About Engine Stalling

Drive by wire throttle body

I found 2 videos about engine stalling and low idle problems that fall into the do it yourself auto repair categories. These are things you can do at home that can help improve these common car problems. I also found an odd video that shows how to clean the throttle body and Idle Air Control Motor.

When I worked in the new car dealership service department they would charge around a hundred dollars for the service outlined in the video below. Note: IAC problems can cause both a stalling and erratic idling condition called hunting for idle. It can also set check engine light codes. If you have a drive by wire Throttle body as pictured on the right cleaning it will not solve codes relating to p0121.

This code is common on GM vehicles and will most likely need a new part.The feedback I hear from consumers is the service center often recommends trying to clean the part, reset the light and see if it comes back on. I have yet to hear that cleaning has solved the issue.

This part is expensive through the dealer. Yes, it can be purchased through amazon for a fraction of the dealer list, but if the computer needs an update a trip to the dealer is still necessary. Presently there is no way around dealerships having exclusive software updates unavailable to the general public.

Now back to what cleaning can do. The videos are posted for your convenience so you can see what is involved with a throttle body service. I also discuss the leading cause of idle problems on older vehicles like a vacuum leak from deteriorated rubber and plastic lines.

Stall Condition or Low Idle

IAC Diagram

But first how the idle air control (IAC) valve works and some of the common problems that affect this system. The IAC is completely responsible for the engine characteristics at closed throttle.

The cars computer controls a pintal valve that allows a small amount of metered air to enter the engine via the throttle body. The computer continually adjusts and meters the air while monitoring engine rpm.

When this system malfunctions you can have a low idle condition or engine-stalling. Sometimes the pintal valve and the airway passage can become clogged and restrict the air flow which degrades the ability to make the idle adjustment automatically.

You can remove the IAC valve and inspect and clean the air passage and pintal valve. This may cure the engine stalling condition. Here is a video that walks you through the basics of the throttle body service.

Engine Stall from a Vacuum Leak

If your vehicle is more than 10 years old this next common condition could also be affecting your engine idle or even cause a stalling condition. Broken vacuum lines are just as common today as back in the 70's.

Even though the vacuum lines are now made mostly of hard plastic they can still crack and break from the extreme heat they are exposed to. A small vacuum line breaking may cause an engine idle to fluctuate at closed throttle. Where as a large vacuum leak will almost always cause a stalling condition.

A close inspection of these vacuum hoses should reveal any broken ones. But pay close attention to 90-degree bends and also the attaching points to the intake manifold and throttle body. These areas take the most stress.

If you have a scan tool you can pull up the data and confirm a vacuum leak by watching the IAC steps. When an external vacuum leak develops the computer will try to compensate for it by running the IAC all the way in and this would read 0 steps on the scan tool.

When it comes to testing the Idle air control motor this is within reach of most diy car mechanics. It's worth the time because this electrical car part can be expensive and is often a non returnable item. This video does a good job of showing you how on a Honda 1.7L. If it is not the cause of your engine stall give it a cleaning and move on.

Why some Honda's have an engine stall problem. There is a technical service bulletin out on early model Honda's with the 1.7L. The TSB provides insight into how the engine could stall because of the PCM (Power-train Control Module).

In more detail the part that controls the fuel system. From what I read there is a problem with the PCM controlled relay that provides power to the fuel pump. You can contact dealers for more information. Or watch my video on how to find auto repair bulletins. Long story short a defect in this relay or it's control system stops the fuel pump from running.

Recommended for DIY car mechanics. Ask a Technician right now about your car stalling problem. Get an answer in most cases within 15 minutes.





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