2007 Yaris INZ-FE Idle Issue

[Joe999]

Hello, 

I am newbie to this site from the USA. I love my Yaris, and look forward to reading about your Yaris stories and seeing pictures of your cars.

I bought a 2007 Yaris Liftback 3 door model with the 1.5 Liter 4 cylinder  1 NZ FE engine brand new back in 2007, the 1st year it was introduced in the USA.  The car is pretty sweet, black exterior, gray/black interior, 5 speed manual transmission, tinted windows, and black steel wheels with black hubcaps.  It's a nice looking sporty small car that consumes very little gas/petrol.  Most cars sold in USA that year were 4 door sedans with auto transmissions. I am very lucky to have found a manual transmission/3 door version of this car, only about 10-15% of cars sold were similar to mine (at least in USA).  Hope to post some pics of car when I get a chance.

 It's ran great for almost 180,000 miles (288,000 km), but noticed something weird regarding the idle after I recently replaced the spark plugs. I'll start out by explaining what I did recently: 

1) Disconnected Battery

2) Removed coil packs with 10 mm wrench 

3) Replaced spark plugs with NGK brand bought at local parts store 

4) Accidentally switched around coil packs 3/4 (looking from Left to Right) 

5) Reconnected Battery

5) Attempted to start engine, but it wouldn't. I realized I accidentally switched 2 of the 4 coil packs around 

6) Turned off engine immediately and switched coil packs around to correct cylinders. 

7) Disconnected Battery again for 5  minutes 

8) Started car again 

Here's what happens: 

1) Engine runs ok, but sometimes idle gets low and engine shakes a little bit

2) It seems like engine computer realizes idle was low, and immediately raises idle 

3) Engine stops shaking after idle raised

4) After awhile idle lowers again and engine shakes a little bit 

5) Idle raises, and engine stops shaking 

Note that I drove car around block and highway at speeds up to 55 mph/90 kph, and acceleration/performance did not seem to be much different before I changed plugs.  I

Questions: 

a. Do you think that when I accidentally switched coil packs on cylinders 3 &4 confused the computer thinking it was a misfire?

b. Do you think that there is carbon buildup in the throttle body, or another bad sensor that could cause the idle to act up like this? 

c. Have any of you seen this in your 1 NZ FE 1.5 Liter gas/petrol engines with 288K km/180k miles? 

d. Other than spending money at shop/dealer, is there something I can do at home to save money and diagnose the engine vibrating/shaking when the idle lowers a bit? As I stated before, the car still accelerates well and maintains highway speeds.

e.  Could the vibrating/shaking have anything to do with a weak/bad motor mount?

Thanks, 

Joe from USA

 

 

 

[stantheman1]

Did the engine check light come on when you first started it up after changing the plugs? Was the idle okay before the plug change?

 

EDIT: Do you have the ac on (or any other heavy load) when this is happening? if so it could be the compressor kicking in and the ecu is compensating for the extra load which causes the'idle up' you mention.

Or it could be the ecu in 're-learning' mode. Is the Battery in good order?

[Joe999]

a. No check engine light after changing plugs 

b. Idle did similar thing prior to changing plugs, I thought that might help.  Plus, plugs were due for replacement anyways.

c. Yes, the AC was on. 

d. I also changed air filter, cleaned throttle body, wiped down air intake filter box, and also cleaned MAF sensor after changing plugs.

e. Idle did improve after the air filter/plugs/throttle body clean/MAF sensor clean, engine still shakes a little bit right after I finished that work this morning. However, idle speed stays constant now.  When i first turned ignition on, it took 1-2 seconds to start engine. However, idle was more stable and acceleration improved.

f. I will monitor engine idle over next couple of trips back and forth to work, perhaps engine is in "re-learning" mode. Thanks for the suggestion.

[wildtapholer]

Don't worry about it, our Yaris did exactly the same after changing the Battery, car has to learn the Battery was disconnected, have a drive around and everything will return to normal.

[flash22]

As you disconnected the Battery the throttle needs to re-learn it can take up to 10-20 miles with varying throttle, the car also needs to run it's readiness monitors

 

[stantheman1]

If you experience the vibrating or low revs at idle again try turning off the ac and if the idle stays constant (give or take a few rpm) then it's definitely the extra load and the ecu senses this and raises the revs slightly to compensate.

[furtula]

As flash said, needs to relearn idle. 

When cold, disconnect Battery for 10 minutes, reconnect, let idle 10 minutes, without any auxiliaries on, so lights, music, fans, ac, everything has to be off.

 After that, take it for a drive, 10-20 minutes or more.

Should be fixed.

 

 

[Joe999]

Tomorrow will be 1st time I plan on driving car for longer than 10 minutes since doing the throttle body/MAF sensor cleaning and plug change. I will drive to work (15 minute drive) with no additional loads like lights/radio/AC/heat and also let idle for a few minutes prior to leaving home. 

 

[stantheman1]

On 4/7/2020 at 2:15 AM, Joe999 said:

Tomorrow will be 1st time I plan on driving car for longer than 10 minutes since doing the throttle body/MAF sensor cleaning and plug change. I will drive to work (15 minute drive) with no additional loads like lights/radio/AC/heat and also let idle for a few minutes prior to leaving home. 

 

How did you get on? 

[Joe999]

Vehicle idle improved after engine had chance to re-learn idle.  Thanks for all the suggestions.