Expert: Ernest (Ernie) Kenward - 6/1/2007

Question
QUESTION: I need to give my truck a tune-up and I want to try to do it myself. i was thinking about getting a tune-up kit off the web and just trudging forward but I not really mechanically inclined. What are some tips you can give me on doing this? Like will I have to set the gaps of the spark plugs and how hard will it be to replace the rotary and cap and do you think I should have the timing checked?

ANSWER: I would definitely encourage anyone to get personally involved in a good preventative maintenance program with his or her own vehicle!  This is the essence of ownership.  As well, there is nothing wrong with "trudging" forward; we learn best from our small steps, and even more from our occasional mistakes.  Having said that, I would not much worry about making too many mistakes with the basic investigative work involved in a tune-up.

I have had a long day, so I will confine my comments to a few starting points for you for the time being, and will be happy to provide further follow-up as you get more into the project.

First, I would recommend that you visit and work to develop a relationship with whatever local general automotive parts house exists in your area.  At the very least, the counter reps are much more likely to make sure you get the right parts or kits than are on-line providers.  

Second, why not pick up the shop manual for your truck, or at least a good guide to, say, tune-up procedures for modern EFI or ECU equipped vehicles.  The OEM manual will have the various specifications for initial timing advance at what RPM, spark plug gap, rate of advance on loading, etc.  I would give you this information myself if I could, but do understand that my own info resources relate to my own Ford cars and trucks (plus my recent Mercedes diesel acquisition), and I have no data on late-model Dodges.  This information will be found in the specifications section of most shop manuals.

Rotors and caps are very simple to replace, as are spark plug harnesses, if needed.  Generally, if the latter look good - jackets clean and undamaged - the leads within probably are good; resistance checking with an inexpensive digital multimeter (DMM) is a good way to be sure that there are no lead open circuits.  Spark plugs generally last quite well in electronically controlled vehicles, but will eventually need to be replaced once the electrodes begin to appear eroded.  Gap setting is easily using a combination gap setting/measuring tool.

Plugs can tell you a lot about the general condition of an engine, and about specific issues with any cylinders should any problems exist.  Generally, a dry and powdery "coffee-coloured" appearance on all plugs is an indicator of an engine that is in good condition and which is in good tune.

Here is one tip: the most common cause of loss of engine performance, roughness in idle, hesitation in acceleration, poor emissions performance (high hydro-carbon HC levels) is usually a very simple problem to fix; these problems most often indicate a manifold vacuum leak, and frequently is caused by a leaky or poorly-fitting vacuum hose or a gasket failure in the intake system.

The more you get involved in this, the more you will able to do and will want to do.  You can pick up helpful tools along the way (dmm, vacuum gauge, timing light, etc) as you go along.

Again, the best start is to introduce yourself to the local parts supply house (aka jobber) and, as well, to check out the books; general guides usually are sold at those shops.

Feel free to ask me more as you get into this.  Enjoy!

Regards ... EGK



---------- FOLLOW-UP ----------

QUESTION: thanks that is some really great advice. I will definitely take it. I'm thinking that beings I work right next door to the public library I will check out the automotive manuals there. How would I go about checking for a manifold, vacuum leak?

Answer
The first thing one should do in checking for a vacuum leak is really just to verify if there is one in the first place.  This is easily done if one has a vacuum test gauge.  Good ones are relatively cheap and are readily available at most jobbers (aka auto parts houses).

Connect the gauge to any available vacuum port.  I can't speak specifically as to the equipment on your Dodge, but can tell you that most engines will be fitted with some form of multiple-tap "tree" fitting on the intake manifold, that being the duct system between the throttle body (whether that is in a carburetor as it is in older vehicles, or in a ported electronic fuel injection (EFI) package as on most vehicles since the mid-eighties) and the intake valves.  Vacuum is drawn in this duct system most of the time, unless the throttle is wide open.  Vacuum is tapped off to provide a fluidic power source for the power brake booster mainly, for emissions controls, and often also to facilitate proportional control of the climate control system.  Usually, there will be a capped-off spare port on that tree, and that will be a good place to connect the vacuum test gauge.

Start the engine and let it warm until it reaches normal operating temperature.  Note the vacuum reading; if the engine is idling smoothly at its normal low-idle speed - about 550 to 600 RPM when the transmission is in N - the reading should be in the range of 18 or 19 inches of mercury (Hg) and up.  If the transmission selector is moved into D, slowing the engine to 500 to 550 RPM, the vacuum may drop also, but not usually below 16 inches Hg.  Those are NORMAL readings, at least at sea-level, and would indicate that there is no steady-state vacuum leak.  This would give the intake manifold and similar gasketed surfaces a clean bill of health.

If the engine idles a bit roughly, the vacuum readings will be lower.  Often, the leak will be at a point where a hose mounts to a hose barb fitting, owing to stretching or splitting of the end of an aging hose.  These can be found (i) by close visual inspection, or (ii) by removing each hose, one at a time, and temporarily plugging the point where it fits to the tree off.  Should the idle improve for the removal of any one hose (once the open port is temporarily capped off), this would be indicative of a leak in that hose or in whatever that hose feeds.  Usually, the problem will be in the hose itself, in which case that hose is simply replaced with vacuum hose of the same correct internal diameter.  Sometimes, the problem will be a defect in the device being driven, a rupture in an actuator diaphragm, in the actuator that might operate the choke or the tempered induction, for example.

It is also possible that a cap might simply have gone missing from an unused portal on the tree!  If so, replacement caps may be bought in packages of several from your auto parts supplier.

Manifold junction leaks can be made visible by spraying a fine mist of water from a Windex bottle or light oil from a can of WD40 along the junction interface.  If a leak is present, the liquid will be seen to quickly be drawn into the gap and out of sight.

On the matter of manuals ... aside from the manufacturer's shop manuals, good general guides are produced by HP publishers, and somewhat passable guides by Haynes.  Both should be available from auto supply houses, and the library may have them too.

Well, it is after midnight here in Vancouver on the West (or Wet) Coast, so I am going into shut down mode for the night.

Carry on and go for it; you are off to a start.

Cheers ... EGK