rob790h

I just purchased a 2001 Taco with the 2.7L engine, 5 speed and 177K. When I took it for a test drive - all went well. Took it home and then realized that it has a rough idle when warm. Researched many threads on this site and others. Many seem to have the exact same problem (or similar problem with an automatic). But no one has offered a solution that was acknowledged as working.

When I stop at a light, the idle is fine. Then 5 seconds later, the stick and steering wheel really start to vibrate. Nothing too crazy, but more than normal (no question it's more than the standard vibration of a 4 cylinder engine). Vibration will go away if I turn on the AC (idle goes up a touch) or when cold (choke keeps idle up as well). The truck runs and pulls well. Starts in a second cold or hot. No other issues with the motor, no check engine light.

Previous solutions to this problem that I've read are:

• Leaking vacuum hose (likely culprit)
• Sludged up throttle body (next likely culprit)
• Bad hanger on the exhaust (possible, the exhaust looks like it's on its last legs although it still seems sound)
• Bad motor mount (unlikely - supposedly these mounts last a lifetime)
• Spark plugs (unlikely - everyone else who's tried this solution has stated that it didn't work)

There are many directions to go in. I'd love to know what I should tackle first.

rob790h

As a quick follow up, the truck is idling at 750 when warm. I'm guessing that's a little low and might be the culprit as well. Can anyone tell me what the proper idle speed should be for the 2.7L engine?

dustrider

I have a 98 taco 2.7 (4x4) 5spd stick and in the same position

found no resolution in the search , lots of drivers living with the rough idle but no solutions found

the manual says idle at 750
mine also idles roughly at 750
if I rev it to about 1100 it smooths a little

I also have intermittent weak power so I am going to check out fuel pressure
and listen to the injectors for operation at idle
and check out the EGR is closing fully
cant find any vaccuum leaks
no codes

possibly an intake manifold gasket failure which would be very hard to find, maybe show up in one plug showing lean color seems most plausible if all else is not working

my factory manual troubleshooting guide points to fuel circuit only under "rough idle"

dustrider

I opened the hood to search for the fuel filter and they have it hidden in hell under the intake manifold
looks like I'm in for a day of cussin and yellin at toyota to try and change the fuel filter
looks like I may have to remove half of the engine to get to it
not that in 40 years of doing my own wrenching changing a fuel filter has ever made a difference , its just something that needs to be done once in a while
This fuel filter looks like the original and probably is judging by how difficult the geniuses at toyota must have gone out of their way to make it inaccessable

dustrider

I kicked the idle up a bit by adjusting the throttle plate opening a little and it smoothed way out

its way,way better now

idles smooth enough that the steering wheel doesnt vibrate anymore , just a slight shake in the shifter

seems like the throttle plate bushings are worn a little, seems to like just a little more opening

not 100% perfect but pretty darn good for 197,000 miles

not looking forward to changing that fuel filter I would like to get some targets made up with a toyota design engineers face on the bulls eye

what kind of sadistic moron would put it there of all places

rob790h

LOL. I'll probably be calling in professional help for the fuel filter in that case - I'm not that handy.

But I ended up cleaning out the throttle body and it really made a huge difference. Besides a tiny shake in the stick (which is probably normal), the shake is gone. It's idling high now but I think the computer needs time to adjust. Hope this closes the books on this one.

dustrider

I may be getting somewhere with mine . I changed the plugs and wires and found the rear plug swimming in oil.
I am surprised #4 can even fire at all that way Evidently it is missing the spark plug tube seals in the valve cover , the rear plug was an old eroded Autolite and the front three were NGK Iridium ......????

it is idleing smoother now but for how long I wouldnt want to guess

the only thing I can figure is that the previous owner went to change plugs and wires and found all that oil on #4 like I did, chickened out and quit

now I got another project

rob790h

@ Dustrider - did you check for codes before you pulled the plug? No codes on mine and unfortunately the rough idle is back. Looks like the carb cleaner upped the idle a touch and when the fumes finally evaporated, the idle went back down to normal along with the shake. I've given up and brought it to the shop today.

dustrider

thanks for the reply

No codes here either. still idles rough but slightly better

please let us know what they found


since my last posting it starts fine but now has also been stalling at stops before fully warming up

carb spray in the intake was no help
took off the EGR and checked it against a new one and it works perfect as well as the switching valves
I changed the coolant temp sensor behind the head and no change
I checked the EGR Gas temp sensor($200) with an Ohmeter and it showed "open loop" when cold or hot, then yesterday I tried again while it was warm and it read the proper Ohms

then last tues the AC pump froze while in stop&go traffic and I had to cut the belt and then wednesday the starter started clicking sometimes instead of turning over (battery and charging system fine)



I might dissasemble and clean the Idle Air Control in the throttle body

motor wont run with the intake plenum off ,
I have to leave it partially in the stream or it stalls
especially if I try to spray carb cleaner in

dustrider

I finally cured my rough idle by doing the following:


Removed the throttle body, removed the TPS and cleaned the Idle Air Control and throttle plate
replaced the plugs with Iridium and new plug wires
found oil on the rear plug wire in the plug tube, it was submerged in oil in the tube, so I replaced the plug tube seals and head cover gasket

double checked for vacuum leaks

none found

idled smoother warm or cold

Idle speed stayed at 750 hot or cold start (?) seemed that the idle speed should be higher when cold starting but it would only go up for a few seconds after starting

also was stalling when cold coming to a stop
it also ran good warm but stumbled a barely noticable little bit coming to a stop when warm so I suspected the EGR. Checked the EGR valve and vaccuum switchgear and it was all good nothing there
one last temp sensor to check , Intake Air Temp (IAT) which is integrated with the Mass Air Flow (MAF) on this model
tried cleaning the MAF sensor and MAF terminal plug but no response
replaced the MAF/IAT (and air filter) and it cured the cold stalling, warm stumble and cleaned up the idle even more. At cold start the idle stays up longer now

bassbro1

Something else I just thought about. At what altitude do you live and drive?

dustrider

I live at 4500 and drive to sea level daily

bassbro1

Hmm, I have read a more than a dozen posts with the same problem and no conclusion yet. This is very perplexing and would love to know the outcome too. I wonder if it may have something to do with the intake manifold itself. Some sort of separation or something.