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Mysterious Ignition? Problem

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ObiRichKanobi

ObiRichKanobi

Jedi Knight
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Over the past month, the Spider has developed a rather annoying problem. On a hot day (let's say mid 80s or higher) after driving awhile, it will all of a sudden "cut out" or "miss." This only happens after driving for about 10-15 minutes, and the actual occurrence only happens for a second or two (car never stalls out). After an occurrence, the car will run fine for another 5-10 minutes and then it happens again. I've intitally pegged it as an ignition problem, since if you press on the gas itthe car goes, unlike a fuel problem. I know it's not a small vapor lock, as the fuel lines are pressurized (fuel injected). It usually happens if you've been cruising at a nice intermediate speed (45-60mph) for a few minutes and then LIGHTLY touch the gas.

I thought it was probably similar to the one I had when I first got the car where the coil was shorting out internally when it got hot. However, after swapping the coil and module (Delco ignition), the problem is still there. Next was check the distributor cap and plug wires. Cap had "score marks" on a couple of the contacts, so replaced that. Rotor looked ok...cleaned it off and put it back in. Put on the spare set of plug wires I had. Spark plugs (Bosch Platinums) are new last year and have less than 2000 miles on them. Still happens.

What else can I look at. Other than this, the car runs fine.
 
Well, if it's an ignition problem then the tachometer should reflect that. No idea what sort of injection system you have, so I cannot speak to that. But if your system uses a mass air flow meter with a hot wire or ceramic sensor, then be very sure that there is nothing in front of it floating around. Anything that could have gotten through the air filter, such as a piece of dehydrated moth wing can float around in there blocking flow across the wire and give exactly that effect. I'd also have a hard look at whatever you use for a pressure regulator. It may or may not be electrically controlled, but it will have vacuum control. By opening the throttle more you dump vacuum, and the pressure increases, so it may very well be vapor lock, or simply too low pressure. Good luck.
 
Have you thought about some bad gas? My car is carb'd, but when i had some sputtering, I syphoned out the gas, and tried a new tank. Problem solved. I know this is simple, but mybee worth a try. Fuel filter too.
 
I'd hate to just throw random guesses, but here's what the problem was on my TR when that or similar symptoms occurred on three occassions.

The first was debris in my gas tank. It was so frustrating because I kept thinking it was a defective fuel pump, but the pump worked fine. Gas would spill out, but the problem was a small piece of wood some jerk must have dropped into my tank years back. I wish I could tell you what I went through before a discovered the source of the problem that time.

The second time it was a bad wire from the ignition to the coil. The wire "looked" fine, and it baffled me that it decided to "go out" right after I rebuilt my carbs. Of course, I thought I had messed up the fuel system. The problem was that one little wire. The car shut off, then wouldn't start. I suppose that might also cause "missing." And, by the way, only a continuity tester could convince me that "clean" looking wire was bad.

Third time it was my distributor cap. I kept looking at my old one thinking it was fine, and going on to some other possible problem. To this day I doubt I even could have seen the problem with my cap with the naked eye, but a new cap solved the problem in five minutes--but after I'd tinkered with the car for several hours, getting nowhere in the midst of rush hour traffic.

Whatever it is, Good luck! Let us know.
 
Ok...pulled the plugs, and it seems they were gapped a little wide (.030-.035, supposed to be .025). So cleaned the electrodes and regapped them...will have to take a test ride later. I've uploaded a picture of one of them...can someone take a look at it and tell me what the plugs are telling me? They have between 2000-3000 miles on them. Thanks, and cross your fingers that the plug gaps were the problem.
 

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The plugs should be a nice light tan. The darker the plug the richer the mixuture. You look too rich to me. You might want to install new plugs to get a better reading. Go for a nice long test drive and drift to a stop, then check the color again.
 
Hi,

The plug gap could easily have been the source of the problem, as might many other possible weak links in the ignition system. I've cured similar misses just by installing new plug wires or even just by applying a little dielectric grease on all the connections.

I agree, the plug seems to show a rich condition.

*But*, I have to assume you drove normally, pulled into the garage and shut down the engine. In that case, the plugs will only really tell you about the operating condition at idle at the moment you turned the key off, not much about the "problem" rpms.

So the "drift to a stop" method already suggested is key. Your problems are happening at a higher rpm. The only possible way to get any info from the plugs is to do as suggested, cruise for a a few minutes at the problem speed, turn off the engine and coast to a stop.

Even doing this, info from the plugs is just a clue and can't tell you a great deal. You'd be better getting a portable fuel/air mixture tester or gas analyzer, or having a mechanic who has one take a test ride with you. That's the best way to get really good, detailed info of what's going on with the engine at various rpms, under different loads and in various conditions.

Good luck!

Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
 
[ QUOTE ]
Ok...pulled the plugs, and it seems they were gapped a little wide (.030-.035, supposed to be .025). I've uploaded a picture of one of them...can someone take a look at it and tell me what the plugs are telling me? They have between 2000-3000 miles on them.

[/ QUOTE ]
Can't exactly tell from the blurry pic, but the ground electrode looks "strangely worn". I realize that the Bosch plugs have a somewhat rounded electrode, but this looks more rounded than normal. The gaps should not widen in such a short time. The plugs may be the wrong heat range for your particular engine. It certainly wouldn't hurt to replace the plugs, & maybe use a colder range.
D
 
Shouldn't Bosch Platinums have a little wire electrode extending from that pointy tip of the metal electrode?

I do not see it in the photo. If that electrode is gone that would leave you with a wider gap and a faulty plug... and reducing the gap would not resolve anything.
 
Hi Geo,
The pic looked so odd that I went to the parts store & looked at a new plug.

This particular plug has a tapered inner insulator that goes flush to the electrode tip. I don't know how you compensate for wear of this electrode. Throw away the plug I guess. Maybe they never wear?
D
 
I tried the platinums in the TR simply because I have heard that they are great plugs. I had some trouble with an occasional miss very similar to what you are describing. But mine occured immediately after I installed the first set, so I pulled them out and 2 had cracked internal insulators. Okay, after some heated discussion, the supplier replaced those two.
After about 6 months, (~ 1500 miles) I started to get that errant miss again. Just knowing that nothing could now be wrong with the plugs, I started checking/changing everything else. As the possibile reasons for the errant miss was eliminated, I finally checked the plugs and again, I had an almost invisible crack in one of plugs internal insulator.

That was it! The Bosch plugs went into the trash and I am now using the NGK's. Okay, maybe the Bosch Platinums are as good as they are supposed to be, maybe these came from a 'dropped case', who really knows, I certainly don't!

I will stick with the tried and true - NGK's which have never given me any trouble and are not as expensive.

Just my $0.02 worth...
 
Hi Dugger,
I totally agree. I switched to NGK plugs years ago, never another problem. NGK's have a somewhat wider heat range for a given plug than some of the others, which also helps. Of course, choosing plugs is a bit like choosing wives, everyone has their own preferences.
D
 
True enough.....
 
Sounds like you guys are onto something here.

I hadn't noticed the Bosch Platinums, before you mentioned them. I've had some trouble with them, too.

My best results in nearly all types of cars and motorcycles have been with NGK plugs. Not the exepensive multi-electrode type, just the plain old cheapest variety. (I did run multi-electrode plugs in a couple water-cooled VWs with good success, I forget which brand though.)

Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
 
Well, stopped by Checker Auto today and bought a set of the good old OEM Champion N12Ys today. Will put them in and see if the problem goes away. They are relatively cheap, but if the problem goes away, I can think about getting more expensive ones (or just stay with the cheap ones). Thanks for all the input!
 
I'm not familiar with the TR7 ignition system. Does it use points and condenser? If so try replacing the condenser. Back in the day I saw brand new condensers that were bad right out of the box. I tuned a friend's TR6 one weekend and he came back the next weekend with a problem just like the one you described. I checked all kinds of things but ignored the condenser because I knew it was new.

If you are running an electronic ignition something to keep in mind...
As the temperature of a conductor increases so does the resistance. A marginal component may fail when the temp increases. Are your ground connections clean and grease free? I've seen problems with dirty ground connections during hot weather.
I use Bosche plugs in my modern cars. They work fine. However I believe their heat range is rather high. (based on input from the parts store). Someone mentioned cracked insulators. This could be from too high of a heat range.
 
[ QUOTE ]
I'm not familiar with the TR7 ignition system. Does it use points and condenser?

[/ QUOTE ]

The Delco ignition is electronic...no points. The heat range of the plugs was something that someone else pointed out too. So back to OEM for now...will put them in and go for a ride tomorrow morning when it's cooler (it's 103 outside right now).
 
Dare I declare that the OEM Champion N12Y plugs solved the problem. Have put about 50 miles on the car since swapping them out, today about 20 miles in 90+ heat, and not a single cough, miss, hiccup, or cutout. Thanks again for all the input, and I'll NEVER put Bosch platinum plugs in it again!
 
[ QUOTE ]
Dare I declare that the OEM Champion N12Y plugs solved the problem....

[/ QUOTE ]
It will be interesting to see if this holds up over time; I won't be surprised, though, if you're ok now. I sometimes think I'm in the minority in having always had very good luck with Champions in all my Triumphs and in a few other cars over the years. In fact, the only other brand of plugs that has never given me cause for complaint is AC, which I always used in my '51 Chevy and almost always used in my 1970 Triumph GT6+. Bosch used to be ok in Volvos and Saabs and such and passable in a late, unlamented Subaru.

Oh...I did have a set of SplitFire plugs once. Thankfully they were free from a friend who worked at the time in an auto parts store...because I couldn't wait to get them out of the car and see just how far I could throw them.
 
[ QUOTE ]
...the only other brand of plugs that has never given me cause for complaint is AC...

[/ QUOTE ]

Okay, Andy. Here's a spark plug trivia question for you (or anyone else who wants to take a stab at it)...

What does AC stand for?

Hint: Colorado folks should know this one.

Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
 
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