'89 4WD V6 Idle Problem
Roadie
My truck has about 266,000 miles on it, and runs almost perfectly, except
recently it started "stuttering" when my foot is on the brake. More often
than not, when I have the brake applied, the engine idle drops suddenly to
about 300 to 400 rpm then jumps back up to normal, down, then up, down then
up, over and over about every 2 seconds or so, until I lift my foot off the
brake, then it idles just fine. It does it as I slow for a stop, and when I
am just sitting at a light, clutch in or out, in gear or not. However, it
doesn't do it when the truck is cold, and the "high idle" is on, then once
it warms up, and the idle drops to normal, it's back to the stutter when the
brake is applied..
I thought it might be electrical, so I tried every combo of lights on,
lights off, AC on, AC off, etc etc. but with no change in idle, then I press
the brake, and "stutter, stutter, stutter".
Everyone I talk to is stumped, anyone have any ideas?
Thanks!
James
Roger Brown
Your hot idle speed is too high.
For an explanation, here's an excerpt from a recent TLCA Toyota Trails "Truck
Tech" column:
Q: I have a 94 4wd p/u w/ 22re. My engine runs great, except for when it is
idling and I depress the brake pedal. The engine then idles really weird, kind
of a strong then weak then strong then weak, so on and so forth. It never cuts
out, though, and continues to idle normally when I take my foot off of the
brake. I've only noticed this after driving, like at a stoplight.
A: Assuming there are no vacuum leaks, such as in the brake booster, it's
likely because your idle speed is set too high. I can exactly duplicate this
"problem" in my '85 by bumping up the idle speed to a bit over 1000 RPM and
it'll act as described. Turn the idle speed back to normal, and it works
fine. It's really not a problem, its supposed to work this way and if
everything is set properly, and you won't have the "problem".
Why is this the case? Because the ECU has logic built in that says if you hit
the brakes and the engine is turning over 1000-1100 RPM, it'll cut the fuel to
the injectors in an attempt to help you stop faster. After all, no sense
pumping gas into the engine when you are braking to a stop. So idle rises,
fuel is cut, idle falls, fuel restored, idle rises, etc. Turn the idle back to
850-900 RPM where it's supposed to be and it'll get back to normal. Idle speed
is adjusted with the large slotted screw atop the throttle body. Turn it in to
lower the amount of air passing through the throttle body at idle (and thus
lower the idle speed).
If you don't want to do that or it doesn't fix the problem, here's a more
drastic fix:
http://www.geocities.com/toyotashawn/bizzareidle.html
Which basically involves cutting the wire that feeds the brake light signal to
the ECU. Without that input, the ECU will never know you are braking, so it'll
not be able to cut off the fuel injectors.
--
Roger
Roadie
> If you don't want to do that or it doesn't fix the problem, here's a more
> drastic fix:
> http://www.geocities.com/toyotashawn/bizzareidle.html
> Which basically involves cutting the wire that feeds the brake light
signal to
> the ECU. Without that input, the ECU will never know you are braking, so
it'll
> not be able to cut off the fuel injectors.
>
> --
> Roger
Setting the idle down did it, thanks!
Roadie