Dodge Truck Stalling At Idle

09 Dodge Ram with 5.9 engine had been sitting unused for awhile so the owner had to jumpstart the battery. He then had to keep one foot on the accelerator giving just a slight throttle or the engine would die. 

If you've been following my posts you know that when you lose battery power you lose adaptive memory. Lose adaptive memory and some things won't work properly until the adaptives are relearned. We'll be looking closely at idle control adaptives on this one but only after making sure we have a good battery. 

The truck idled with no stalling when I drove it into the shop. This means the computer had probably relearned idle on the way here. I wanted to save the adaptive memory but I needed to test the battery. A memory saver will keep the computer powered while you disconnect the battery and you won't lose adaptives. 

The old battery was bad, so out with the old and in with the new.

Once the replacement battery was installed I removed the memory saver. Since the idle adaptives were relearned and since I saved learned idle I could look at idle air control counts for a problem. There are some things you can only see with a scan tool. IAC counts are one of those things. The ideal range here is 10-24. If you see higher numbers the computer is having to command more idle air to maintain idle speed. Usually there is a buildup of carbon on the throttle causing this. 107 here meant the throttle plate might be dirty. 

After cleaning the throttle I checked the counts again. 

They were much better but still higher than our target range. I knew the throttle was clean. There is a minimum air adjustment that can be checked. Very easy to check when your scan tool will command it. Minimum air takes the idle control motor out of the picture. Only the air allowed past the throttle is maintaining idle speed. Just enough rpm to not stall when placed in gear is my rule of thumb. The minimum air was fine. Using the scan tool I did a minimum throttle relearn twice. I've ran into that before on Dodges, sometimes more than one relearn. But it worked.

Thanks for reading!

Kenneth Hayes

G&G Auto Repair

Another Ford Lean Code

This Mustang w/4.0 engine was setting a lean code for bank 2. 

At idle and low rpm both O2 sensors were switching normally so I ruled out a vacuum leak being present. A fuel delivery problem would most likely affect both banks and I only had a code set for bank 2. I took a look at the freeze frame for the lean code. Freeze frame is a sort of snapshot of sensor data during the event that set the code. 

Short fuel trim for bank 2 shows a LOT of fuel being added. It isn't likely I had a fuel delivery problem because bank1 looks to be in fine shape. I could also see this event was on a warm engine at highway speeds. I set up to monitor both O2 and went for a test drive. When I went from a steady cruise to a hard acceleration the bank 2 sensor went to full lean but bank 1 showed the increased fuel. 

It was at this point I felt I was dealing with a bad sensor, bad wiring, or bad ecm. Easiest test from here would be replace the sensor and re-test. I did a wiring harness wiggle test while monitoring the signal and found nothing. Replacing the sensor and recording again under hard accel I could see I found the fix. 

Not bad!

Thanks for reading.

Kenneth Hayes

G&G Auto Repair

Lean On Me, Or Not

I had this '97 Ford F150 in the shop with a P0174 code stored. The customer had the problem "diagnosed" by one of the parts stores as a bad pcv valve and hose. I imagine that was an employee armed with a code reader pulling a lean code and printing a list of suggested possible causes. A pcv vacuum hose leaking is a very common problem on a Ford but just a wild guess at this point in time as to the cause of the P0174. There is a lot of difference between diagnosing a problem and guessing what it might be..... but I digress. This engine has a fuel monitor O2 sensor on each engine bank. Passenger side is bank 1 (with cylinder 1,2,3,4) and driver side is bank 2 (cyls 5,6,7,8). P0174 means the trucks computer has determined bank 2 to be running a lean fuel mixture. Too much air or too little fuel, in other words. If I had a lean code for both banks, P0171 and P0174 then I might be thinking vacuum leak too. A pcv hose pulling extra air will usually put both banks lean at idle and it will be stored in freeze frame as a problem at idle or low rpm. I decided to not immediately look at freeze frame but to first look at the live data from both upstream O2 sensors. Now, most of the time a lean, or even a rich fuel condition code sets because the oxygen sensor is working fine. I mean the job of the sensor is to report the amount of oxygen in the fuel mixture. Don't kill the messenger, right? I even saw more than one tech site that said a lean fuel code won't be a bad sensor. Well..... never say never.

I captured the data from both upstream sensors. On the top half of the first picture is the sensor that did not set a lean code. The lower half of the pic is the O2 that did set a lean code. This is a live datastream with engine running at about 2000 rpm. An oxygen sensor range is from 1 volt to 0 volt. 1000mv to 0mv. Anything below 500mv is lean, anything above is rich. A good O2 sensor with a good fuel control should switch well between the two conditions. Now since I didn't find an obvious problem with the truck, such as a bad pcv hose and since I see no particular problem with the way it is running or with anything that would affect only bank 2 I think it would be worth replacing the bank 2 sensor and running another data capture. 

After replacing the bank 2 sensor the next capture looks like this:

Notice how the sweeps are in a much wider range now even on the "good" bank 1 sensor. The bank 2 difference is very substantial. I haven't done anything to change fuel mixture other than replacing the bank 2 sensor. Now we have full fuel control and fixed a lean code without finding a lean condition. 

Hope the pics are viewable. 

Thanks for reading,

Kenneth Hayes

G&G Auto Repair

Jeep Liberty stalls at idle.

This Jeep would not stay running if you released the accelerator and tried to let it idle on its own. Just a slight throttle opening and it would idle at normal speed. So, the idle rpms were too slow. I'm going to make this one quick and simple, because it turned out that way. I like to pull up iac counts and engine rpms for a quick way to see if the throttle plate may need cleaning. Ideally the counts should be between 10 and 24. Higher and it probably needs a throttle cleaning.

This one does need cleaning.

After cleaning you can see the counts have dropped dramatically.

I said 10-24 is ideal. A idle relearn and all is good. 

No stalling. Good numbers.

Thanks for viewing!

Kenneth Hayes

G&G Auto Repair

G&G Pops the Hood Part 2

In part 1 of this series we got the hood open and secured. 

Depending on your car, there are a lot of things to take in. Look around a bit. You can't spot something wrong until you've learned what right looks like. Hopefully by the end of this series you'll be so familiar with your under hood inspection that any problem will be obvious. 

Now we have to start somewhere. Checking oil level is a good place to start. A LOT of cars in the shop these days are low of oil. I know from talking to customers that some don't realize a car can need oil added even when it isn't time for an oil change. Usually the oil level stick isn't too difficult to find. Some are marked, some aren't. 

Ideally your car should have been sitting long enough the engine is cool and the oil has drained back into the oil pan. When the engine is running oil is being pumped to the various areas it is needed. After the engine is shut off it takes a minute or so to drain back to the crankcase. The oil level stick reaches down into the oil and has markings to indicate how much oil is in the pan. When you have identified your oil stick, grasp the handle and pull straight out. Plastic handles have been known to break so don't be over aggressive. Once you have the stick out and in your hand you should see oil on the lower end. Note the condition of the oil. If the oil is terribly dirty you probably need an oil change. Discolored and thick like milkshake could mean coolant is getting into the oil. If the oil doesn't look normal to you then you should let someone more knowledgeable take a look. For our purposes here though we'll continue with how to check the oil level. Wipe the oil off of the stick. There will be a full mark and a one quart low. Insert the cleaned stick fully into place then remove to see where the oil level is on the indicator. The truck below had an oil change a few weeks ago. The clean oil is hard to see in the picture but shows a slight overfill just at the last L in full. About a half quart over. 

Let's try another. The oil condition looks good in this one and it is about half a quart low. Don't add a half quart. Just remember to check later on. Some cars can burn a half quart or so quickly but take a long time to need a full quart. If you try keeping it topped off you would be constantly adding oil to a car that would be fine if left alone.

If you do need to add oil use the manufacturers recommended oil as outlined in your owners manual. Add oil as needed by removing the oil filler cap. A funnel can help prevent spilling to the exterior.

Stay tuned for part 3!

Kenneth Hayes

G&G Auto Repair

G&G Pops the Hood Part 1

Not many people take a look under the hood these days. That seems odd to me since I was taught to keep an eye on fluid levels and check for obvious problems.  I know cars are generally more dependable and longer lasting now but if you run that car out of oil or coolant you will still end up with a major repair problem. I want you to know your way around your car. Let's start with opening the hood.

Most cars have a hood release under the dash that you pull to release the hood latch. 

When you pull the release you are pulling a cable attached to the hood latch. The cable pulls the latch release and a loaded hood spring can then let the hood pop up. 

If the hood release doesn't work as described you probably need some lubrication of the latch. Bump the hood with your hand and/or just grab under the front and pull up. 

Once released, the hood should spring up enough to engage the safety catch. The safety catch is usually a hook that must be released before the hood will open fully.

You may need to both feel and look for the release to see how it works on your car but it isn't usually difficult. Once you have the hood open you need hood support. There are various types of hood support but all are there to keep the hood from crashing back down when you let go after raising it. 

There are hood support rods on some cars. Basically metal rods that prop the hood up. 

Some people choose a custom design.

There are hydraulic supports.

If your hood uses these and you don't feel them helping to raise the hood they need replaced. Or, use the custom broom handle method. 

Kenneth Hayes

G&G Auto Repair

Why is this truck stalling?

03 Chevrolet Silverado Z71 LS 5.3

The complaint is the engine dies (stalls) after the battery failed and after battery replacement. 

The first thing comes to my mind is an idle control problem. The trucks engine computer has been adapting programming as needed to compensate for wear and age conditions. When the battery power is lost so is the adaptive programming. Commonly the throttle bore and plate have been building over time a layer of carbon. Because this happened slowly the computer was able to make changes in idle control strategy and maintain idle. The loss of battery power reverted the system back to factory settings and since there was no carbon then, the settings aren't correct for maintaining idle now. If this is the problem then I should see the stalling being related to a slow idle speed and a slow response to an rpm drop at idle. 

You can see the idle drop to a near stall in this pic when I place the shifter from park to reverse. The iac counts are a rough indicator of how hard the iac is working to maintain idle speed. You can see iac is slow to respond to the rpm drop. So there is probably a carbon problem.

You have to get in there with a rag and some cleaner. Hold the throttle plate open and wipe the area clean.

Now after reassembly we start the engine to clear any excess cleaner and let the idle stabilize. Look now how quickly the iac responds and how easily it maintains idle rpm as I move the shifter this time.

A test of alternator and battery draw and this truck is fixed.

Kenneth Hayes

G&G Auto Repair