Engine stalls at idle?

Tiny
BMRFIXIT
  • EXPERT
Thank you fisherman
Another carpros tech
He came with this
hope that can help

(the IAC valve its not adjusted right! The ECU should take care of the "load" of the A/C and power steering!

Here a text about IAC Valve:

Basically, as we already know, the IACV regulates idle speed, raising and lowering it as needed. It does this by opening and closing a "trim" valve to allow more or less airflow into the intake manifold when the throttle is closed.

The adjustment we make on the IACV is for setting the "base idle". By unplugging the TPS (and the IACV in some cases) we tell the ECU to completely close the trim valve in the IACV. When this happens, the idle airflow comes completely from a needle valve - the very one we are adjusting when we turn the screw on the IACV body.

If everything in the fuel and intake system is operating properly, the idle speed will not be able to drop below this setting. A few things can cause the base idle speed to go out of adjustment.

First, the needle valve can become clogged with dirt or carbon, reducing or completely blocking off airflow through the needle valve. This would reduce the airflow through the needle valve and cause the ECU to rely partially or fully on the opening of the trim valve in the IACV to maintain target idle. This would mean that the idle could possibly fall below 750 before the ECU could intervene.

Second, the trim valve within the IACV could be rendered partially or totally inoperable, either through blockage or failure. If this valve is blocked open, idle speed would be high unless the needle valve's opening was reduced to compensate. The result of this may be the inability for the ECU to compensate for all idle conditions - base idle would be set for Y percent trim valve opening, leaving only X-Y percent of the operating range of the trim valve for ECU adjustment. If the trim valve is not blocked open but the passage to this valve is partially clogged, it would require the ECU to open the valve farther than normal to allow a given amount of airflow to pass. This would also reduce the amount of compensation the ECU can apply to idle speed.

To sum it up, there are two idle speed adjustments to control idle on our cars. First is the manually adjusted base idle setting, which determines the minimum airflow through the IACV (and minimum warm-idle speed). Second is the ECU's control over the "trim" valve within the IACV, which compensates for hot and cold idle and engine loading (power steering and A/C operation).
Was this
answer
helpful?
Yes
No
+1
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JASON SCARBROUGH
  • MEMBER
  • 1989 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 98,000 MILES
My truck has a 350 with throttle body injection. It was running fine now it won't idle. Could the fuel filter cause this
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
Ok well I see I need to get a different iac I bought an idle air control valve from oreillys that has only been in the truck a few weeks but right after I put it in there were still no improvements what name brand iac should I get and again tell me how to set it once I get one also I want to tell u exactly what its doing. In the morning or after the truck has been sitting a while I go to crank it up and it does not idle rough as long as the motors cool even if the air is on and its in gear and you turn the wheels there is no stuble and no rough idle once the motor heats up to normal operating temp the truck starts to idle rough sitting still at a light and if u slightly turn the wheel the idle drops and the truck trys to stall and shakes real bad then after the idle drops it will surge up and then back down to a rough idle it also makes the motor feel like it is missing but its not a miss because I have changed all of the igniton components so thats exactly what it does its the most aggrivating problem I have ever run across please reply back
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
Is the SES light on? If yes pull the codes, but check the EGR for sticking open, and the Idle air control, it's bolted to the side of the throttlebody. A badly clogged filter might cause it...


https://www.2carpros.com/forum/automotive_pictures/62217_95_OlderGM_2.jpg


Check codes this way, jump these two connections at the ADL, turn the key to "ON" then count the flashes. a 22 will count as 2 flashes a short pause the 2 flashes, if more than one code is stored, the pause is noticably longer between codes! The codes will flash 3 times! Write them down and post them here...
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
BMRFIXIT
  • EXPERT


https://www.2carpros.com/forum/automotive_pictures/99387_silverado1_1.jpg

Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
I appreciate the pic but I kinda cant see it all is there anyway for me to see the other half thanks
Was this
answer
helpful?
Yes
No
-1
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JOSH71411
  • MEMBER
Good news I fixed the missing problem and most of the stalling problem when the wheel is turned I took the iac out which was factory preset and screwed the valve in which immediately fixed the problem when I started it back up and let it warm up but I still have the steering problem but I think it is in the actual power steering here is what it does if your in park with air on and u turn the wheel without foot on the brake its usually fine if its in gear its usually also fine but if the brake is applied and u turn the wheel the wheel wants to lock and u have to let off of the brake for it to unlock but the power steering is NOT in full lock position therefore I have reason to believe it might be the power steering pump getting weak or the steering gear locking up when the wheel is turned but I dont see what that has to do with the brakes thanks for helping fix one problem just one more left =)
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
DAVE DAUGHERTY
  • MEMBER
  • 1988 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 156,000 MILES
The engine will idle forever no problem. Put in drive still idles fine, put on any gas it bogs. If you give mass gas it will shut off otherwise let off gas idles fine. Put gas on a little bogs over and over cannot drive. About to lose my home over this.
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
KEN
  • ADMIN
Hello,

Lets get this truck fixed then. Two things come to mind first is a plugged catalytic converter. This guide will help you confirm or not.

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Next would be weak fuel pump or clogged fuel filter. Here is a couple of guides to help you run some tests, if you don't have a fuel pressure gauge you can rent one for free from the auto parts store.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

and

https://www.2carpros.com/articles/how-to-change-a-fuel-filter

Please run some tests and get back to us so we can continue helping you.

Cheers, Ken

Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
CHEVYUP
  • MEMBER
  • 1988 CHEVROLET SILVERADO
  • 243,566 MILES
Wires are good no codes, some times it will idel and some time it will not idel, when put in gear, if I fether the gas pedel it will stay running, but if I just drop it in to gear it will die, I can drive it, and it runs great it just will not idel in gear
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Vacuum leak at throttle body or a bad idle air control

roy
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
ALLEN134
  • MEMBER
  • 1987 CHEVROLET SILVERADO
  • 2.0L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 20 MILES
My Chevy truck is a 1987 model its fuel injected and when I crank it it wont idle and if u come to a comeplete stop it will shutoff what is wrong with it can u help im sick of not knowing what to do
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
HMAC300
  • EXPERT
Scan for codes and have fuel pressure checked first. Then spray choke cleaner around tbi unit and see if there is leak under it. That is a common problem as well as soft hoses leading to map sensor an dpcv.
Was this
answer
helpful?
Yes
No
Thursday, September 3rd, 2020 AT 6:37 PM (Merged)
Tiny
JGEASLEY
  • MEMBER
  • 1991 CHEVROLET SILVERADO
  • V8
  • 4WD
  • MANUAL
  • 235,000 MILES
I have replaced the throttle position sensor and the idle air control valve both to no avail. When idling the truck will idle real low and most of the time die. Just tonight after replacing the IAC valve it wants to die even if it is moving if you are not accelerating.
Was this
answer
helpful?
Yes
No
Thursday, September 10th, 2020 AT 2:44 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
HAve you checked for vacuum leaks? Has the check engine light come on?
Was this
answer
helpful?
Yes
No
Thursday, September 10th, 2020 AT 2:44 PM (Merged)
Tiny
JGEASLEY
  • MEMBER
I am going to do a thorough check for vacuum leaks this weekend, but no the engine light has not came on.
Was this
answer
helpful?
Yes
No
Thursday, September 10th, 2020 AT 2:44 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Let me know what you find.

Joe
Was this
answer
helpful?
Yes
No
Thursday, September 10th, 2020 AT 2:44 PM (Merged)
Tiny
JGEASLEY
  • MEMBER
Ok I am really stumped now if I take the vacuum hose off my brake power booster my truck idles and runs fine except no power brakes.
Was this
answer
helpful?
Yes
No
Thursday, September 10th, 2020 AT 2:44 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Okay, if it runs good with that disconnected, then the engine is running too rich. The extra air you get is helping smooth it out.

Have you checked fuel pump pressure? I'm wondering if you are getting too much pressure to the injector or if the temp sensor is bad.

The temp sensor tells the computer the ambient temp and the coolant temp. From that, the computer determines how rich or lean to make the fuel mixture. If the sensor tells the computer it's -40 degrees, it will dump fuel for the engine to run.

Also, did you check to make sure the catylatic converter is plugged?

Let me know.
Joe
Was this
answer
helpful?
Yes
No
Thursday, September 10th, 2020 AT 2:44 PM (Merged)
Tiny
JGEASLEY
  • MEMBER
Where is the temp sensor?
Was this
answer
helpful?
Yes
No
Thursday, September 10th, 2020 AT 2:44 PM (Merged)

Please login or register to post a reply.

Sponsored links