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1979 Phaeton Coupe part-throttle detonation problem

Started by Benzilla, March 18, 2013, 04:05:41 AM

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Benzilla

Since this is my first topic on this board, I'll take a moment to say hi! I have a '79 Coupe DeVille Phaeton, and '90 Brougham d'Elegance which I've owned for 7 & 8 years, respectively. I've been an avid member over at CadillacForums.com for several years, and recently discovered this forum through a link to a thread. When it comes to classic Cadillacs, I'm a purest, right down to correct width of whitewalls.  ::)

My Phaeton has had an ongoing problem of pinging, that I've been trying to figure out for ages. Maybe someone here can shed some light on something I've possibly overlooked.  It only pings once it's heated up to full operating temp, and even then seems to do it only at will. Over the course of a road trip, it might ping under medium throttle for a while, and then it can subside completely, only to return later in the trip, without the car having even been turned off. At first I just ran 93 octane to try & keep the ping away, but that has minimal effect, even with added octane boost. Timing was re-adjusted to factory (23 DBTDC @ 1600 rpm); new distributor base, rotor, cap, spark plugs, wires, ignition coil; SeaFoam treatment through carburetor; EGR valve checked for correct operation, removed, cleaned, re-installed.

This was originally a California car that I'm basically federalizing over time. The replacement distributor is a standard 4-pin module, to eliminate the California ESS box.

All vacuum routing & condition has been checked, with only the following modifications: EGR running directly to carburetor port vacuum with no line to charcoal canister, TVS bypassed. Vacuum canister running off of manifold vacuum, like a federal car. I recently discovered that before I bought the car, someone bypassed the TVS for the EFE valve (separate from EGR TVS in '79), effectively giving it constant vacuum with no shut off when the engine heats up! Ouch! To remedy this, I just bypassed the whole EFE system, and the heavy fuel usage monitor system, which communicated with the ESS box, and will not be missed! lol

The distributor replacement was the latest big change. I've considered the thought of a worn / stretched timing chain, but the timing mark on harmonic balancer is pretty steady under a timing light, and it exhibits no other symptoms. Is it correct to assume that if it was the timing chain, it would be more of a static problem? As a side note, the engine amazingly has 231,188 mi at the time of writing this

Very excited to get to know the members here!
Thanks,

cadillacmike68

Hmmm.  I had a similar problem in my 1968. Too much advance. I still have the problem, but being 7,000 miles from home, the car isn't getting used, just going around the block once a week.

read this and I recommend the crane cams adjustable vacuum advance. For HEI, I think it's it's part # 99600-1. It is widely available.

http://www.460ford.com/forum/showthread.php?t=117504

Regards,
"Cadillac" Mike

R Schroeder

#2
Ben ,
There are a couple of things that hit me right away, and they all have to do with the mileage on the car.
One is if the previous owner had direct vacuum to the heat riser all that time, this would cause the engine to run hot, because your routing the exhaust through the intake all the time. Hence the pinging.
Now I know you said you found this out when you bought the car, BUT, my thought would be that the heat riser could be stuck in the closed position, because it had been held shut all those years.
Two with the mileage that is on the car, you could have a plugged catalytic converter. These converters were not the best because the pellets inside would plug up. If this happens your holding back exhaust, hence running hot.
Three there are different distributors for these engines. See chart in pictures.
You stated this was a California car, so it would have a California carb on it, which I believe runs leaner than the Fed carb. My 78 has the Fed carb on it. 17058230.
  The distributor that runs with the Fed carb is marked in the chart below. It is the one used in my car. It is also the one that has the most advance of all of them. California distributors only advance to about 10 degrees . Mine will go as far as 29 degrees ,depending on the vacuum at the time. The California distributor is right under mine , on the chart.
So, you could be running a lean carb, and a distributor that advances it to much.
Yes the vacuum advance is suppose to retard spark under load , but it may not be retarding it enough.
To help, you may want to unplug the vacuum advance and idle it way down, and take a timing light reading on it , to see where it runs when this is disconnected. I believe mine is at 5 degrees before TDC. You could try setting it at O, to see if it helps.
Four, your cooling system could be plugging up too. Radiator might need a flushing. Ports in the heads could be closing up. Water pump not putting out enough ......etc
Five the use of high octane fuel in a low compression engine will cause carbon build up. Everyone seems to think this is helping an engine to use high octane fuel in a car to clean it out, or stop pinging. Does just the opposite , it carbons it up, and the carbon can ignite the fuel prematurely.
I did answer your previous posting on the vacuum lines too.

http://forums.cadillaclasalleclub.org/index.php?topic=120786.msg227654#msg227654

I think you lost your purists classifacation ,with the changes you made. Your now a semi-mod guy.............ha. I will give you credit for the white walls though.
Anyway, you can update your answer, and we will go from there.
Roy

Click on picture to make bigger.

R Schroeder

#3
I am assuming you also have the set back timing light .
Checking the car without one is near impossible with the higher advance readings , if your checking the advance at 1600 rpm's.

The other gizzmo that is nice to own is the temperature gun. They give instant readings. Good for checking radiator temps side to side of radiator .
You also could use it on the exhaust to check temp differences on inlet and outlet on converter. You will only be able to check this as it warms up, because the temp gun cuts out at 600 degrees , but it will show if there is a big difference while it warms up. Could give you a hint if the converter is plugged.
Big use would be to check the manifold temps in different spots. Would be hotter if the heat riser were stuck shut, near the center of manifold.

Dave Shepherd

#4
Make sure the egr valve is working this is the most common cause of the described condition. Apply vacuum to it make sure it lifts, also could be the egr passages are blocked up. 

TJ Hopland

I really can't imagine that kind of miles on a original plastic timing set so it must have been replaced at some point in its life.

Your valves could look like this, pulled apart more than one Cad motor with valves like this one.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

R Schroeder

Wow T.J.
Thats the worst valve I have ever seen. What was the guy burning in there , coal dust ?
Roy

Dave Shepherd

Seen it before, not quite that bad though, stop and start driving in Brooklyn, NY for 15 years..  LOL

Benzilla

#8
Thanks everyone! This gives me a lot to absorb & contemplate. In light of advice given, I should add a couple of things:

I wondered about the EFE being stuck open, but it does seem to run better, and take more of a load without pinging when I have it bypassed completely, so I assume there's something moving in there.
I did a coolant flush, new heater core & hoses, new 190 degree thermostat last November, however I have no idea if the water pump has ever been touched, and it's something I've been thinking about.
I was aware that I have a different carb than standard, but I don't fully understand how the lean jetting interacts with the amount of vacuum advance? I will also be replacing my tired, lean carb with a rebuilt federal carb off of a '78 Sedan DeVille (same part # as Roy's original carb) sometime this spring, if all goes as planned.
It seemed to ping worse with the original California distributor than it has with my standard replacement
I do not have a setback timing light, nor did I know they even existed. Just looked up the function, I must have one! Mine is a dippy standard one from harbor freight. I've never been able to check my total advance well, and nobody ever told me this even existed to help! Thanks!
Also, if my valves do look like that, is there anything I can do about it without tearing into the engine?

Roy; to verify what you were talking about checking on the amount of vacuum advance, do you mean unplug the vacuum as one usually would when timing, run engine at low idle, and see where the timing mark is?

Thanks again!

EDIT: went & looked at cadillacmike's link. That helps me understand even more than I did! very good read, thanks.

R Schroeder

Roy; to verify what you were talking about checking on the amount of vacuum advance, do you mean unplug the vacuum as one usually would when timing, run engine at low idle, and see where the timing mark is?
-----------------------------------------------------------------------------------------------
Yes, you would remove vacuum from distributor, and plug the line. You also have to plug the line feeding the EGR valve. Lower the idle as low as you can and see what the timing mark is at.
A regular timing light will work for this, if it is a good one. Found out that my 50 year old one didn't flash like I wanted it too. So, I bought a new set back one. Bought mine at Sears. Pretty nice one. DONT BUY CHEAP. Stay away from Habor Freight..........ha
They are nice for checking mechanical advance and vacuum advance , because you just dial in the reading and check it at the timing mark. It will show up reading  O down at the engine, when you change the timing light.

You want the exhaust valve ( EFE ) to be open. Just blocking the vacuum line to the unit, doesn't mean the valve is open. These are hard to get at, even to see them on this car. The vacuum valve has a shaft on it that pulls the valve shut. You want to make sure the valve shaft is out as far as it will go. Away from the vacuum control. If it is in the exhaust valve is closed.

I doubt if your valves in the head look like that. VERY rare to see them that bad. T.J. like to scare you young guys.

I think the difference on the carbs is in the jetting and rods , because there isn't much different in rebuilding them and setting up all the rest. Choke settings are a little different, but nothing that would give you any problem.

You didn't mention if you have the original catalytic converter on there . It looks like a very big pan type .
I bought ,this year, a whole new system. It is from Walker. New cat and exhaust. Converter is a direct fit. No mods needed.
Being that I don't like people working on my car , and I'm an old stubborn f@rt, I put it on the hard way. No hoist.
I think every new home should have a hoist built in the garage right off the bat...........ha
but thats another posting.

Keep in touch.
Roy

R Schroeder

This is what heat riser looks like. You can see when the vacuum shaft is out the valve is open.

Benzilla

#11
Thanks! I do have a catalytic converter, it looks to be OEM, but I have no idea if it's the original. Until I replaced all exhaust behind it, the car still had a factory looking system with an OEM resonator at the tailpipe, so it's probably been quite some time since it was thought about. If I wanted to replace the cat, would it be best to get a direct replacement, high flow, or straight pipe bypass?

I've looked through the EFE removal procedure in my service manual a few times, **but shudder at the thought of checking it in my driveway, without even a set of oil change ramps (temporary apartment living... right?), and never having done it before. might be a job for my trusty back-up mechanic shop ;)

I've had this car & been restoring it bit-by-bit for the last 7 years, this June. When I bought it, I was an ace at detailing & cosmetics, but didn't know nearly as much about the mechanics as I do now. The carburetor was rebuilt (horribly, by a horrible mechanic) in 2007, before I really knew nearly enough to tackle it myself. It has run decently enough to ignore it for a while, but it's time for an upgrade! My accelerator pump leaks fuel, and has a shim on the top of the plunger that looks like it's held on with chewing gum...lol. No telling what other atrocities are lurking inside that thing... I can't wait to replace it.

Roy, that's a beautiful coupe! Mulberry, correct?

EDIT: Just thought to add that as soon as I bypassed the EFE, the car developed a more pronounced off-idle stumble when cold, and takes longer to warm up than it did when the vacuum was actually run to it. Would that be a good indicator that it's at least opening to a certain degree?

**EDIT 2: I think I understand now how I can visually check my EFE installed on the car to determine by the rod position if it's open or not. I will try to see it when it stops raining here!  :)

R Schroeder

Yes the car is Mulberry. All original, except for the fender fillers in back. 22,000 miles on it.

The heat riser on my car is held in the open position. It makes no difference as far as how it runs cold or hot. I was down back yesterday and started it up. Ran solid and smooth right from the get go, and its 30 degrees here.
If you have a rough running car when cold it probably is a bunch of other things. Choke set wrong , vacuum lines that are old and etc. Takes a good going over everything to make it run right.
Mine is ready to run right after starting without any stumbling or rough running.
If the cat is a big flat pan shaped one it probably is original. Probably plugged up too with that mileage on it.
The exact replacement cat is what you need if you have to have your car checked for emissions.
If not , your local muffler shop MAY weld a pipe in there , or you will have to build something to replace it.
I decided not to have the resonator on the replacement exhaust. Wanted it to sound a little more like it had a 425 in it. Removing that and muffler choice made that possible.
In time you will get it all fixed right. Just take your time and do it right.
Roy

Benzilla

Thanks, Roy. My car has always had some degree of a stumble, and I know it's caused by the rickety carb. It did get worse when I unhooked the EFE, however looking back on it, I unhooked the fuel monitor vacuum line at the same time, which relays information about engine vacuum to the ESS box. Could very well be the no-engine-vacuum signal to the ESS made it run funky. Federal cars are so much simpler...

Forgot to mention I have another '79 CDV, red w/ white quarter top, federal car, 130k. It has a replacement carb and runs beautifully. However it always bugged me how much better that thing will run on any gas you put in it, while the Phaeton has to be high-maintenance, lol.

I don't have emissions testing fortunately. Planning to do a straight pipe at some point if I can find a shop willing to. I also deleted the resonator as you did, never saw the point of it. If you don't mind, I'm curious what muffler you chose for yours?

Thanks again to everyone for the great advice posted thus far!!

936CD69

Quote from: Roy Schroeder on March 18, 2013, 04:31:18 PM
Yes the car is Mulberry. All original, except for the fender fillers in back. 22,000 miles on it.

Roy you fibbed..Mulberry has incorrect 3/4 inch whitewalls!

Sorry to horn in on your post..I could not resist!
Craig Brillhart CLC# 26217
1993 Sedan deVille Spring Edition Carmine Red White Top-SOLD!
1993 Sedan deVille Spring Edition Triple Black
CLCMRC Benefactor #302

R Schroeder

#15
Got you Craig. I was referring to the paint..............ha

White walls are actually 11/16. I figured I better say that before you know who gets in here, because he has a picture I sent him of the white wall.

BUT , I STILL LOVE IT THAT WAY.............................ha
Roy

Ben the muffler I believe was called a Walker Silencer. Stainless pipes inside.

I thought in your first post you said you bypassed the ESS.

Benzilla

Quote from: Roy Schroeder on March 18, 2013, 08:24:58 PM
Got you Craig. I was referring to the paint..............ha

White walls are actually 11/16. I figured I better say that before you know who gets in here, because he has a picture I sent him of the white wall.

BUT , I STILL LOVE IT THAT WAY.............................ha
Roy

Ben the muffler I believe was called a Walker Silencer. Stainless pipes inside.

I thought in your first post you said you bypassed the ESS.

I did bypass the ESS, recently. In fact that was the latest thing that's been changed. Everything mentioned took place over time, through trial & error.

Correct 1.3" whitewalls are getting so hard to find! Ugh, don't get me started on the 'American Classic' rolling abominations, lol

thanks.

Scot Minesinger

My GM did the exact same thing, pinged after it was warmed up real good under a mild load.  You discuss the EGR valve, but did you check it with a hand held vacuum pump?  It might be bad with a ruptured rubber piece inside that actuates the EGR.  This causes a huge vacuum leak that leads to pinging and poor perfromance.  I replaced my EGR after going through a great deal and wow it ran great after that.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

bcroe

I once had a 79 with big pinging problems.  After trying everything (including water
injection), I changed the timing chain.  It hugely reduced the pinging, to where I no
longer needed the water injection.  Now any "new" old car I get immediately gets the
OEM chain replaced with a roller chain, all steel set.  Yours is WAY OVERDUE, the
plastic teeth could fail at any moment.  Bruce Roe  CLC # 14630

TJ Hopland

You can get a decent look at the cam gear and chain by pulling the distributor and looking down the hole.  If the engine is real dirty in side its hard to tell much buy you can usually tell if its plastic or not.   If you have a bore scope you can tell a lot more.   Most people don't even think of that because they are used to rear distributor motors where there is nothing to see sown there.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason