HOW BOUTS…Since this is a 4.6L Ford Modular V8…The plastic intake manifold has begun to leak and is now leaking coolant down into the spark plug wells…where the coil over plug system exists. When this occurs the spark grounds out in the spark plug well and this issue is OUTSIDE the engines monitoring system since it is not the coils fault…If a coil fails to fire you will get a DTC…If coolant is inside the plug hole…no DTC will post.
The issue occurs for a while until the engine gets hot enuf and then suddenly goes away when it can evap some of the liquid/dry off the junction of coil over plug etc…let it sit for a while…and more coolant seeps back into the plug holes.
Ive repaired this issue on so many 4.6L V8 its silly…the first time I encountered it…there were no codes at ALL…and then I went about poking around…In my instance it was rather easy for me to figure out…I was however surprised that no code would post… But it makes sense to me now
CRAP/Coolant down in the plug well causing the ignition system to randomly short to ground…but since the coils ARE firing…they post no DTC…she runs like crap and has serious miss issues…it also affects the plug TIP color due to not firing the plug while fuel is still being supplied…the plug will appear fouled. Those damn 4.6L PLASTIC intakes are a ticking timebomb…
Oh I see the answer…I didnt think the 4.6 HAD plug wires…it doesnt in the mustang or town car…why would they go backwards like that.
Interestingly enuf however…my guess is the same thing as a bad wire…which doesnt throw a code…you would think it would…
If I knew this motor HAD wires I wouldve said dead wire…its the same exact thought process I was using for a shorted to ground coil over plug system…same exact failure mode…
Damn I wish I knew it had wires…I wouldve WON the GRAND PRIZE HERE…LOL
Now that I hear the issue…SURE…goes hand in hand with what I was trying to postulate with my shorted to ground coil over plug system…I learned the hard way that this failure does NOT throw a code…and you need to go back to basics and drop all the computer diagnostics.
Im still confused why this vehicle is using wires instead of the coil over plug
@Honda Blackbird “Oh I see the answer…I didnt think the 4.6 HAD plug wires…it doesnt in the mustang or town car…why would they go backwards like that.”
None of the 4.6 had coil on plug until about '99 or so. For the first 7 or 8 years they used 2 coil packs and wires that were ridiculously long. Also ok4450’s 4.6 isn’t the same as Town Car, Mustang, T-bird, etc. He has the DOHC.
“.3 or .2 hours to find a problem…riight…you can’t drive the car around the block and get it hooked up in your stall in .2.” @asemaster–I think the money should be in correctly diagnosing a problem. Instead of depending on computers to do the diagnosis and the mechanic changing the parts, let’s pay the mechanic to do the diagnosis with the help of modern computer equipment and have robots change the parts. Some surgical procedures on humans are done by robots. My point is that there should be good compensation for diagnosing a problem. This is the skill that separates the mechanics from the parts changers.
Years ago, my parents bought a color television. They had it less than a month and the picture went haywire. The set was on warranty, so they took it back to the dealer. He replaced some integrated circuit chip in the automatic gain control circuit. The set was fine for another month and the same thing happened. The dealer sent the set back to the distributor where an engineer looked at the set. He replaced the same module and the results were the same. The set operated properly for only a month. The set went back to the dealer whose technician replaced the same module. The same thing happened, but by this time the 90 day warranty was up. While my parents were on vacation, I took the set to a trusted independent technician I knew. This technician called me when he had repaired the set. When I went to get the set, he had changed the same module. I remarked that that was the fourth module that had gone out. He said, “Let me keep the set and maybe I can figure out why this is happening”. A couple of days later, he called me and had the set repaired. “I hate to charge you additional money, but I got to the root of the problem. A fifty cent resistor was bad and let too much voltage through the circuit. That ultimately caused the module to fail”. I gladly paid him an additional $27 because he spent an afternoon chasing down the problem. The set was then good for 20 years.
I am certainly willing to pay a diagnostic charge that gets to the root of a problem.
Here is an example from computer science that illustrates the difference between diagnosing a problem and just changing code which is similar to just throwing parts at an automotive problem. Some 35 years ago, I was teaching a course on computer programming in BASIC to graduate students who needed to learn about computers and programming, but were not computer science or math majors. One female student, who was very attractive, came in about 15 minutes before the class and her computer program executed, but the results were wrong. I had her log into the mainframe computer we used in those days and brought up her program. I didn’t see the problem right away, but said I would look at it after my classes. One of our graduate assistants, who liked to impress the women with his knowledge, said that he would look at the program. The student and I went on to class. I had three hour night class that followed the class the student with the programming problem was taking, so I didn’t return to the office until close to 10:00 p.m. He said he had just finished up fixing her program. When he told me what code lines he had changed, I said that his changes couldn’t have made the difference. I then replaced his new lines of code with the original lines and the program still worked. I then asked him what else he had done. It turned out that while he was logged in under the student’s login ID, the time limit was exceeded when there was no activity. He then completed re-entered all the code under his own login ID. The program then worked. The graduate assistant said that after his changes, he had entered exactly the same code. I printed out his version of the program and compared it to the student’s version. It was almost identical. However, there was one variable name that was different. The student used a variable name she called “NTOT”. However, at one point, she spelled it “NT0T”. If you look closely, the first time the third character is an “O” while in the next call to the variable, the third character is a zero, thus naming a new variable. Now had the graduate assistant done some thinking, he should have known to look at the variables as opposed to just changing code. He inadvertently made the program work correctly, but it took him about 5 hours where, with a little thinking, he should have found the problem in less than half an hour.
@Triedaq said:
“I think the money should be in correctly diagnosing a problem.”
“I am certainly willing to pay a diagnostic charge that gets to the root of a problem.”
You sir are correct. Alas, it seems you may also be in the minority. In some of the examples from above, a dealership mechanic my be paid .3 hours to diagnose the cause of a check engine light. But the labor manual may show that he will be paid .6 hours to replace the oxygen sensor that is at fault.
The “free code scan” has become so widespread that people now seem to expect it. And they also seem to think that the fault code tells exactly what is wrong with the car. You and I (and many others here) know that that is simply not the case, but the public in general does not.
I am a State Authorized Emissions Specialist. I often get people come to me after failing an emissions test, showing me the inspection report and asking me how much it will cost to fix. I tell them the standard diagnostic fee for an emissions failure is $90 plus tax. They will respond “I just got the report, it says right here ‘P0401–Insuffucient EGR flow’ I’m not going to pay you to tell me the same thing. I just want it fixed.” These people would never think of asking for a dental exam for free or a plumber not charging for a service call. People seem to be willing to pay $45 for a cooling system pressure test and diagnosis but nothing for a check engine light. As often as I see this it still never makes sense to me.
Honda Blackbird, the DOHC engines do not seem prone to intake problems (thankfully) and the Marks did not use COPs until 1997. Some Mark owners have done a COP conversion just to clean up the engine bay and get rid of the spaghetti mess of ignition wires.
@asemaster, let me put the scenario this way. I’m Ms. Smith, know nothing about cars, and had my lousy running Lincoln towed to you for repair. Your diagnosis after a scan was a bad plug wire on No. 3. I tell you to go ahead with the pricy wire replacement. So the questions.
Once the 3 wire is removed are you going to visually check it and test it with a VOM off the car?
If that wire looks and checks as new will you install the set of new wires and call it good while being 100% certain that 3 wire is totally dead and no other problems exist?
Or will you at some point during the process call me later and state that any or all below will be needed?
A. Spark plugs
B. Coil pack due to the misfire on No. 3
C. Intake manifold due to a runner crack.
D. Fuel injector peeing off which killed the plug and then the wire; along with the coil pack.
E. Head gasket due to coolant seeping into a cylinder and killing the plug. See above.
For what it’s worth, I’ve never been one to claim that a numerical code is the answer to any problem. I’ve always stated that it’s a starting point for diagnosis although the CEL should get the ball rolling.
My diagnosis would involve a scan of all data, not just the generic data provided on a code reader and would also involve testing the fuel injection, ignition system primary and secondary circuits, checking coil current draw waveform for irregularities, concentrating on the coil that fires #3 cylinder. After all, I’ve got the scope out already to diag the ignition wire. Current ramping the coil would take, what, another 3 minutes at most? Any abnormalities would have me recommend replacing the coil in addition to the following:
Without any other service history of the car, I would recommend replacing plug wires, all spark plugs (not just #3) with the labor to be included with the plug wire change. Coolant in the plug well would show evidence when I pull the spark plug. A leaky injector will not cause plus wire failure, so I won’t even go there. Following the ignition service the car would be warmed up and driven for 4 miles to verify proper operation. Only then will the “odometer surfing begin”. “Mrs Smith, your car runs quite well now. I see you have 92,000 miles on your car now. Ford recommends new counterbalance muffler bearings and fresh turn signal fluid as part of a 90,000 mile service. We can do that today for $1.29.”
I would not check the wire on the bench. It has been tested and proven functional or not while operating on the car. I don’t do resistance checks on wires of any kind, I get more info testing in its working environment. But that’s what works for me. What works for you is great. Getting the car fixed is what matters. Lots of roads lead to the same place.
BTW, what I was getting at earlier is that code or not the misfire diagnosis stay the same. The procedure for finding and fixing a misfire on a 94 is the same as a 96. Forget about misfire codes, check spark, check fuel/vacuum, check mechanical.
Hydro-locked while it was parked for two hours due to fuel or water entering one or more cylinders, thus damaging those cylinders upon second start-up?
There are no issues with coolant or oil in the plug wells nor is hydrolock to any degree a problem.
@asemaster, I totally agree that when it comes to a plug or wire replacement it means an entire set; none of that piecemealing business.
If you look at a voltage spike on the scope then how do you determine if it’s the wire’s fault or if it’s the spark plug? The scope patterns I’ve always seen translated to one and the same for the most part.
I do respectfully disagree that a fuel injector won’t kill a plug wire. Lousy injector kills to some degree the spark plug which then kills the wire and then potentially the coil. Just basing that observation on personal experience with that particular problem and often exacerbated by the driver motoring on with a poorly running engine.
Don’t get me wrong on diagnostics. I’m a firm believer in verifying as close to 100% as possible the cause of a problem rather than random stabbing at it but the fact remains that countless vehicles of every single make every single day are given a clean bill of health after going through a scan, or multiple scans by very experienced mechanics; both at dealerships and independents. To me, that doesn’t mean the techs are incompetent; at least for the most part.
To be honest, guessing at something or worse, sorting out someone else’s guesswork, just pxxxxx me off to no end.
The lingering question for me is why the CEL did not illuminate or flash (yes, it’s operative) on that Lincoln or why the 96 Chevy that I transferred that wire over to did not illuminate the CEL either although the Chevy ran like garbage with that wire in place.
The only reason I did the wire swap is because the Chevy was there and 1 of the 6 wires on it is very easily accessed.
@ok4450, depending on what kind of scope trace you’re looking at…a trained eye using a screen capture that you can scroll and zoom in on, you can tell the difference between the spark happening in the combustion chamber or outside of it. You can watch the firing line and calculate burn time and use the ignition pattern to find a restricted injector in one cylinder. Of course some of this is academic and just for fun, sometimes I’ll be playing with the labscope on an ignition system and one of the guys will see me staring at a screen for 20 minutes and come over and say “Just put wires on it, I can see the bad one from here.”
I may be getting lazy but my goal is to diagnose engine problems without actually removing any parts. I want to be able to look at a scope pattern, like a manifold vacuum waveform and be able to tell what condition the piston rings are in. I’m getting there…
As far as the lingering question, well, I don’t have an answer. I don’t think there is an easy one. Just the other day I was checking a GM product for something or other and decided to watch live misfire data. No codes on this car, yet I could watch #2 misfire intermittently maybe 3-4 times per minute. I think manufacturers have some leeway in how they log and record misfires. Some cars only record misfires in closed loop, some only while driving.
And remember, a misfire code can only be set and the check engine light can only be turned on if the fault is severe enough that it can damage the engine or catalyst or cause the tailpipe emissions to rise to 1.5 times the federal standard.
“And remember, a misfire code can only be set and the check engine light can only be turned on if the fault is severe enough that it can damage the engine or catalyst or cause the tailpipe emissions to rise to 1.5 times the federal standard.”
Which leads me to ask these questions:
Which sensor tells the computer there’s a misfire?
Why can’t a misfire code be set at a lower threshold, before possible engine/cat damage? I’d rather know about a misfire before it’s severe enough to cause damage.
"1. Which sensor tells the computer there’s a misfire?"
If only it were that simple. The federal government has no business telling people how to build engine controls, that’s up to carmaker. There is no misfire sensor, every carmaker can use any method it wants to monitor misfires as long as the end result meets the criteria above. Generally speaking the computer looks at the crankshaft sensor; a misfiring cylinder will cause a momentary slowing of the crankshaft since it is not contributing power to the engine. It’s up to the computer to determine if it was a misfire. Many late model cars with coil on plug ignition systems also monitor ignition primary signals to determine if the coil fired. Also misfire detection is generally disabled on wide open throttle, during ABS operation or events, and at certain other times. Every manufacturer has a different strategy, and none are foolproof. I once replaced an alternator for a misfire code. The bearing was seizing, jerking the belt (and therefore the crankshaft) enough that the ECM thought is was seeing a misfire.
"2. Why can’t a misfire code be set at a lower threshold, before possible engine/cat damage?"
Because then we’d be complaining about having to take our cars to the dealer all the time because that light is on again. No engine runs with absolutely no misfires. While starting, while running wide open 85mph uphill, while suddenly decelerating, while driving over a washboard road with 1/16th of a tank of gas, etc.
Remember, OBD2 is an emissions control device, not a diagnostic aid for mechanics or drivers. It has very little to do with cars and the maintenance and repair thereof. The primary goal is cleaner air.
Well, I learn something new here almost every day. I didn’t know OBD2 was only for emissions control.
Which means that 99% of the driving public probably doesn’t know that either, unfortunately.
