Stalls at idle and surges when accelerating

GLENN GILBERT

MEMBER
1997 DODGE AVENGER
2.5L
V6
2WD
AUTOMATIC
152,000 MILES

I have the car listed above ES 2.5 model. I do most of the maintenance on the car but I just cannot figure this one out. When the car is first started and when I am backing out of my garage, driveway is on a pretty bad slope, the car will stall. The idle will get real low and unless I give it gas it will stall. After I get going and accelerate it will buck at times until the car gets warmed up. After it gets warmed up most of the time it will be alright but might stall at times at an idle. Stopped at a light or stop sign or backing out of a parking spot etcetera.

I have changed the TPS switch, cleaned the throttle body the best I could on the car, replaced the fuel relay and changed the fuel filter. I also added some gas additive to the tank, which made it run better but now that I have gone through that tank of gas it is back to where it was. I am also getting very poor gas mileage and poor acceleration power.

What possibly could be going on?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi and thanks for using 2CarPros.com.

There could be many things causing this problem. I will run through some of the most common, but to be honest, if it is running as you described, the check engine light should be on which would indicate there are trouble codes stored which could lead to the issue.

Now, since the idle is an issue, these vehicles depend on an idle air control valve (IAC). When your foot is off the throttle, the throttle plate closes completely. For the engine to keep running, the IAC meters air into the engine. Most times, and IAC bad IAC will cause the idle to rise and fall over and over. However, it can do what you described.

Before I get into the IAC diagnosis and inspection, if the check engine light is on, scan it first. Here is a video showing how if you need it:

https://youtu.be/YV3TRZwer8k
___________________________________________________________________________
Now for the IAC and idle speed. Here is a check from alldata:

Curb idle speed check:
Before inspection and adjustment set vehicles in the following condition.
Engine coolant temperature: 80 - 95°C (176 - 203°F)
Light*, electric cooling fan and all accessories: OFF
Transaxle: Neutral (P range on vehicles with A/T)
Connect the scan tool to the data link connector.
Start the engine and run it at idle.
Run the engine at idle for 2 minutes.
Check the curb idle speed. The standard value is 750 ±100 RPM .
NOTES:
The idle speed is controlled automatically by the idle air control system.
If the idle speed is outside the standard value, inspect the MFI components.
In vehicles for Canada, the headlight, tail light, etc. will remain lit even when the lighting switch is turned OFF but this is no problem.

________________________________

Here are the directions for checking the IAC / see pic 1. Also, the IAC is located on the throttle body. See Pic 2.

Disconnect the idle air control motor connector.
Measure the resistance between terminal 1 and terminal 4 of the connector at the idle air control motor side. Standard value: 38-52 ohms [at 2O°C (68°F)]
Measure the resistance between terminal 2 and terminal 3 of the connector at the idle air control motor side. Standard value: 38-52 ohms [at 2O°C (68°F)]

If you find that the IAC tests good, remove it and make sure it is clean and free of carbon and dirt.

_____________________________________

Next, another common problem is a vacuum leak. Here are directions for locating and repairing a vacuum leak:

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

_____________________________________

If everything is checking out good, next check the catalytic converter to make sure there is no restriction. Here are links for symptoms of a plugged converter as well as how to check one:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

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

___________________________________

Okay, I think there is enough to get you started. I will remind you that the 2.5L V6 does have a timing belt and if it has never been replaced, is way past due. Keep in mind, engine timing can do the same things you mentioned. Additionally, this engine is an interference engine. That means if the belt breaks, there will be major internal damage to the pistons and valves. Not a good thing!

Let me know your thoughts or if you have other questions. I am here to help.

Take care,
Joe

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Thursday, June 21st, 2018 AT 7:43 PM

GLENN GILBERT

MEMBER
44 POSTS

Thanks for the information. I was going to either try to clean or replace the IAC but with one of the screws buried behind the IAC I was afraid that if I did get it removed I would have a very difficult time putting it back in. I also tried to take off the throttle body but had a difficult time trying to remove the accelerator cable. If you have any tricks to getting either of these done please let me know. Also, when the vehicle is still cold and after I get going upon acceleration the vehicle with surge badly at times. I am not sure if it is the same problem or if it the transmission getting ready to go. I changed the fluid recently and the transmission is shifting smoothly and not slipping but like I said when it is cold it will surge at times.

Thanks for any other help you can give me.

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Monday, June 25th, 2018 AT 4:37 AM

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi again:
If the transmission is not slipping and is shifting properly, I do not think that is the problem. Have you checked the items I originally mentioned? As far as the screws you are having trouble with, can you upload a picture so I can see what you are dealing with? I do not recall having any issues in the past, so you have me stumped. LOL

As far as the throttle cable, I have attached all the pics I have for you to review. There is a throttle cable, and if the car has cruise control, there is a cable. To remove the cable, with the engine off, manually open the throttle the entire way. Swing the cable downward toward the opening on the throttle and slid the retainer out. See pictures:

Let me know if this helps.

Take care,
Joe

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Monday, June 25th, 2018 AT 7:40 PM

GLENN GILBERT

MEMBER
44 POSTS

I do not think it is the timing belt as I had that replaced a while back. I did replace the TPS switch but that did not help. The vehicle does have cruise control on it but I only see one cable attached to the throttle body, but since the throttle body is real close to the firewall I may be missing it. Just like when I was going to try to flush my heater core and found that the hoses are lower on the firewall I decided to wait on that until it gets cold again. Anyhow, I have attached some pictures of my throttle body. If you have any other information please let me know.

Thanks

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Wednesday, June 27th, 2018 AT 2:12 PM

KEN L

MASTER CERTIFIED MECHANIC
47,513 POSTS

First I would remove the throttle body to clean it because it is the backside of the throttle plate that needs to be spotless. We need to run the code to see what comes up as well.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back.

Cheers, Ken