'03 Tacoma 2.4L Base with bit of rough idle

A month ago we got a "New To Us" 2003 2.4L Base Tacoma for my son. I've read allot of posts on this subject so I'll cover what I've inspected and I hope someone has a suggestion for me that I haven't thought of and dismissed.

Symptoms: Normal idle speed 700(+-50) with A/C off but enough vibration you can see the seat covers vibrate and the steering wheel.

Replaced
-Spark Plugs with Iridium properly gapped. Inspected after 1000 miles and color is good.
-Spark Plug Boots and seals
-Air Filter
-Transmission Mount

Cleaned
-Throttle Body (wasn't really dirty, clear someone been there fairly recently)
-IAC Valve (again, hardly dirt at all)

Inspected
-MAF Sensor: At idle speed reads about 3 g/s which seems normal and graphs linear to throttle position. (I don't have any other MAF symptoms but thought I'd mention it to say I think I ruled it out)
-Air Intake Hose: No apparent cracks or leaks
-Fuel Trims: Long Term -3.5% / Short Term 0-.5% usually (seems like no unmetered air getting in)
-Engine Mounts: I did some power braking in Drive and Reverse and the motor hardly moves at all.
-Exhaust: Someone here mentioned they had a sympathetic vibration with their exhaust and when they locked it down it solved there vibration but I've been under the truck with it in gear and don't observe anything unusual.

So that's it, the only thing I can think of now is maybe some sort of other vacuum leak? Or maybe the mounts are bad? Not sure if the picture will help.

 

Bump?

 

Just for the "historical record", I checked the valve clearances today and they are all within spec.

 

Definitely not a vac leak. You’d be running lean but it’s actually rich.

I’d be looking at the injectors.

 

thanks for the reply. I thought anything under 10% fuel trim was nothing to be concerned about. I’ll research injectors next.

 

Actually. Never mind. I thought about that and you’d be lean with a crappy injector as well.

And that trim is good. So forget what I said.

 

Appreciate the input any way. Thanks

 

We just checked valve clearances and all 16 valves are comfortably within specification. Timing chain tension seems tight and the marks are aligned.

Rechecked fuel trims this morning and LTFT is at 0%

Mystery continues

 

total miles ????

compression (each cylinder ) ??

 

Thank you for your reply. 133,000 miles. I haven't checked compression, chalk it up to if I found something, I probably wouldn't do anything about it. I also assume if I had poor compression in one or more cylinders, I would see something on plugs or in the fuel trim and O2 sensor data. Instead my plugs look perfect and my LTFT is 0%. Not to say I won't check it, I'll probably borrow a tester soon and report back.

Thanks again, Rob

 

Just thinking out loud here. If you had poor compression I’d assume blow by and high crankcase pressure would come with it. So you might see more oil in and around the PVC and runners.

You could also run a pressure test through the dipstick. IIRC it would only be a very small amount while running. Maybe no more than -1–5 inches of Mercury?

EDIT: fixed

 

Thanks, when I replaced the PCV valve I shot parts cleaner through the hose and there was very little oil in the hose.

 

Wish I knew more to help you out. I’m still learning. But I can tell you that on my v6 I had an annoying vibration. Especially with the AC on.

Ive changed so many things I don’t know what helped it but I think the new exhaust helped dampen it out as weird as that sounds. I noticed immediately after changing it out it was better.

In my case the crankshaft bolt was drilled a little crooked from the factory. So when I clamp the crank pulley it clamps it down harder on one side than the other which gives it a slight wobble. When the AC kicks on it makes the AC clutch wobble. New compressor did the same think so I know it’s the crank. I can see it especially with a slow motion video.

It just is what it is.

But It drove me absolutely crazy for a while. My neighbors probably think I’m a crazy person always popping my hood looking around and messing with things.

 

I can relate, my son and I have had the hood open so many times chasing ghosts but were getting a good education from the experience. There is another example here on TW (maybe it was you) of someone who had a vibration they traced back to their exhaust as well. I've also considered at my fan/clutch set up. There is no slap that I can appreciate but someone else noted they had vibration from their fan. I can't see any wobble in the front dress.....my gut instinct still says it's timing related even though the timing marks lined up. ::shrug::

 

I also think that my IACV could be bad or "lazy". I thought about buying a $35 replacement to see if there was any improvement. I can only see my idle via my scan tool, its possible its fluctuating faster than my cheap tool can keep up.

 

Worth a try on the exhaust. Get something like a Borla Pro XS. Mine did not make it much louder at all. It’s either the crappy chambered muffler bouncing around sound waves or the bushings. When the exhaust guy welded it in all the bushings were removed and probably given a good massage.

Pro tip. Check Amazon returns on mufflers. I think I paid $50-60 for one with no dents or anything that retails for $100. Then 40-50 to weld it in and you got a muffler for around $100.

 

Your tacoma is in such nice condition!

 

thank you. At 10’ it’s not bad.