High Idle Issue Mechanic Can't Figure out issue

2005 Tacoma- v6 4.0l

Replaced the battery, then we ended up with High Idle. Brought it to shop to do relearn. 3 times. Each time it would go to normal idle but the minute you shut it off and start it, it goes back to high. Around 1100 each time.

Brought to a different mechanic. They did idle relearn same thing went back to 1100, asked them to look at it more, they did vaccum test found no issues. Then my husband told them that it was so odd because he just tried to install a radio and blew a couple fuses, replaced them and then all this.. (You know making small talk). The mechanic looks at it again, and pulls the radio out sloppily.. puts electrical tape on wires that weren't in a harness (not bare wires), then blames the high idle on the radio install. Says just drive it at 1100 won't hurt it. WTF?

Third mechanic. We removed the damn radio. This mechanic is convinced radio installs have nothing to do with high idles even if it involves the maestro for steering wheel controls. --- Does idle relearn. Same results. Does vaccum tests, can't find anything there. Says 95% sure that it's probably the throttle body. Can't test the throttle body so ok, they put one it from the dealer -OEM part. Just got call that at first the first two starts idled great, then jumped to 1100. They are looking some more, but before they recommend the computer, they have made the suggestion that we bring it to the dealer for further diagnosing.

Under unbelivable stress and anxiety is high. Bought the truck used, still making payments, and we are getting pretty high dollars. Can't afford a new vehice at all so stuck trying to get it fixed and put it on a credit card. ugh.... BUT WHAT IS WRONG WITH IT? Has anyone else had this problem?? What was the solution??

 

Going out on a limb, but were the three mechanics Larry, Moe & Curly, or Daryl, Derrel, and my other brother Darrel?

There are a very limited number of things that can cause a high idle, and I would say that the radio is pretty low on the list. It's not impossible that something could have happened in the radio install that caused it, but it would be a real stretch.

When you say they did a vacuum test, did they actually get a smoke machine out and 'smoke' the system, or just put a vacuum gauge on the manifold? Step one is getting someone who can put a good scan tool on it, and watch the various PIDs change. The good news is that because a 'relearn' will cause a predictable pattern of behaviour, this shouldn't be all that difficult. Did anyone actually examine the IDLE air control?

 

Drive it around for awhile. 1. the truck needs to warm up for idle to settle down to ~ 550rpms in gear ~ 750 in park or neutral. and 2. the truck needs to be driven to figure out its baseline.

 

Sure feels like it. One of the shops is giving me back our money. The second I might have to go back and ask, as they charged 2 diagnostics-the second diagnostics is when he said it was the radio. 3rd guy I guess worked with the new throttle body and said in drive it drops down to about 850, in park at about 1000 and said that it is acceptable. My husband can live with that as long as it's not screaming at 2000 as it has done a couple times. The mechanics are dead set against it being a computer issue as everything checks out. Oh.. and one of the mechanics took a long hard look at the schematics and said a radio install would have no bearing on an idle. Just dumb luck I guess.

 

1K is still a bit high; it's something you can live with, but I would keep trying to track this down. You need to search for a shop that is skilled in diagnostics and who can actually track down the problem instead of guessing. Did the problem occur immediately upon start-up after the new battery was installed, or was it later on?

 

Welcome. Not to be an ass, but we know that you have a Toyota Tacoma by the very fact that your here asking a question. We however know nothing other than that.

4cyl? V6? Base 5 lug? SR5? Prerunner? 4wd? Miles... Putting this info up there at the top saves you a lot of typing in future posts and gives us an idea of what you have so that we can apply our knowledge correctly.

For example: I have a V6, am not at all familiar with the i-4.

There are commonalities between the two as well as peculiarities.

I will however suggest buying a can of MAF sensor cleaner and a can of throttle body cleaner.

The MAF sensor is usually between the air box and the throttle body. Unplug it, remove the screws, and pull it out and spray the appropriate cleaner in it. You will see something hanging down inside of there, do not touch it! Just hit it with spray from a little distance. Clean it all up shake it dry and reinstall.

With the V6, my gas pedal is not physically connected to the butterfly valve. It is referred to as drive by wire. Or throttle by wire. The throttle body has a motor that opens the butterfly in relation to the gas pedal input. Over time, build up where the blades would be closest to the bore when closed will cause the throttle body to open up to compensate. Use the throttle body cleaner and a q-tip to get into the nooks and crannies around the butterfly. If you attempt to move it you risk breaking teeth off the plastic gears that drive it. That is why I go the q-tip room with liberal application of the throttle body cleaner.

Disconnect the battery before you start. Or, do like me and just pull the parts out and clean them and put them back. When I started up I have a rather high idle that I will watch drop down in increments to its normal idle.

Edit: look for vacuum leaks too.

 

Sorry.. yes I should have qualified. This is a V6 4.0L. Maf was cleaned. Vaccume test done with smoke. And yes, drive by wire as we have discovered. New throttle body was installed, now idles in park I guess at 1000, drive around 850. Husband is picking up the truck this afternoon.

 

We'll see what my husband thinks. Having it to three mechanics and down to one car for a week was not fun. And the bill matches the frustration. The final shop we brought it two stated they had diagnostics, and a couple mechs with 40 years experience.

And yes, issue started after we installed the battery. However.. my husband isn't 100% sure if it idled that high before but i'm guessing it didn't... after a while things become a blur.

 

The MAF could be the issue, as could the IAC, and a few other components; a lot of folks (including mechanics) forget that the bits that connect the sensors to the rest of the car (aka "wires") are just as important, and just as prone to failure as the components at the end of them. For instance, let's assume the MAF is the root of the issue; it could be that in fact the physical sensor is fine, but there's a corroded ground and when a particular ground wire moves a bit the wrong way, it imparts a higher than normal resistance on the MAF signal line; not enough for the ECM to know that something's wrong, but just enough to cause it to "see" a change in conditions and adjust the idle to compensate for them. This could also tie in to the battery replacement by virtue of the fact that when replacing the battery, wires were moved which caused the situation to occur, and now that they're disturbed, it keeps reoccurring. It may sound far-fetched, but this is the sort of thing that happens very frequently with modern vehicles.

The downside is that trouble-shooting these problems can be time-consuming, and they're straight-time jobs, not book time. It could easily take 2-3 hours to work through all the various circuits, testing each leg, connector, etc. It's not actually difficult, but it does take time and a professional's time is expensive.

 

There's no idle air control on these trucks, the idle speed is controlled by the same throttle valve that normally controls air flow via the driver commands. If vacuum leaks have checked out SAT, and there is no MIL then there is no problem. My guess is the previous grease monkeys don't know what an "idle relearn" entails on these trucks, which is simply driving it around and allowing it to self calibrate. The idle curve is based on the learned idling air flow volume, VPA and VPA2 voltage, and throttle position sensor.

 

Great info, and my fault for not actually paying attention to the vehicle that the OP had!

 

I believe I've been to both these shops.

 

Haven't we all?

 

When I first checked everything out buying my vehicle, I was looking for the IACV as all my older vehicles had one and didn't find one here. I guess that's good since it's one thing less to break LOL

 

When you replace the battery it is common when the new one is installed for the idle to be really high for a short time since the power to the system was disconnected. The computer goes into relearn mode and needs to learn your driving habits again. It eventually goes back down to “normal” in a day or so, depending on how much you drive. If the idle relearn thing keeps getting done it sounds like the computer isn’t getting a chance to figure things out.
Hope it’s as simple as this, good luck

 

I googled idle relearn and I learned something...

https://youtu.be/wLw4NkKmsA4

In the description for the video it states rough or high idle. Worth a shot.

 

What he said ^^^

Since it has been messed with by so many 'mechanics', I would start fresh. Take a battery cable off, wait ~10 minutes, then hook it back up. Start truck, it will run rough. If it dies, wait a minute then restart it. Then take it for a drive. Take it out on a highway up to the speed limit. Go home, shut it off. Repeat a time or 2. Idle better now?

As an aside, if your husband blew fuses when installing a radio, he should not be installing a radio. No offense meant.

 

You can typically unplug the MAF to test it. The truck should go back to factory fuel values. If your idle changes back to normal with the MAF unplugged you'll need a new one (especially since you said you already had it cleaned).

 

It was a mistake with him blowing a fuse, and he recognized it. Last mechanic replaced throttle body and did the batter cable thing. Truck still idles at 1100 in park/neutral. Still trying to figure it out.

 

It's been driven plenty to warm it up and a few days still 1100 rmp in park. Last mechanic replaced throttle body and did the batter cable thing. Truck still idles at 1100 in park/neutral. Still trying to figure it out.