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Automotive/misfire codes showing


QUESTION: 2000 Mercury 3.0 First of all, engine was "scoped" & shows good compression. Started to get loss of power/bad mileage. Light came on code #2 cyl. Did complete tune-up, cleared code, no change. Used fuel additive. no change. Took it to mechanic, paid $175 for ONE fuel injector [parts/labor]. Now it's showing code for cyl #3. I have talked to all the mechanics in town to pick their brains & gotten different answers. Simple things first, what should I do now? for some reason they "stall" when I ask for a diagnosis.

ANSWER: Recent (1990 and since) vehicles are not core to my areas of automotive interest, which is much more in the "legacy" or classic stream, so my answer here will necessarily be brief.

Having said that, I do note that one (only) fuel injector (presumably that for cylinder 2) was replaced by the garage which serviced your car.  Your indication of the history of the car also suggests that the car has generally performed well, until recently, and that the problem was of recent onset.

Revised: Note as well that items such as fuel injectors age more or less equally (have a lifetime that can be specified in some mean number of hours, assuming standard operating temperatures) on an engine (as do spark plugs, for that matter) and so the failure of ONE injector - thus necessitating its replacement - as that mean number of hours approachs really should be taken as a message that others can also be expected to also fail within the reasonably near future.  (An exception to this can occur; power-electronic devices can, on occasion, be subject to what the elex industry often refers to as "infant mortality", where failure can happen long before the device's expected time.  If a relatively new injector (or similar device) fails, replacing that unit as a "one-off" would be reasonable, along with a hard look at the original device's installation, to look for possible excessive temperature in the region where that device is mounted, or for possible excessive or transient voltages at that device.        

Revised: If end-of-life replacement is warranted, then any shop that is of the mind to provide good service to its customers (and who should NOT be of that mind, for that is the cardinal way by which to earn appreciation and lasting customer loyalty) could be expected to recommend that the whole set of aged injectors be replaced with a fresh set at the one and same time, so as to put the problem on aging injectors behind the client, in one visit.  (Spark plugs, after all, have been changed as sets for years, and for a good reason beyond the relatively low price of plugs!)

Now, it may seem that replacing all injectors at once would be "pricey".  However, doing them all at once will (or should) involve one labour charge for the full package.  In general, much is saved in repeated and redundant labour when an engine is accessed and taken down as necessary to remove-and-replace several parts at once, rather than when it must be subject to the same re-and-re process several times, as would be the case if items which should be replaced as a set were replaced one each visit.  (One could not really imagine this for spark plugs, after all!)

As you can imagine, and should expect, the cost of repeated re-and-re labour can be much higher than the cost of the time-saving labour to do the whole task once only, saving a number of otherwise redundant steps.

There are some operators who might tell you that they are "saving you money" by replacing ONLY that item which failed; after all, the purchase price will be for one item, ie: injector only.  This will be less than the total for four, six or eight injectors of course, however, the "per-unit" or single-package price of many such parts which would be applied in quantity  would generally be higher on that one only) basis than they would be as a collective package of all units needed for your engine.

Too, an operator offering such a deal probably would not discuss the higher per-unit labour charge for replacing one injector only (at a time) versus what should be a competitive price for the replacement and setup of all at once.  The individual who replaces these one-at-a-time (very!) likely is counting on getting those further individual labour charges to do the second, and maybe even the third, before suggesting to the owner that he/she can do the owner a "favour" by doing all the rest, to end that problem.  As you have noted, there are those who "for some reason (will) "stall" when you ask for a diagnosis."

* * *

If you are looking for a good shop, you might try asking fleet operators such as some taxi companies, or taxi owners, delivery-truck fleet operators where they get their work done.  

Too, if you have a good relationship with an automotive parts supplier or jobber, ask that supplier the same question.

Hope this helps!  Best wishes ... EGK

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

QUESTION: That's interesting. it makes me think i'm being taken advantage of $$$. I just wonder why I can't get a diagnosis; that's what i really need. I might not need the injectors replaced, just have them cleaned. Shouldn't that be the first step? That will cost me only $100. Does cleaning the injectors really help, or is it just a "band-aid"?  i bought a manual because I'm getting frustrated with the mechanics in my area. I want to test first, which is what they should have done and then discussed it with me.  I enjoy reading how things work, thanks! I also like to find out what my options are, and of course the simple things first. PS I always ask for the old part.

While cleaning some assemblies (called by some "solvent rebuilds"!) can restore or at least improve performance, fuel systems which get a lot of "through-put", that is, the car is driven enough to use fuel so that the tank does have to be refilled reasonably regularly, one to three times a month being fairly typical, then the fuel (gasoline, in this case) in the system at any time could be expected to be reasonably fresh, and not inclined to break down.  That, plus being sure to replace the one or more fuel filters in the system on a regular basis (at least one a year is good practice), should obviate or at least limit the need for specific cleaning of the injectors.  There are also tank-additive cleaning agents which may aid in keeping the a system clean, however fresh clean fuel which is regularly refreshed by refills on a car which is driven regularly probably is the best and simplest approach.

At this point - with a sixteen-year-old car - clean fuel may be academic.  Injectors are robust, but do not last forever.  Gasoline injectors do operate in a hot environment, just upstream of the intake valves for each cylinder, although nowhere near as hot an environment as faced by Diesel injectors, which must overcome both heat and and near-peak pressures in order to inject their fuel charge directly into the cylinder (direct injection) or into a pre-combustion region (indirect injection) - this is why Diesel injectors must provide for excess fuel into the injector, so that excess fuel oil - over and above that needed for the combustion charge not needed for combustion - can leave the injector via a fuel-return line back to the  tank, to carry away the heat.

In my experience, the life-limiting concern for electrically-operated magnetic devices such as gasoline injectors would be the solenoid coil that activates the valve in the injector to enable the fuel (pressurised by an electric fuel pump at the tank) to be injected into the cylinder.  The tank pump, in this application, provides for fuel flow and injection pressure both.  The cylinder pressures within a gasoline (Otto-cycle) engine are much less than they are in a compression-ignition engine, such as a Diesel.

The solenoid comprises a wire winding, usually copper, around or within a ferromagnetic core, the latter being needed to concentrate the flux from the energised coil so that sufficient force can be produced when the coil is energised to be able to do the job at hand, in this case, open the valve.

That coil wire is insulated, and that is where the eventual problem can develop.  Electrical insulation generally is based on organic material (thermoplastics, for example, are carbon-based) which (like most everything else, alas) ages. As it happens, aging is accelerated by heating; as operating temperature rises, the material will age more quickly, and ultimately begin to fail more quickly. (There are some based on inorganic material as well, mica being a good example - unfortunately, even if the ravages of heat are less of an issue with it, the ravages of vibration stress are an issue - mica cracks, much as did also the kapton insulation used on many airliners (the ill-fated flight 800 747 of 1996 having been one).

Coupled with the aging of organic insulation, accelerated by temperature rise, that causes insulation to break down, is the simple physical fact that the copper conductors in a coil will expand with heating to a greater extent than will the iron or similar ferromagnetic material of the magnetic core - copper has a greater coefficient of expansion that does iron.  This means that, as temperature rises, the copper conductors will swell to a greater extent than does the core upon which it is mounted.  That will have the effect of squeezing the insulation, which can then open cracks, and lead to electrical faults.

This is a well-understood problem with coil windings in electrical power equipment, and is the reason for carrying out a program of regular insulation testing on industrial and transit motors and on utility transformers.  (Reference IEEE-43, IEEE-43-2000)

For you, if the car is in generally in good shape and you wish to keep it, this is as good a time as any to carry out some preventative actions - ie: fix those items that are inclined to break before they do.  Scheduled and pre-emptive procedures generally assure a long life!

Buying the car's shop manual was a "best" step, especially if it is the manufacturer's manual.  There are quite good ones by general automotive publishers, but many of these can have errors - even those said to be based "on a complete teardown".  If in doubt, check.  Many shops have subscriptions to Mitchell's Online manuals - a helpful mechanic could check into questionable data for you.

Sorry for the delay in getting back to you - I have had a number of things on my plate.    

Best regards ... EGK  


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Ernest (Ernie) Kenward


The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!


A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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