Idle very high after fuel induction service

After purchasing my 96 Tacoma with the 3.4 V6 and driving it home from Colorado I had it inspected at an independent shop recommended by a friend as "the best Toyota guys around." They found no problems, but a week later the check engine light came on, so I went back to them. On their recommendation I had the O2 sensor replaced, which helped. They further recommended a "fuel induction service," and a few weeks later I had that done. When I picked up the car the cold idle was very high, upwards of 2000, and only dropped to 1200 after heating up. The mechanic said "that's common, it takes a few days for the computer to adjust to the better air/fuel mixture, and the idle should return to normal after a few days of driving." They said to come back if it didn't return to normal. It did drop to about 1500 cold and 1000 warm, but that wasn't 750 as it had been before. I took it back and they kept it for the day and gave it back, and now it was back up to 2000 cold and 1500 warm. Once again they told me to drive it around for a few days, but once again that didn't help. It did go down to 1500 cold and 1100 warm, but that just isn't acceptable. When I brought it back they said "we recommend replacing the throttle body and mass airflow sensor" at about $1000.

So... I kind of lost faith in these guys, did some research, realized this "fuel induction service" wasn't that complicated a job, so now I'm considering removing and cleaning the throttle body again myself "the right way." I'm wondering if anyone has had the same or similar experience and has any recommendations. Are they right? Does the throttle body and MAF need replacing? Is there any way to adjust the idle manually (I grew up in the 60s when this was done by turning a screw)? Etc...

Any help/advice appreciated.

 

Check every vacuum hose for dry rot and replace any that are cracked or brittle. How old are the spark plugs?

 

I have some receipts. One says plugs replaced when he did the timing belt at 122K miles, which is about 85K miles back. FYI this guy took very good care of the vehicle, always followed the recommendations of his mechanic, so I assume he replaced them when recommended.

 

I would start with new plugs. 85k is toast

 

Check your iac valve on the bottom of your throttle body.. i just had a similar issue after cleaning my tb with brake clean.. i didnt realize i washed some extra gunk down in the air port below the butterfly blade.. there are 4 phillip head screws that hold it on.. it is used by the ecm to contol air flow for idle... After cleaning mine it went from a 1500 cold idle and 1900 hot to about 1100 cold and 650 hot idle...

 

A fuel induction service can be a few things. Depends on who the supplier is and which tools they used.

Likely it was a injection flush, where you bypass the fuel pump and run direct cleaner through the injectors and clean. This is good and hard to mess up.

Some induction flushes spray in though the intake, they disconnect an intake pipe and clip in a spray nozzle that cleans everything after the MAF.

This makes me suspect of the intake piping and the large vacuum/PCV hose. You may have to remove the pipe and inspect it for cracks. This can cause a high idle. Often a CEL for lean.

Next possibility is that the intake spray actually damage the IAC valve. It may no longer be adjusting properly.

I've yet to change and IAC on a 3.4 for any reason, but abnormal servicing would make sense. Hard to put the blame on them for that.

Other possibilities is the throttle position sensor is out of whack.

You could just try a used throttle body from a wrecker.

 

Try cleaning the MAF sensor yourself and see what happens.

 

Thanks for all the input. I removed the throttle body myself and did a thorough cleaning (it looked like they hadn't removed and cleaned the IAC, so I did that, but the rest of the assembly looked like it had been cleaned). Butterfly valve looks OK but I can see where it's been resting against the side of the intake port when closed and has worn a bit of the metal away, possibly creating some extra air flow. Runs much better but still idles high. What's odd is that I disconnected the battery to reset the ECU and then let it idle for 20 min, and the idle went down to about 900 during that time. Now it idles hot at 900 UNTIL I drive it and then it idles hot at 1200. Next step is to replace the IAC valve. Also got a CEL but I'm waiting for my bluetooth reader to arrive.

Also, I did clean the MAF with MAF cleaner. Don't think that was the problem.

 

Test the IAC before replacing. When the IAC is removed you can test it following the instructions in the repair manual. Basically you hook 2 of the terminals to 12v battery and check that the valve fully rotates, then reverse polarity and check it rotates the other way IIRC.

The electronic part of the IAC (solenoid) is on the outside of the valve, so it's unlikely "the best Toyota guys around" damaged that part. It's more likely they gunked up the mechanical part. If you cleaned it and verified it rotates without resistance then it should work.

The throttle plate linkage should have a stop screw that is set right at the point where the throttle plate is fully closed. This screw takes the impact of the closing throttle plate off of the intake port surface and prevents the plate from gouging it. I'm not sure if the wear you describe is normal or an indication that the set screw was not set correctly. (I'm going by my knowledge of the 4-cylinder, but I'd guess the 3.4 is the same.)

 

I’m curious to know what the cel is, sounds like the IAC if not a small vacuum leak. But most likely the IAC is bad.

 

Removed the throttle body and the IAC and gave them a thorough cleaning. IAC rotates but I did not test as I wasn't sure which of the 3 leads to connect. One thing I noticed was that it was a little loose, meaning when turning the gate mechanism by hand it was loose for about a 16th of an inch before it engaged with the spring. Not sure if that matters. Reassembled and it runs much smoother at speed but idle is still high.

BTW the CEL was an O2 sensor error which I cleared and which has not returned, so I think it might have been a reaction to the new air fuel mixture from the cleaning.

Some pics of the throttle valve etc. below.

 

Still could be the IAC I suppose, have you sprayed any brake clean on your vacuum hoses just to rule out a leak? My money on high idle issues is usually the IAC.

 

Replaced the IAC, idle still high, interestingly I can see it trying to lower itself sometimes when I come to a stop, as if someone's revving the throttle a bit, then go back up high.

Was that a joke about propane and the vacuum hoses? How does one check vacuum hoses with propane, or brake cleaner for that matter? Spray volatile, flammable gasses while engine is running?

 

No as far as brake clean it’s not a joke lol, of course use caution around elec wires etc. just spray a small amount on your vacuum hoses if it’s leaking it will suck the chemical in and cause a change in the idle. I’m kinda thinking you could have a ecu issue. A quality mechanic would have a scan tool that he can manually open and close the IAC and look at values to see if the ecu is getting the right info from various sensors. What rpm is the warm idle now?

 

I remembered long ago my daddy told me to spray brake cleaner on vacuum hoses to find leaks but I must have forgotten. You can tell I'm not an experienced mechanic (although when I was 16 I took the head off my Ford Econoline straight 6 and when I put out back on I only had a few extra parts). The warm idle is still 1700. Tomorrow I'm taking it into the mechanics who replaced the O2 sensor cuz that's the CEL I'm getting... will see what they say.

 

It's my fault. I ordered 22270-62050 instead of 22270-62040, apparently a part for Tacomas built after Sept 1996, which mine is not.

 

Was that the issue