Dr. Gizmo Automotive Question & Answer Column

 "Dr. Gizmo"
By Phil Arendt
 

Malfunction Codes Indicate Trouble In One Engine Bank

Question 1
My 2000 Ford Expedition idles rough and hesitates on acceleration and the check engine light is on.  I went to a repair shop where a technician did some tests and found codes 156 and 174.  The mechanic said he needs time to determine the cause of the trouble but I needed my truck.

The trouble is constant.  My engine is a 5.4-liter and it has 144,000 miles.  Do you have any idea what causes the symptoms?  K.G.L., email

Answer 1

The codes indicate a problem in one bank of the engine.  Your engine has two banks of valves each serving four cylinders.  Your technician needs to focus on trouble in one bank.

There are many possible causes for the two different malfunction codes.  Troubles range from air leaks in the exhaust or intake systems to dirt on the mass air flow sensor.  Even a clogged fuel injector could cause the trouble.  Additionally, a failing fuel pump, faulty wiring, leaky positive crankcase valve or leaky seal on the oil dipstick could turn on the check engine light and cause the performance issues you describe.

If you are mechanically inclined, check the positive crankcase valve for leaks.  Also, make sure the oil dipstick is properly seated in the tube.  Check for leaks at vacuum hoses and make sure the duct work of the air filter system is secure.  If you find no trouble, it’s time to return to your repair shop.

Looking For Vehicle To Tow Behind RV

Question 2
Recently, I purchased a Class C RV.  Now I’m looking for a car to tow behind the RV on all four wheels.  I’ve heard many automatic transmission cars cannot be towed because the transmission will suffer damage.   

Will any front-wheel-drive manual transmission car be safe to tow behind my RV?  Does the odometer register mileage when being towed?  C.M., email

Answer 2

Congratulations on the new RV.  Not all manual transmission vehicles can be towed with all four wheels on the pavement.  When considering a vehicle, check with the carmaker before making a purchase decision.  Since towing a vehicle with all four wheels on the pavement limits vehicle choice consider dolly towing.  This will greatly increase your choice of vehicles. 

Additionally, no matter how the vehicle trails behind your RV be sure to shield it from chipped paint to a broken windshield.  Optional shielding is available at many RV supply stores that protects towed vehicles from rocks, gravel and road debris that inevitably flings from beneath an RV.

As for mileage registering on the odometer, it will not.  Have fun in your travels!
 
Tests Inconclusive

Question 3
When I shift gears in my 2007 Jeep Wrangler the 3.8-liter engine hesitates or surges.  Once the surging stops the engine runs fine.  There are no warning lights on in the dash.  The engine starts fine.  The gas mileage has not gone down. 

I went to a repair shop where tests did not find any trouble codes.  The mechanic tested the ignition coils and found one a little weak on cylinder three so he suggested replacement might cure the trouble.  It did not.  He also suggested replacing the spark plugs and wires but I did that work myself. 

The problem continues.  Do you have any suggestions?  G.P., email

Answer 3

If tests reveal one particular cylinder misfires more testing on that cylinder might find a faulty fuel injector, low or inconsistent compression, fuel mixture troubles caused by a leaky hose, gasket or seal.  If the misfire is random in several cylinders, fuel mixture trouble might be the cause.  The fuel pump might need replacement.

 

Time For New Spark Plugs

Question 4
My 2010 Jeep Grand Cherokee Laredo with a 3.7 engine and 73,000 miles occasionally stalls at stops.  I called my dealership about the trouble.  A service man suggested tuning the engine but I did not make an appointment to have the work done.  A friend told me that spark plugs last 100,000 miles.

When the engine stalls there is no warning.  No warning lights turn on, the engine does not spit or sputter it just shuts off as though I turned off the ignition.  Up until now I haven’t had a bit of trouble.  I haven’t had to do anything to this vehicle except change the oil and replace brakes and tires.  What do you think causes the trouble?  N.L.D., email

Answer 4

There are many reasons for an engine to stall and weary spark plugs is one possible cause.  According to the manufacture recommended maintenance schedule the spark plugs in your vehicle need replacement every 30,000 miles.  The plugs in your SUV have done more than expected so it’s time to replace them.  The work may just cure the stalling trouble.

Additionally, while your vehicle is at a shop consider a flush of the transmission fluid as that service should have been completed at 60,000 miles.              

Oil Leaks From Distributor

Question 5
There is oil leaking from the distributor in my 1990 Honda Civic.  It’s not real bad but I can see a drip of oil on the lower part of the distributor cap where the cap and distributor meet.  It does not look as though this has been going on too long because there is not oily residue in the area of the distributor.   

The engine runs fine.  Does this mean the distributor needs replacement?  T.N.J., email

Answer 5

It’s possible that the distributor shaft is suffering from excessive wear.  If so, the unit needs replacement.  If excessive wear is not the issue it is likely a leaky seal is the trouble.  It is possible to replace seals but since your vehicle is rolling 20 plus years a new distributor is the likely fix.

 

Foreign Object Impairs Engine Starts

Question 6
Once in a while the 4.4-liter engine in my 2004 BMW 545i will not crank and I can’t remove the key.  The engine starts fine in neutral but when the shifter is in park I have trouble.  Sometimes If I move the shifter back and forth the engine starts in park and the key comes out fine.

More than once I have taken the car to my dealer.  They can’t find any problems.  The car works fine for them.  I also went to a small local repair shop that specializes in foreign car repair.  No problems were found.

Do you have any suggestions?  K.M., email

 

Answer 6

Sure, it’s time to trade for a Smart.  All kidding aside after visiting a professional internet site there may be a need to remove the center console for inspection.  If you store coins in the ashtray it’s possible a few slipped into the transmission shift assembly causing the shifter not to fully go into the park position.  When park is not fully engaged the engine does not start and the key does not come out of the ignition slot.  Removing coins from the shift assembly might be the cure.
 

Thanks for all of your 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 P.O. Box 548, Cary, IL. 60013 or e-mail address mailto:drgizmo@hotmail.com. 05/06/2013 ® DR. GIZMO © 1989 - Present