8th Annual ‘Tips From Techs’: Service Technicians Share Tricks of the Trade
It’s all about information. The more we know, the better job we can do. No one is an expert on everything. That’s where information sharing becomes so critical. Every tech has faced a problem wherein the remedy isn’t easily found in a repair manual. When a specific problem is faced and a technician discovers a fix, sharing that information with others helps those who may be faced with the same challenge. We’re in this together, so let’s help each other out.
LS THRUST BEARING
A customer recently had an LS2 engine rebuilt. He ran it for a few hundred miles. During the first oil change, he noticed copper “dust” in the drained oil. To make a long story short, during the teardown we saw that the thrust bearing (located at the center, number 3 main cap) was badly worn, just on the thrust faces. We determined this was due to improper installation.
When installing new main bearings in an LS engine, initially tighten the main caps to only about 10 ft.-lbs., then use a brass hammer and knock the crankshaft forwards and rearwards several times. This helps to “square” the thrust bearing surfaces to the main cap and main web. Tighten further to about 40 ft.-lbs. and knock the crank back and forth again, and check for ease of crank rotation.
Once the main caps have been fully tightened (using torque plus angle if using OE bolts) or torque only (if using aftermarket bolts), check crank thrust/endplay with a dial indicator. Mount a dial indicator at the front of the crank, on the nose or the front counterweight face.
Using a screwdriver as a pry bar, push the crank full rearward, then zero the dial indicator gauge. Next pry the crank forward using only moderate force. The factory OE specification lists a fairly wide range, from 0.0015-inch to 0.0078-inch. Ideally, crank endplay should be between 0.004-inch to 0.006-inch.
When installing the new main bearings, in addition to applying assembly lube to the upper and lower bearing faces, be sure to lube the front and rear thrust surfaces of the bearing shells, as well.
I don’t know if anyone else has run into this, but we recently serviced a 2015 Kia Soul. The owner complained of a “noise” in the rear. During inspection of the rear disc brakes, one pad had the lining completely gone (metal to metal).
Both rotors were rusted because the pads were so badly stuck in the caliper brackets that they couldn’t move. We had to beat the pads out with a hammer after we removed the brackets from the car. The old pads and even the new pads seemed to be extremely tight in the brackets. We filed the ends of the pad backing plate tabs a bit to free them up for a proper fit.
Universal Undercar Service
UNDERSTANDING FUEL TRIM
This may help new or apprentice technicians who may not be familiar with fuel trim. There are two types of fuel trim, long term and short term, and the numbers are displayed on the scan tool as a percentage of fuel added to or subtracted from the pre-programmed fuel quantity.
Volkswagen calls fuel trim “oxygen sensor adaptation,” and Ford classifies fuel trim as a “continuous monitor” that runs when the fuel control system is in closed loop operation. This shows us that fuel trim is an ongoing calculation based on data reported by the oxygen sensor.
Extra oxygen in the exhaust indicates a lean air/fuel mixture, so the PCM increases injector pulse width to add more fuel (positive fuel trim). Too little oxygen in the exhaust indicates a rich mixture, causing the PCM to reduce injector pulse width (negative fuel trim).
The formula for fuel trim calculation is:
- Fuel mass = air mass x (short term fuel trim x long term fuel trim) divided by (equivalence ratio x 14.64).
Understanding these terms and their relationship will help you understand how to use fuel trim data shown on a scan tool.
Allstar Diagnostics & Repair
If you’re not already familiar with the Ford EcoBoost engine, the use of an electrically controlled thermostat is not the only way that the cooling system can be mapped or controlled for better overall efficiency.
Ford uses an arrangement of control valves to control coolant flow on their 1.6L EcoBoost engines. The idea is to warm up the engine as fast as possible, reduce the internal engine operating friction and in turn lower emissions, and aid in heating the passenger compartment faster.
This engine still uses a conventional wax pellet designed thermostat and thermo-syphon cooling to cool the turbo when the engine is shut off, but fine-tuning of the cooling system incorporates a coolant shutoff solenoid valve, and a coolant bypass solenoid valve. These valves are controlled by the PCM using a low side driver and allow the PCM to calibrate and tailor the coolant flow in four distinct operating modes, or “phases” as Ford calls them.
With an ambient temperature of 60-75 degrees Fahrenheit (16-24 degrees Celsius) or above (this temperature range can be customized by the engineers), both the coolant shutoff and the coolant bypass solenoid valves are closed. The coolant does not circulate in the engine or through any other cooling circuits. This lack of flow significantly reduces the warm-up time of the engine, and reduces start up emissions and lowers fuel economy during warm-up.
With an ambient temperature of 60-75 degrees F (16-24 degrees C) or below (again, this temperature range can be customized by the engineers), the coolant shutoff valve is opened; this allows coolant to circulate through the engine into the heater core, engine oil cooler, transmission oil cooler and around the bottom of the thermostat housing to warm the thermostat.
When the coolant reaches 158 degrees F (70 degrees C) and the engine load is greater than 70% or the engine is revving greater than 4,000 rpm, the coolant bypass solenoid will open. This allows more coolant to flow from the engine to the thermostat housing, increasing the coolant flow through the engine, reducing cooling system pressure and better regulating temperature variations in the engine block.
When the coolant reaches 180 degrees F (82 degrees C) the thermostat will open and allow coolant to flow to the radiator. The PCM can vary the temperature of the coolant coming in contact with the thermostat by using the coolant bypass solenoid. This results in a variable operating temperature zone of between 180 degrees F (82 degrees C) and 198 degrees F (92 degrees C). This allows higher operating temperature during part throttle resulting in increased fuel economy.
Both of these aforementioned solenoids can set trouble codes for circuit diagnostics and electrical faults. The standard thermostat codes P0128 and P0125 can easily be due to a faulty wax pellet thermostat, as well as a low coolant level. As memory serves, Ford did have a recall on some of these engines for a failure of the bypass valve that accidentally allowed the engine to overheat.
CRANK BUT NO-START
When beginning to diagnose a crank-no-start condition, here’s a tip that can help you isolate the problem.
You already know that when a cylinder misfires continuously, the PCM will turn off the dead cylinder’s injector to avoid sending gasoline straight into the catalytic converter. However, it doesn’t remember the misfire, as it discovers the misfire anew each time the engine is started. So the PCM will operate the injector during cranking and for a short period right after start-up until it knows for sure the cylinder isn’t firing.
If you’re watching the injectors on a “scope” and they all operate during the first 200 engine revolutions at start-up, the injectors are OK.
CAMRY SMART KEY
The sixth generation Toyota Camry is the first available with an optional Smart Key system that has an Engine Start button in place of an ignition key.
The Smart Key system adds a major layer of complexity because some engine operations are controlled by what Toyota calls the Main Body ECU (aka Body Control Module or BCM). The fuel pump is still operated by the C/OPN relay, and power for that relay’s contacts still comes from the main EFI relay.
However, power for the C/OPN relay coil comes from a third relay labeled IG2 (ignition 2) that also provides power to the injectors. Power for the IG2 coil comes from the BCM when the Smart Key is detected.
On the Smart Key system, the BCM and the PCM control the starter together. When the Engine Start button is pushed, various on-board control units verify that the correct key has been detected in the vehicle, and then accessory power is turned on by the BCM. When the Start button is pressed with the gear selector in Park or Neutral and the brake pedal depressed, the BCM activates both ignition relays, unlocks the steering and sends a “start” request to the PCM. The PCM will then request a cut in accessory power (from the BCM) while it activates the starter relay. Once engine speed reaches 1,200 rpm, it will release the starter relay and terminate the accessory-cut request.
If the brake light switch or circuit fails, the engine can still be started by pressing the Engine Start button once to turn on accessory power, then pressing it again and holding it for 15 seconds. If there is no fuel in the tank (or if the fuel gauge sending unit fails), the start sequence will not be initiated.
Bobby Y Service
HONDA ELECTRIC POWER STEERING
There are a few known issues on the Fit, Civic and Insight. The steering racks are built lighter and are more compact than hydraulic units, so the rack fits into smaller spaces. Unfortunately, this makes it a bit more susceptible to collision damage.
Since there is no hydraulic fluid, a cracked housing is not always obvious. In fact, Honda techs and collision repair shops have reported that steering rack damage can’t be seen with the rack mounted in the car. Also unfortunately, on most models, the subframe must be removed in order to remove the EPS steering rack.
Fortunately though, the control unit is inside the vehicle, usually under the right side of the dashboard or behind the right kick panel. It can be easily accessed once the trim panels are removed.
Mechanical wear or damage to the rack or motor will usually produce chattering noises or rough steering, often more pronounced when turning one direction. Boost in only one direction also indicates motor or rack problems. However, if these symptoms go away when the motor is disconnected, the rack is probably OK and it’s time to look for fault codes.
Valley Car care
GM CRANKSHAFT POSITION SENSOR (CKP)
A P0336 code on an LS-engine-equipped GM vehicle refers to a problem with the CKP (crankshaft position sensor). The CKP is a two-wire sensor (signal and ground). The sensor features a permanent magnet (or three-wire hall-effect sensor, featuring ground, voltage and signal) mounted in the right rear side of the engine block that aligns with a toothed reluctor wheel that is attached to the crankshaft. As the crank rotates, the reluctor wheel passes by the magnet, generating an AC signal that the ECU uses to identify engine speed.
Depending on the engine design and model, the number of reluctor wheel teeth may vary. In the early LS engines, a 24-tooth reluctor wheel was used, followed by the use of a 58-tooth wheel in later versions.
Keep in mind that even within the same engine family (the GM LS engines are an example), the tooth count will vary, and the tooth count must be matched to the programming in the ECU.
In combination with the camshaft position sensor (CMP), the CKP signals are used by the ECU to manage fuel injection and spark delivery.
A faulty CKP (or CKP circuit) can easily cause an intermittent misfire, which naturally results in what the driver may perceive as a surging effect. A bad CKP can also cause a no-start and intermittent stalling issues.
The root cause may involve a faulty CKP, or in rare cases, damaged or missing teeth on the wheel or metallic contaminants on the teeth. In even more rare cases, the reluctor wheel may have loosened (these are press-fit to the crank).
Naturally, another possibility would be a short or open in the sensor wiring harness. If the wheel loosens and moves out of position (out of phase or crooked), and if this problem is suspected or confirmed, this must be addressed immediately, since a loose reluctor wheel can not only cause misfiring issues, but if severe enough, can also create mechanical damage (block interference or possible piston skirt damage). If, on the rare occasion that a reluctor wheel must be replaced or repositioned, DO NOT attempt this without the specialty tool required to properly register the wheel in-time with the crankshaft. This service is best performed by an engine builder who is familiar with the specific engine type at hand.
If the problem is mechanically severe enough, the easy way out would be to replace the crankshaft with a new crank that already features a properly installed reluctor wheel. The installed phase position of the wheel is critical.
STICKING SPARK KEY
We recently had a 2013 Chevy Spark come into the shop, with the owner complaining that the keyless entry remote is inoperative at times.
We quickly found that this was caused by the ignition key cylinder door sticking in the up position. When this happens, it will disable the keyless remote start and the door lock functions. A chime sounds when the key is out of the ignition and the driver door is open.
The cause was a sticking ignition key cylinder door on the plunger to the micro switch. We used a Lubriplate-type of lubrication spray to lubricate the ignition key cylinder door. Insert the tip of the key in and out to verify that the door of the cylinder is not sticking.
Rogue Valley Service
If you encounter a 2010-2011 Chevy Equinox or GMC Terrain or 2011 Cadillac SRX, where the owner describes an intermittent no-crank concern, the problem may involve the Circuit 6 purple wire going to the starter solenoid not being fully seated, or because of excess plastic flashing on the male terminal of the starter solenoid terminal.
Check the purple wire circuit 6 at the starter solenoid to make sure the connector is fully seated and locked into place. If the connector is fully seated, disconnect the starter solenoid connector and very carefully examine the solenoid connector at the starter to see if there is plastic flashing molded to the male terminal. The plastic flashing acts as insulation and the partially covered terminal prevents good contact to the female terminal. The plastic flashing can be removed with a sharp tool (we used a razor blade). Make sure to check the female terminal tension for the circuit 6 connector because the male terminal with the flashing may have spread the terminal.
Harvest City Car care
PRE-OIL TO AVOID A DISASTER
Once in a while, we have customers who bring their vehicles into the shop with what turns out to be a major engine problem. The cause is commonly a lack of proper maintenance, involving a lack of oil change, running the engine with critically low oil level, engine overheating that resulted in a cracked cylinder head, warped head, warped block deck, or cracked block, or possibly coolant migration into the cylinders that resulted in a hydraulic lock, bending connecting rods and possibly breaking pistons, or a timing belt that failed because it was never changed, with the customer ignoring the owner’s manual recommendation for a belt change at a certain mileage point, resulting in valves crashing into the pistons in an interference-type engine.
There are a number of other potential causes, but you get the drift. Depending on the type and severity of the damage, you may advise the customer that the only practical option, based on both time and money, is to simply replace the engine short block or long block. From a standpoint of time, it’s likely faster to purchase a new or reman engine, as opposed to having the original engine locally rebuilt.
After spending a considerable amount of shop labor time to remove the original engine and to install and complete the assembly of the fresh engine, obviously you want to avoid any problems that could damage the new engine. Several aspects of the job involve proper planning. If the engine is outfitted with a remote engine oil cooler, and if you suspect that debris may have entered the cooler (dirt, grit, bearing particles, sludge, etc.), don’t assume that you can reconnect that cooler. It’s best to replace the cooler and either flush or replace the cooler lines. If contaminants entered the cooler, it will be next to impossible to properly flush the cooler, so don’t even waste your time. Just replace it.
Another thing to consider is engine oil. In my opinion, and in the opinion of most engine builders, you should never start a fresh engine with a full-synthetic oil, because a synthetic oil may be too slippery to allow the piston rings to properly seat in the cylinder bores. Use a petroleum-based engine oil for ring break-in, followed by draining and refilling with the specified oil for that particular engine. If you’re dealing with an older engine that features flat-tappet lifters, it is absolutely imperative to use a break-in oil (or break-in additive) that features a high concentration of ZDDP (zinc phosphate high pressure lubricant) to avoid lifter and camshaft damage. If the stock-type engine features a roller camshaft and roller lifters, the higher concentration of zinc additive isn’t necessary.
Finally, and the most critical aspect, is to pre-oil the fresh engine prior to initial startup. While the new or reman engine should have been assembled with bearings and frictional surfaces coated with a lubricant, the oil circuit is likely empty. While cranking the engine, it will take a while for oil to be pumped from the oil pickup, through the oil pump and into the main and valvetrain oil galleries. This can easily result in momentarily starving main bearings, rod bearings, camshaft bearings, lifters and rocker arms or cam followers. If you’re lucky, no damage will result. If you’re unlucky, there’s the very real possibility of bearing and valvetrain damage, negating all of your hard work to this point.
Play it safe. Always pre-oil any fresh engine before attempting a start. This isn’t difficult. In the “old days” when engines were equipped with a distributor, the common approach was to remove the distributor and to turn the shaft-driven oil pump with a drill in order to allow the oil pump to send pressurized oil into and through the oiling circuits. Since today’s distributorless engines make this approach impossible, simply use an engine pre-oiler canister. This is a metal “pot” that contains a rubber internal bladder. Simply fill the canister with engine oil, and then charge the canister with compressed shop air. This pushes the bladder against the oil. Connect the canister’s hose to the engine, at an oil port (the oil pressure sender port is a common choice). The canister will include a variety of fittings appropriate for today’s popular engines.
By the way, these engine pre-oilers are available in either steel or aluminum. I strongly advise buying an aluminum unit, to avoid the possibility of internal rust scale buildup which can exist when the pot was made, or in the future if the pot sits unused for a long period.
Remove the engine’s spark plugs and valve cover(s) in order to be able to visually observe the rocker arms. With the pressure pot’s hose connected to the engine block, open the canister’s pressure valve. The pressurized oil will then be pushed into the engine. You’ll likely hear gurgling noises as this occurs. Observe the rocker arms. Within a few seconds or as much as a few minutes, you should see oil bring pushed out at the valvetrain. Using a hand wrench, slowly rotate the crankshaft a full 360 degrees. This allows oil to more easily be pushed out of the upper main bearing saddles into the main bearings as the oil holes in the bearings pass by the main oil passages.
At this point, replace the spark plugs, valve covers, etc., remove the pressure pot hose, reinstall the oil pressure sender, and check the oil level in the oil pan sump (since the process of pre-oiling may have overfilled the sump). You’re then ready to fire it up.
By pre-oiling the engine, you avoid the very real threat of a potentially severe dry start.
HUMMER SKID CONTROL
A customer brought in a 2006 Hummer H3 that was experiencing unintended skid control activation intermittently. The customer complaint was that the truck hesitates/quits when pulling away from a stop. She almost got T-boned by a tractor trailer and came in crying.
She first brought it to another shop as well as to the dealer multiple times, with multiple RR speed sensors replaced due to a stored code. I drove this vehicle for 3 days before it acted up.
I had the scope on the RR speed sensor harness (at the EBCM). The 12V power stayed constant but the signal flat lined when this occurred. We found an EBCM flash to correct unintended skid activation after a reverse maneuver while turning. We performed the flash and drove it again, and once again it acted up. Next we swapped speed sensor pins at the EBCM and when it happened again the code switched wheels, verifying the issue was in the RR. When looking in through the speed sensor mounting hole and rotating the axle we verified that the interrupter was intact with no missing teeth. However, I spun the axle fast and something covered the hole for a split second. I pulled the axle shaft and found chunks of rubber from the speed sensor interruptor/reluctor laying in the bottom of the tube and when starting from a stop they would move with the gear lube and cover the hole (see photo). ■
Cunningham’s Automotive Repair