Sunday, February 15, 2015

Quick and Dirty

2005 Ford F-150 with 136,471 miles on it. This vehicle has the 5.4 Liter 3 valve engine with VCT (Variable Cam Timing). Shop owner tells me that that the customer is complaining of a rough idle and the Check Engine lamp on. This truck is super clean. I arrive at the shop and indeed it has a rough idle. Seems to improve with rpm. This is my first clue. The title here is "Quick and Dirty". I want the most information in the shortest amount of time.

I run a KOEO self test with my IDS. The vehicle has no on demand codes. But, has quite a few KOEO CMDTC's (Continuous Memory Diagnostic Trouble Codes) commonly referred to as memory codes and a pending code. Let's go through them. The P0012 is very common on these engines. I highlighted it for a reason. With IDS you get a decent code description. As you can see it is an issue with cam timing on bank 1. P0172 is bank 1 rich. P0174 is bank 2 lean. P0301 and P0303 are misfires detected for cylinders #1 and #3. P0316 is a misfire detected at start up.  More clues here. But, let's look at some live data.

I load some pids I want to see on Datalogger on my IDS. I immediately see that bank 1 has issues. At an idle both banks should be near zero degrees for error and advance. Bank 2 is and Bank 1 is not.

Here is another truck I took a snapshot on that was running well. At this point I can also take a look at a couple of other great functions of IDS to get more information.

Here is a live power balance with IDS. Dark blue is where you are and grey is where you have been. It is called a histograph. Cylinder numbers in the vehicles firing order are up top and the green horizontal line represents 0. Below the zero line is a cylinder that is not contributing. The histograph shows cylinders 1, 2, 3, and 4 are below. Cylinders 5, 6, 7, and 8 are above. This is not uncommon to see cylinders following a misfiring rise above the zero line. On a good running vehicle the dark blue line is straight across the green zero line. So now I know that cylinders 1, 2, 3, and 4 are not contributing properly. From the layout of this engine these cylinders are all on Bank1 which is passenger side of the vehicle. I am starting to build my case. One more great test and I think I will be ready to present my case to the shop owner.

This is the relative compression test results. This function with IDS will compare cranking cylinder contribution and compare against each other. It is a great test. The test will automatically suspend injector pulse and prompt you to depress the accelerator pedal all the way down, and prompt you to crank the engine for 10 seconds. As you can see our problem cylinders 1, 2, 3, and 4 have low contribution compared to the others. I usually will investigate if its a 2% difference. We are looking at a much greater difference here. Sometimes, when there are cam timing codes this test can get altered or refuse to run. I did backup this finding with a cranking amperage scope test to confirm.

   Here is vehicle that has no issues. Big difference. At this point I have a pretty good case with either a timing chain issue on bank 1 or a stuck phaser on bank 1. More likely bank 1 chain is off. I see this issue where the tensioner goes bad and leaks internally and doesn't provide proper tension on the chain or bank 1 timing chain guide broke and caused the chain to skip. The other issues that lead me here are the opposing fuel trim codes one side lean and the other side rich. Also, the fact that the misfire improved with rpm. All signatures for a mechanical valve timing issue. I present my case to the shop owner. I can pinpoint it further but would need additional time and diagnostic costs. He refuses at this point until he informs the customer. The customer was figuring on some plugs and coils was going to take care of this unfortunately not. I also discussed with the shop owner the oiling issues with this engine. I always advise my customers not to do any internal engine work on these engines until a thorough manual oil pressure test has been performed with the proper weight and amount of oil. Shops are always surprised when I tell them you need to have a minimum of 20psi hot in gear and the needle should be rock stable. If it does not meet this minimum reading or the needle is erratic the oiling system must be repaired first before repairing other issues. The whole VCT system revolves around proper oil pressure.


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