Dr. Gizmo Column

“Dr. Gizmo”

By Phil Arendt

Loss Of Magnetic Field 

Question 1

The check engine light turned on in my 2007 Volkswagen Jetta Wolfsburg Edition.  It has a 2.5 engine and 107,000 miles.  The engine was running normally but I took it to a reliable shop that has been servicing it for many years.  They did several tests.  They checked for compression and misfires.  They found one cylinder was misfiring more often than others.  They replaced the fuel injector, spark plug and ignition coil but the mechanic says this cylinder and others still misfire.  He does not know what causes the trouble.  He says I should drive it until it gets worse.  I took the vehicle as is.

I feel the car is running normally but the light is on.  I’ve owned it since it was new and it seems fine.  I do need to get this repaired before a state emission test but for now I’m going to drive it.  Could this be caused by a computer problem?  H.K., email

Answer 1

Maybe, but more probing is needed.  It appears your technician found random misfire codes with one cylinder misfiring more often than others.  He attempted to resolve the issue with the parts he installed but the misfire condition continued. 

At this point it is time for him to think out of the box.  Maybe this will help.  A search of professional web sites found a rare case with similar symptoms.  In this case a technician found a magnetic dead zone on the crankshaft ring.  The crankshaft ring is monitored by a sensor.  The sensor sends a signal to the engine computer.  The engine computer uses the signal to fire the spark plugs.  If the magnetic field on a portion of the ring is lost, the spark plugs will not fire at the proper time.  Perhaps your technician might take this into consideration the next time your wheels roll into his service bay.  If he finds this is the cause of the trouble replacing the ring will cure the issue.

New Pump No Cure

Question 2

The power steering failed in my 2011 Chevrolet Silverado 3500 HD.  It has 142,000 miles.  I went to a shop where they replaced the pump.  This reduced steering effort but now fluid leaks from the cap on the reservoir and the steering is not as easy as it used to be.  My shop replaced the cap but this has not fixed the trouble.  They said they contacted a tech line and were told to check for blockage in the steering gear.  They replaced the gear but the trouble continues.

Do you have any suggestions?  D.L., email

Answer 2

It’s possible the newly installed pump is defective.  It’s also possible lines connected to the pump were not properly installed.  Perhaps the hydro-boost unit in the system has a defective valve.  Since fluid is leaking from the cap, suspicion points toward an issue with the pump or installation of the hoses connected to it.  Ask your shop manager to consider another look at the installation.

Blown Tire Impairs Engine Starts

 Question 3

The right rear tire blew out on my 2014 Dodge Charger R/T.  I limped to the roadside and shut off the engine.  As waited for road service I attempted to start the engine but it did not respond at all.  I had it towed to a shop where the car would not start for them.  They replaced all four tires and performed several tests to determine why it would not start. 

They told me to come to the shop with all my key fobs because they thought there was an issue with the one I gave them.  The car does not respond to either key fob.  The door locks and other functions do not work.  When the start button is pressed to start, the car does nothing.  They checked the car battery and batteries in the fobs.  The batteries are fine.  Now they suggest that I have the car towed to a dealership for further diagnostic work.  Before I do that do you have any suggestions?  R.B., email

Answer 3

It’s time to trade it in for a 2018 Dodge Charger Hellcat.  All kidding aside it appears excessive tire spin wear might be an issue and possibly the cause of this condition.  If so trading your wheels for a 707 horsepower Hellcat will cause more trouble.  Since the no-start problem began with a blow-out at the right rear tire it may behoove a technician to look for damage beyond the wheel house liner.  It’s possible tire debris damaged wiring or components hidden behind the liner.  If there is damage to conductors or components this causes modules to go bonkers.  This could cause the all the trouble.  Repairing a broken or shorted wire might be the cure you seek.

Many Appreciated Thanks

Question 4

Good morning.  As always you have excellent articles.  Recently, I read a question from L.M. about an S10 and another question about a 1997 Dodge that stall after 10 minutes.  I'm going with a failed crankshaft sensor.   Will I see the answers down the line?  D.D., email

Answer 4

The answers accompany the questions.  It indeed is possible that a failed crankshaft sensor is the cause of the stalling engines in both vehicles.  Sometimes we receive an update from a reader.  Often we do receive a thank you that states the diagnosis and repair has cured an issue.  When we do receive a thank you, it is much appreciated and is the main reason for writing this column.

Ticking Sound Ends With Expensive Repair

Question 5

Dear Dr. Gizmo, keep up the great work.  I’m writing in regard to H.M.'s letter in today’s paper about a tapping noise in his 5.3-liter engine.  I too suddenly developed a loud banging tappet noise that proved to be a $3,500 serious problem.  When the problem occurred, I was able to limp into my Chevrolet dealership.  This engine has roller tappets.  Groups of four tappets are incased in a hard plastic-like housing, which guides their up and down movement while riding on the camshaft, holding them at the correct angle so that the roller stays parallel to the cam lobes. Unfortunately, this housing wears out allowing one or more tappets to start to rotate eventually to the point where the roller no longer rolls but starts to slide 90 degrees to the camshaft causing damage to the lifters, valves and camshaft.  I understand that this is not an uncommon problem with this engine.  My 2008 Avalanche was seven years old at the time of this problem with 63,000 miles on it.

I hope this is not the problem with H.M.'s 2008 Silverado.  Do you?  P.G., email

Answer 5

H.M. was concerned about a ticking sound in his truck.  It is possible the 5.3-liter engine is suffering from the same condition.  Let’s hope not.  Ticking sounds are a symptom of several afflictions.  A simple problem such as an excessively worn serpentine belt might exhibit ticking sounds. 

Add-On Damages Engine Computer

Question 6

I have 2004 Chevrolet Silverado 2500 HD with a 6.6-liter engine that I purchased about a year ago.  It has 115,000 miles and is in like new condition.  Recently, I took it for an emissions test.  It failed.

I went to a shop that specializes in GM diesel repairs.  A technician tested the computer and found that his test equipment does not communicate with the truck.  It’s the same problem the emission center was having.  My mechanic proceeded to reprogram the computer but had the same problem.  After some examination he found a tuner device was installed.  He removed it but the computer still did not respond to reprogramming.  Now he says the computer must have a virus or was corrupted by the tuner device.  He says he needs to replace it.  Does this sound right to you?  R.S., email

Answer 6

Congratulations on your recent purchase.  Once this issue is resolved it might roll along for another 200,000 miles or more before the engine needs major repair.

First, some readers might not know what a tuner is.  It’s an aftermarket electronic device that a person adds that alters factory computer programming.  It is intended to enhance engine performance such as fuel economy and horsepower.

As for the trouble, the tuner might have permanently altered the engine control module.  If so, the fix is to remove the tuner and replace the failed module with an original equipment part.

 

Thank you for all the great questions.  Dr. Gizmo can’t wait to answer more.

Phil Arendt is a columnist, consultant and A.S.E.-Certified Master Technician.  Readers may send questions to Dr. Gizmo at his e-mail address drgizmo@drgizmo.ws.  More information is available at http://drgizmo89.blogspot.com  01/22/2018 ® DR. GIZMO © 1989 – Present