Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
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.
Navigation
[0] Message Index
[#] Next page
Go to full version