Hello all! This is my first message on this forum so apologies if im posting in the wrong section. I acquired an 86’ Pontiac Parisienne with an olds 307 engine back in November and since I have done a fair bit of work on it that has gotten me not very far. When I first got the car, it would start and run fine except when you would try to go after a full stop it would have a good chance of stalling as soon as it began to move. Then once you got to your destination and turned it off, it wouldn’t want to go again. It would start however it would audibly run with very low RPMs until it eventually died, and you had to hold your foot on the gas for about 2 minutes to get it warm enough to stay running. I decided I would rebuild the CCC quadrajet, and after I did all of that I could never get it to run right again. The car wouldn’t idle below around 1400 RPMs and the computer would be constantly trying to lean the mixture as shown by a dwell of around 11 degrees. After around 5 months of tooling around with this carburetor I figured I must have done something wrong in the rebuild and given that the quad was already warped horribly, I bought a rebuilt one from a reputable shop nearby. I bolted it on and it ran perfect, sat glued at 600 RPMs cold, and I was even able to take a drive around the block a few times. When I returned I noticed that my idle had increased noticeably just by listening to it. I checked that the choke was fully opened, it was, and I checked the RPMs and it read around 1400. I turned my curb idle screw down which lowed it to about 1200 before the throttle linkage couldn’t go back any further. I assumed a vacuum leak so I tested my vacuum lines with a smoke machine and couldn’t find anything. My engine pulled around 15 inches of vacuum, which I heard was perfectly fine yet my idle was stuck high and it wasn’t stable, bouncing around the general area of 1200 RPM. I heard that the PCV valve, the little rattly thing, can cause bad vacuum leaks if faulty so I pulled it and capped the line going to it. On starting I still pulled around 15 inches of vacuum and my idle was still bouncing around 1200. I checked my dwell meter and saw that the needle was fully to the high side, off the scale even, which from what I gather means the engine is doing everything in its power to lean out the mixture which would make no sense with a vacuum leak. I thought maybe the AIR pump which was pumping all of its air into the exhaust could be screwing with the 02 sensor reading so I popped the hose off. No change. I did one last Hail Mary and thought maybe I was just on the high idle cam this whole time so with the engine fully warmed up I tapped the gas and now my idle dipped to around 600, and then shot back up to ~1200. Im currently at a loss as to what could be causing this issue, I cannot lower my idle any further with the curb idle screw, my computer thinks that the the engine is pig rich, and I want to say its a vacuum leak as if I put my hand over the primaries nothing changes, but if the computer tells me its fully rich, that doesn’t make sense. I’m completely puzzled and if anyone can offer any kind of help it would be massively appreciated. Apologies for the long post I wanted to give as much context as possible. Thank you

 

You mentioned you bought a new carburetor. It was a CCC Quadrajet, correct?

 

Yes, I bought a remanned ccc pontiac carb, from what I see its identical to my old one

 

Welcome!!!

Any trouble codes stored?

Can you hear the mixture control solenoid chattering/cycling?

Pull the canister purge valve to check it for raw gasoline, there shouldn't be any and they usually show a code 45 when bad.

Disconnect the brake booster line and plug it to check for vacuum leaks of course unless it uses a Hydra-boost.

Ignition timing dialed in?

How many miles, compression test?

 

First, even a brand new CCC carb MUST be adjusted on the specific car with the engine running. There is a lengthy and detailed adjustment procedure in the factory Chassis Service Manual. It must be followed EXACTLY. You cannot simply bolt on a new or rebuild CCC Qjet and expect it to run correctly, and you certainly cannot adjust the idle mixture screws the way you can with pre-computerized carbs. Few people knew how to adjust these properly when they were new and nearly no one does now. Also, the CCC system is pretty stupid and has precious little computing power. It lacks most of the monitoring capabilities of the OBD II systems. The result is that very, VERY few faults will set a code. You have to diagnose the problem using what you can glean from the system. Be aware that any improper connection, leak, or damage anywhere in the miles of vacuum hoses will cause the ECU to go apoplectic. Get the CSM and read it.

 

If you don’t have one. Get a factory Chassis service manual for your car. There are adjustment procedures for your carb that have to be done in a specific order. Also disconnect your throttle cable to make sure it isn't holding the throttle open at idle. Maybe Joe P will chime in.

 

Apoplectic - love it!

 

Beat ya by six minutes.

 

I’m a slow typist.

 

Thank you all for your responses, I’m going to respond to all of you in one message to simplify things
Firstly, I have no trouble codes stored, my MCS clicks and I don’t have any raw gas in my purge valve. My ignition timing at warmed up idle shows ~ 24 BTDC, car has 80,000 miles and I haven’t performed a compression check. I checked the brake booster line and it checks out ok as nothing changes with the line capped.
Second, is the chassis service manual specific to the exact car and year? I have a E4ME & E4MC service manual that goes over adjustments like MCS height, and has charts for adjustments that are for specific model/engine configurations, would that suffice?
Lastly, as I was thinking over my situation during lunch I thought I may have figured out at least part of my problem. I have not adjusted the mixtures of this carburetor since buying it, which leads me to believe that the carburetor is running rich. Would this explain the high idle and dwell as the computer is allowing more air into the mixture to try and lean out the far too rich mixture resulting in much more air and gas going into the engine than is needed?

 

Go back and read post #5

 

Got it, but just to make sure the shop service manual to my car is the same as a chassis service manual? I just want to make sure of that before I spend a good chunk of change on something that's only partially useful.

 

I don't know about the manual coverage.

Forgot to ask, does it give a code 12, no distributor reference signal?

 

 

I checked a few days back and it does give me a code 12 in diagnostic mode, and I just ordered myself a service manual, thank you guys for the advice so far.

 

Hello, I'm back again and I hope you all have been doing well. I spent the last 2 weeks dialing in my carb to the specs shown in the chassis manual, and to my knowledge I have everything set up as it should be now. As with my luck, I am running into a few issues which I would appreciate help with. Apologies for the fact that this post is a soup of a whole bunch of things going on, there is a lot of variables possibly at play here and want to cover all that I know of. First off after dialing setting up my base adjustments, I managed to at least partially fix my high idle problem by attaching the vacuum hose that went to my rear vacuum break to the vacuum nipple on the back of the carb, right next to the brake booster port. According to my vacuum diagram, the nipple on the back of the carb should go to a solenoid, and the line to the vacuum break should come from another solenoid on the drivers side valve cover. After doing this and plugging the now unused vacuum ports from the solenoids I noticed a slight reduction in idle speed, which is a step in the right direction I suppose. Next I moved on to plugging every vacuum line that went from the carburetor to somewhere else in an effort to tackle my low vacuum (15 Hg) issue, which succeeded by bringing it up to around 19 which I have heard is acceptable for these carbs. After that I went after my mixtures and found that my dwell will sit within the specified range in the manual at half a turn out, which seemed very low to me but thats what the ecm liked as shown by the dwell. I should include that I am not using a traditional dwell meter, instead im using at OTC monitor 86 to read straight from the ecm, which is telling me my dwell among plenty of other things. One concern I had about this ecm reader is that when I power it on and start communicating with the car, the car seems to go into a sort of half diagnostic mode. I say half because the MCS starts clicking which it normally does not do until the engine is running unless it is in diagnostic mode, and the service engine light sort of flickers like a bad fluorescent light as opposed to doing the normal flashing 12 it does in diagnostic mode. I have heard these OTC monitors are good tools for these cars, so I wanted to double check if this is normal or a sign of trouble. After tooling around with the mixtures I got my idle down to about 800 RPM, and I checked back on my vacuum readings and it is now once again at around 15 Hg and the engine vibrates quite a bit. The idle also likes to surge up and down within a range of about 100-200 RPM, and the vacuum level follows the surging. Lastly, I placed the car in gear when it was warmed up and idling around 800, and the car stalled almost immediately. I'm scratching my head trying to figure out what could be causing these symptoms, and any and all help would be massively appreciated. Thank you.

 

15" of Hg seems pretty low for a CCC Quadrajet. Make sure you don't have a vacuum leak.

 

I managed to get it up to 19 Hg by plugging vacuum lines, I’m fairly certain its due to the canister vent solenoid that I thought was still good but upon closer inspection was soaked in gas. Nothing has changed since getting 19 Hg except adjusting mixtures, so I’m not sure whats causing the sudden drop.

 

A bit more info. I was able to stop by where the car is stored and take another look at it on my way back home from school today and I tried a few solutions listed in the service manual such as disconnecting the ecm power for 10 seconds or so to clear its long term memory, which didn't seem to help.