My Cutlass has suddenly developed a misfire. It can be heard at idle and also while cruising at low speeds. Above a certain RPM (sorry, no tach...yet), the misfire seems to go away. Sounds like a half miss if you ask me. I recently changed out the spark plugs to the AC 43S because it had the wrong plugs in it when I got the car about 2 months ago (it had the AC 45S plugs in it). The engine has no trouble firing up either cold or hot but power wise, it seems a little down.

I did a little troubleshooting and I had some good parts to try out from a friend. I swapped out the cap, rotor, points, & condenser but it made very little difference. The coil looks old...a little rusty and leaking a little oil. The coil wire is stamped "65" so that's definitely overdue to be replaced. The plugs wires look "ok" and each wire measures about 700-800 ohms but have no brand or date stamping on them. I checked the vacuum advance hose and it's not cracked or clogged. I also looked at the mechanical advance and it looks like it binds up a doesn't return to the the "closed" position unless I push it back with my fingers. It also has a little surface on it which is probably why is hanging up.

I obviously have to do some work to do the ignition system but I was wondering if anyone can help out with any other suggestions or ideas about the misfire.

I plan to replace the points with the PerTronix Ignitor II solid state ignition along with a new PerTronix coil, new cap, rotor & wires. Any other suggestions on these parts?

Thanks.

 

You're running a set of wires from 1965 ?!?

Ummm, no offense, but, Duh, you need new wires.

I'd change the cap and rotor while you're at it, and check to make sure your points are good (I am nervous about replacing older, well-functioning points and condensers with new, Chinese versions).

And, is there REALLY oil leaking out of your coil ?
If so, then change that right away, too.

Worry about the Pertronix once you get the car running right.

- Eric

 

MDchanic...thanks for the reply and no offense taken. I have owned my car for only a couple of months so I am in the very early stages of becoming familiar with it. I had plans of going through everything, including the ignition system, but this misfire has got my attention now.

The points that were in the car looked worn. I replaced those with a good used set...practically brand new...which also had a good condenser built onto it. I wanted to at least try it to see if it would make a difference. As stated in my first post, I also swapped out my cap and rotor with a good slightly used set. The parts I used came out of a car that was running fine.

The Pertronix ignition I was referring to actually takes the place of the points and condenser in the distributor cap. It is solid state electronics so no need to worry about points wearing out or setting the proper gap.

The coil wire is stamped "65" but no stampings on the plug wires. The coil is wet with oil where the coil wire plugs into it.

Any other comments/suggestions are always welcomed.

Thanks.

 

After you get a new set of wires and a new coil on her, make sure your dwell is set to 30*, no higher, no lower. Make sure your plugs are gapped correctly, out of the pkg gap may not be correct. Put a new fuel filter on it. Set your timing to 12* BTDC for a start. And then adjust your idle a/f mixture and speed. Ensure your choke is operating correctly. Look down into the carb and make sure you are not getting big drops of fuel at idle or when you raise the rpm a bit.

Then check your advance, rev the engine to about 3500 RPM, mechanical advance should go up to approx 30-36* BTDC without vacuum, and somewhere around 50* with. It should be smooth as the rpm increases so will the advance.

 

What is this dwell you speak of ? I dont know if you can even get a new dwell meter anymore can you ? I picked up a like new sun tune up kit with tac dwell light but
getting harder to find a shop or to know what that means

 

You can still get a tach and dwell at sears, online, swap meets, etc... There are many shops that still work on older cars!

 

So do you set it while running ? Or ? is it static ? Many speak of setting the timing but the dwell is not as comon or talked about .

 

The only way to be sure the point gap is correct on GM is to attach a dwell meter and adjust points with engine running. There are those that have adjusted them by experience and can tell by how it is running, but those are very experienced GM mechanics. I believe in theory dwell is the amount of degrees they are open, but others here would know the theory better then me. It is a more accurate way and makes up for minor differences in distributor wear.
Do not forget to lube distributor lobes.

 

Thanks I must say I have older brothers that talk about setting the dwell but have not had to do it I have a breakerless ignition in my last two cars and before that it was just a cool buzz word.

 

Yes, while running.

You DO have a Chassis Service Manual, don't you?

- Eric

 

Sounds like the mechanical advance is sticking and applying to much lead at idle. After you've replaced the parts recommended above and have the timing & dwell set and cleaned & lubed the mechanical advance the next thing to check is the amount of vac advance at idle. Too much spark lead at idle will cause a pop/miss out the exhaust. Get an adjustable vac advance can (adjustable travel not adjustable rate) install it and adjust it to give the distributor aprox 10-12 degrees at idle in addition to the base setting.
So set your base timing with the vac can disconnect and plugged off to aprox 10-12*. Have the vac can bring in another 10-12 for a total of 20-22ish at idle. Now with a setback timing light and an RPM meter have the mechanical/centrifugal advance bring in the remaining total advance all in at 2800-3000RPM. For a total of anywhere between 36-42* All this is aprox due to your driving style ambient conditions, above sea level elevation and octane & quality of gas. It’s a matter of trial and error. The general guide above works well for me and I’m running 11:1 at sea level on Sunoco 93 with 104 boost. I do have to back it off some on a real hot day.
The weights and springs can be mixed and matched. Most people think you need to use them in matched sets or automatically go with lighter springs...not so. Use whatever combo it takes to obtain the desired custom spark curve.
There are several companies that will tune your distributor for you. If all this sounds like too much for you send it out. The results will be noticeable; smoother, stronger running engine and may save a few pennies of gas to boot.
A vacuum leak will also cause a pop out the exhaust.

 

This is just a few I have

 

The Motors manual is my bible!

 

In addition to all of the excellent advice everyone has offered, confirm that the firing order is correct. Even if you did not cross any wires it may have been incorrect before you started.

 

Thank you guys for all the advice and comments. I am sure I will be using the information gathered here to my advantage. I will continue to troubleshoot and I will be replacing all of the ignition components. I will report back with my findings.

 

Well I worked on her some more and this is what I did:

1. Freed-up the mechanical advance with a good soaking and cleaning using WD40...everything moves freely now and the weights close once the tension is released on the springs. Although I will replace the springs as they seem a little weak.

2. Cleaned up the lobes on the distributor and gapped the points to .019.

Results: The miss is gone and she seems to be running like before.

Sugar Bear: I verified the firing order of the plug wires and it's correct.

I am a little more at ease now that she's running like she did before. I am going to proceed with replacing the coil, wires, cap, rotor, mech advance springs, & replacing the points with the PerTronix points conversion.

Thanks again for all your replies and help...it all helped!

 

If you haven't already bought the Pertronix gear, go for the Ignitor III. For the Ignitor III (adds multiple spark discharge) and a Flamethrower III coil, I spent maybe $15 more than the II series, and even without a high-rpm engine, there are some minor benefits in combustion efficiency with the MSD.

 

A couple of questions regarding setting base timing:

1. What RPM should the engine be rotating at when setting the base timing?

2. Which notch on the engine block tab do I use to set the base timing? My
car has 3 notches.

Thanks.

 

Base timing should be set at idle, usually 600 to 750, vacuum advance unplugged. As for which notch, clean any grime off the tab and post a picture. If there are no numbers on the tab, usually the shape is enough to tell.

 

Should be the first notch facing the front of the engine on the right. If you clean it you will see a "0".

 

Okay. I know that I am being a complete jerk here, but it looks like someone's got to do it.

1. You never told us the year and model of your car, and the engine type.
   From your posts I am assuming you have a 1965 car with an original engine, but I know nothing more.
2. You posted a photo which includes a Chassis Service Manual from 1969.
   Tune-up specs are different for 1969 and 1965.
   That means you do not have the correct manual.
3. If you did have the correct manual, you would see this on page 5-2, under "Engine Tune-Up:"
   
   
   
   
   
4. For the seven hundred and seventy-seventh time in this forum, you can get the darn manual on line for free from WildAboutCars right here, so why not do that?

Sorry.

- Eric

 

Eric...thanks for your help.

I downloaded the manual from your link so I promise not to be a bother anymore.

A wise man once told me to never be sorry, just be careful.

 

It's a personal obsession of mine - for stock engines, the manual can answer pretty much any possible question better than any of us can, but people constantly ask certain questions over and over again, and then other people give their best answers, which are usually at least good answers, but nobody just looks in the manual.

I think it's because I'm old, and in those dark days before the internet, if you wanted to know anything, you had to actually go out and get a copy of the manual if you didn't want to just guess.

So, I'm sorry for being a jerk.

Also, re-reading my post, I see that I needed to include the actual tune-up specs table, so here it is, just for the sake of completeness:



I hope this helps.

- Eric

 

That was my post with the 69 manual . Not Highcompolds since I was asking about the how too's . Your question seemed to be pointed to me.

 

The one thing I want to bring up regarding the tune-up specs in the manual is they are just a starting point. A generic setting that in most cases, for most engines will work. If you wish to wring out every bit of stock performance from your engine, you need to tweak from there.

If you have modified your engine with distributor, carb, cam, exhaust mods., etc..., the changes in tune can be dramatic.

 

Doh.

Sorry about that.

Guess I should actually read what people write .

- Eric

 

you also want to clean and lube your rubbing block.


bill