Driveway Diagnostics: Taking on self diagnosis

July 29, 2015
Tackling a 1999 Ford Ranger with a 3.0 liter V6, automatic transmission, 4WD and 175,432 miles that runs rough and has the MIL on.

I must admit, when I was repairing other people’s cars fulltime the last thing I wanted to do on the weekend was work on my own. But for the last 5 years or so, I find myself spending more time behind a computer keyboard and less time under a hood. It is vitally important to me that I keep a connection with all of you, our faithful readers, and I do all I can to keep some grease and callouses on my hands so I never forget how tough it can be to make a living in this business of ours.

Vehicle At A Glance 1999 Ford Ranger 3.0 liter V6, automatic transmission, 4WD 175,432 miles Complaint: Runs rough, MIL light on

So I welcome the occasional challenges offered to me by family and friends, and the occasional help request I get from local shops. Of course, I take care of my own small fleet of vehicles including the subject of today’s story – my 1999 Ford Ranger. The MIL (Malfunction Indicator Lamp) has been on for some time now and what symptoms there are have not been serious enough (I think techs and customers have different levels of “serious”) to cause me any real issues. The 3.0 liter V6 bucks and runs horribly for the first few minutes of operation, then settles down and runs fine until the next overnight soak.

I’ve had the truck for a while now, having acquired it from my youngest son in exchange for the 2007 Toyota Corolla I once owned. No, it wasn’t an equal deal; it was more of a “dad” thing. Now it’s time to sell it off in favor of a later model truck I’ve had an eye on, and before that happens I need to find and correct whatever ails the Ford before passing the keys on to the next owner. The quest for a cure also allows me to share my diagnostic process with all of you and perhaps, together, we might learn a little something along the way. Watch some of the adventure here.

What comes first
Pretty good bet I already know the kind of code(s) I’m going to find when I connect my scan tool to the truck. The rough running scenario I described earlier must have certainly caused a misfire code of some kind. And while my first diagnostic step is to interview the customer (or service writer that wrote the repair order), I think it safe to bypass this step and move to my next – connecting a scan tool and taking a look at what the ECM (Engine Control Module) has to share.

Sure enough, a P0302 (Cylinder 2 Misfire Detected) is stored in the ECM, as is a P0455 (EVAP System – Gross Leak Detected). With the codes retrieved, my next step is to check the associated Freeze Frame data to get an idea of when and under what engine conditions the misfire code was recorded. Had I not been already familiar with the cold start symptoms I mentioned earlier, this information will help me simulate those conditions rather than rely on how the truck runs at idle in my bay. The Freeze Frame data confirmed what I suspected – the misfire occurs when the engine is cold.

Now let me ask you, should I seek out Freeze Frame data on the EVAP (Evaporative Emissions) code? Watch more of the adventure here!

In my opinion, while it may be stored, there is no real need to review it. The reason? The EVAP monitor is a non-continuous monitor that runs through its tests only once and follows an outlined test procedure. The Freeze Frame data would only indicate the conditions I already know the monitor has to be in to run. The misfire code (as well as fuel trim codes) is a different story. These codes are continuous monitors, running over and over again, and testing the system(s) under a variety of rpm and load conditions. And that is information I have to have to accurately and quickly diagnose the causes for these codes.

Screen shot of scan tool (Launchtech USA X-431 PadII). I suspected I’d have a misfire code stored, but wasn’t expecting the EVAP code.

Screen shot of freeze frame data (Launchtech USA X-431 PadII).The Freeze Frame confirmed what I already knew – the misfire occurs when the engine is first started.

Screen shot of mode $06 data (Launchtech USA X-431 PadII). Pre-CAN Fords have a misfire counter of sorts in Mode $06.

Next – fact finding
Now that I have an idea of what ails the Ford, it’s time to move on to a quick visual inspection. At this point, I’m not going to get to deep. I just want to take a look and see if there is anything that immediately catches my eye, anything that doesn’t appear right. And I also want to get an idea of how the owner takes care of his vehicle. Does it look like it is getting the maintenance it needs, or is he just driving the wheels off of it?

The 3.0-liter V6 uses a DIS (Distributorless Ignition System), and I had replaced the plugs and wires for my son shortly after he got the truck. I like to baseline maintenance items on used cars I buy, so I can start the “clock” from that point forward. I took a look at wire routing to see if any of the ignition wires were in contact with the hot exhaust or rubbing on engine brackets and saw no issues there. There were no major leaks visible (oil or coolant) but the coolant reservoir was very low – nearly empty as a matter of fact. A peek at the oil dipstick showed no sign of coolant intermix, but the level was low as well. A look at the oil fill cap also revealed no sign of coolant in the oil (that chocolate milk looking mix we see all too often). Still, that coolant had to have gone somewhere, so I kept that information filed for later use.

With the visual inspection done, it was time to do some homework. Before I grab the first tool or make the first test, I want to gather all the background information I can, especially if I’m diagnosing a system I have little or no experience with. And though I felt relatively fluent on the Ford systems I would be working with, it never hurts to refresh your memory. I want to understand what the code definition really is (NEVER rely on the abbreviated definition for ANY code), what the enabling criteria are, how the ECM tests for the codes I’m chasing and how the engine management systems work. With that in mind, I can decide what test(s) I want to make, saving me time over just jumping in with a “hit or miss” plan of attack.

My first stop was MotoLOGIC, a relatively new service information system that features all OEM content. Its search function is similar to what you’re used to with Google. Simply start typing in a code, system component, or whatever and it begins to populate a list of suggestions to help speed up the process. It also has a “Quick Spec” tab that brings up the most common service specifications on one page as well as keeping a record of the last 10 vehicles you searched, listing the last 10 items you searched on each one. That makes it nice when more than one tech is using the same access point.

I decided to dig into the misfire code first, pulling up the first article that appeared in my MotoLOGIC search which just happened to be a detailed description of how the Ford’s misfire monitor works. The Ranger, as do most OBDII engines, monitors misfire rate by monitoring the crankshaft sensor signal. Fluctuations in speed that exceed programmed thresholds are logged as a miss. On Fords, anytime the battery is disconnected or power is lost to the ECM’s Keep Alive Memory, the ECM has to first relearn what a normal crankshaft position sensor signal is before it can once again resume monitoring the engine for misfires. In some older trucks, like this 1999 model, harsh roads or bouncing around off-road could cause a misfire to be recorded. And we all know that the Ford threshold is kind of high, with many models exhibiting the signs of a misfire without codes being set. However, that doesn’t mean that the ECM doesn’t see the misfire. While there is no misfire-related PID (Parameter Identifier) on your scan tool, there is help in Mode $06 on Ford products (and all makes that use a Controller Area Network (CAN) protocol). You can find out more about the use of Mode $06 on the Motor Age website.

While I’m in there, I checked for TSBs (Technical Service Bulletins) out of habit. The MotoLOGIC search revealed none related to the miss (but a few that may shed light on the EVAP code), I next hopped over to some other tech resources I like to tap into to see if anyone else has dealt with a similar problem to mine. With that all completed, it was time to absorb that new found knowledge and come up with a process that would help me quickly nail down the problem.

MotoLOGIC uses OEM service information, so I started my research on the P0302 code by first learning how the misfire monitor works. (Courtesy MotoLOGIC) The Quick Spec feature is just one of the time saving tools on MotoLOGIC. Now I know which cylinder is the #2 cylinder on this 3.0. (Courtesy MotoLOGIC) The coolant level was nearly non-existent with no visual leaks found on my initial inspection.

Time to test
When chasing down a misfire, it is critical to remember that ANY factor that can result in a cylinder contributing less than it’s share can be a cause. That’s why I recommend taking the time to become familiar with the specific systems and code requirements you’re dealing with on a particular car. Take the time to think about all you know about those systems, and add in the information you have from your customer, the recorded Freeze Frame data, and your visual inspection. Consider what you see, hear, feel – even taste.

For many, the next step is to begin testing to eliminate all the possible causes you can, and do so in as few tests as you can. Many techs refer to the process as “general” testing, helping them to quickly home in on a particular area where they can begin more “pinpoint” testing to home in on the culprit. For others, the process entails the formulation of a hypothesis – taking all the information they have to date and then considering what the most likely causes of that problem might be. Testing is then done to confirm or eliminate the possibilities until the problem is confirmed and repaired. I tend to combine the two; depending on what kind of problem I’m facing and what I know is going in. Let’s summarize what I know so far regarding the misfire on cylinder #2.

According to the “customer”, the engine runs rough, at times very rough, when first started. After a few minutes of operation, the engine smooths out and appears to run fine. The Freeze Frame data confirms what the customer has to say, showing the misfire code recorded while the engine is still cold at an rpm consistent with a fast idle warm-up. Fuel trims are no help here, so they are ignored for the time being. The visual inspection uncovered an unexplained loss of coolant but there was no sign of coolant intermix in the oil. No smoke of any kind is visible on start up coming from the exhaust either.

I took the latter with a grain of salt, because I have seen catalytic converters do a good job of eating whatever smoke was passed through them. I remember more than one make that I’ll not name that was notorious for burning oil at rates that would keep any Middle Eastern country in business all by itself, yet no telltale smoke exited the pipe. I’ve also seen cases where coolant was getting into places it shouldn’t be with no sign of contamination in the oil. In fact, many coolant manufacturers will tell you that coolant leaking into a combustion chamber is more common than you think but that’s the topic for another conversation.

My first test was a continuation of the visual inspection process. Since the truck had now been sitting all night and had not been started yet, I removed the #2 spark plug to see what stories it had to tell. I found the plug tip heavily coated with deposits and wet. The presence of the deposits was enough to let me know that something extra was invading the cylinder. I saw no real color in whatever it was that was causing the wet appearance but the fact that is was wet for so long took fuel out of the equation. Fuel, I thought, would evaporate quickly, especially in a hot engine.

I suspected I had found the coolant leak I was looking for. If it was indeed leaking into the combustion chamber, I should see even more by looking down into the cylinder. The angle of the plughole and its placement, however, made simply shining a light down in for a look impossible. The folks at Automotive Test Solutions, though, had recently sent me a borescope to try and that was my next step. This tool has an excellent resolution and the ability to manipulate the tip, similar to medical grade borescopes, and it provided me the last piece of the puzzle I needed to confirm coolant contamination was the issue. The top of the piston was glistening in the light of the borescope’s camera with individual droplets clearly visible. Just for comparison, I looked at the adjacent cylinders and found them both dry.

As I mentioned earlier, I had seen similar losses before. What happens is relatively simple. The leak is relatively minor, so much so that any loss while the engine is warm and running is burned as quickly as it enters. However, once the engine is shut down and the system is still under pressure, coolant is allowed to pool on top of the piston in sufficient quantity to contaminate the air/fuel mixture on initial start up, resulting in the cold misfire.

Last step? Time to pull the cylinder head and see whether or not it’s a gasket problem or a crack in the head. Time to look up the labor time and procedures in MotoLOGIC, get some tools together and enjoy a cold beverage before I dive in. Repairing your own cars at home does have a few advantages!

As part of the initial visual, I checked the ignition wire routing for any obvious signs of problems. The #2 plug was fouled with heavy deposits around the electrode and inside the shell. Obviously something extra was getting into the cylinder’s combustion chamber but what? Sending the borescope probe down into the cylinder while looking at the image on my little PC provided the final clue – droplets of water on the top of the piston. (Automotive Test Solutions borescope)