I have been tracing a vibration in idle for longer than I even care to admit. During warm up ( until operating temp ) it idles rough. After it warms up, it get better but still not where I know it should be. I know the 1ZZ isnt the smoothest by design but Heres my story.
-Replaced all engine/trans mounts twice and I will explain why: Early 2020 I replaced the front and side mounts myself. The rear mount ( firewall side ) looked to be too much to handle so I decided to have a mechanic take care of that one. COVID came in and I did not feel comfortale taking it to a shop...so for 9 months the car vibrated terribly and violenty. I found a mechanic that would come to my house so it will be safe repair pandemic wise. He replaced the rear mount and it was shot, completely torn. Practically driving with 3 mounts. After having that last mount replaced, I still had this vibration at idle. Being that I drove with a mix of new/old mounts....I suspected after 10,000 miles maybe I prematurely worn the new ones. So I did a little experiment: I replaced one mount at a time and see if the issue improved...and it did. As I replaced each mount, the vibration became less and less. So its looking good here right ? When I had the rear mount left and still just a bit of vibration, I thought that this last mount would finally do the trick. It did not change anything. So I guess I can rule out engine/trans mounts now LOL. The mounts are all Toyota OEM.
-I do have a PO 442. Replaced both gas caps, purge and vent evap solenoids had a mechanic do a smoke test. He couldnt find any leaks, he suspects the charcoal canister maybe leaking internally. In my opinion if the leak is that small, it wouldnt contribute to THAT rough an idle. I could be wrong though.
-Replaced all plugs in the last month, the coils are Denso units that are 2 years old from a missfire I had, so replaced all 4.
-Fan assembly. The other day I noticed when I had the key on/ignition off there was a vibration in the steering wheel. Weird because the engine isnt running. The fan was on high ( car was just driven and I was ready to start it again ) I did this a 2 more times and noticed the same issue. The fan seem to have excessive vibration on high speed. When the car was off I turned the fan blade by hand and just before it stopped i heard a small squeal. My logic...the bearings are worn, and putting a electrical load and causing a little vibration. New fan assembly and no change. I also noticed the vibration was more apparent when the AC condenser fan kicked in on high and that also led me to beleive the fan assembly may be causing my issue. That leads me to the next thing....IAC valve. Im also experiencing a hard start when the car has been sitting after it has been driven. It starts up fine in the morning.
-The IAC and throttle body was cleaned 3 years ago. Aprox. 25K miles ago. This was the 2nd time it has been cleaned. I cant see it being that dirty that it would cause rough idle. Even at the dirtiest it never idled this way. Unless the IAC is just faulty. I do have 272,000 miles now. With the AC on it does idle about 800 RPMS and the idle doesnt dip with a load from the AC. So its seems the IAC is working correctly. I understand that the IAC is supposed to bump up the RPMs when the AC condenser fan kicks in, but my RPMs are steady at 800 and not fluctuating. Again....I can be wrong, thats why I havent fixed it LOL.
Any ideas ? Im stumped. Im starting to think I did some kind of damage driving with a bad motor mount for so long.
CEL gave me a PO303 ( misfire cylinder #3 ) and PO420 ( Catalyst System Efficiency Below Threshold (Bank 1) It would also stumble a little into 2nd and 3rd under hard throttle. I had a spare coil and swapped it out, cleared the code and its been 2 weeks and the 303 and 420 code have not returned. When I replaced the coil I did a little under hood inspection and found the center bolt for the front engine mount completely loose. I tightened it up and went for a drive. Car drives MUCH better, throttle response is improved and the car doesnt feel like its struggling anymore, and not stumbling into 2nd and 3rd. Shifts are very crisp. It still idles a little rough when cold and when the AC condenser fan is on HI, but its improved.
SOOOOO.....Last week I bought a can of Cataclean ( yeah I know
) in fear of the PO420 code and gave it a shot. Followed the directions and ran the Vibe HARD. Guess what ? The idle improved, maybe a clogged injector ? Again idle is not perfect but better. Slowly but surely here.
At this point I feel like taking shots in the dark, so I decided to pickup a new MAF sensor. To my surprise, it did smooth out the idle ( old one was cleaned to rule that out ) I even swapped the old one out twice to compare between new and old. New MAF it seems to run better. Have no clue why....
The only time where I feel it idles rough is when the engine is below operating temp OR when the AC condenser fan kicks in on HI. When the fan is on LOW speed I really cant tell the difference now. It used to idle rough in HI and LOW speed.
So after 1 coil, loose engine mount, new MAF sensor and a bottle of Cataclean the Vibe is idles WAY better. Even when I lightly feather the throttle around 50 MPH it feels very smooth. I still have a bit of vibration at idle when the AC fan is on HIGH but its tolerable now. Im begining to wonder if I have another coil that hasnt thrown a code yet, that may be starting to go. I might replace the coils one at a time and see what happens. Driving today I noticed a little stumble when I give it a light throttle coming off a traffic light around 1200 RPMs. Sign of another bad coil ? Either way I feel like Im VERY close to solving my idle issue.....WHEW ! It has been a LONG journey !