but as soon as clutch in rpms back up. After returning to shop and turning engine off and on again down to a consistent 1500, and letting it run for a bit it will creep down to 1300.

i did notice on getting it home the 20 miles though that on both the downhill onramp and the downhill offramp if i threw the clutch in and pumped the brake with significant force the rpms would nose dive to 1000, no matter how high they were.

I had just 2 weeks ago for good measure used a smoke machine to introduce smoke into the air intake to see if i could find a vacuum leak to get from the 950-1050 I was running down to the 650. but the reading was so minimal without live diagnostic data it didn't seem like an issue.

at this point the IAC is new, I'm running a K&N cone filter, got no codes on the scan tool yesterday which I should at least got EVAP code as there is no EVAP equipment installed. I've also metered the IAC wires and get the correct -,0,+ values. And I've checked the inputs on the ECM to check IAC wiring is correct and matches on both harnesses.

Also have a nonworking stock oil pressure and water temp gauges...

Nissanh - thanks for posting I will look into coolant temp sensor next,

Also, looking for some discussion here - kinda at a loss what else to do.

- Aaron
 
I brought this to the local toyota dealer and the service manager's response was that the tbody is from an automatic, and they "recalibrated it for the manual trans using the adjustment on the back of the tbody to lean it out."

Wondering if someone can explain that to me as I didn't come across that during internet search when trying to figure it out?

- Aaron
 
Ive seen them need adjustments because some moron tinkered with it prior. I have done swaps with auto motors and mt ecu. Non issue. My good buddy does TONS of 3.4 swaps and never saw or heard of anything other than i mentioned.
 
Ive seen them need adjustments because some moron tinkered with it prior. I have done swaps with auto motors and mt ecu. Non issue. My good buddy does TONS of 3.4 swaps and never saw or heard of anything other than i mentioned.

Just an FYI, the throttle body part numbers are different auto vs. manual. The diagram shows some parts that are MT specific, though as best I can tell they are related to the dash pot.
 

this was my initial thought too. Also why I wrote briefly - hoping someone would confirm this without me suggesting it or talking you into it.

Ive seen them need adjustments because some moron tinkered with it prior. I have done swaps with auto motors and mt ecu. Non issue. My good buddy does TONS of 3.4 swaps and never saw or heard of anything other than i mentioned.

In all fairness - I started grabbing stuff from a parts stash onsite where i attempt to tinker. I tried 3 different TBs hoping one would work. The one that came with my truck when I bought it should have worked, but I'm certain I had multiple issues going on and should have tried that one again after resolving other items. The other 2 could very well have been jacked up by someone, one of which is now on my rig and I now know that it was an automatic part number.

Just an FYI, the throttle body part numbers are different auto vs. manual. The diagram shows some parts that are MT specific, though as best I can tell they are related to the dash pot.

The dashpot was something that I was suspecting but didn't get to the point of gaining enough knowledge about it yet.

Ya and the fact that it needs provisions for kick down cable etc

I don't fully understand this. So, I don't have a kickdown cable, so nothing was pulling the butterfly back closed enough? This being a problem because it is the auto TB? and if I had the manul TB this issue would not have happened?

>> After pressing the service person for more info, he left me on hold to talk to the tech, who couldn't approach the phone at the time to talk to me. But what was relayed to me this time was that "the valve wasn't closing all the way, so some return springs were adjusted by tightening the screws on the pivot bar, thus causing it to close more." I'm guessing that valve is the butterfly, but I had tried the washer shim method and it didn't solve it for me - so I was kinda just wondering for my own knowledge what I could have done as a next step. I wouldn't know how to tighten spring tension and am not even aware of any screws or nuts for that matter on the rod.

I do have to say that the dealership was in no way a negative experience, and the fee was very reasonable for the time they indicated, especially compared to the number f hours I spent trying to resolve it. also glad that they took the time to fix it and not just tell me I need a new TB.

I am however very curious as to how to do this in the future.

I also am wondering - when they initially said recalibrate - is there any way that all they did was disconnect battery for an hour to relearn the ECU? I was uncer the impression that me driving it for 4 weeks and approxiamtely 1,000 miles that that the ECU would have successfully relearned.
 
Toyota ecu does not really "relearn" like gm.

The dealer fixed the monkey i described.

My comments about kick down cable is simply about different bracketing.
 
Not sure about the 2003 versions, but the 3.4 in my 95 T100 had the exact same issue after I "cleaned" the throttle body. There is a special cleaner that you have to use or it will strip the film off of the inside of the TB, letting more air go by. I fought with mine extensively, and though I am not a dealer tech, and may not know all of the ins and outs of the TB, I had to replace mine with one from another rig....problem solved.
 

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