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Diagnostics of engine miss?

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Tinster

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I was out for a spin today and quickly noticed the engine
stumbled badly at 2300 to 3000 rpm. 2nd and 3rd gear basically.

On the highway I had no trouble doing 70MPH.

Is there a diagnostic method to determine where the specific
cause of engine miss firing originates?

Yes, I have several sets of complete spare ignition systems
but I hate throwing out good components to find the bad one.

Almost everything in my present ignition system has less than
500 miles on them. Except the rebuilt dizzy and the GM alternator
and the points.

Any ideas where and HOW to check individual parts?
Or just bite the bullet and replace everything once again?

OR!! Could a thrust washer have fallen out and this is the beginning of the end of my engine?

thanks,

dale
 
Dale,

Diagnosing a problem like this via the forum is tough, because there are many variables that play a part in this.

Does the engine skip or buck under a load in fourth gear when lugged down?

Does the engine do this only when hot, or does it happen with the choke out?

It sounds like it may have farted some gas (literally) under a load and passed it through. You didn't say if the problem still exists at any other speed, so are we chasing a one time, just happened and went away problem?

Is there anyway that you can round up your posse and have Gardener or Jose go for a ride with you to verify a bit more about it?
 
Tinster said:
I was out for a spin today and quickly noticed the engine
stumbled badly at 2300 to 3000 rpm. 2nd and 3rd gear basically.

On the highway I had no trouble doing 70MPH.

Is there a diagnostic method to determine where the specific
cause of engine miss firing originates?

Yes, I have several sets of complete spare ignition systems
but I hate throwing out good components to find the bad one.

Almost everything in my present ignition system has less than
500 miles on them. Except the rebuilt dizzy and the GM alternator
and the points.

Any ideas where and HOW to check individual parts?
Or just bite the bullet and replace everything once again?

OR!! Could a thrust washer have fallen out and this is the beginning of the end of my engine?

thanks,

dale
Click to expand...

<span style="color: #FF0000"><span style="font-style: italic"><span style="font-weight: bold">Your engine is missing? Better call the police!</span></span></span>
<span style="color: #006600"><span style="font-weight: bold">sorry I couldn't help it!</span></span> :devilgrin:
 
Still waiting for a report on what operational battery voltage, measured at the battery posts, or output terminal on the alternator is....

Wanna see what the max voltage(most modern vom's come with a max reading setting) after it's been run for 30-40 minutes...
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]OR!! Could a thrust washer have fallen out and this is the beginning of the end of my engine?[/QUOTE]

It's more likely that one of the spark plugs that's been taken in and out about 20 times has finally cracked and is arcing.

It just wouldn't be a complete day without mentioning the thrust washers, replacing every part of a system or Pedro, would it?

Round up the posse and drive down to the biker bar. Let's see what the diagnostic team comes up with. Better to have three people actually there looking at it than fifty of us guessing what you've done and haven't done.

If they don't figure it out, and I'll bet they do in about 3 minutes, let's go over it here.
 
RonMacPherson said:
Still waiting for a report on what operational battery voltage, measured at the battery posts, or output terminal on the alternator is....

Wanna see what the max voltage(most modern vom's come with a max reading setting) after it's been run for 30-40 minutes...
Click to expand...

<span style="color: #990000">My bad!

14.6 V at the battery terminals

d</span>
 
Plenty of diagnostic methods but it has to be DOING the "bad thing" in order to FIND it. Systematically, one thing at a time... Oh... it ain't the alternator, BTW.

I like Paul's WAG th' best. Plugs first. Wait 'til dark, raise the bonnet, start th' engine, watch the light show under-hood.... :shocked:
 
I just cured the missing in my Stag. I put an inductive timing light on each plug wire individually, and determined the ones that were missing. I pulled and cleaned all the plugs. Some looked like they might have been fouled from the anti-seize compound on the threads. All of them were gapped to about .032. they are Bosch platinum plugs, but I have the points ignition and standard coil. I re-gapped them to .024, and the missing went away.
With an electronic ignition, and a super coil, the larger gap would have been fine, but the smaller gap fires just fine now.
 
I think I read you replaced the throttle linkage. Be sure the choke is coming all the way off. Just because the dash knob is flush does not mean the choke is off. (it may need re-adjustment). Just a quick and easy check.
 
Why'd ya put anti-seize in th' plug throats?!? :jester:

Funny thing about Bosch plats... some engines LOVE 'em, others won't even start with 'em.

0.032" is the gap I use in this Alfa 1750 with a conventional iggy (points, standard coil) and they seem to run in spite of looking like lumps of coal when removed. If I try 'em in the MGB, it'll run for less than a week and when pulled look FAR better than what is still working in the Alfa. The gap for the MGB ones can be anything (0.025" to 0.032") and the results are always the same.

I've given up and run Champ RCN9YC's in the B. They last a looong time in there. But foul nearly instantly in the Alfa.

I'm now attributing the whole effect to voodoo. :jester:
 
:devilgrin:
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Does the engine skip or buck under a load in fourth gear when lugged down?

Does the engine do this only when hot, or does it happen with the choke out?

It sounds like it may have farted some gas (literally) under a load and passed it through. You didn't say if the problem still exists at any other speed, so are we chasing a one time, just happened and went away problem?[/QUOTE]


Still waiting for the answers to the above three questions......
 
Hey Dale....just a thought.

Could this be related to last weeks vapor lock diagnosis by the PRT team? I thought that you were going to put the custom heat shield that you made back on after that.

Did you ever get it on? Maybe they're related somehow?
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Plenty of diagnostic methods but it has to be DOING the "bad thing" in order to FIND it. Systematically, one thing at a time... Oh... it ain't the alternator, BTW.

I like Paul's WAG th' best. Plugs first. Wait 'til dark, raise the bonnet, start th' engine, watch the light show under-hood....[/QUOTE]

Dale,

How about Doc's suggestion for the "light Show" after dark?

Anything to report on that? Rev it up to the problem rpm range and see what happens.

Let us know.
 
Dale: Was the hesitation at a steady rpm and throttle setting, or during acceleration? If during acceleration, it could be as simple as a low oil level in the carb dampers. Or perhaps in the lovely warm weather there, you might want to try a slightly heavier damper oil.

Tom
 
Brosky said:
Does the engine skip or buck under a load in fourth gear when lugged down?

Does the engine do this only when hot, or does it happen with the choke out?

It sounds like it may have farted some gas (literally) under a load and passed it through. You didn't say if the problem still exists at any other speed, so are we chasing a one time, just happened and went away problem?
Click to expand...

<span style="color: #3333FF">No engine wire sparks in the dark garage.
NOT a vapor lock- I know what THAT feels like.
A constant miss at mid-rpms in 2 and 3rd gear, under mild acceleration
No miss while car is on choke warming up.
Yes the choke closes completely
Plugs look good.

Jesses sent me a gizzmo that tells me the strength of the spark
going to each spark plug wire. I'll use it today.

Then I'll start rebuilding the ignition system again.
Rotor first since they cost so little money.
I;ll take the car out and try to lug down 4th gear and see what happens.

thanks all,

dale </span>
Click to expand...
 
Engine started with some difficulty today.
Carb dashpots filled to perfection
Chokes working just fine

After warmup:

Timing still at 10* advance
Pulled #4 plug - looks brand new

<<<<<<<<<<<<<<<<<<<<<<at 2500 RPM
Put time light pickup on all six wires-#5 looked iffy
Put Jesse's spark plug tool on all 6 plugs-#5 barely sparked
Pulled #5 plug - looked brand new
Pulled #5 wire at dizzy- ooopps, bent connector!
Repaired #5 dizzy connector and got a strong spark.

Will test drive in a bit.
Hoping for the best because we have friends from California,
visiting and they would love a drive to Guavate in AMOS.
Several hour r/t trek from my house up into the mountains.

DALE
 
Gonna rain cats and dogs so a short test drive down the expressway 4 miles r/t.

First two miles I thought I was breaking down.
At 45 to 50 mph the engine was bucking, missing, sputtering, etc. It would not exceed 55 mph.

Made the exit U-turn just as it started to rain. An uphill
entrance ramp. Nothing to lose so I just punched it in first,
to 4000 rpm --in 2nd to 4000rpm and 3500 rpm in 3rd.

Not a miss or a sputter and the car pulled hard.
I made it home.

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<,
Too short a test drive to determine much of anything.
I put together a kit this morning with five complete
ignition system replacements and tools required.

Maybe tomorrow will be a better day for diagnostic test
drive?

dale
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Made the exit U-turn just as it started to rain. An uphill entrance ramp. Nothing to lose so I just punched it in first, to 4000 rpm --in 2nd to 4000rpm and 3500 rpm in 3rd.

Not a miss or a sputter and the car pulled hard.
I made it home.[/QUOTE]

This car needs to be driven. Period.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Too short a test drive to determine much of anything.
I put together a kit this morning with five complete
ignition system replacements and tools required. [/QUOTE]

That is part of the problem. The constant on and off of parts. How do you think the connector got bent? Do yourself and everyone who has tried to help you a favor and just drive it. Mine doesn't run great after sitting for awhile until I take it out and just drive it hard for a bit, then it's fine. We've told you about the starting and running a limited amount in the garage on choke, then pulling plugs, etc., etc., ad naseum and to no avail, but what this car really needs is to be driven daily and not psycho-analyzed every time it hiccups a little bit.

There is no one on this or any other forum that replaces their entire ignition systems every 500 miles. That is a sign of automotive hypochondria at it's max.

Either that or a bad case of "over tinkeritus".

I don't want to sound negative anymore, so I'm pulling out of these threads for good. Good luck. I hope that you work it out.
 
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