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Engine Tune-Up 2003

Is the tune-up dead? Do we still need to tune-up our cars and engines? The answer in a word is YES!
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The Battery
Today's vehicles place a heavy load on the battery. They have a constant drain on them by PCMs with keep-alive memories, radio memories and other such devices with adaptive learning strategies. This makes clean, corrosion free battery terminals very important. Even a slight corrosion film on a top or side post battery terminal can cause a memory to be lost or cause a charging problem.

On a top post battery, remove the terminal and with a wire brush clean the post until it is just shiny and scratchy. Do the same to the battery terminal on the cable end. If the battery post is too far gone, you will need to replace the battery. If the battery cable terminal is too far gone, you can get a replacement battery cable. Yeah, I know they sell replacement terminals, but I only use them as a last resort. Most times they only allow a corrosion problem to return with a vengeance.

On a side post battery wire brush the face of the battery and cable terminal until it is shiny, scratchy clean. When you reattach the terminals make sure it goes on straight and not cross-threaded. Also don't tighten the terminals too tight. You will rip the connections inside the battery apart. There is a reason why that big terminal has such a small hex head on it.

Then wash the battery and keep it clean. Dirt and oil on the top of the battery will cause a parasitic drain that reduces battery life. When everything is clean and tight, a coating of white lithium grease or spray battery terminal protector will keep the terminals from corroding again. If you have a can of spray paint in the garage, use that. The idea is to keep air from getting to the lead. Don't forget to get the underside of the terminal, between the terminal and the battery.

Where To Get Service Information
When you perform any diagnostics it's not much good to get, say, a voltage reading if you don't know what the correct reading is supposed to be. And testing has become an exact science. Diagnostics have to be performed in a certain order or the test results you get could very well be meaningless. So you need to find the latest factory diagnostic sequences and specifications.

Some vehicle manufacturers have web sites with this service information, and you'll be able to access the data on a daily, weekly, monthly or annual basis.

But, as my Grandfather used to say, there is no such thing as a free lunch. There is a charge for this information. At present, Ford Motor's information is available for $9.95 for a 72-hour access period at Motorcraft Technical Resources.

GM offers a similar program at their ACDelco Tech Connect web site. Or you can get a low-cost subscription from Alldata DIY. In addition; AutoZone offers free scan tool connections and readouts at its stores when you have a lit MIL.

A great place to get service information for free is your local Public Library. The Reference Section has all the different service and repair manuals from Chilton, Haynes, Motor and many others. If they don't have the one you need, ask at the Reference Desk and they will get it from the main branch.

Many public libraries subscribe to online services like Alldata and Mitchell On Demand and can print out the information you need.

Under Hood Checks
The best way to start a tune-up on today's engines is to access any codes that may be stored in the Powertrain Control Module (PCM) with a code reader or scan tool. Just because the Malfunction Indicator Lamp (MIL), such as a Check Engine Light, Service Engine Soon or Power Loss light, is not on doesn't mean there are no malfunctions found or codes stored.

The MIL only comes on when a malfunction occurs that directly effects emissions and on the systems it was designed to check. Most Diagnostic Trouble Codes (DTC) will only show up with a code reader or scan tool. In addition, it is not uncommon for many "No Code" problems to arise.

If there is a DTC, you should check the whole circuit to locate the problem. If you get a DTC "P0185 Fuel Temperature Sensor B Circuit Malfunction" don't assume it means a bad Fuel Temperature Sensor. While eight times out of ten it is, there is a 20% chance it is a burnt wire or bad connector terminal. While it's not too bad to gamble with a $20.00 part, it is an entirely different matter when a $900.00 distributor is indicated.

Another thing to be careful of is mis-interpreting a DTC. A DTC of "P1130 Heated O2 Sensor (HO2S) 11 At Adaptive Limit" may sound like a bad HO2S, but what it's really saying is "Hey, I've corrected as much as I can. This problem's worse than I can compensate for." So you need to look for a problem in the fuel delivery system because the HO2S is doing its job correctly and replacing it is just throwing $100.00 out the window. It's like your wife telling you your car is on fire and you go out and get a new wife.

Okay, so you checked for DTCs and there were none. Now what do you do? The first tool to use is your eyes. Look under the hood for damaged or disconnected vacuum lines, loose or dirty connections, cracks in the large air intake hoses or a loose, burnt or disconnected ignition wire.

You can still do some basic checks of the engine controls and sensors. If you engine has timing marks, you can check the ignition timing with a timing light to see if it is within specifications. Always refer to the under hood emissions label for the proper procedure for checking ignition timing. If there are no timing marks, you can use a scan tool to check the ignition timing.

Set your scan tool to Timing Check and read the timing. Gradually open the throttle to about mid-range and look for a smooth, steady increase in ignition timing. If it is not smooth and steady, it may indicate a loose timing belt or timing chain.

If the timing is good, you can check the Throttle Position Sensor (TPS) and Mass Airflow Sensor (MAF). These, too, should show a smooth, steady increase as the throttle is increased. If there are any voltage spikes or dips, the sensor is bad. You can also tap the TPS and MAF to see if there are any voltage spikes shown on the scan tool or hiccups. If there are, then the sensor is bad.

Another common problem is the Coolant Temperature Sensor (CTS). With the engine cold use the scan tool to see what temperature it is reporting. It should be within four or five degrees of ambient air temperature. Now start the engine and watch the temperature reading. It should climb smoothly and steadily up to normal engine operating temperature, usually in the 190° to 230° range. The Manifold Absolute Pressure (MAP) sensor would be the next thing to look at. Disconnect the vacuum line from the MAP sensor and hook up a hand vacuum pump. Now slowly apply vacuum to the MAP sensor.

• When manifold pressure is low (high vacuum), sensor output voltage is low, under 1 volt.
• When manifold pressure is high (low vacuum), sensor output voltage is high, 4.5 volts.

Again, it should show a smooth, steady increase in the voltage readings.

Okay, now you've checked all these things and you still can't find a problem. The next thing to do is to locate and expose the PCM. In some vehicles it's located under the dashboard behind the glove compartment. In others it's under the hood. But most often it is located behind the right hand kick panel.

Once you have it out, and with someone slowly increasing engine rpm, tap the PCM and see if there is any effect on the engine. Also move the wires going into the PCM back and forth. If there is an effect on the engine, you have a bad wire and/or connection at the PCM.

» Part 1       » Part 2       » Part 3

Additional Information provided courtesy of and Warranty Direct
© 2000-2007 Vincent T. Ciulla

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