next to it so that
other techs can validate the tip. When we get enough techs
agreeing with the tip, it will become permanent. As this section takes shape, we will index it based on year, make, model and system. It will become a TSB list by technicians, for technicians. As the list grows, we will add search capabilities to it so that you can find answers fast.
If you have a diagnosis
or fix for a problem that you have seen in your shop more
than once, send it to us at tips@shoptrac.com and we will post it with a next to it so that
other techs can validate the tip. When we get enough techs
agreeing with the tip, it will become permanent.
If you can validate a tip or have any other comments or suggestions, let us know at tips@shoptrac.com.
Practical Service Bulletins
You will notice that we have titled this column "practical service bulletins", this is because as an independent repair shop technician, I am tired of reading in trade publications, the bulletin about the rattle in the 1996 Jeep Wrangler. This is a car that I probably will not see in my shop until the warranty expires which could be 2 to 4 years from now. In this column and in future issues I hope to inform you of manufacturers bulletins concerning problems that you see in your shop on a frequent basis.
When is a bad timing belt NOT a
bad timing belt?
We all know the symptoms
of a bad timing belt or chain. Crank the engine and it
spins as if there is no compression. Verify by taking a
compression test where you find little or no compression on any
cylinder. Not much else it could be, right? Wrong!
We found these symptoms on a 93 Infinity Q45 with less than
50,000 miles. This engine has two timing chains, one for each
bank. If one of them were bad, it would still have compression on
half the engine, right? So what else could cause these symptoms?
Did you ever hear of a condition known as Cylinder Wash?
This occurs when too much fuel gets into the cylinders for some
reason and causes the compression rings to lose their seal. I
have seen this problem on two Q45's and have heard about it on an
88 Honda Prelude!
To test for and also correct this problem, take a vacuum hose and
connect one end to a vacuum source on the engine and put the
other end in a can of oil or transmission fluid, crank the engine
and let it suck up some oil. If the problem is Cylinder Wash,
then the oil will create a temporary seal and allow the car to
start (you should probably do this outside because your shop will
fill with smoke). Once the engine is running, the compression
rings should re-seat themselves and make you a hero.
Let us know if you encounter this condition and the type of car
at tips@shoptrac.com.
Cadillac reports that on 85-92 De Villes and Fleetwoods and 86-92 Eldorados and Sevilles, intermittent miss/surge, backfire, loss of power, black smoke, detonation or dieseling, can be addressed by service bulletin T92-76. These conditions may be caused by a poor engine ground or a poor sheet metal ground. The remedy would require the cleaning of all grounds and the use of cadmium plated fasteners. The new cadmium plated fasteners provide a superior path and will inhibit corrosion. Star washers should not be used with these new fasteners.
Also from Cadillac, ECM/PCM damage due to incorrect "tap-testing" procedures. This bulletin affects all models using ECM/PCM'S. Cadillac has found physical damage to ECM/PCM'S due to over aggressive "tapping" by technicians. When "tap testing" parts for intermittent failure diagnosis, it should be done with the tip of your fingers lightly. Some technicians have been using their fists or even small hammers. These computer parts are very fragile and too much shock can cause immediate failure.
Some 1988 Chrysler products may set an intermittent code 22- Coolant Temperature Sensor. Refer to Chrysler bulletin 18-03-89, which says that all coolant sensor checks should be run and if no problems are detected, replace the coolant temperature sensor connector as outlined in the service bulletin. You will have to order from Chrysler a connector PN 4414901 and heat shrink tubing PN 4400683.
To check for pinging on 1984 and up Honda Accords, Honda suggests another timing method, which allows you to verify the condition of the advance diaphragms. First warm-up the engine, connect a timing light, disconnect vacuum hoses from advance diaphragms, the inside hose should have vacuum and the outside hose should not. Plug hoses, timing should be 3 degrees BTDC, reconnect the inside hose, timing should advance to the red mark. Connect a vacuum pump to the outside diaphragm and apply vacuum, the timing should advance an additional 4-6 degrees. Remove the vacuum pump from the outside hose and reconnect the outside hose. Now set the timing to the specs given in the service manual. Here's what you have just done; you've verified the condition of both vacuum advance diaphragms and the advance mechanism. and you have set the timing accurately.
