Question about 1995 Toyota 4Runner
Sometimes I'll start it and it'll want to idle high around 1500rpms, but than it will start and idle low enough to kill motor
Rule 1 on all otto cycle gas engines.
idle is the last thing to work right.
on EFI , its under control at all times.
but if the engine runs bad, it goes out of control.
IS THE CHECK ENGINE warn, lamp glowing running, ????
yes, why not get the DTC codes, (flash error codes now)
when it runs bad, is it misfiring, and shaking engine, weak power from engine,, bogging, or only stalling.
low rpm is near stall and is same thing.
1500rpm is perfectly normal for any cold engine.
Hot , its not.
first off check all fuses.
The idle controls are called ISC, "idle speed controller"
its a slave valve and ECU logic and servo controls.
the ECU works overtime , keeping idle right.
if the ISC sticks, it fails.
if the EGR sticks open , the ISC loses control
if the you get intake (induction) air leaks it loses control
same for misfire, gross, flooding. same for gross lean.
so how do we do this? find a cause.\
easy we give that long missed 60,000 mile tune up.
and during that i clean the ISC and EGR main valves.
on any old car like this, wow, its sure to be a mess, if not serviced.
then make sure the EGR main is closed,
i see if my ISC is trying to work.
i then check my fuel mixtures. to see if the engine EFI
reaches and holds closed loop.
oops, it cant be cause the 0xygen sensor died, 100k miles ago.
no OTC scan tools for 1995 ( sure hackers have em)
so is very hard to get this information, i use a scope to watch my oxy sensor, if stuck rich i fix that first. if stuck lean , i find the exhaust crank causing it. or other cause... long list of tests.
in a real shop the start at the tail pipe end, OMG this puppy is rich as a pig and work forward, is start at the oxysensor
i get it working by any means.,
then fix idle if not already magically working. as most do (cleaned)
here is a very common example.
1: EGR sticks open at idle. IDLE RPM drops like rock. ( it must)
2: ECU sees illegal RPM and opens the ISC fully, to no avail.
some cars EFI hunts the ISC causing surging.
others ECU just slams the ISC wide open and does a software hope thing. in this case, does nothing,due to gross EGR misfire effects.
the idle controls are a SERVO,. a closed loop servo system.
it regulates idle until , something horrible happens.
it fails when conditions are outside it's range of Authority.
Posted on Feb 12, 2014
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Posted on Jan 02, 2017
SOURCE: fuel injection idling to high
Try this: Remove the rubber pipe that goes to the throttle plate at the end of the intake manifold. Open the throttle flap valve and inspect the interior for excessive carbon buildup (black gunk around the flapper and the outer circular bore)...If it is dirty, get some carb cleaner & spray the daylights out of it until it is clean clean clean. Reattach the tube and start the engine, it will smoke quite a bit until all of the cleaner in the intake is digested by the engine. This should improve the idle. What may be happening is the black gunk may not be letting the throttle valve to close fully, and WILL keep the idle up.
Posted on Sep 19, 2008
Ok, there are four problem spots that i recommend inspecting the first would be the air filter.
The air filter may be clogged or dirty. this can decrease the power out put and it can also affect the idle as well. the next check point would be inspecting the spark plugs. make sue the plugs are correctly gapped and are not fouled in anyway. if they are fouled or incorrectly gapped, this will cause the symptoms you are experiencing at this time. Another check point will be the wire set(spark plug wires). make sure the wires are in good condition. remove all wires from the plugs and look inside the wire head t inspect the contacts. they should be nice and clean.if the wires are worn, replace them accordingly. the final check point will be checking the PCV valve. this valve is located Under hood, center, upper engine area, top of engine, mounted in valve cover. the testing procedure to be preformed on this specific device is stated below.
PCV VALVE TESTING PROCEDURE---
# Check the ventilation hoses and lines for leaks or clogging. Clean or replace as necessary.
# Locate the PCV valve in the cylinder head cover and remove it by pulling it upward.
# Blow into the crankcase end of the valve. There should be free passage of air through the valve.
# Blow into the intake manifold end of the valve. There should be little or no passage of air through the valve.
# If the PCV valve failed either of the preceding two checks, it will require replacement.
You will find the problem for you erratic or low idle in the areas above.
Please rate and god bless:)
Posted on Apr 27, 2009
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