Idle speed high, then low
#1
Registered User
Thread Starter
Join Date: Dec 2006
Location: Annapolis, MD
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
Idle speed high, then low
I have a 1992 3VZE 4x4, and it seems the idle has a mind of its own. When I start my truck up in the morning when it's cold, idle can be as high as 2,000 rpm, or, normally, ~1,600rpm. Sometimes it will "only be 900-1100rpm"... it just seems like it depends on what mood my truck is in. As he warms up, the idle speed will drop. Some days it'll drop to a normal ~800rpm, but other days it will be low enough for the idle to lope (~350) and the oil pressure will look dangerously low on the stock gauge, such that I'll blip the throttle at a stoplight to keep decent oil pressure.
Are these wild idle fluctuations normal, or is something broken? BTW, I did replace coolant temp sensor #2 that's on the back of the motor, passenger side near the firewall a few years ago. I also have a K&N air intake system w/ the less restrictive air intake tube and huge K&N cone filter. Truck has 177 / 500+k on the clock. About two years ago I had to take it to my friend's shop as it wouldn't run for snot and was stalling a lot and yet wouldn't throw a code on the dash flashing light when you jump the 2 connections under the hood w/ a paper clip. Turns out the ignition control unit that I had replaced 6 months previously with a $50 junkyard part bit the dust, so after Tim's mechanics mistakenly replaced my EGR valve and wasted a lot of my money, they figured out it was the ICU and replaced it w/ a new OEM one. That's all the major repair/mods the engine has seen in the 9 years I've owned the truck.
Thanks,
Dave
Are these wild idle fluctuations normal, or is something broken? BTW, I did replace coolant temp sensor #2 that's on the back of the motor, passenger side near the firewall a few years ago. I also have a K&N air intake system w/ the less restrictive air intake tube and huge K&N cone filter. Truck has 177 / 500+k on the clock. About two years ago I had to take it to my friend's shop as it wouldn't run for snot and was stalling a lot and yet wouldn't throw a code on the dash flashing light when you jump the 2 connections under the hood w/ a paper clip. Turns out the ignition control unit that I had replaced 6 months previously with a $50 junkyard part bit the dust, so after Tim's mechanics mistakenly replaced my EGR valve and wasted a lot of my money, they figured out it was the ICU and replaced it w/ a new OEM one. That's all the major repair/mods the engine has seen in the 9 years I've owned the truck.
Thanks,
Dave
#6
Registered User
Join Date: Mar 2008
Location: Temecula Valley, CA
Posts: 12,723
Likes: 0
Received 4 Likes
on
4 Posts
The dashpot is the little diaphragm thing on the throttle body that the throttle cam contacts when it's closing / closed. It's purpose is to keep the throttle from slamming shut. It holds the throttle open for a second or so then lets it close. This helps keep the engine from backfiring, etc. due to the rich condition that would occur if the throttle slammed closed too quickly.
#7
Registered User
Join Date: Mar 2008
Location: Temecula Valley, CA
Posts: 12,723
Likes: 0
Received 4 Likes
on
4 Posts
Considering it's an intermittent unstable idle at cold start and warm start, it'd be the first place to look in this case. Next would be cleaning out the throttle body then checking the auxilary air valve- if it's sticking, that will mess with the idle too, so maybe a good flush of the cooling system, including flushing the coolant hoses to / from the AAV wouldn't hurt.
Trending Topics
Thread
Thread Starter
Forum
Replies
Last Post
ZONAYODA
86-95 Trucks & 4Runners
12
07-13-2015 07:17 PM