Weird idle

Hello all,

i am a relatively new tacoma owner (truck has 154k miles) and i’m trying to chase down this weird issue. I’m also fairly new to mechanical work, but so far I have replaced just about every vacuum hose, EGR modulator, and cleaned the EGR temp sensor and throttle body (i read a number of cases where this caused idling issues plus i had a P0401 code that has since subsided). The truck idles fine in drive and reverse, but sits around 980-1100 when fully warmed up and bounces slightly. I know typical suspects are vacuum leak, IAC, misfires, injectors, and fuel pressure regulator. Is there any way to narrow down my culprit? 2RZ-FE 2000 model RWD and no distributor

(Edit) Any advice to help me get this truck to 300k miles would be fantastic. I am doing the rounds with fluids, ball joints and leaf spring bushings seem fine as well.

 

A scan tool with the capability to read live data is going to be your 'go to'... being able to look at all of the parameters and see which one(s) are either out of spec, or just don't look right is going to get you in the right direction.

 

I chased a similar high idle for a while with new parts as you describe. Turned out to be the aftermarket IAC. I have a thread on here somewhere about it. The aftermarket IAC valve opening setting was different than the OEM, more air in so higher idle. They also lack a thermocoupler? Style spring like OEM which farther adjusts idle gradually. Long story but the original was gunked badly, stuck open fully and with 1100 rpm idle. Replaced and aftermarket would not go below 900. Cleaned original OEM and put it back in, worked a while but had intermittent problems, solenoid was weak. Got a new OEM and 700 rpm per spec for a manual transmissio, fixed, purrs. Good luck.

 

Do you know where I can find the OEM specs? My scan tool does read live data and is the only way i can actually see my rpm lol.

 

Air intrusion between maf and valves would be first thing to eliminate...

lots of sources there.....vac lines, evap sys, B booster, stuck egr, pcv grommet .....lots...



next and long term.....

I would make it a hobby to go thru whole engine and check and replace all engine sensors back to oem...
to have a spare is not a bad thing......and a lot of the ones online are counterfit ...

first on that list would be that IAC that Thatt threw out there.
ebay ones....$30.........the real one $300.....
....window to get an oem one will eventually end.

with these nearing 1/3 of a century they need the neglected areas tended to.
and take super care of the major parts, that will eventually become unobtanium...

 

You said P0401 subsided
Every listed cause is EGR but one



Old silver has told others here about the dreaded header crack(and myself)

 

Here are my nasty IAC b4 and after pix

 

Were you running more lean or rich? Currently my truck is running at around -13% Lt/St and it has about 7-9 g/s on the MAF

 

Thank you! I see its like a $50 difference to buy the throttle body assembly, after some further diagnosis, i’ll just pop for the whole thing

 

Idk. Would guess rich. I’ve got a 151k on my 2.7l. Had cracked exhaust manifold, leaky gaskets in exhaust, P0420 codes as result. So multiple things to chase. After all that, the aftermarket IAC. Did an ‘02 exhaust pipe manifold install, cleaned intake all the way to block. Much more responsive now. You really should pull the EGR and check that port into the intake. Bet it’s carboned up. And lastly since I ain’t seen it mentioned yet, and you said idle bounces slightly, maybe check TPS. Had issues with that where I watched it bounce around at idle (scan gauge) but also an occasional stutter at rpm. OEM and fine since.

Personally, I wouldn’t suspect a throttle body is the issue with only 150k on it. Good luck.

 

I was having the same problems. My truck is at 149k and was having the high idle issues, after going through everything I finally came to the conclusion it was my worn out butterfly valve. Wanted to send it to max bore but unfortunately he passed away. I lucked out on a cheapish brand new throttle body on eBay and I have not dealt with any idle issues since then.

 

how did you diagnose this?

 

There was a significant gap in between the butterfly valve and the inside of the throttle body.Shine a light behind it and you may see it peaking through said gap. Another way to test this is pulling the actual linkage of the throttle body towards yourself while the truck is running. When I did that it would always bring my idle down to the 800 normal operating rmps.

 

went through and replaced all these hoses you mentioned so thank you. Replacing the PCV i found the hose is cracked but unfortunately a special part. I had to order one but it was delayed. Do you think a cracked pcv hose would cause this?

 

Yeah maybe.......I replaced mine with a piece off coil of snowmobile 5/16 clear fuel line...

every 2 or 3 years I just cut another piece off for it...

thats a trouble spot for hard to find vac leaks

the older ones the grommet fails right there.......and that hose gets ate up from the fumes eventually...

 

I wanted to thank you o’ silver taco for your help. I followed your advice and Thatt. This was my IACV after I pulled it off, also once i replace the pcv hose the idle dropped about ~100 rpm. The iacv was completely seized at the half open position. Lots of TB cleaner and Pb blaster later i was able to fully free it up and the engine runs significantly better. One last i gotta address is the sudden jerkiness of the truck. Thanks again!

 

That looks like a bunch of crud on the antifreeze side. Would make sense to me that if you aren’t getting good flow there it would keep the temp lower on the IAC which in turn would affect the thermal spring thingy on the IAC valve, keep it opened more than it should be, jack idle higher as a result. Either way, it needed cleaning. I’d be looking into a rad flush too. Good luck and glad you are making progress.

 

Thank you! Radiator flush is on the horizon, although it seems the previous owner recently replaced the radiator cap and coolant (its green now and not an OEM cap)

 

If it ever had stop leak added in it, a very extensive coolant system cleaning is in order.
Flushing will not get it all out, especially in small, low flow areas like in the IAC.

 

Bumping this again, with more information.

still struggling with rough idle, smoked the whole evap and vacuum system, no leaks at all…

replace a bunch of hoses at my wits end. No CEL but it isn’t normal. The car seems to idle fine then it’ll “jump” and shake a bit like its misfiring almost then clear itself out. No clue what it could be..my guess at this point is something fuel system related potentially? Injectors? Fuel filter? Fuel Pressure Regulator? Any input appreciated. Short term and long term fuel trims are still at -10% and definitely getting bad gas mileage