[cadejohnson58]

Hey guys I’ve been having a high idle issue in my Impala, it stays at 1300 or so RPM no matter what. I figured I would take off throttle body to clean and replace with a different idle air control sensor (need to know which brand you guys run?) or just clean the one on it?
It drops to normal RPM range around 900 but shifts hard into drive or reverse.
I also was able to plug into my laptop and have eeHack datalog to maybe find the culprit and be in the right direction. I was messing around with the cut cylinders option and when I got to #4 nothing happened, no noise change like the others if I turned the other 7 cylinders off, no difference so now I’m concerned I have a dead cylinder so I’ll be checking spark plug and wire then to fuel injector if it persists. Thank you for all your help

 

[roy williams]

USE THE VACUUMM GAUGE OF THE INTAKE MANIFOLD SEE IF IT LOOKS UP

 

[91ss]

USE THE VACUUMM GAUGE OF THE INTAKE MANIFOLD SEE IF IT LOOKS UP

What does that mean???

 

[BALLSS]

a very common cause for high idle is a vacuum leak. Check all your vacuum lines on intake manifold and the one under the throttle body

Also your IAC (idle air control) valve "may" be sticking. Removing it and using throttle body cleaner (read not carb cleaner) spray it off. do not pull or push on the end of the sensor (IAC)

 

[sherlock9c1]

Use eehack and make sure your TPS is reading zero when your foot is off the gas. I've seen floor mats holding the pedal down, return spring came off the throttle body, all sorts of stupid things.

Also check your MAP and MAF readings. At idle a stock B-body should read around 35kPa at idle and roughly 5 grams/sec airflow.

 

[cadejohnson58]

a very common cause for high idle is a vacuum leak. Check all your vacuum lines on intake manifold and the one under the throttle body

Also your IAC (idle air control) valve "may" be sticking. Removing it and using throttle body cleaner (read not carb cleaner) spray it off. do not pull or push on the end of the sensor (IAC)

Mine is currently 1500 RPM, 12.30 g/s, and 27.0 kpa

 

[cadejohnson58]

Use eehack and make sure your TPS is reading zero when your foot is off the gas. I've seen floor mats holding the pedal down, return spring came off the throttle body, all sorts of stupid things.

Also check your MAP and MAF readings. At idle a stock B-body should read around 35kPa at idle and roughly 5 grams/sec airflow.

It is reading zero. My left O2 sensor said lean so the engine light came on

 

[cadejohnson58]

Do you guys think I have a stuck injector?

 

[cadejohnson58]

When I put in drive it goes to 890 RPM range, 11.87 g/s, and 44.0 kpa

 

[95wagon]

Take the intake elbow off and stick your thumb or a rag in the IAC port.
Does it slow down ?
The air is getting in somewhere.
IAC counts ?

PCV valve jammed
Brake booster has failed ( giant hiss under dash )
Vacuum line ruptured
Intake gasket sucked in

 

[BALLSS]

the two most useful tools for finding a vacuum leak is your eyes on every vac line (read in all areas of a line) and a vacuum gauge. Scan tools do not identify vacuum leak source...just what sensor it affects.

vacuum leaks of whatever kind, including intake manifold, will play havoc with fuel trims and cause PCM to dump fuel and 02 sensors to read high

classic symptom is high idle

One of the most overlooked vac lines, the L shaped one under TB. Another is crack intake elbow

 

[cadejohnson58]

the two most useful tools for finding a vacuum leak is your eyes on every vac line (read in all areas of a line) and a vacuum gauge. Scan tools do not identify vacuum leak source...just what sensor it affects.

vacuum leaks of whatever kind, including intake manifold, will play havoc with fuel trims and cause PCM to dump fuel and 02 sensors to read high

classic symptom is high idle

One of the most overlooked vac lines, the L shaped one under TB. Another is crack intake elbow

We sprayed brake cleaner all around every vacuum line and didn’t hear it go up in revs. We sprayed intake elbow too, everything after the MAF sensor we sprayed down. I’m thinking if the left O2 sensor is lean and #4 cylinder won’t shut off when I try to force it off, seems to me like a bad injector since it’s not even on in the first place. Left O2 sensor would be driver side right? Thank you guys again

 

[cadejohnson58]

So I put a rag in the IAC hole and it immediately wants to idle a lot lower. Should I get a new IAC or try to clean mine that’s in it already?

 

[95wagon]

Any missfire for any reason will show lean due to excess oxygen.
Rich to the point of missfire
Lean to point of missfire
Ignition missfire
They all put excess free O2 in the exhaust.
What the above typicaly does not do is make the engine idle fast.
A giant intake leak near #4 could kill it and raise idle.
Like I asked , what are the IAC counts?
This will give an idea is the management is trying to slow the engine but cant or for some reason is raising the idle

 

[cadejohnson58]

Any missfire for any reason will show lean due to excess oxygen.
Rich to the point of missfire
Lean to point of missfire
Ignition missfire
They all put excess free O2 in the exhaust.
What the above typicaly does not do is make the engine idle fast.
A giant intake leak near #4 could kill it and raise idle.
Like I asked , what are the IAC counts?
This will give an idea is the management is trying to slow the engine but cant or for some reason is raising the idle

I don’t know how to check the IAC counts

 

[cadejohnson58]

This is my old TB with the thing I added to it in the middle.

 

[95wagon]

Scanner or free software the LT1 guys here could turn you on to.
Wouldn be surprised if Ehack can.
( it came along after I was kinda LT1 done )

This is likely not your issue but remember
"
from alldata... "
Reset IAC Valve Position:

1. Depress the accelerator pedal slightly.
2. Start and run the engine for five seconds.
3. Turn the ignition OFF for ten seconds.
4. Restart the engine and check for proper idle operation."

Also after mucking , the throttle needs at least one ignition on WOT.

All the above does not address your " dead " #4 though.

 

[roy williams]

What does that mean???

the vacuum gauge is 17-21 inches needle is steady ;;;;
then the vacuum gauge is the needle flipping around look up the engine damage of the needle ..

How To Diagnose Common Engine Problems with a Vacuum Gauge

One of the easiest, cheapest, and fastest ways to check an engine for serious issues is to perform a vacuum gauge test...

m.roadkillcustoms.com

 

[cadejohnson58]

The RPMs did not go any lower when I installed the middle piece (in pic) into current TB. I’m now thinking about taking off TB, cleaning it and IAC sensors (I have 2, my old one never idled this high) put on new gaskets and hope for the best. Then once the idle is fixed hopefully my lean problem goes away with it. If not I have more digging to do. I appreciate all your guys’ feedback and tricks

 

[91ss]

the vacuum gauge is 17-21 inches needle is steady ;;;;
then the vacuum gauge is the needle flipping around look up the engine damage of the needle ..

How To Diagnose Common Engine Problems with a Vacuum Gauge

One of the easiest, cheapest, and fastest ways to check an engine for serious issues is to perform a vacuum gauge test...

m.roadkillcustoms.com

No to belabor this, I would not take "SEE IF IT LOOKS UP" as what you just said here...