MankinToy

I hate to post this....another rough idle, could be a million different things. But, I'm at a loss and at least if I'm going further into just replacing things, someone will have advice to guide that effort.

1987 4runner. Had the motor rebuilt last summer at a local machine shop. Added a enginbuilder 261 cam. Ever since, it has had an odd idle phase.

It fires up great and fast, runs smooth, but doesn't run as high as it used to...1,000-1100 rpms. It'll do that for 2 or 3 minutes and then drops down to 500 or less. Doesn't quite die, but runs real rough. But, if I just start driving it runs fine and once it is fully wamed up it idles fine...but high, usually between 1100 and 1500 rps.

I've been kind of just dealing with it, but in the last week it has gotten worse. now it runs real rough when going through this cycle of running rough....but it does smooth out at higher rpms and drives fine. Then, once fully wamed up its running fine with a highish idle around 1100 rpms.

So, now I'm worried. what would cause the idle to run so low and even skip a little and then clear up after it's warmed up? any insight is welcome. I'm thinking it's the idle air valve thing...but they are pricey to replace. TPS? but wouldn't that make it run poorly all the time?

bbrideau

you could be throwing a code 52, check to make sure u have a bulb where your check engine light is if you do pop the top on your diagnostic plug and jump connector t1 to e1 with a paper clip turn key to on count the flashes you will get a 2 digit code if there is any. sometimes your ecu will store a code even without showing a CEL. my truck started doing what yours is doing and i noticed i had a few plugs that were broken and the wire from the harness to the Knock sensor was missing. awaiting the pigtail wire its only 20 bucks straight from toyota and they commonly wear out

MankinToy

yeah...this thing is killing me. It doesn't throw any code. knock sensor wire is there...but yeah, the wires and plugs are sad looking. When I was reassembling last summer I often thought to myself "I should just replace these wires and plugs".

But I'm not sure where to get the parts? What exactly do you mean by the pigtail wire? is that the whole harness from the ECU? I cant imagine that whole thing is $20? Any insight would help.....thanks.

Neil

bbrideau

well the knock sensor is about 175-280 for an aftermarket one DO NOT GET BOSCH they will fail in no time, the KS itself from toyota is about 300 bucks but when i talked to the toyota dealership i talked to a mechanic and he said in the 30 years of being a toyota mechanic he has never replaced a knock sensor on a 22re. now that being said the pigtail wire is about 12 inches long it plugs into the knock sensor and to the harness. toyota was smart in the design because they knew the wire would become brittle and break over the years.

some other causes of your rough idle could be a few other things too tho. if your not throwing a code then it most likely isn't the Knock sensor wire. your AFM could be dirty your throttle body could be plugged up, your idle adjust screw might be to closed and your motor could be falling on its face trying to stay running. could be something as stupid as a vaccuum line. i believe there is about 10 feet of vaccuum lines on the 22re i just picked up some new hose and will be replacing it all shortly.

its to bad your not throwing a code because it makes it hard to diagnose especially for someone like myself not being able to see it for myself haha

abecedarian

Does the cam have specific valve lash adjustments? Have you tried tightening the valves to the small end of the specification? Have you even recently checked your valves' lash?

Are you getting voltage to your IAV? (It's under the throttle body.)
If you block the air passage to the IAV, does that affect cold engine operation? ... warm engine operation?

MankinToy

Valve lash is good...I've only got about 2,000 mi on the rebuild, I adjusted them at 500 miles, per the machine shops guidance, and checked them again when this issue started to worsen...they were all good still.

I replaced all the vacume lines a month ago and have double checked everything.

The IAV kinda confuses me, I've read a lot of posts on here and it isn't clear to me how it operates...but, my guess is that it is the culprit. I don't think there is power going to it though? I'll check first thing in the morning. I guess I'll reread the manual too see if it has insight.

MankinToy

duh yeah....there is a plug on the IAV....I'll check for power in the am.

MankinToy

I reset the ECU and ran it...then tested again and it threw a code 11....which according my manual is either the ac switch or the TPS. Tested the TPS and couldn't get it to specs....at idle it showed no resistence. So, I pulled everything off to try to adjust it on the bench, but can't get it to register resistance at idle....so looks like it might be the TPS? it's a start anyway, gonna go pick up a new one and see if I can't get that one adjusted to specs.

MankinToy

ARGH!!! I got a new TPS, adjusted it and it ran great....for a while. I couldn't get it to do the funky idling thing again at home....took it on a a couple day ski trip and it started to crap the bead again after re-starts...got home and it wouldn't throw any codes. So, I'm thinking the IAV is closing too soon and making it run rich at lower temps. Is that a stupid idea? I'm out of ideas so I'm going to flip the bill for that overpriced temperature activated valve.

MankinToy

Air Flow Meter? before I wasted any more money I took apart the plenum, cleaned everything, tried blocking the egr, readjusted the TPS (like 3 times)...and then decided maybe I should check the AFM. the third test in the book failed. NO matter how hard i tried to rub the connection to make it work I couldn't get any continuity between E2 and VB. Before I go and buy one of these things, can anyone confirm that that problem could cause this issue?

mpwarfy

im not sure if i can help you or not but I think my 88 runner is running bogged down kinda how you described your issues and i swapped my air flow meter with a buddy's and it made a pretty big difference. so thats the part im hunting for now

MankinToy

Thanks for the insight...looks like it isn't too hard to find a used AFM. I've been slacking on the search since the truck hasn't acted up since the last time I took the plenum off and cleaned everything. The only issue I have now is that it doesn't have a cold temperature start rpm rise. That is, it starts up at about 800 rpm and never rises or drops. Doesn't seem to matter...probably need a cold start injector sensor...but I'm taking a little break on parts purchases and messing with this rig....other hobbies have been negected lately.

Swamp Pirate

My truck was doing almost the same thing a few weeks ago. It would idle really high when cold, would warm up and idle ok sometimes or idle at like 4-500 rpms like it was gonna die. I managed to get a new (and FREE) afm and it stopped all of that. I still have two more problems, one being my knock sensor plug thing is literally broken off the sensor itself and im throwing an o2 sensor code which Im damn near positive is in my wiring (Because my o2 sensor is a brand new denso direct-fit). Will the knock sensor being bad (or in my case) not being hooked up at all cause problems of any sort.

bbrideau

Your knock sensor when it doesnt send a signal ur ecu will autonatically retard your timig to 5 degreea which will cause horrible economy. No power really and basically rhns it rich. Nothing to bad can happen at least if you dont mind cleaning all the carbon build up in your engine

Swamp Pirate

Damn, no wonder I've been getting worse gas mileage lately. I dont know when my knock sensor broke because my check engine lights been on for a LONG time for lean mix (code 25 - now gone) and o2 sensor (code 21), but lately, for the last two months maybe, I've been getting 17-18 mpg MAX, when I drive like a grandma, don't tow anything, don't use my 4wd, and baby it as much as possible. Most of the time, I'm getting 14-15 mpg when I'm relatively nice to the old girl. I can't really tell if I'm too down on power because my transmissions been slipping through first gear and it's going downhill pretty quick. Matter of fact, that transmission got a running start and leaped off a cliff ever since last time I went swamp diving and got my ass buried in the middle of nowhere. (I always find a way to get more stuck than ever before every time there's a new girl in my truck )

MankinToy

Yeah, all these little things can really make a difference...my problem was ultimately the MAFS and the throttle position sensor. I'm not sure the TPS was contributing to the rough idle, but it was contributing to generally poor operation. Runs like a champ now. But, the biggest lesson I had was when my original toyota TPS didn't work, I replaced it with a duralast TPS from Autozone. Despite the frequent assertion on these threads to go with toyota products, I've never really had a problem with autozone parts. Well, my tune has changed. The duralast kinda worked, and was almost perfectly adjusted, but it wouldn't adjust perfectly (i.e. the resistence on the first check was always like .1 over), and even kinda went out of whack after running it for a week. I wasn't sure it was a real problem until I put down the money for the toyota...what a difference! It adjusted to specs just like it said in the manual and the performance is noticable. Fortunatley Autozone took back their POS and refunded me. So let this be a lesson to all those who blow off the warning to buy certain things from the dealer...it would have saved me a few weeks of heartache in the end!