Rough idle after warm up--2.7 1999 4X4 5 spd.

Starts up OK and not too rough with the idles where it's supposed to be a little over 1100 rpm but after warm up it drops to below 500. It hasn't stalled yet but shakes and almost dies. No CEL and I put my code reader on and nothing shown as pending. See photo below of some of the readings, I honestly have no idea what these mean. I haven't done anything yet except tired to find an vacuum leaks. It's been awhile since it has had plugs because it's just an errand truck now and really only make one trip a week to the dump.



Brian

 

Got the plugs out....Parts store only had 1 on the shelf.



Brian

 

Best things I ever did to my 2.7 were new iridium plugs and clean the MAF. I did them both at the same time so I can’t be sure which had more of a positive effect but together they fixed my idle and bogging problems.

 

I cleaned the MAF and will put the new plugs in tomorrow....I will report back on the progress. Something I wish more folks would do.

Brian

 

Completely beside the point but I woke up this morning wondering why a parts store would have an odd number of plugs on the shelf.

 

I noticed yesterday what looks like a crack in my exhaust manifold....I didn't take a photo but I will today and post. Looks like I'm going to be replacing that as well. I think I'll swap to a mini header set-up if I can find one at a pull-a-part junk yard.

Brian

 

Got the plugs in and the issue is still present. It's hot day here about 90 deg and I even got the low idle on a cold start. I'm leaning towards a IAC valve problem. Still no CEL. I put an eBay cheap IAC valve on it a few years ago and was warned it might not last long. I'll put a link to that post below. The problem isn't the same but close.

https://www.tacomaworld.com/threads...code-need-advice-please.513111/#post-16379653

Brian

 

If it’s upstream of your o2 sensor it could be messing with the reading.

 

I don't know if I'm late to the thread but this is my 2 cents. Let me just mention, I am not a mechanic nor a technician of any sort. Before spending more money and replacing parts that may or may not be bad, try this. I just did it on an 87 Camry a month ago and fixed the rough idle and the surging compressor as well. Most recently, just did the same on an 05 Honda CR-V and so far so good, as a matter of a fact it has never ran better but I'm still keeping an eye on that one. I have 02 Tacoma prerunner 3.6 that I intend to do next but haven't gotten to it. Take apart the intake and the filter and the mass airflow, all of it. Locate the throttle body and iac and clean the throttle body. Clean the heck out of it with the throttle cleaner. Shoot you don't even have to remove it if it's not too bad (if left on do not stick your hand in it, use a wooden stick of some sort I used the handle from a broken hammer and lots of paper towels). You'll need some help to do it as the throttle opens and closes when the accelerator is pressed but only if left attached. Do not do it while car is running, only on "on" position. There's tons of videos online teaching you how to clean a throttle body. The iac might be bad but from my experience, the mechanical throttles last a lot longer than electronic. If you see it looking gross like syrup or something spilled all over the butterfly when you first open it up I'm willing to bet that's your problem right there. Next, check the idle adjustment screw as it might just need tightening as well. Look for that bolt and adjust as necessary, again refer to videos. I am not a mechanic. After all of this, you'll need to preform an idle reset. Super easy and simple. Not entirely certain it will be the same on yours than it was on the Camry so you'll want to do your own research but shouldn't take more than 20 minutes. And if some horrid smelling white smoke comes out, don't worry apparently that's normal. I suggest running the truck for a while after at least 10 miles so it relearns the idle and driving patterns. The entire process took me about 2 hours as someone who had zero experience. Hope this helps. Good luck and keep us updated!

So in short,
1)Clean throttle body and intake and filter and mass airflow box

2)Adjust idle screw

3)Preform idle reset

4)Drive

 

Reporting back....I thought about trying to clean the throttle body and IAC but decided to just replace the IAC. The low idle issue is gone and it's working it's way through an idle relearn. The hardest hoses to get off are the two coolant lines on bottom, taking the throttle body lose helps to get to them easier, same with the electrical connection. Don't forget to hook them back up before bolting it back on.

Brian

 

I had the same issue after cleaning my throttle body (without taking it off). I then had a choppy idle after warmed. Everything else was perfect; new plugs, clean MAF, clean air filter, new 02 sensors. I replaced the entire throttle body (and IAC) as the original was old and I didnt feel like chasing things down. Installed the new throttle body... and it was still choppy! I just got used it. Then a few months later I did a 200 mile freeway road trip and it started idling perfectly after that. My thought was all these short 5 mile trips around town wasnt enough to reset the computer after installation.

 

The first time I cleaned a throttle body, I did a reset but didn't run it after. That was a mistake. Had to disconnect the battery and drain it and redo the idle reset again. Trial and error, right?

 

When you say reset are just talking about driving it or some other procedure....?

Brian

 

pull off the whole intake assembly and clean it.

if ay grime builds up around the throttle plate, definitely can cause idle issues.

doesn't hurt anything to clean the intake and replace the plugs.

 

just disconnect the battery for like an hour.

this will soft reset the ecm

 

I suggest preforming an actual reset for the idle not just disconnecting the battery. It will include running the rpm at a certain number for a while until the fans kick on. It's different for makes and models. And then don't forget the drive the vehicle so it relearns the idle.

 

I haven't found exact instructions for doing the reset on a 1999 2.7 4X4 5 speed. Most say to disconnect the battery and then drive it. I haven't put many miles on mine yet and I have disconnected the battery twice now and it's not seeming to relearn. I may have to change the exhaust manifold to get it back right.

Brian

 

https://youtu.be/_S9B3IhK_Tc


Check this video out!

 

That didn't work either....Still have an idle around 1200. I bought part# 22270-75040 but was sent 22270-75030. My truck is a 5 speed and part# 22270-75030 is for an automatic. I'm not sure if that makes a difference or not.

 

Unfortunately I'm not certain If it makes a difference. Is the idle like that the entire time or only when you first start it up? There's a screw for the idle. Have you tried to adjust the screw?