Asemaster is correct about the wet plug tip and lack of spark but it wasn’t because of one of the coil packs.
The lack of spark was due to a stone dead No. 3 plug wire in spite of what the resistance reading was and it’s not the first time I’ve ever run across this. That wire had died as quickly as a light switch can be flipped and would not pass even the tiniest of sparks.
The wire looked new, had zero corrosion or rust on the terminals, and maintained the same resistance no matter how it was flexed and the ends twisted in an effort to determine if there was a break inside the wire.
Just for hoots, I transferred that wire to another car (also OBD II) and the miss followed that wire with the second car also not illuminating the CEL or setting any codes in spite of running like garbage.
The point here being that a miss this severe should have shown up with the CEL and code being set on both cars and in theory anyway, the VOM showed the wire to be fine.
Interesting. You’d think it would que up a misfire DTC straight away as a stored code anyway. Maybe it has to occur for a certain amount of time before it turn on the CEL or even stores a code. I’ve had problems with spark plug wires ohming out ok but not working on the car, usually if I wiggle the wire a little it will start running better, which provides a clue. Never happened on my Corolla but on my Ford truck and VW Rabbit I had that happen. I switched my Ford truck to copper wires for that reason.
I know you were working at home and not at the shop/store/garage (or are you retired now?) but wouldn’t that have shown up on an ignition trace with a scope or graphing multimeter and secondary kv probe? How would you have gone about testing if you had access to all your tools and equipment? Or could you (did you) have just started pulling plug wires (or injector wires) one by one until you found the dead hole?
I so very rarely measure resistance anymore, I prefer to test components in action in their working environment. But I (and you) have stuff the average guy out there doesn’t.
As for the no-code part, well, we’ve been there before, and every car was that way before 1996.
I had one 4 cylinder car missing to the point that the car would barely move, bucking, smoke etc. The CEL never came on. Looked at the plugs and 3 of them didn’t even have a tip left. So not having a CEL with misfires does not surprise me. I guess it is about tolerances.
Great brainteaser. It proves to the doubtful that malfunctions that should throw codes can occur without doing so. It also confirms that going back to basics is always the best place to start, as well as confirming the value of “reading” sparkplugs.
Now, about that SAAB vacuum/carburator problem. Did you ever solve that one?
By the way, thanks for noticing. It’s humbling to be remembered.
"I switched my Ford truck to copper wires for that reason."
I did that to my VW when I was in school. That really played havoc with my radio reception. I’d hate to see what it would do to a modern car’s electronics.
@asemaster, semi-retired but being somewhat of a gearhead I can’t let it go. I do have several code readers (one is OBDI, irrelevant) and a scan tool for OBD II. Neither one showed a problem nor did the CEL ever illuminate on that car or the guinea pig car I transferred the wire to as a test.
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Granted, I probably could have pulled wires but I’ve never been keen on that method no matter the car type. When that problem started as I backed out of the drive my wife said “bad gas” and my response was no, it feels like a plug or plug wire died; it’s just a matter of sorting out which cylinder was the problem child. It wasn’t that big a deal really once the intake ducting and the EGR and variable intake runner solenoids were removed. I was looking for an excuse to run a compression test anyway.
There was also no signs of arcing on the wire either and probably due to the spark never making it to the plug well. There were no signs of arcing on the coil terminals either, go figure.
No matter, it runs like a sewing machine now.
Mountainbike, I never did get that SAAB issue resolved and it’s the only one that I can say stumped me. It involved a CIS injection issue and to this day I can’t figure it out. I know the injectors are not spraying due to the air sensor plate not lifting in the airflow but as to why it’s not lifting I cannot determine.
The only reason for the plate not to lift would be a vacuum leak, sticking plunger in the fuel distributor, or incorrect system pressures in the upper and lower chambers of the fuel distributor and none of that is the case. I have the specialized fuel pressure tester so pressures are not an issue.
Suction will flatten my hand against the throttle body but very little suction is felt after 4 feet of intake tract at the air cleaner and the air cleaner is where the sensor plate is located… Logic would dictate there’s a leak in the intake tract but it’s a simple layout that has been removed and carefully inspected for cracks. Even a smoke test showed there’s no problem and the turbocharger impeller spins freely with the sensor plate being properly centered…
“semi-retired but being somewhat of a gearhead I can’t let it go.”
Well when you like what you do…
I have a Snap-on clip on KV probe, it’s just an inductive probe with a dial labeled 0-30KV. Put the probe on the wire, turn the dial until the light blinks regularly and that’s your KV at that point. Crude and inaccurate but good help for finding an open wire, fouled plug, etc. Not nearly as good as a labscope but tons quicker when you know it’s an ignition problem, and it sounds like you knew right away it wasn’t bad gas. That sure gets used a lot. My car won’t start, must be bad gas. Idles rough, bad gas. Check engine light, bad gas. Flat tire, bad gas. If people only knew how hard it was to get bad gas.
I’ve worked on a few of those DOHC engines in the fwd Continentals. Blech. Fun to drive, but to work on…
You’re bringing back some unpleasant memories for me
When I was at the Benz dealer, there weren’t any mechanics who actually enjoyed working on the CIS systems
For the life of me, I could never figure out why some manufacturers stuck with CIS as long as they did. Amazingly, I heard that some other manufacturers had it even longer than that.
Benz stuck with it through 1993 (the 190E was the last holdout), but EFI had been out for years by then.
Apparently GM thought the CIS system was pretty good, because they copied several aspects of it when they came out with CPI, CSFI, etc. At least those vehicles were easier to diagnose, because you could actually hook up a scanner and do some bidirectional testing. Unlike CIS, with their BS blink codes, on-off ratio, CO tower with the check ball, etc.
There’s a website (forget the name though) about CIS and the person running the forum states that CIS is the greatest thing since sliced bread. It’s also stated that the fuel filter is changed regularly it’s a system that is trouble free and never needs to be touched for any reason…
Drugs or alcohol; it has to be one or both…
I have somewhat of a question for asemaster or db4690 or ? and freely admit that I’m a bit oldschool with some things.
With my Lincoln I didn’t really even need to pull codes because I knew from the get-go it was a single dead cylinder with no other issues involved and when the No. 3 plug was removed I was utterly confident that there was really no need to even pull the remaining 5 plugs.
My question is this. How do you explain the vast number of people who have their vehicles into a shop for poor running with repeated scans, small fortunes invested in replacing this, that, or the other, and still suffering the same problems with or without a CEL and even on near new cars?
Granted, there is no doubt some incompetence here and there but I cannot believe that incompetence is applicable to so many mechanics and shops. There is a countless number of threads on this forum alone in which someone has had their vehicle into the shop X number of times with no improvement, etc.
There’s even the current Lemon TDI thread which resulted in a buyback and this kind of gets to my point about a scan possibly not providing an answer to a problem.
ok4450, I wouldn’t say incompetence so much as that it seems (from my own limited experience as a car owner/shade tree mechanic, and from reading threads here) that there seems to be a lack of interest and/or ability on the part of too many mechanics to systematically diagnose problems. We read so many times about mechanics throwing parts at a problem, or apparently not doing basic diagnostics that would quickly narrow down the problem. What’s the deal with that? Do auto repair schools not emphasize diagnostics enough? Or do some mechanics bypass systematic schooling and just “learn on the job” from others who may not be thoroughly versed in diagnostics themselves?
My favorite book on this subject is Zen And The Art of Motorcycle Maintenance. The author has a technical background and experience troubleshooting his 1965 Honda Super Hawk. He talks alot about the imoortance of the scientific method: making accurate observations, forming hypotheses, and testing each hypothesis systematically. If every mechanic worked as methodically, there would be a lot less guessing, wasted time and wasted money.
For example, it astounds me how many times I read here about mechanics installing new catalytic converters just because the CEL sets with a “bad cat” code, when most times it’s likely due to a bad O2 sensor that the mechanic doesn’t bother to check.
You are a pro, whereas I’m not, so perhaps you have a different perspective. But, from the other side of the wrench, it does seem to me that too few mechanics do thorough systematic diagnostics before throwing parts at the problem.
I feel there is a pretty big void in the average technician when it comes to diagnosing electrical problems. Which is getting more and more important in today’s cars. Just understanding how basic DC circuits work and proper trouble shooting techniques would go a long way in making a better tech.
In 1953, when I was in 7th grade, I started reading “Tales from the Model Garage” a running feature in Popular Science magazine. I was the first one to our small school’s library to grab the magazine. The proprietor of the Model Garage, Gus Wilson, would find the problem with a car where lesser mechanics failed. The reasoning that Gus used in solving automotive problems taught me a lot about solving problems in all kinds of settings. When I taught courses in computer assembly languages, I helped students debug their projects. I equated finding the problems in their program to the following: 1) if the program won’t assemble, look for a syntax error. This is equivalent to a car not starting because it won’t turn over. This is usually simple–power isn’t getting to the starter motor usually due to a dead battery. 2) program assembles, but will not execute. This is the situation analogous to an automobile that cranks, but the engine doesn’t fire up. Solving the problem is similar to finding out what is causing the auto engine not to run. One of the ingredients of fuel, spark, or compression is missing. 3) program executes, but the results are wrong. This is similar to an engine that runs, but doesn’t run properly. This takes more trouble shooting skills. The point is that solving a problem in a piece of software is not unlike solving problem with an automobile engine.
One thing I think would help students become better problem solvers would be to have them do more application problems (i.e. word problems) in mathematics courses. When I taught calculus, I assigned the word problems. The students always groaned, but it paid dividends in really grasping an understanding of calculus. In a ten week term, my students completed two more chapters than students in classes where the word problems weren’t assigned. One of my colleagues in the applied technology department made the statement “If one can’t apply mathematics, one doesn’t know mathematics”.
With that said, ok4450 stumped me with his puzzler. I guessed that it was one cylinder that wasn’t getting ignition, but I had the cause as a defective spark plug and not the spark plug wire.
Re CIS. My prior car, a late 70’s VW Rabbit had CIS fuel injection, J-tronic I think it was called, port injection with electric fuel pump but not electronic. The problem was the sensitivity to dirty fuel. Any dirt or sand in the fuel would clog up the fuel metering valve. The symptom would be the car would just gradually lose power, and eventually wouldn’t run at all. I’d get one bad tank of gas, and that was enough to do it in. Even if the dirt in the gas was just gradually accumulating, proactively replacing the fuel filter – an idea that would seem like it would work and I tried – wasn’t as effective as you’d think, because doing the replacement seemed —for a reason I was never able to explain – to introduce dirt into the system that wasn’t there before, and that would quickly lodge in the metering valve. Replacing the fuel filter was an almost sure way to end up with a clogged metering valve within a week.
