TiSA Misfire Help, Toby, Byron et al.

[Preyupy]

Do you know for a fact that it ran well with the 300deg cam and the carburetor jetting you currently have in the car at some point? 

 

You have changed all of the ignition pieces and the misfire happens at exactly the same engine speed load or no load? 

 

Are you sure the tachometer is reading correctly?  You should be able to calculate your engine speed based on MPH. 

 

I have seen electronic tachometers that have internal issues that cause a misfire, try running it with the wire from the coil to the tach disconnected. 

 

Try adjusting the rev limiter as high as it will go or turn it off if possible.  If you are getting some kind of electrical feedback you might be getting some kind of false trigger of the limiter.  If you were still running points I would suspect points bounce and the limiter will trigger early when that happens. 

 

[Mike Self]

Coupla things...

 

1.  Verify that the accelerator linkage is properly adjusted--from the pedal to the carbs.  Have someone floorboard the accelerator pedal (engine off, of course ;-) while you shine a flashlight down the carb throats (both pairs) to insure they butterflies are completely open.  Had a friend with a 59 Caddy that wouldn't go faster than 45 mph 'till we figured this out.

 

2.  Make sure the bakelite terminals on the plug wires are firmly attached to the wires--and that the wires are copper.  

 

Can't help you with suggestions on the 123 dizzy, MSD setup, etc.  My dizzys still have points.

 

Please let us know whatcha find--this sounds like a really good learning experience for all!

 

cheers

mike

[Preyupy]

Most modern rev limiters do not like solid core copper wires. There is some RF feedback and it causes the limiter to trigger early. It is just counting pulses per second and if it sees anything extra it just adds to the count and assumed you are already at your limit even if you aren’t. MSD has had the instructions “No Solid Core Wires” on everything they have made for at least the last 35 years. I run into this at least 10 times a year with someone at the track with a misfire. Disconnect the rev limiter and it goes away, then they want to blame the limiter, put a new one on and you get the same orobkem all over again. 

[andyleonard]

+1 with Preyupy and Mike....get the tach and limiter out of the circuit. Try again . If no change, go for the wires.

[tisalover]

Thanks guys, I've been working on it this weekend.

Have been through all the basics timing, check cam timing marks, fuel flow etc.  At  Jim Gerock's excellent suggestion I ran a second ground wire from the voltage regulator to the battery ground and cleaned up the battery body groundstrap. As I write this I just thought that maybe I need to cleanup the motor to body ground strap on the bell housing. (it is probably the same connection from 1965 at the body) It really seems like an electrical problem, it is confusing that the symptoms remain the same despite changing the usual suspects: distributor and coil. Today I tried a different rotor in the one two three distributor, it is a standard bosch non-rev limiting rotor. No improvement.The plug wires are solid blue magnecore race wires, which I didn't think would be a problem because they worked fine with the old MSD before these problems began.

I will see about swapping out a set of stock plug wires  though, as Byron's suggestion about weird electrical interference goes best with these bizarre symptoms.

As regards the broken valve spring I could not see anything obviously broken with the valve cover off. The cylinder head was redone by Korman, and has their  springs in it with a stock factory 300° camshaft. I guess if it comes down to it I will have to take the valve springs out and inspect them more carefully. I'm very grateful for the freaky electronic suggestions, I will get the alternator tested, however, I note that with all lights on, and running the driving lamps and windshield wipers to stress the system fully the symptoms are unchanged. I have a spare voltage regulator that I can change out, however this one is only  five years old. As regards the tachometer as a problem, it is the original TiSA  tachometer which never had any trouble with the old MSD system. Additionally perplexing that this misfire occurs with both the MSD/old pertronix system, and 123 distributor at the exact same RPM both without load and underload. The MSD ignition had a different rev limiter, I don't know if it works on the exact same principle as the 123 distributor, it probably does. The misfire occurs under load at the same revs in all gears. The throttle, as regards Mike 's suggestion has a beautiful fully adjustable stop on the pedal On it, which I had custom fabricated after a near death (jammed throttle) experience in my 911 several years ago. (I am now fanatical about Setting up Weber carburetors as I also once bent a throttle shaft on the the 911 , causing a carburetor fire. It was Beyond horrible just imagine the melted venturis  sucked down into a motor) It is unchanged, and I built my own cable linkage years back, so I'm confident that this is not a linkage limitation.

As regards a misreading tachometer that is definitely not it, I used to run the car to 7 grand regularly and the  300° camshaft doesn't really take off until you have 4000 on the clock. The Best part of power band is between four and 7000. I will double check plugs, as I write this it occurs to me that bp6es are getting hard to find without the resistor. (i.e. bp6res)  Is it possible that a NGK plug with the resistor in it would throw off the electronic ignition? I may have absentmindedly put the NGK plugs with resistors in without thinking about it just taking some plugs off of my shelf. I will switch plugs and put some old wires on it next I think. For the ignition timing set up on the one two three distributor I researched it here on the FAQ and then added a little more Full advance, at approximately 33° with no detonation.

In summary I will make changing the plug wires, plugs, and Setting the 123 distributor revlimit are at a highest Point and see if that makes any difference. Then disconnect the tachometer wire at the coil. I thank you all very much for helping me think out-of-the-box on this. I will let you know what it finally turns out to be. Electronics have always been a weak point for me.

I'm will say I drove this car since 1988, yes 30 years with just setting the points and the ignition timing and of course no ignition troubles.

Again to paraphrase Voltaire sometimes the "enemy of good is better."

Best regards and thanks again, Peter

[Preyupy]

Those are carbon core wires so I doubt that is the problem. If you turn the engine like you are adjusting the valve lash and at the poin you would be adjusting each valve you can take a flat blade screwdriver and push on the back side of the adjuster. You can compare the opening pressure on each valve this way. A broken spring will be very noticeable. 

[Schnellvintage]

Good morning, I would try replacing the distributor with the original points setup and then work back from there. Sometimes the parts that we assume are perfect, may not be working perfectly. I have never used the 123 dizzy as I have not had a need for it. I have used points, pertronix and crank fire ignition systems without an issue or problem. I’m not saying that the 123 dizzy is bad. Just not had any experience with them. Go back to the basic parts. And see if the problem still presents itself. I am curious about these adjustable switching units (123 distributor).
Matt


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[Hans]

So just to review, things start to go bad over 5000 rpm? Consistently, or at random?

[tisalover]

Hans -Consistently no change in the pattern whatsoever, at anytime. 

 

Thanks Byron for the recommendation on how to check the springs, and also thank you for saving me the trouble of changing the Magnecor plug wires out- they had always worked fine.

 

. Best regards, Peter

[ray_]

Well, I haven't seen it mentioned... so check your fuel pressure and volume also.

 

Edit:  also one of those newfangled inductive pickup timing lights which displays RPM as well could maybe isolate a misfire if you attach is it various plug wires. And the coil wire...

 

Good luck,

Edited April 17, 2018 by ray_

[markmac]

Seems like quite a few folks running these 123 distributors without issue (or at least haven't heard of folks complaining).  Curious as to what the result would be if you took all of it off and put the original distributor back on with coil and points.  We were having a hell of a time dynoing my Schnitzer engine with the new Magnecor suppressed wires.  Had to take them off and use unsuppressed wire, honestly though I don't know how much it had to do with the motor running right or not right and fouling up the data acquisition.  Probably not related to your issue, but .... bluetooth, suppressed wire and....?  more than you want to know about ignition wire below from Magnecor.

 

https://www.magnecor.com/magnecor1/truth.htm

[jireland2002]

This is a very interesting problem.  If it pulls strong under load then it should easily rev with not load.  If the problem is exactly the same under load and no load, I would think it is not fuel delivery.   You have changed the distributor so probably not the distributor.  The suggestion of putting a timing light on each cylinder will provide useful info.  If not fuel, the problem has to be either ignition or internal mechanical.   The timing light should shed some light on this.

[williamggruff]

Peter,

 

You’ve indicated that you changed the distributor and yet the problem remained. Is there any element of the ignition that you haven’t changed out? Cap? Rotor? Coil?

 

One way to test the alternator and regulator is to temporarily disconnect the alternator/regulator and see if the misfire goes away.

[tisalover]

Thanks Jeff, Ray and Mark,

I will go check out the magnecor website now -Great idea Mark .The next plan is  to follow Byron's recommendation for evaluating the valve  Springs, and to put the adjustable timing light back on it. I hadn't thought before about checking on each wire individually this way. I did check fuel pressure, replaced all fuel lines and filters where possible. It still seems that it should rev higher offload  eliminating fuel and even a Single plug wire or single valve Spring/ cylinder as an issue. It would/ should/probably pull higher revs even if it were running as a three cylinder. The car runs quite shockingly strong all the way up to 5100 RPMs. This brings me back to Byrons excellent theory of strange electrical interference,(with premature activation of the 123 rev limiter) given that it acts like it has a Rev limiter versus a Valve Spring issue. It is notable that it demonstrated these exact same symptoms with the pertronic's and MSD system in the car. I may return the old girl to stock points ignition if the valve springs don't turn out to be an issue.

 

Again many thanks, I will let everyone know what this problem turns out to be.

 

Sincerely, Peter

[zinz]

Perform a plug-chop with the engine misfiring (run it up to point it is misfiring and hold it there as long as you can then turn off the ignition)  Pull the plugs and check their color/condition)  Perhaps you can pinpoint the problem to one cylinder...

 

In the case that it MIGHT be fuel related. ...while you are pulling the plugs above, take the tops off the Webers and confirm fuel level is adequate during the times when the misfire is occurring.  

 

You'll find it...hopefully soon.

 

Ed