Vacuum system / idle going from 1500-2000 rpms

[csmith1976]

Starting to put together my list of things to do from my previous post. This is item #1:

When idling my tracker is idling from 1500rpms to 2000 rpms going up and down, up and down, not finding a place to idle. It is doing this once warmed up. It is not going down to the 800rpm level that it should. There are no check engine lights on. (I just bought it, I am not even sure if the check engine light works)

I have been told that this is most likely a vacuum problem, but I am not sure where to start with this particular motor.

Can someone help me with an process of how to figure this problem out? Thank you!!

Check out my build thread below for more information about the vehicle... Thanks!


http://www.suzuki-forums.com/suzuki-...er-new-me.html

[CR88Ranger]

So as soon as you start it up, the idle goes up to 1500-2000 and never comes down as it warms up? I would definitely check to make sure you don't have any codes (check engine light on when key is on, off once engine is running), and go over every vacuum line you can find to make sure none are torn or popped off. Spraying throttle body/carb cleaner is a good way, or you can try pinching each line to see if any of them make a difference in idle. This is also assuming that the car is timed properly.

[csmith1976]

New task: make sure check engine light is working. It might not be. I have a computer and will plug it in this weekend and check. Thanks for additional tips, i will try them out and let you know what i find!!

[Bex]

Check engine light must be on with the key on, and off once the car starts. You should advise in more detail what the car does from cold start - cold idle and how/if it drops down to warm idle.
You may also want to check your idle speed solenoid - pinch the air hose that connects it to the air intake pipe, and see if your idle drops down at all. It should. You can also check by putting your headlights and heater blower on high, and advising what your idle does then. It should remain the same and not drop down appreciably. Normally vacuum leaks will not cause a 'hunting' idle (going up and down), but will just cause them to be high. The ISC works off of a vibrating 'plunger' which vibrates something like 20x a second. This can be carefully cleaned with carb cleaner, to make sure that it's not sticking.

[csmith1976]

Originally Posted by Bex

Check engine light must be on with the key on, and off once the car starts. You should advise in more detail what the car does from cold start - cold idle and how/if it drops down to warm idle.
You may also want to check your idle speed solenoid - pinch the air hose that connects it to the air intake pipe, and see if your idle drops down at all. It should. You can also check by putting your headlights and heater blower on high, and advising what your idle does then. It should remain the same and not drop down appreciably. Normally vacuum leaks will not cause a 'hunting' idle (going up and down), but will just cause them to be high. The ISC works off of a vibrating 'plunger' which vibrates something like 20x a second. This can be carefully cleaned with carb cleaner, to make sure that it's not sticking.

Thank you for the information. I am going to be working on the truck on Sunday and will see if I can get it fixed. If not, will report back my findings.

[xxx]

read my bad idle page

first off your CEL lamp is dead,or ECU dead. (dead ecus can go to backup mode)
FIX THE DEAD CEL FIRST.

BAD IDLE CAN BE MANY THIHG'S. (just a symptom or actual air leaks)
Bad motor.
bad spark timing, some PO(MAD) cranked the dizzy base for crazy advance???
bad fueling?
bad air (leaks)?
or in limphome,idle is cancelled?
in backup, cel and idle are dead ,will be canceled.?

Normally? vacuum leaks will not cause a 'hunting' idle (going up and down)

is not true the ecu can hunt idle, any time it can not gain contol of it.
not always, and never in limphome as its dead anywhy
defeat the Dash pot and watch a normal ECU, hunt. sure will. (not in limp)
the correct way to say that is , SOMETIMES.

the idle servo has 2 modes.
I can control it. (ecu = I)
i can not!

if you add air, the ecu cuts air by the same amount and idle is unchanged
if the ecu can not cut air , to lower it to 800rpm it must hunt.
what other choices does it have.
thank that through with simple logic. (it keeps trying! and some ecu hunt
by resetting,them selves, it can't get there, so assumes, it's stuck so resets the iSC and hunts it again. my 91 did that, as did older)
this is all hard coded in an algorithm, so try it and see.

the software, keeps trying at all times. to hold it at 800 hot
and will hunt it,, (thus the name servo) and will not give up
until it hits limphome or backup mode. (not normal LIMP, sure.) but key fact.
if the motor is hot , and the TPS idle switch is closed, (normal) it will run
the servo.

this shows all idle tests, and reasons for 3 generations.
http://www.fixkick.com/IDLE-AIR/idle-index-home.html

[csmith1976]

WOW!
I haven't even dug into this project and am already feeling overwhelmed!!
Check out this article... 57 steps to freak you out and/or drain your wallet!
Prerequisites
prerequisites for the actual problem...
I got a bad idle , cold or hot engine!

[xxx]

it just all list
so show how futile it is to guess,, nothing more and that idle works right LAST!

IDLE a and advanced feature will not work right with
a dead engine /cylinder
or other gross failure, over 60 failures,,
but in the macro, DONT FREAK!
bad motor
bad spark
bad fueling, JUST 3 ! all mechs know that, its not magic or unique.

ignorance can be bliss, drive it and be happy it all works, together.

idle is just an ISC servo device.
if the engine cant suck, it cant idle
if the fueling is way lean, it cant idle
if the spark is bad or timed way off, it cant idle right
see?
if the ecu adds air and it's too lean, now, it gets worse and stalls.

IDLE IS LAST on the list.

my list shows the futility of guessing,all my lists are for that.
its not a punch list
it means do the basic tests that lead you too the 60 ways.
see?
what is really common is 2 or more problems at once. very common .

[csmith1976]

Originally Posted by xxx

it just all list
so show how futile it is to guess,, nothing more and that idle works right LAST!

IDLE a and advanced feature will not work right with
a dead engine /cylinder
or other gross failure, over 60 failures,,
but in the macro, DONT FREAK!
bad motor
bad spark
bad fueling, JUST 3 ! all mechs know that, its not magic or unique.

ignorance can be bliss, drive it and be happy it all works, together.

idle is just an ISC servo device.
if the engine cant suck, it cant idle
if the fueling is way lean, it cant idle
if the spark is bad or timed way off, it cant idle right
see?
if the ecu adds air and it's too lean, now, it gets worse and stalls.

IDLE IS LAST on the list.

my list shows the futility of guessing,all my lists are for that.
its not a punch list
it means do the basic tests that lead you too the 60 ways.
see?
what is really common is 2 or more problems at once. very common .

I understand and thank you for the help. I think I will go through the list and do the major items. Timing, tune up, replace old, cracked or loose hoses, etc etc. Needs some new parts and such. Hope doing all of that will correct the idle issue. I did not check compression, but am fairly certain the motor is good. I was able to run 70mph up a slight incline with a 3" lift and 32" super swapper on it...

[Bex]

You need the foundation of proper timing and tuning, plugs gapped properly, etc. before diagnosing anything - idle is a symptom of a problem, and not normally a problem itself. Normally, vacuum issues - such as vacuum leaks in hoses, etc. will cause the idle to be high and steady - ECU sees additional air and provides additional fuel to maintain proper fuel/air ratio. Hunting issues can often be picked up by the ECU, so it is a good idea to get your CEL working first thing, and see if there are any codes.