1976 Cadillac Quadrajet idle problem

[jbmoffo]

Good Morning,
I own a 1976 Coupe DeVille.  35,000 original miles.  Original everything!  AC does not work, so the climate control is kept OFF.  The car is garaged all the time. I start it once a week, and it is used once in a while during nicer weather only.

Wondering if someone has had this same experience: When I start the car with a cold engine, I pump the accelerator twice.  Choke closes, the engine turns over, pull off opens the choke plate slightly and then the car idles high until I kick it down. (usually after about 2 minutes) Then I  need to kick it down a second time, wherein the idle goes down to what I would consider "normal" but only after the car is fully warmed after 8 minutes or so.  Otherwise, I cannot kick it down.  It then idles perfectly - the engine is barely a whisper.

However, once the car is out on the road for a few minutes and after a few traffic lights, the idle creeps back up to a much higher idle, an idle way too high, causing the car to run too hot and almost allowing it to lurch forward when I take my foot of the brake.  I have not used a gauge,  but the high idle is very obvious without even a tachometer.   People have told me it could be a LIST of things...but I thought I'd ask here first.  I have sprayed the linkages on the choke side...and even on the throttle side... 
Thanks

[429bbf]

im guessing its got a hot air choke. id say the coil  in the choke is failing and not keeping the choke fully open . it shouldn't take that long to open the choke and it should stay open. or your vacumn line going to the coil housing has a hole in it.fwiw

[429bbf]

forgot to ask do you have the 350 or 500 ?i had the 500 my neighbor had the 350  he got about 12 mpg and with the 500 i got an easy 18 plus. that big old engine just purred down the interstate at 100 mph. you could set the cruise and sit back and relax. fwiw

[Cliff Ruggles]

Could be several things, most likely idle mixture screws are just set too lean, so as the engine heat soaks the idle speed climbs higher.

This may be due to some restriction in the idle system, "varnish" in the idle tubes, etc.

If the choke is coming back in it would be evident by the fast idle cam not being in the down position. 

Most likely it's just time for a complete/correct rebuild with modern parts.  Might need to install primary side shaft bushings while you're in there.......Cliff

[jbmoffo]

It's a 500.  Cruises on the highway like you are on a cloud.  I love the ride it offers.  And you can barely tell the engine is moving 5200 pounds at 75 mph.

The choke is electronic.  Not hot air.  It does seem to take an awful long time to get the choke plate to open.
I am not sure if someone has ever timed it...but mine takes about 6-9 minutes to fully open. Sounds too long, right even if ambient temps are in the 60s.

If I can get it to stop running high, I'd be all set.

[429bbf]

try this .i don't know if you have rivets or screws in the choke. if you have screws great .loosen the screws and turn the housing. mark it where you started.i think cw is lean can't remember. turn it about 1/4 inch. if its got rivets you will be drilling them out on an overhaul anyway. cliffs kits come with all the parts to replace the rivets. anyway with a little patience you will be able to determine if the coil is bad or you have other problems. forgot to ask do you have voltage at the choke.also as cliff says you may have to open up the idle screws. with today gas you don't get near the bang for your buckfwiw

[jbmoffo]

Attaching a photo of mine.  Looks to me the choke coil was replaced at one time.  I have only owned the car one year.  I had another 76 where the coil was riveted.
Usually, there are markings to indicate RICH vs LEAN.

So, seeing it is idling too high, it may need to be dialed more lean...?
It seems to almost get stuck back on the idle cam's higher steps...kind of hard to see as the steps are behind the choke....once the accelerator is pressed again.

[429bbf]

obviously the car s not running . usually when you install a quality coil the plug in is located more straight up and down  almost on the bottom also from your picture it looks like your a 1/2 off. the little line on the coil should be somewhere closer to the hash marks on the housing.the first thing id do is pull the cover off and see if the coil is attached properly to the peg. also there should be an insulator on the peg. another thing to do is engine off. push the acc.1 time and turn on the key after a couple of minutes you you should be able to bump the throttle with your hand under the hood and watch the choke open.fwiw i see it has a rear pull off also .fire it up and make sure they both work.if the rear doesnt  it can cause things not to work right.you can remove the rear and the linkage you dont need it.

[jbmoffo]

I actually loosened the screws (thanks to PB Blaster) and the bugger immediately shot back to the marks along the top of the housing...rendering the connection at the bottom like you said.  I have it dialed on the last spot/mark on the left, and it ran MUCH better.  The car started...pull off opened plate slightly and the choke even opened quicker and I was able to kick it down right away as well.  In the past, the car would run nearly 3- 5 minutes before I could even think about kicking it down.
I do get a bit of hesitation on acceleration if the car is not fully warmed up...
Anything I might try for that?
What exactly is the purpose of that SECONDARY pull off?

[429bbf]

the secondary pull off is just to assist  the front pull off .kind of like a insurance policy. i don't use them. it sounds like your acc. pump is giving up the ghost. id get a kit from cliff and do a complete overhaul. your parts will not hold up to the new gas for very long. fwiw

[jbmoffo]

I thought you'd say the acc. pump.
Never rebuilt one...so...how difficult are we talking?

[429bbf]

first step . buy cliffs book off this website. then order an sr. kit total for the 2 appox.100.00 it doesn't have a lot of miles but be sure to check for throttle shaft wear. most will need bushings. cliff also sells a kit for that. if you just want to get by you could buy the acc.pump and float but buy the time you buy a gasket and such your just going backwards. i usually spend around a 100 for parts that would also get you a new electric choke coil.you can spend upwards of 200 if you need pull offs and idle tube or you can buy a
[remanufactured carb
 . and have to do the work twice.get the book do some reading and make a decision.fwiw

[Cliff Ruggles]

The choke flap should be fully open in about 2-3 minutes.  Most likely the E-choke is defective and it's just opening due to engine heat not from the choke.  This will cause all of the issues that you are seeing.....Cliff

[73ss]

First things first..... Is there 12V present @ the choke. Most of these were wired through a oil pressure switch so 12V would be present only with the engine running.

I didn't think they had elec choke in '76... Was it converted over?

[jbmoffo]

Not coverted.  12 volts present.  And Oil switch is brand new.  Did this before the switch was replaced, too.
After I turned it clockwise toward the notches, it lines up with the LAST notch for RICH and seems to be running much better.  I don't get much of a chance to drive it, so the next time I am out with it, I am going to see how she responds.  The accelerator pump really needs replacing though.