otravacaine

I believe the problem started awhile back. It would idle rough from a warm, nothing major, and as soon as you started driving it would be fine. Then it seems to developers into a problem everytime it would get to temp. Cold start was fine, then the idle would bog down and become rough once warm. A week or so later, it kept quitting on my husband while driving to work. The motor would cut out and kick back on, on it's own. We checked all out grounds, wires, plugs, cap, rotor, and fixed anything that looked bad. Started up fine, idling normally, warmed up, stumbled a bit and died. Will start back up no problem, but will just stumble and die. Got it towed to a shop; dude could not re create the problem. Messed with our timing and the idle......when we got it back, it was idling really low and hiccuping a bit. Decided to swap out the plugs, wires, cap and rotor. Now it will start idle too high, then drop super low, and die out. If you feather the gas it will idle around a grand....but you take your foot off, it stumbles and dies almost immediately. Thoughts? We're kinda stumped.

Co_94_PU

iTrader: (-1)

You are all over the place and vague about your testing.

What do the old sparkplugs look like? Can identify a head gasket failure (wet or steam cleaned), or valve seals (oily or coke build up), also leaks in the intake piping causing lean misfires (ashy and white), and over fueling from looking at the plugs..

The first two require engine work, but the second two are usually something you can fix in a day or two in the driveway.

I would start with inspection of the throttle plate, it should consistently return to the same position wether the throttle is slowly closed or snapped shut. (Problems here are worn shaft, hanging up in the cable, dirty dashpot, carbon buildup, ect.)

Next move to the idle adjustment screw, mark a tick mark on it (with a sharpie) and the throttlebody so you can line the marks back up, now run it all the way in and write down how many full and partial turns that takes. Now you can take it out and inspect the oring is still there intact and still soft. Also a good opportunity to run some throttle body cleaner into where the idle screw goes if the screw looks grungy.

Next is the intake piping, on the non turbo engines these are possible signs of a leak in the accordion pipes, the equivalent on the turbo version is the elbow on the turbo inlet.. A word of warning this is a two layer rubber elbow it's going to be brittle and it is no longer available, if you damage it taking it off or putting it back on you will be looking at $60-100 in a new silicone elbow (from memory also the headache of it being two different sizes on each end, I don't have my notes handy.). On the upside you can visually inspect about 2/3rds of it for cracks by cranking the front wheels all the way to the left and looking in from the wheel well. If you see cracks/checking on the face against the turbo, start budgetting for that elbow to be replaced.

If you have an air leak, as above, between the throttle and the air meter the fuel pump can shut off due to the fuel pump being controlled by the air meter. What happens is during a misfire or during acceleration these pipes move and the "small" leak becomes a big leak and the vane in the VAFM (air meter) closes and shuts off the pump.

Now turn the front wheels to the right. Looking in from the other side you can see the air valve that controls the warm up idle. It's bolted to the front area of the lower intake and below the throttle body. You want to inspect the hose on the front of this is intact, firmly attached, and not damaged.

Some more hoses that will give you issues if damaged or not firmly attached are the two hoses of the PCV system. One of these (fresh air) routes across to the drivers side and is bridged by a small metal pipe welded to the turbo output pipe to the intake and attaches to the front of the valve cover. (This one is also a molded hose with two sizes at each end, and not available from Toyota.)

.. That covers all the easy mechanical stuff, you've hopefully only spend $5-10 on an oring and some throttle spray ..

Now we are onto the electrical bits.. You'll need a multimeter, maybe a small screwdrive or pick, a few wire brushes, a pan to drain the engine coolant, a bit of dielectric grease, and the usual assortment of wrench's and sockets.

You want to clean the two temp sensors in the front if the lower intake manifold. Clean the sensor tip, the sensor body threaded section, the electrical connector on both ends, and the threads they go into the intake. These sensors get crusted in scale and it makes them send inaccurate information, they also require good clean electrical connection since they are grounded through thier threads.

At this point you can test the sensors with the meter for piece of mind, or just reinstall them.

(RAD4Runner, has a detailed thread with images for this process.)


There are some other electrical tests you can do as well..

.. Now you have spent about $20-30 and eliminated quite a few suspects ..

If you have had no improvement yet it gets more expensive and time consuming.

​​​​​​​Test the coolant for combustion byproducts, cylinders for proper compression, maybe pull the aux air (idle air valve) and clean it.

otravacaine

Plugs were definitely ashy and white. So, gonna check for vacuum leaks. This guy had my truck for over a week, so who knows what he may have fiddled with.