472 started but can't get idle rpms down

[rms70]

 Brought in analyzer and have been starting car.  No problems with it firing up and no strange ticking or knocking sounds but the engine has been racing (2100 rpm) and even when warmed up is at high rpm. I realized the throttle rod I had put back on was holding the throttle lever open so I removed it, backed off idle speed adjusting screw and pushed throttle lever forward to the end of it's travel. Then I moved idle speed screw in until barely contacted lever and restarted. Initial rpm was 1400 but it dropped and held steady at 1100. If you can see from the photo the end of the idle speed adjust screw is not in contact with the throttle lever and it's difficult to push lever forward ( I did depress throttle dashpot plunger when trying) but it will move and drop rpm to about 950 then move back to 1100 when throttle lever is released .With idle so high I can't t check advance but what I've seen so far is timing mark considerably above the scale. As mentioned in previous posts the carb had been worked on(don't know the guy's skill level)  and  reinstalled when the head was removed but I don't remember or would have realized the idle was high back then. I just remember the engine dying when put into drive because he had mixed up some plug wires. At least it doesn't seem to leak fuel.  Any suggestions to getting rpm down appreciated.                 


                                                                                            Rob

[Dan LeBlanc]

Hook up a vacuum gauge and take a reading.  Possible you've got a massive vacuum leak somewhere.

[klinebau]

Is the choke hanging open and is the fast idle lever all the way down (other side of carb)?

[Jeff Rosansky CLC #28373]

Are all linkages the same from before it was rebuilt and after? Builder could have something on wrong. Hold it open manually and wiggle every linkage to see what is loose. Then let it close all the way and wiggle the same linkages. Do any seem tight with the throttle closed? If do look at them for a possible source for holding the throttle open. Plug all vac lines and see if that helps. Can you look down the throat to see if the plates are closed (engine off of course)?
The timing will be advanced mechanically at that point so don't worry about the timing until you get the rpm down. If still no luck, disconnect all linkages (be sure to take pictures 1st to help it go back together) and see if the idle will go down.
Jeff

["Cadillac Kid" Greg Surfas 15364]

I would first check the choke high speed linkage and adjustment as has been said.  You will find this on the passenger side of the carb, "buried" behind the choke pull off and thew choke linkage.  I would be sure all the choke linkage is free and the choke opens fuly when warm.
Greg Surfas

[rms70]

I may not get back to this until thurs or fri but it seems like I should pay more attention to choke side of carb. The choke was opening but something must be hanging up over there.  Will look through engine fuel section in shop manual in the meantime. Thanks.       
         

                                                                                     Rob

[bcroe]

I had inconsistent idle speed on a high miles setup, the throttle shaft
bearings were so worn that the throttle plates would not always settle
into the same closed position.  Check yours.  Bruce Roe

[TJ Hopland]

Ya a worn shaft is a possibility.   I had a car with a Rochester 2bbl that was so worn sometimes the shaft would wobble and catch on some part of the linkage and stick on a very high idle.   

I don't think I have a Qjet handy to look at but is there a way that the secondaries could be getting stuck open?  I know normally there isn't but I seem to recall noticing that on one I had laying around one time I was just playing with it and something was catching keeping the secondaries open like maybe 1/4".   

[rms70]

Started this morning with initial high idle-1100 rpm- when warming but fiddling with fast idle can and then a  quick pull and release of primary throttle lever the engine settled down to a slower but what seemed like a slightly hesitating idle of 650 rpm.  Picked up timing gun to see where it was and again it was above the degree indicator to what would have been 25-30 degrees.  Turned the distributor clockwise and timing dropped about 7 -10 degrees before the vacuum advance housing  hit the intake manifold and would move no more. Just to note that at higher rpm engine was running smoothly without pinging or knocking noises and engine  was not difficult to start, just a few cranks and it started.  Will be able to get back to car for a couple  of hours after 5pm,til then what might be going on?   

                                                                                           Rob

[bcroe]

Picked up timing gun to see where it was and again it was above the degree indicator to what would have been 25-30 degrees.  Turned the distributor clockwise and timing dropped about 7 -10 degrees before the vacuum advance housing  hit the intake manifold and would move no more.    Rob.

If the timing cannot be properly adjusted, the distributor and shaft need
to be pulled and turned (together) one tooth to get more adjustment
room.  Bruce Roe

["Cadillac Kid" Greg Surfas 15364]

Was the vacuum advanced connected when you got those readings, and if so where was it connected, manifold or tmed port?
Greg Surfas

[rms70]

Vacuum advance was disconnected and hose was plugged..Any other vacuum port has a hose or is plugged as far as I can tell. I was leary about pulling distributor out but it seems to make sense, it's just a pain to line up the oil pump shaft slot.   

                                                                                      Rob

[70DeVille]

Hi,

Owned more than 50 472's. I think I've come across your problem a few dozen times.

"Then I moved idle speed screw in until barely contacted lever and restarted. Initial rpm was 1400 but it dropped and held steady at 1100. If you can see from the photo the end of the idle speed adjust screw is not in contact with the throttle lever and it's difficult to push lever forward ( I did depress throttle dashpot plunger when trying) but it will move and drop rpm to about 950 then move back to 1100 when throttle lever is released .With idle so high I can't t check advance but what I've seen so far is timing mark considerably above the scale."

You most likely have a bad THOTTLE BODY in your carburetor.

While your engine is racing at high RPM's, you should push BACK  on the throttle of the carb. (the part where your accelerator rod attaches to the carb.). If the engine settles back to the set screw RPM, you have a bad THROTTLE BODY in the carburetor. Been there a few dozen times. Have to rebuild the carb and change the throttle body. It is a very common problem with Quadrajets.

If you remove the vacuum advance to the distributor, check the timing and it's OK and it still happens, it isn't timing or vacuum advance.

Hope this helps.

[rms70]

Here's where I left it sat evening but  was getting confused. Was removing distributor to move it back a tooth (or should I move it clockwise?)but when I finally get it aligned with oil shaft and twisted the distributor in, the rotor would shift  (which I felt was another tooth over) leaving it  in a position I felt would be firing on a different   cylinder in relation to where the engine is when I pulled the distributor out. On my last attempt the rotor was pointing to it's initiall position so I just bolted everything back together before it got too dark. I'll try to restart Mon am just to make sure I haven't messed up at least what I had but I doubt the timing will be more adjustable.  Was the rotor shifting normal or am I making this more confusing than it should be?  Is it supposed to be a tooth clockwise or counterclockwise?  In addition , the vacuum advance module  is limiting distributor adjustment by hitting intake manifold(cw) or the a.c. compressor(ccw) and seating the distributor on install is requiring a clockwise turn further limiting the amount of timing retard I can make. It's this clockwise twist that's giving me problems and doubts that it'll be right. 
Thanks for the heads up on possible throttle body problems, I could probably use a rebuild to fix the sketchy "rebuild"  done  in late 90's(don't  think I drove car 20 miles after he reinstalled it).  After manually "gunning" throttle lever engine did settle down and it might drop further( idle mixture screws are still out 7 turns) and didn't have car in gear or compensator pin depressed,  hoping that rougher idle was caused by way too much advanced timing.


                                                                                            Rob

[TJ Hopland]

If its running ok ish I would not be too worried about the timing till you can get the idle speed and carb to start responding correctly.   Yes the timing will effect idle speed and quality but it sounds like at the moment timing isn't your biggest issue. 

Has this got an HEI or is it a original points dizzy?   I don't remember the points being as limited range for timing as the HEI but I suppose it could be because I think it sat lower so the vacuum can would just hit things sooner. 

I'm not quite sure what you are asking about the rotor.   Its normal for it to rotate as you drop it in due the helical gears.    When I mark one I will mark its normal resting position then be ready to mark where it stops when I lift it.  You don't want those marks on the distributor body, you want them somewhere else on the engine that isn't going to move. 

If you are trying to move it a tooth its normal to have to fight the oil pump shaft.  I have even had it on a hot engine where I was trying to put it back in the same place and the shaft moved.  Must be residual oil pressure or things cooling.   I don't know any tricks for the oil pump shaft other than to maybe do it several times a day and be able to eyeball things.

Another trick or sometimes necessity if you are running out of timing range is to just move all the spark plug wires over one position.  I have had engines where you have to go back and fourth between the wires and the teeth a few times before you finally get the correct positioning of everything.

[70DeVille]

i thought your initial problem was a high idle the couldn't be adjusted down.
Please read my last response. The FIRST thing to do is PUSH BACK on the throttle. If the idle goes down, you have a bad throttle body. This is the first item to be tested before going into anything else including the distributor.

[rms70]

Postings are far apart because it's difficult to find time to do anything other than sat afternoon/ eve. Here's where it is now.  Repulled distributor and after the hundredth try dropped it into oil pump shaft slot as close to TDC for cylinder #1 as I could(the last time I tried it was #4 cylinder and must have missed causing the real high advance problem). When it started there was a definite change in the sound of the engine, still no pinging or knocking but smoother and not as loud, rpms were 1000-1100,oil pressure steady at 38 psi and  the choke steadily moving open. All good except fast idle cam stayed up after it's first initial drop. Tried pushing throttle lever back and letting it snap shut but that did not drop fi cam,it only brought up rpms to a higher level. Finally I gave the fi cam a knudge and it fell down to where it's suppose to rest, idle rpm was around 700 but throttle lever plate was not against curb idle screw. Pushing throttle lever forward caused rpm to drop to 600-650.  Seeing rpms holding steady there I had to pick up timing light and could see I was now around 5 degrees BTDC and although I realize it's not in exact service manual curb idle set parameters I had to adjust it 7.5 degrees and tighten the hold down nut. While I was there checked dwell and adjusted to 30.  Now back to throttle and fast idle cam, the cam drops easily after being helped so I'll try more carb spray. The throttle lever side has what I think is the original return spring and it seems quite thin and lacking in tension for the job. Since both sides of the throttle have issues, could the primary throttle plate shaft be the problem?  Is it the throttle body?  Having it properly rebuilt would probably be best but are there any other suggestions of things to do?

                                                                         Thanks
                                                                                   Rob
                                                                                     

["Cadillac Kid" Greg Surfas 15364]

Rob,
You know the answer. Have a reputable company rebuild the carb.
Greg Surfas

[chrisntam]

Send it to the rebuilder and be sure to let them know what the issue(s) is/are so they can be on the lookout for the cause to be sure it/they is/are remedied.

[rms70]

Rebuild should solve the problem but I'd like to understand what's going on.  The cam follower seems to have a lot of tension on it which is not allowing the fi cam to drop. This morning I moved choke out of way and backed off fast idle screw til the cam follower was loose enough to let the fi cam  move along with the vacuum break lever as it falls, moved the screw in and out so there was just a slight drag on the follower and fi cam.  When I tried starting at this setting the throttle plate was too closed in that the  low speed idle screw was resting on the primary throttle lever which I left last weekend at 650-700 rpm.   Moved low speed idle screw in a few turns and it fired up but of course after car warmed up it's stuck at 1100rpm . On choke side the fi cam moved along with break lever without any prodding from me. The cam follower seems to be attached to the throttle body by a screw which tightens onto.   a spring which I'll assume is putting pressure on the follower. Could  this screw be taken out a turn or 2 to relieve the pressure? Am I way off base with this or is the follower supposed to be  tensioned like the throttle plate to snap back against fi cam?  If I turn fast idle screw back in to it's manual spec of 1900 it will  not  allow fi cam to move with the break lever. Hope my description makes sense.  BTW it's a later 70 4MV with the "freeze plug" choke well.

                                                                              Thanks
                                                                                    Rob