Testing VVT solenoids

Goodevening,

So recently i got back into fixing cars and a month ago i joined a jaguar and land rover dealership. Last week we had a car in with codes for the exhaust VVT solenoids being bad and with engine light on. The service manager instructed me on changing the solenoids because it's a common problem on the 2 liter petrol engines.

The next day we had a car in for regular service and a customer complaint for non stable engine idle, after reading codes indeed we had codes for VVT solenoids and again instructions were to change solenoids. I changed the solenoids but still it didn't feel good.... The last 8 months i'm looking into doing serious diagnosis and even though the solenoids are like 20 dollar a piece I still wanted to know how to properly diagnose these kind of faultcodes, not all codes just disappear by changing the solenoids. I had a car in 3 months ago from a friend who changed the solenoids and still had a code P0014 it ended up being bad adjusters setting a P0014.

So i found the fault by doing a cam and crank correlation on the engine. To finish up my question how do you quickly and effect test bad solenoids? By scoping cam and crank? Btw scoping cam on these engines are pretty easy to get too but I just need to figure out how to quickly test crankshaft. I know just change the damn solenoids they are cheap, but this keeps "haunting" me for a week on how to quick and effectly test these solenoids. When i changed them, the solenoids had a good resistance value the only thing i could find was the ability to fairly easy push the tiny rod back when energized.

Actually I don't know any code that indicates a VVT solenoid is bad. I do know codes indicating problems with the VVT system.

As with other fault codes as well you'll have to find/invent testing procedure to confirm or discard specific conditions.

With regards to VVT solenoids I find it helpful to confirm circuit conditions, eg. power & grounds, resistance check of the solenoid, current measuring of the component looking for the pintle hump indicating physical movement, looking for the control signal, action/reaction testing thru bidirectional control, if necessary with cam/crank relation. In-cylinder is another possibility, at least In theory. For VVT though it's not high on my list.

I know it flys in the face of the "Test Don't Guess" mantra, but when it comes to intermittent VVT codes, I have gotten to a point where after a few tests, I just have to believe the trouble code and change the solenoid. I have many accumulated hours trying to prove VVT solenoids. They fail intermittent, they fail in stupid positions, they get clogged with debris, then they work fine! They'll ohm to spec, they'll click-clack on the bench and still be junk. Sometimes they'll change the idle when activated, but with a new solenoid the idle will change more drastically. If possible to do quickly, I dont mind moving a solenoid to a different position to see if the code/symptoms will follow.
Most of the time, if the timing is not off right NOW, but a code is set and the oil is full and clean and the circuit checks good, then it's probably going to get a new solenoid in my bay. Usually with an education to the customer about the importance of oil maintenance, and the the complexity of the VVT system. This is the easiest, cheapest, most failure prone part of the system, and if the code does set again in the future, it's only getting more involved and expensive from here. That's just real world auto repair some times.

sean.parmentier wrote:

To finish up my question how do you quickly and effect test bad solenoids?

As for the electrical integrity, any solenoid (voltage and current) can be tested, just as an ignition coil, or fuel injector, is tested. I, sometimes, use a powerprobe to, momentarily, supply power to the solenoids. I compare the voltage spikes. A solenoid that does not spike high enough is a flag.