ChrisM

Hello all, I have a problem I can't figure out. Every once in a while since I have owned my '73 Delta 88, the engine will miss(by "miss", I mean that it sounds and feels like a cylinder or two doesn't fire). Recently, I upgraded my points in the distributor to a Pertronix ignition system, and it misses very frequently now, especially when I step on the gas. My ideas are problems with spark plugs, plug wires, coil, or possibly some sort of grounding short in the ignition wiring. Please help me out, as I am clueless as to how to proceed!

Thanks,
Chris

dar83501

replace your spark plugs first and see if that fixes it, spark plugs are cheap.

J-(Chicago)

and if the electrodes are badly blackened, you are running too rich.

ChrisM

that reminds me...I forgot to mention that the car does smoke a bit, especially when it isn't completely warmed up. There is also a strong exhaust smell as well. If it is running too rich, would that cause it to miss, and how can I adjust the mixture?
Chris

PetChemMan

A slightly rich mixture at idle will smell bad, but won't usually cause misfire at higher speed unless your spark plugs are getting fouled with black, sooty deposits. If they are, you might try leaning out the idle mixture jets , if you have access to them. The car makers started putting hardened steel plugs over the idle jet holes around 1972, and to get to the idle mixture screws you have to remove them. That's best done with the carburetor removed from the engine. A sharp blow with a center punch just below the steel plug, on the base gasket side , will break them out . A sulfur dioxide smell ( rotten eggs) can come from an exhaust catalyst , if your car still has one . Also, be sure your choke isn't adjusted too rich, or staying on too long after the car warms up. If your spark plugs have oil deposits on them, the deposits will look shiny and wet. Those deposits can certainly cause misfire. If the plugs look brown , with little or no black deposits, your misfire probably isn't coming from a fuel probelm, but probably from an ignition problem.
Spark plugs, as pointed out above, are cheap, and a new set of plug wires is also a good idea. Make sure your distributor cap is clean, inside and outside, and isn't getting moisture condensing inside it. Spray it down with WD-40 inside and outside .

Oldsguy

when you converted to the petronix did you wire a full 12 volts to the distributor instead of the lowered voltavge from the stock resistor wire? This may be the cause.

Olds64

Since you just put in the Pertronix ignition kit make sure you do a tune up. You want to set idle, timing, and carb settings any time you change something in the ignition or fuel delivery.

ChrisM

PetChemMan,
Thanks for all of the input. I am not too comfortable with the carb, so I am going to have the carburetor professionally tuned up, so I hope that will straighten out any fuel delivery issues. Will the WD-40 affect the sparking inside the distributor cap?

Oldsguy,
I hooked up the Pertronix kit per the instructions, so I don't really know if the new setup delivers a different voltage to the distributor or not. I could be wrong, but I didn't find a resistor on my coil to tie into.

Olds64,
I set the timing per manufacturers recommendation and changed spark plugs, wires and coil. I am going to get the rest professionally tuned soon.
After setting the correct timing, the engine still missed, and felt sluggish. I advanced the timing a bit past the recommendation and the engine does not miss anymore and is overall much more responsive. Any ideas on why the recommended timing didn't work?

Chris

Oldsguy

Chris, the original wiring has a resistance built into the wire.

PetChemMan

That's interesting that the recommended timing was too retarded , and your engine runs well with advanced timing. Usually, retarded timing will cause sluggish acceleration, but not an engine miss. It may have been a combination of retarded spark and too much fuel at some point that caused the miss. But, if advancing the timing solved your problem, then so be it.
It's possible that your factory timing marks were altered or incorrect for your engine, either on the timing tab orthe harmonic balancer. Your distributor may have been off one tooth on the drive gear, although that makes a very large difference in timing.
Whatever the cause, you can run your timing as advanced as you like, as long as you don't get into detonation ( knock ) on the fuel you use. Listen for knock, and back off your timing in 2 degree increments until the knock disappears. Also, remember that to set the timing correctly, the distributor vacuum advance should be inoperative, which means disconnecting the vacuum hose and plugging the vacuum leak. Some of those engines had "ported" vacuum, which means the vacuum source from the carburetor did not operate while the carburetor throttle plates were nearly closed, as at idle. If that ported vacuum is not operating properly, or the vacuum has been connected to another source, the distributor may be getting vacuum at idle. So, disconnect the vacuum hose anyway while checking the timing. And, be sure the engine rpm is low enough at idle so that the mechanical spark advance isn't coming into play. And, WD-40 inside the distributor cap will cause no problems, although I do avoid spraying it directly onto ignition points. And, the suggestion of Oldsguy to run full voltage to the new distributor is a good one, if the installation directions call for 12 volts and not a reduced voltage.

88 coupe

From my last Pertronix install:



Since you followed the directions, your resistor wire is intact.

Leave it like it is.

As part of the install, you disturbed the mechanical advance. Make sure the spring and weights are intact, and that the mechanism turns smoothly.

18° BTDC at idle, would be a good start, except for the corresponding increase in total advance.

Not a good idea to go much past factory settings without limiting the mechanical advance to about the same as an HEI.

Always beware of the "knock" that you cannot hear.

Some of them?

If an Olds came from the factory with vacuum advance, it was ported. If there were any exceptions, they would have been prior to '49.

Norm

PetChemMan

Ported vacuum for distributor advance was introduced primarily as an exhaust emission control technique, and was rarely found on pre 1971 cars, or on many later cars with catalytic converters, the exceptions being cars sold in California. My '79 Olds doesn't have ported vacuum for the distributor, but uses it for the EGR valve. My '55 and '62 Olds don't use it for the distributor either. As for knock, you will hear destructive knock if you know what to listen for.

88 coupe

Urban Legend.

Olds used direct manifold vacuum, for the first time, in '68. They had been using ported vacuum since their first vacuum advance in 1936. It was not added as part of the emissions system, but because of it, as I explained in posts #11 and#12, at the following link.

https://classicoldsmobile.com/forums...um-switch.html


They are your cars, you can run those hoses any way you care to. As long as you are happy, that is all that matters.


For anyone else, I suggest you consult your Factory Service Manual before changing your vacuum source. Following is an example:




Unless yours is a '49 manual, it will look a bit different but, it will say "above the throttle valve".


Tell us what to listen for, in order to hear inaudible detonation.

Norm

captjim

" Always beware of the "knock" that you cannot hear."

Great advice. There are lots of guys out there with 10.5 to 1 "pump gas" engines that think there is no problem because they can't hear it. The rod bearings (and pistons, if it is real bad) will tell the true tale.