Chevy Truck Misfire Quick Check

The 2010 Chevy Silverado had a misfire complaint. There was no misfire on starting to drive into the shop but the MIL (malfunction indicator lamp) was on so some sort of trouble code was stored. I could go drive the truck under different conditions and try to recreate a misfire but if it did miss I still wouldn't know why and the engine would need to cool for awhile before I could test. First thing then was check for stored trouble codes. P0300 is a misfire code and it does mean the engine was running badly at some point but it isn't especially helpful in diagnosing the problem. But suppose there was a misfire on a specific cylinder that just hasn't yet set a code. On the GM I could access stored misfire history and look for a problem.

Cylinder #7 has logged 2,116 misfires. All the others, 0. Looked like I should start with a look at #7 spark plug. Original plugs, 94000 miles. I replaced spark plugs and plug wires.

Thanks!

Kenneth Hayes

G&G Auto Repair

Battery Checks

The complaint on this Chrysler Sebring was that the battery would not stay charged. It was dropped off after-hours and sure enough the battery was dead next morning. A jumpstart was needed and I tested the alternator voltage while the car was running. The alternator was working.

In theory my tester can check a discharged battery. It works best to disconnect the cables from the battery since there could be interference from the car's electrical system. I put the memory saver in to keep settings and system memories alive before disconnecting the battery. The battery tested bad. Now sometimes I can get a *bad* reading testing a battery that is very low that turns into *good* after an overnight trickle charge. I put the charger on the battery for the slow charge and installed a known good battery on the car to use for further testing in the meantime. 

At this point I had tested battery and alternator. I needed to see if there was something on the car draining the battery. With the good battery on the car and with the memory saver removed I tested the battery draw. I wanted to see less than 50mA. Battery draw was good. 

To wrap things up, the battery never came to full charge and would lose what charge it did have very quickly. Bad battery. 

Thanks!

Kenneth Hayes

G&G Auto Repair

Diagnostic Tools: Amazing What You Can Do With A Cellphone cont.

The Lincoln Navigator I had used for an example in the first part of this article had no trouble codes stored, which was fine for my purposes. I just wanted to introduce you to the cellphone possibilities. I also had a Ford Explorer which did have a pending code stored. When a car with OBDII system sees a fault that it is programmed to notice, it stores that as a pending code. Based on programming as well it can move that code to current if it is noticed again. Usually three logged faults and the code will set as current, or hard and the light will come on. I won't go further down that road in this article but did want to briefly explain what a pending code is.
I scanned the Explorer for codes and found P1443. The definition information shows the code is pending and is listed as Evaporative Emission Purge Valve Malfunction. The U-Scan app has a *smart* link as well called code connect. Code Connect will let you in on the most common repair for the problem. In this case, the most common fix for a code P1443 is to replace the EVAP canister purge valve. Now, exactly because I always stress there is no machine to tell you what is wrong with your car, let me stress that we don't know what is wrong with this car. <vbg> We have a pending code for a fault that is often caused by a bad purge valve.

That is information we can use though. If I were going to go further in diagnosis I'd have a place to begin testing. What I did further with the cellphone though is input the vin to the OReilly store where I could get a price and availability of the purge valve. With that I could make an estimate on a likely cost range and get an ok to go further with tests. Yes, very useful. 

Time for a phone call and coincidentally the phone was in my hand. 

Thanks!

Kenneth Hayes

G&G Auto Repair

Diagnostic Tools: Amazing What You Can Do With A Cell Phone

It is actually very amazing to me how far technology has come in my own lifetime. Modern cars are like computers on wheels. The testing equipment used to work on cars has changed at a pace that is truly dizzying. The old Sun Engine Analyzer was a fond memory of days gone by.

found at http://bambam.gmu.edu/sun/

http://bambam.gmu.edu/sun/ has a very interesting collection of old testing equipment. Very much worth a look. 

Time marched on and the tools now look very different from then. Some aren't what you would think of immediately when working on your car but can be helpful to do just that. Let's start with something very common. 

I'm not going to pretend that I use my cellphone a lot when testing cars. I don't. I have other equipment that is arguably better for most things. That doesn't mean the phone can't be useful or even downright impressive in its possible uses for car repair. Let's walk through a scenario. I have installed on my phone a scantool app called Actron U-Scan. There are lots of similar apps out there. I can't comment on those or compare them. U-Scan works for me and I have it on both an iPad and the Samsung phone. 

A wireless bluetooth connector plugs into the diagnostic lead on the car. After linking the connector to the phone I can do a scan of the system. Just how comprehensive a scan or how many modules can be accessed depends on the particular car. I can read or erase codes, access datastreams, graph data, or even share information from the app online. 

Now, I want to jump from the scan app discussion to talk about another app. This particular app is from O'Reilly Auto Parts. There are of course, other apps like this but as with the U-Scan, I only know the one I'm using. 

I can scan the vin or type it in. The scan feature is great when the car allows it. Many cars don't have a scannable vin. 

Once the vin is entered I have access to more information about the vehicle such as sub-model and engine size. When the vehicle is validated the vin and vehicle information is stored in the apps "garage" along with other cars and can be pulled up later or deleted when no longer needed. 

The validated VIN information is also sent to the OReilly online site. If I go to the store's online site the car will already be entered and I just have to navigate to what I want to see that is related. All being done with the phone. Repair information is available onsite. It isn't parts only. 

Amazing stuff! All packaged together in a small handheld device. Since you also have the power of the internet you can google, email and access other data based sites. We'll do a walk through of initial diagnostics using the things I've mentioned in the next part of this series. 

Thanks!

They Die In Threes part 3

In part 1 the Impala was repaired with a new starter. In part 2 the Mazda got new spark plugs and an ignition coil. Part 3 is the Buick that usually needs a jumpstart of the battery. The reason I had to let the car sit for a length of time before testing for battery draw is that there are several module/computers on a car that don't shut down immediately just because you have turned the key off. They do timeout or go to sleep mode after enough time has passed if the car isn't disturbed. I had opened the hood prior to waiting so that I wouldn't have to open a door to pop the hood later and start the cycle over again. If a circuit is disturbed it will wake a system so I use an amp clamp that goes around the battery cable and doesn't require a connector to be removed. The battery ground cable on this car had two leads so the clamp had to be placed on each, one at a time. The rule of thumb is that I want to see less than 50mA of parasitic draw on the battery with a sleeping system. 

Both leads show acceptable draw. I started the car again and it cranked normally. I put a voltmeter on the battery with the engine running and noticed slightly high charge. That is a sign of a low battery voltage. 

I shut the car off with the meter still connected to see what the battery voltage was. It was just under 13 volts *but* when I turned the lights on and key on it took about 4 seconds to drop to under 6 volts and kill the battery. The connections were tight. Bad battery. 

Tools to diagnose:

Thanks!

G&G Auto Repair

They Die In Threes part 2

In part 1 I walked you through the diagnostics and repair of an Impala with a bad starter. I still had the other two cars to work with. The Buick with potential battery drain still needed to sit so I could be sure the computers were timed out. I hadn't been able to get a misfire from the Mazda but a scan for codes showed it had been missing on cylinder #1. The car had 130,000 miles and it wouldn't be a crazy idea to check the spark plugs. An easy way to see if a car needs spark plugs is to pull one out and look at it. Well, sometimes easy. 

It wouldn't be easy to remove the actual #1 cylinder spark plug. It's buried pretty well under the upper intake or plenum. 

You know what though? All I really needed to do at this point was find out if the car needed spark plugs. The front bank ignition coils were not hidden. I said I like to go for easy if the car lets me. 

Pulled one of the spark plugs from the front bank and yes it had worn spark plugs. Original plugs with 130,000 miles. 

The customer gave the go-ahead and I went after even those hard to reach spark plugs. The car got new plugs and a new coil on #1 cylinder. I know #1 was misfiring even if I couldn't re-create the problem. Driving with worn spark plugs causes damage to ignition coils and you really don't want to put that same coil from a misfiring cylinder back in that hole. 

Tools to diagnose:

Tools to repair:

Thanks!

G&G Auto Repair

They Die In Threes part 1

I started the day with three automobiles to take a look at. The 08 Mazda CX-9 had a misfire complaint. The 07 Chevy Impala had a no-crank complaint. The 02 Buick Rendevoux had to be battery boosted to start. No problem. I'll just grab the machine that tells me what is wrong with a car and get started. Oh wait, there is no such thing. It would be kind of cool to grab a tricorder and run diagnostics quickly just to see what the problem is. That isn't in the real world, though I do know a lot of people believe that to be how it works. 

I'll explain how I do diagnostics and repair. At least, I'll give a few examples. First, I guess it is similar to triage. I have to take a look at each job on the schedule and see how to best get the work done. The 07 Impala had been towed in as a no-crank. I should explain no-crank. The starter is supposed to turn the engine, or crank it over. If that doesn't happen it's a no-crank. If the starter does turn the engine fine but the engine doesn't start, that's a no-start. The Impala, for me, did crank but very slowly. It did start as well and I drove it into the shop. Because it cranked slowly I suspected I might have a low battery condition. Low battery could be caused by an alternator not working. Since the car was runnning and might not start next try it seemed like a good time to see if the alternator was working. I put a voltmeter on the battery and could see just over 14 volts so the alternator should be ok. 

You want to see the battery voltage reading with engine running to be more than battery voltage with engine stopped. The meter was already connected so I just had to notice the reading after shutting the engine off. Just under 13 volts and steady even with lights and key on. Basic testing, but looked like the alternator and battery were probably ok. 

I still had two cars outside that needed checked so this was a good stopping place. I'd probably be looking for a bad connection or a starter problem on this one. I went to the Buick that was having to be jump started. I tried the start first with no booster and it cranked fine. Not even a slow crank, a nice normal fast spin and started right up. I drove the Buick into the shop. I tried restarting several times and found no problem. A basic rule of diagnostics is to "verify the complaint". It's nearly impossible to find a problem that you can't re-create. My plan with the Buick was already formed though. Open the hood, pull the key, shut all the doors and let it sit right there at least 3 hours. After that I would test for battery current draw. Maybe the battery was being drained while sitting.
I now had two of the three vehicles situated and had to take a look at the 08 Mazda. The Mazda was towed in but only because the owner did not want to drive it with a misfire. The complaint was a misfire. The car started and ran fine with no miss. I tried to load the engine a bit by power braking but still no miss. I decided to let the Mazda sit inside as well and rest. When the engine was cool I would use a scan tool to see if a particular cylinder had triggered a misfire code and begin checks with that cylinder. So.... back to the Impala since it was the only one with the complaint verified and present.
Now the Impala was the no-crank complaint that had cranked slowly for me. I tried to start and now it was no-crank. I didn't hear a sound from the starter solenoid which is usually a click. I watched the lights and they didn't seem to be losing power. The headlights go out normally on crank with this model so there was a bit of room for error in judgement. If the lights go out on a crank you probably have a bad connection. Here they seemed ok but since I wasn't sure I wanted to test the battery connections. You can make things complicated or you can make them easy. I prefer to work with easy and let any complications come from the car, not from me. I could take the connections loose, clean them and try again that's one approach. I could even do voltage drop tests with a meter while trying to crank. What I did was put a booster/jump pack on the battery connectors. If it then cranked I had a bad battery connection. It made no difference. I put the booster negative cable directly to the engine block and no difference so the negative cable was probably ok.

Next up would be to check at the starter for battery power to the solenoid. I ran a jumper wire down to the starter and to a test light placed where I could see it from the driver seat while cranking. I had power to the starter battery terminal and I had power to the solenoid wire from the starter relay. I could have enough voltage to light the test lamp but not to engage the starter and I could do voltage drop testing at the starter but I chose the tap test or whack it with a hammer method next. After tapping the starter with a hammer it did engage on a crank and did crank slowly. Bad starter. 

Diagnostic tools needed:

Tools needed to repair:

Thanks!

G&G Auto Repair