My engine will not idle?

Good afternoon.


This sounds like you have a vacuum leak, dirty throttle bore or the IAC motor is not working but to be sure lets check out these guides to help us fix it.

https://www.2carpros.com/articles/stall-at-idle

and

https://www.2carpros.com/articles/throttle-actuator-service

and

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge


if okay the first thing I would do is check the actual fuel pressure. Low fuel pressure will cause all these codes.

You can rent a tester at a parts store. There is a test port on the supply line back by the distributor. The tester just goes on that fitting for the test.

Roy

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

The knock sensor and the mass air were both the problem. The mass air flow was bad and the knock sensor was unplugged and bad I bought a new one of both and installed them and it is running fine.

Okay, good find.

Glad you got it fixed.

Roy

I'll start the car and and take my foot off the gas it'll cut off. it won't keep up with rpm.

HI Gerald,

Based on what I read here it could be a couple of things.

First it could be the Idle Air Control valve is not working properly. (See link below)
https://www.2carpros.com/articles/idle-air-control-valve-service

Or it could be a large vacuum leak (See link below)
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Just note that if it is a vacuum leak it would have to be significantly large, something the size of the PCV valve line.

Regards
Jon

My vehicle started shortly after hurricane Michael, acting up. It would sputter every now and then when I sustained a specific speed and rpm for too long, and would sputter or stall when idled or stopped, and only idling at 50 rpm. Whenever it has shut off I have been able to jump into neutral and start it did not back up. Tried cleaning my throttle body, used some sea foam to clean the fuel system. It has aggressively gotten worse however. I took it to my mechanic and he said it seemed to be misfiring and suggested a new distributor cap (I do not think it has one) new plugs and injectors. I have been trying to make it last as long as I can without the parts because my money is tight since hurricane Michael came through Panama City. Last night it shut off when I was slowing down but now it does not start back up. I am about to go try to change my spark plugs in hopes I can at least get it home. Any and all help is welcome. Please

Hello,

I would start with a tune up but let's check the battery and the connections which can cause the issue you are describing. Here are two guides that should help us get started:

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

(use OEM parts)

and

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

with

https://www.2carpros.com/articles/car-battery-load-test

Please run down these guides and report back.

Cheers, Ken

When I start it it will start, but soon as I take my foot off the gas it shuts down.

This can be the result of a few things. An engine vacuum leak, dirty throttle body, or even the idle air control valve.

What I suggest is to first confirm there are no engine vacuum leaks. Here is a link showing how that is done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Next, consider cleaning the throttle body / throttle plate. Here is a link showing how that is done:

https://www.2carpros.com/articles/throttle-actuator-service

If that still doesn't help, then I suspect it is related to the idle air control calve (IAC). The IAC is responsible for maintaining idle speed. Take a look through this link. It shows in general how one is serviced and the second shows general replacement.

https://www.2carpros.com/articles/idle-air-control-valve-service

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

__________________

Here are directions specific to your vehicle for replacement. The attached pics correlate with the directions.

________________


2002 Chevy Truck S10/T10 Blazer 4WD V6-4.3L VIN W
Procedures
Vehicle Powertrain Management Fuel Delivery and Air Induction Idle Speed/Throttle Actuator - Electronic Service and Repair Procedures
PROCEDURES
IDLE AIR CONTROL (IAC) VALVE REPLACEMENT

REMOVAL PROCEDURE

pic 1

1. Turn OFF the ignition.
2. Remove the air cleaner outlet resonator.
3. Disconnect the idle air control (IAC) valve harness connector.


pic 2

4. Remove the IAC valve mounting screws.


pic 3

5. Remove the IAC valve and O-ring from the throttle body assembly.

CLEANING AND INSPECTION PROCEDURE
1. Clean the IAC valve O-ring sealing surface, pintle valve seat, and air passage.
^ Remove excess carbon deposits with a small amount of carburetor cleaner on a parts cleaning brush. Follow any instructions on the cleaner container regarding cleaner usage.
^ DO NOT use a cleaner containing an extremely powerful solvent such as methl ethyl ketone.
^ Shiny spots on the pintle and seat do not represent a bent or misaligned pintle shaft.
^ If heavy deposits are present in the air passage, remove the throttle body for a complete cleaning.

IMPORTANT: DO NOT reuse the original O-ring.

2. Replace the IAC valve O-ring.

INSTALLATION PROCEDURE

IMPORTANT: Use an identical pan when installing a new idle air control (IAC) valve. The IAC valve pintle shape and dimensions are designed for specific applications.

pic 4

1. On a new IAC valve, measure the distance between the IAC valve pintle and mounting flange. Use finger pressure to slowly retract the pintle if the distance is more than 28 mm (1 - 1/8 in).

pic 5

2. Lubricate the IAC valve O-ring with clean engine oil.
3. Align the flange holes with the mounting holes on the throttle body assembly.
4. Insert the IAC valve through the O-ring into the throttle body assembly.

NOTE: Refer to Fastener Notice in Service Precautions.

IMPORTANT: The screws used to attach the IAC valve are coated with thread locking adhesive. Clean the attaching screw threads and apply thread locking material GM P/N 1052624 or equivalent.

pic 6

5. Install the IAC valve mounting screws.

Tighten
Tighten the screws to 3 N.m (27 lb in).


pic 7
6. Connect the IAC valve harness connector.


pic 8

7. Install the air cleaner outlet resonator.
8. Perform the IAC Reset procedure:
8.1. Turn ON the ignition, with the engine OFF, for 5 seconds.
8.2. Turn OFF the ignition for 10 seconds.
8.3. Start the engine and check for proper idle speed.




Let me know if this helps or if you have other questions.

Take care,
Joe

My car ran just fine until yesterday when I stopped at a store, shut it off. When I came out and started the car it would not idle in drive. If I put it in neutral it would idle but very poorly. I drove home between drive and neutral at stop signs to keep it running. This morning the car seems to be fine, It had been sitting out for about 4 days in the cold. But I have driven about 25 mile with no problems before it acyed up

Has the check engine light come on? Also, when was the last tune up?

yes, actually its been on for some time.. the dealer says nothing is wrong and just resets it. I guess just some kind of error code. The car does have an extended warranty, maybe they just dont want to fix it

2000 Blazer 4WD 78,500 miles Automatic
Just recently I have had issues with my blazer quitting after stopping at a stoplight. Generally when I first drive the vehicle it runs fine but after driving for a while and I stop at a light - then i press on the gas - it will just quit - it will start right back up and I can be on my way. Then randomly at another light it will quit.
I just had a 75, 000 mile service where they replaced the fuel filter and spark plugs and whatever else goes along with it. However it will still quit running randomly after its been running for awhile. And not sure if it matters but its las vegas so its been 110 degrees out lately. Also when the air is running sometimes when you step on the gas - it doesnt always move right away. What do you suggest?

when you say it doesnt move right away, does the engine rev up like the trans is slipping? When it dies, does it sputter out like it has run out of gas or does it just shut down?

I guess when i say it doesnt move - I am pressing on the gas many times to the floor but the blazer doesnt accelerate, it is moving at a maybe 5 miles per hr but wont go any faster - then finally it does move and accelerate.
When it stalls it always been after stopping at a stop light - I go to press on the gas to go and sometimes it will move forward but be jerky then stall, but then there have been times when I have stepped on the gas and it has just quit. It always starts right back up and I can be on my way.

Start by having the PCM scanned for trouble codes

I found a sensor or solenoid on the transmission that when i unplug it it doesnt do it but the truck doesnt have an acceleration if someone can tell me what this sensor is it plugs into the tranny has like 10 prongs and 2 sets of wires hooked into it

Please help


Thanks matt

I feel that you have unplugged the main transmission harness, from what you describe i feel that the TTC lock up solenoid has failed, i suggest that you get a diagnostic scan done to confirm this, start here.

When i step on the brakes, i get resistance as it only goes down a bit and the car doesnt slow down. I have to step on it hard to stop the car and i hear what sounds like a hissing hydraulic sound. My car sometimes stalls when i try to move after a stop. I usually put it in park at a stop sign to prevent this stalling.

That sounds like a bad vacuum booster unit. When the pedal goes down is it much harder than it used to be? If so check the large line to the booster and the check valve as well. If they are OK Disconnect the hose and plug it. Now test drive it. If the stalling has gone away and you don't hear the hissing the booster is bad. Not hard to change out if you're mechanically inclined.

It's a '95 Blazer 4x4 4.3L Vortec, it will fire but stalls immediately. Checked for fuel in upper intake and nothing is there. If I keep my foot on the gas it will stay running at about 2,000 rpm, as soon as you let off the gas it will idle like a dragster for a second and then die. Today i went out and started it and it idled for about 30 min, shut it off and waited a few hours and now it's acting up again. Put a fuel pressure gauge on it today, turned the key on, the pressure goes up to 62 but drops down to around 25. The books says it should hold steady between 58 and 64 with the key on.

I have the same issue with mine. After about 6 months of putting up with it. The truck would not start unless I hammered on the bottom of the gas tank whule trying to start it. Acouple weeks later I replaced the Airtech fuel pump with an AC Delco fuel pump that comes with a different sending unit than what the Airtech has.I was told blazers came with airtech brands. But this is my 3rd fuel pump in 4 years.So I went with AC Delco. It did not matter .I still got the same problem BUT not as often. I replaced the Idel sensor. That did not matter. I adjusted the idling screw higher. That helped for a while. The final result has come down to that it will mostly keep running after start up regardless of the way it is started but if I stop at a red light the RPM will drop low ( below 1/2 )and idle low and check gages light will come on then truck will SOMETIMES die at the traffic light unless I barely hold the padal down enough to keep thr RPM above 1 and the gages light will go back off then push the gas pedal normally to get moving without restarting. I just live with it and adjust the idle screw for higher RPM 1 1/2 on the gage. Try adjusting the idle screw a little higher and see where it does from there.

Some of my info says 54--64 psi. It also says, with engine running, quickly hit the throttle while watching the gage. Should be close to 64psi, if not, replace the spider system.

The problem is I can't get it to start and idle. My book says turn the key on and pump should run for 2 seconds then shut off, which it does. Then the book says after the pump shuts off the pressure should hold steady, which mine doesn't do. It jumps up to 63 when pump comes on but, as soon as the pump shuts off it drops to around 25 then slowly keeps dropping. It gets to 20 in about a minute, am I doing something wrong? I'm doing what the book is telling me to do...

Engine cranking, do you have spark at the plugs? Do you have an injector pulse, use a noid lite.

You should have pressure also with engine cranking? With fuel pressure loose, possibilities, pressure regulator leaking-- fuel injector leak-- pressure is leaking back through the fuel pump. Any applicable trouble codes? Are you fully obd1 compliant?

I have spark, and the pressure while cranking pulses about 55 to 65. If I go out and activate the pump by turning the key on, and do it 4-5 times and then try and start it, it will start and idle really rough for about 5 seconds then die.

The spider fuel system is noted for problems. Any applicable trouble codes?

I don't think the pressure should leak down like that. I already gave some of the leak down possibilities.

No trouble codes, don't have a scanner. I can get it running if I pump the gas pedal when trying to start. After I get it running if I let off the gas it will die, but, if I keep my foot on the gas I get it to stay idling at about 1,000 rpm with little pressure on the gas pedal. But, it idles like it's missing a plug. If I rev it up the motor smooths out to perfect. While idling the pressure is around 62, but, if I rev the engine the pressure drops to around 52-55. Another problem is while I have my foot on the gas to keep it idling it will rev up to about 2,500-3,000 rpm and then back down to 1,000 rpm all by itself.

And thank you for answering back...

Take the throttle body off and clean it, check the iac/ idle air control.

After you build fuel pressure, block the return fuel line, this is just key on engine off, see if pressure holds. If it holds, I'd have to check the pressure regulator. Don't damage the fuel line.

So, I have to block the return line? Why did the book not say this? It just says to turn key on, pump should run for 2 seconds, which it does. Then the pressure should hold steady, which mine doesn't do. How would I go about blocking the return line? Do I need a special tool?

Quick question, could the CTS (Coolant Temperature Sender) cause this to happen? Someone suggested I check it.

The engine is a 4.3L Vortec CMFI

Thanks again for the help!

As far as the pressure leaking off, no, the cts wouldn't cause that. I don't know anything about your manual. Below is info from MOD about fuel pressure test. That's all I have.

Starts shuts off after a minute.

Hello,

This could be a problem with your vehicle's Crankshaft Position Sensor (CKP) starting to fail. The CKP sensor is used by the vehicle's Vehicle Control Module (VCM) to determine the rotational speed of the crankshaft and uses this signal to start both spark and fuel injector control. When the CKP starts to fail, it will fail when it starts to get warm. I have included a few links for you to go to below:

https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works
https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor
https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

I have also included location and operation information in the diagrams down below for you as well. Please go through these guides and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros

i have replaced fuel reg fuel pump ok with in specs new distiputor plugs wires coil it wont start unles i use starting fluid i know, bad, but when it starts i cant get it to idle i have checked all the vacum lines there good could the egr keep it from starting are not let it idle i'm at a loss please help or could the distiputor be 60 out and fire or is it like most chevy distiputors and either 180 out or on

If it starts with starting fluid, then your problem is fuel related. Have you checked to see if the injectors are getting power?

the injectors are a spider assembly plastic no power accept to the cpi it self

Chances are the spider is the problem and may be dumping fuel.

my truck all of a sudden is having a issue wanting to stall when i come to stop and hit the accelerator. if i don't pulsate the gas pedal by stepping on it and letting it off and stepping on it again. it acts like it getting way too much fuel. because i noticed i used three quarters of fuel to 162 miles. i've changed out alot of stuff. i'm lost and need help please help me

With an idle issue, I take the throttle-body off and clean it, Check throttle position sensor. Use a gage and check fuel pressure, check trouble codes. You said you changed a lot of stuff, was that an overall tune-up?

I have fixed the o2 senser, oil pressure senser, oil pressure sending unit senser, spark plugs, had the chevy dealership look at it and he said that the exhaust manifold gaskets could cause that. also had them run scanners and they said it was the the o2 senser that it was reading and all of my electrical was good in the truck. and even they checked the fuel pressure at the fuel line by taking off the fuel filter. but the problem is i've already spent 400 dollars on the truck in two days and still haven't got no where. i was just curious if it could be the fuel pump relay, the fuel injector regulator, fuel filter or the fuel injectors its self. but how do i test each one of them with out the equip of a guage. their expensive.