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I have seen this one jam people up over and over, so I wanted to make a reference thread.
CCT - Cylinder Contribution Test: The CCT is done with the more powerful scan tools - this is in contrast with a scan gauge. A scan gauge reads data, and a scan tool reads the data as well, but it can also send commands to the modules on the vehicle. The PCM monitors the Cam Position Sensor (CPS), this is the sensor that knows not only how fast the engine is turning, but exactly which cylinder is TDC. By monitoring the time it takes to get from one TDC to the next, the PCM can sense when a single cylinder is "contributing" to turning the engine, when it's not, and when it's only doing a partial job. This is where the CCT comes in - it tells the PCM to monitor the performance of the engine for about 2 minutes, then report a "fail" of the specific cylinder(s) that have a time-to-TDC above a threshold. It also reports other codes, like Intake Air Heater... but I am unsure of the entire list
What is the threshold you say? My experience has shown a sustained PERDEL above 2% will do it - but we're not ready for PERDELs just yet.
The proper procedure for a CCT:
Get the engine up to operating temperature (at least 140 degrees F).
Once things are toasty, turn off all cab heating/cooling.
Put the vehicle in Drive - I am unsure what to say to those with manual transmissions. Maybe idle in 1st gear on level ground will work, but I don't know.
Start the CCT from your scan tool.
Don't touch the throttle, just sit and sip your selected soft drink.
*Optional, but useful* - select Cylinder Rotational Velocity for all 8 cylinders, plus Engine Oil Temperature. Start recording before triggering the CCT, and stop recording within about 30 seconds after the test is done. This will give you a manageable amount of data to view on playback.
When the test is done, you will get "P0269 - Cylinder 3 Injector Circuit Contribution / Balance Fault" (as an example of a fail), or you may only get the common "P0541 - Intake Air Heater A Circuit Low", which is a pass on trucks with the AIH-delete mod. #8 frequently "false-fails" the CCT with the gray CPS, and #3 sometimes false-fails as well. This is when the CRV is helpful.
CRV - Cylinder Rotational Velocity: As mentioned before, the PCM measures the time between each cylinder TDC, and the CRV is a reading you can see/record on the data display with a number value - with zero as ideal. That number value is referred to as a PERDEL (from the teaser above).
PERDEL - PERcent DELta: Any time it takes longer or shorter for a single cylinder to reach TDC than another cylinder, that difference is measured in percent - with 7 to 9 being about max for a dead hole (momentum is a wonderful thing). If you have 100%, that would be something like a hydrolock or a bad CPS... and I doubt you'd concern yourself with looking at rotational velocity in this case (engine won't run). Any number into the double-digits would likely warrant looking at something other than the injectors alone, but I have not seen PERDELs that high yet to verify this theory. I have had dead injectors before, so I do know they read the aforementioned 7 to 9 PERDELs. You'll feel a PERDEL of 3, but it will be subtle at idle. You may or may not feel a PERDEL of 2, but I can feel it - and hear it.
I have recently received a perfect example of a couple of injectors going South, but not quite dead. All the cylinders read at or near zero (not easy to achieve with some of the CPSs), except for the troublemakers.
Please note I set the MAX scale to 10%, this make graphing much easier. AE has a default scale of 100%, and graphing a 5% reading would hardly be noticeable. When looking for a bad hole, you don't want those lines on the graph under 10% to wiggle like worms - you want them to pop like prairie dogs.
Just for comparison - here is the graph from the same truck under the same conditions within a few minutes of the data taken above, except the readings were taken in neutral:
Caveats: A high PERDEL doesn't always mean "pull this injector". I don't yet know for sure what happens when you have a hot stick. An over-fueling stick could possibly make a high PERDEL on the hot one and the subsequent healthy injector - or it may just show a high PERDEL on one or the other. This question may be resolved as more readings and experience are amassed by the brotherhood.
This has been a public service announcement from the Stink-N-Rich research and development team.
Get the engine up to operating temperature (at least 140 degrees F).
Once things are toasty, turn off all cab heating/cooling.
Put the vehicle in Drive - I am unsure what to say to those with manual transmissions. Maybe idle in 1st gear on level ground will work, but I don't know.
Start the CCT from your scan tool.
Tugly...
Where did you get the idea that the engine had to be 140 degrees to run a CCT? The PCED manual only calls for 70 degrees for this test.
Where did you get the idea that the vehicle has to be in gear? The PCED does not have any "put vehicle in drive" type of requirement for the CCT.
I've attached a copy of a GIF image of the Ford PCED manual summarizing the steps for the CCT. I apologize that the image turned out so small.
I have the PC/ED as well, and I've read that. Unfortunately, the real world didn't sync up with the book in this instance - hence my documenting it.
I don't know if this is true with your factory tester, but AE shows no CRV data until about 130 degrees F. While the CCT can work with the lower temperatures, the pass/fail can be deceptive without the PERDELs. CCT can show a cold stick, but then what? You could have the infamous false-fail of #8, or #8 and #3 - but you don't know if that's the CPS or a true fail. In the case above, it looks like the black CPS is in place (one of the few instances where I see a zero PERDEL on #8), and #3 clearly has a problem... with #1 following behind.
One glance at the neutral vs. in-gear graphs above demonstrates where real-world experience carved its own exit off the by-the-book superhighway.
A "cool" CCT can show an injector that's sluggish with cold oil, but that's the only solid purpose I can think of for this particular test. That's not to say I'm not wrong on this... these threads invite very useful feedback and corrections like you have provided.
In the case above, #1 and #3 show a problem. I find it interesting that two cylinders right next to each other in the same head are having issues. Knowing how common the UVCH is the root of all evil in our trucks, that would be my first test. I would use the UVCH link in my signature. I would also try the Buzz test, since a scan tool that does the CCT will likely do the Buzz as well. If that didn't shine a light on the demon's cave, I'd have to go spelunking - pop the valve covers on safari for the bugger.
Are the drain spouts working? Is oil oozing out from under the injector? Is there cackle? How do the pushrods look... do they spin without wobble? Do I need to do the Cody test? How is the injector hold-down bolt torque?
Those are interesting observations. I figured something or someone influenced you to recommend going "off book", and I was curious what it was.
Part of the boredom of stock tuning is that I don't get the opportunity to experience all the problems that might arise from being off book. All the factory tests have worked for me, as per the factory script, using the factory tool, with the original factory black CPS and stock injectors and PCM. Yawn!
If you are interested, I can try to run some tests on a room temperature engine (70-80) degrees. Not sure that my findings will help you any though, as your set up is indeed off book, but I'll be happy to run whatever you ask.
My observations are on stock trucks as well. It just takes enough data samples of various trucks with a variety of problems to learn some of this stuff. Testing a healthy truck may very well be a yawner.
I am curious if you can see CRV on a "cool" truck with your tester.
Tugly, the GIF instruction summary above came from an online 2003 PCED manual, most recently revised by Ford in 2013. I just now checked the original 2000 PCED manual, last revised by Ford in 2000, and found the following sentence in the instructions for conducting a CCT:
"For automatic transmission vehicles, the best results are reached with the Parking Brake set and the transmission in DRIVE."
Thought you would find that of interest. The temperature called for still remains at 70 degrees F minimum.
PERDEL - Percent Delta - here's what Ford's documents explain about it and misfire monitoring:
Low Data Rate System
The LDR Misfire Monitor utilizes a low-data-rate Hall Effect camshaft position (CAMP) sensor signal triggered off a 24-tooth camshaft-timing wheel. One narrow window and an opposing wide window provide sync pulses to the CAMP sensor to indicate camshaft position for correct cylinder timing. The PCM calculates camshaft rotational velocity for each cylinder from this position signal. The acceleration for each cylinder is then calculated into a percentage delta change decrease in velocity for use by the misfire algorithm. The resulting deviant cylinder acceleration values are used in evaluating misfire.
Misfire is defined as a loss of compression. The amount of compression loss in a cylinder that misfire monitor will detect is referenced as a 3/16" or larger hole in a cylinder or valve train component.
Misfire Algorithm Processing
The acceleration that a piston undergoes during a normal firing event is directly related to the amount of torque that a cylinder produces. For misfire determination the CAMP signal is processed at the peak instantaneous inverse velocity angle of 90 [degrees] after top dead center (ATDC) from the previous cylinder-firing event. The calculated inverse velocity of a cylinder under test is compared to the previous cylinder-firing event to establish a percentage delta velocity change decrease. A cylinder with a misfire is identified by a large delta velocity value. When the delta value exceeds the calibrated threshold, the misfire algorithm increments the specific cylinders misfire counter.
The numbers of misfires are counted in a block of 1000 revs. (The misfire counters are not reset if the misfire monitor is temporarily disabled such as an off idle condition, etc.)
To insure accurate misfire calculation and reliable cylinder misfire quantification, misfire data is sampled at engine speeds below 750 RPM. Misfire data becomes unreliable in an operating range outside of the idle region. For this reason other engine operating parameters are monitored to insure misfire operates in a region that yields accurate misfire results. The following table outlines the entry conditions required in order to execute the misfire monitor algorithm.
CRV - Cylinder Rotational Velocity: As mentioned before, the PCM measures the time between each cylinder TDC, and the CRV is a reading you can see/record on the data display with a number value - with zero as ideal. That number value is referred to as a PERDEL (from the teaser above).
PERDEL - PERcent DELay:
Originally Posted by Tugly
I am curious if you can see CRV on a "cool" truck with your tester.
There is no "CRV" test per se on the factory scan tool, nor is the term "CRV" used in the PCED.... so I ran a PERDELs on all 8 cylinders, with EOT and RPM.
With EOT at 75 degrees F, and 700 +/- RPM, in Drive, with the A/C heater off, all 8 PERDELS values maintained 0.0%.
With EOT at 145 degrees F, at 650 +/- RPM, in Drive with the A/C heater off, all 8 PERDELS values maintained 0.0%.
I then drove it to get the EOT to 194 degrees F. While driving, all 8 PERDELS maintained 0.0%. I started getting hot though, as it was 86 F ambient, and I wanted to keep the windows rolled up, so I caved and turned on the A/C. Sorry about that.
During the trip to warm up the engine oil, I locked out overdrive and kept the RPMS above 2100. While idled in drive a stop sign, with EOT now in the 185 degree F territory, and with RPMs between 657 and 711, I saw some PERDEL movement in all 8 cylinders. The percentage deltas deviated continuously during this idle period, with cylinders 2 through 7 not venturing beyond 0.7%.
Cylinders 1 and 8 had peak recorded deltas of 1.4%. While watching the trending in real time, I observed that Cylinder 8 deviated above 1% more often, and higher, than Cylinder 1. As a side note, I have all 8 identical original AD injectors, as my truck was built before Ford began installing AE injectors in Cylinder 8.
This hot idle test should be invalidated because I had the AC on, which may account for the idle cycling deviation between 657 and 711, as the AC clutch cycled on and off. The idle deviations were metronomic on the graph, consistent with AC compressor cycling.
With engine oil at 194 degrees F, my PERDELS were naturally 0.0% while driving, but during a hot idle in drive on the way back home, the truck reported a momentary peak PERDELS in Cylinder #8 of 1.8%, which was the very highest momentary percentage delta recorded of any cylinder during any condition, and that peak disappeared as instantaneously as it appeared. No delta value of any cylinder endured for longer than a millisecond. It was a dynamic jumble of percentage values all well under 1% in cylinders 2 through 7, and under 1.4% in Cylinder 1, and under 1.8% in cylinder 8.
The truck passed the CCT, but I didn't remember your original post carefully enough to try and run the EOT and PERDELS PIDS underneath a CCT. I'm not even sure that is possible with the factory scan tool. The KOER tests are in a different menu tree.
Again, sorry I turned on the AC. If you want, I'll wash the filth off of my windows so I can roll them down, and redo a test in the morning, if it will help the R&S R&D team.
The service manuals I have agree with Pikachu's correction that the acronym "PERDEL" stands for Percentage Delta, not Percentage Delay.
I don't see how perdels could be measured while driving, or have any meaning. It's a measure of variation when all input variables are (theoretically) held constant. Driving ain't that. So I'm thinking the 0.0% result is a default or something. Plus I've never heard of straight zeroes on a perdels, and it seems unlikely. Perhaps the NGS is just saying "nothing to see here Mr. Ford Tech, move along".
CRV is an aftermarket scan tool thing, but the results show up as PERDELs.
As for the PC/ED documentation, sometimes I get lazy and use the later PDF - because it has search capability. When checking the paper copy from 2000, I found the same reference you did. So... Ford says do it in gear, then they omit that instruction later.
I don't see how perdels could be measured while driving, or have any meaning. It's a measure of variation when all input variables are (theoretically) held constant. Driving ain't that. So I'm thinking the 0.0% result is a default or something. Plus I've never heard of straight zeroes on a perdels, and it seems unlikely. Perhaps the NGS is just saying "nothing to see here Mr. Ford Tech, move along".
Just to be clear, the intent was to measure PERDELS at idle, while IN Drive, not while driving. However, the intent also was to measure PERDELS at three different EOTS, which could only be arrived at in a short period of time by driving. And since I had the scan tool hooked up while driving, I reported what it said then too.
0.0% at 75 degrees IN drive, not driving
0.0% at 145 degrees IN drive, not driving
0.0% at all temperatures while driving
Small values as described earlier in post above at 185 degrees
Small values as described earlier in post above at 194 degrees
As for whether or not 0.0% is anomalous to my truck or to the scan tool, I have noticed that most enthusiasts who have AE and are running PERDELS also run tunes or programs of one sort or another, whereas my truck has stock injectors and not just a stock "tune" but a stock PCM with zero "tunes". I'm not sure if that has anything to do with what is considered to be a "normal" finding on the forums or not. In 14 years, I've never encountered a problem with this truck that required running a PERDELS to diagnose it, so this has been interesting.
09-17-2014, 08:27 AM
The temperature called for still remains at 70 degrees F minimum.
