88 olds 307 started and drove when parked a month or 2 ago just seemed to idle low and after hitting throttle it would dip its rpms a bit low but never died.

Now i try to start it and it wouldnt start without me fiddling with the gas, and would only stay running if i feathered it.

I've replaced every vacuum line and triple checked that its correct and messed with the thermo choke to where it will start right up on its own but always in high idle, when the throttle is touched it will die unless i hold the rpms up or hold the choke a 1/4 inch open. Any more it stalls and any less it stalls.

I'veeven gone as far as shoving a vac line in my ear and listening EVERYWHERE.

What the heck is going on.

 

Is it reaching operating temperature? Does the electric choke thermostat work meaning open completely when warmed up?

The choke does need to open slightly immediately upon start-up. It is opened by the choke pull-off, the diaphragm inside them do fail. The amount the pull-off opens is adjustable and must be set properly.

If it won't run warm with the choke open it sounds like a restriction in the carb. Try getting the engine warm, rev it and at the same time manually push the choke blade closed. It will load up and stumble quickly, release the choke blade before it stalls, let the engine get to idle and repeat 3-4 times. By doing this while the engine is revved, fuel is pulled copiously through the carb passages cleaning them. It works pretty well, I've had it smooth out many idle problems without disassembly of the carb.

Good luck!!!

 

I have checked both pulloffs, they both hold vacuum and everything is bone stock. The choke originally wanted to open all the way once warmed up but will die if i dont hold it almost closed. I feel that it was originally in a decent position but ive richened it up to the point that it will start on its own accord but only in fast idle, as i have the choke so rich.
Upon warm startup it is in high idle and choke is 45°. I can tap the gas immediately or wait 5 minutes and the result is the same, the engine slowing to normal idle and dying. I can only keep it running after taping the gas by holding the choke like 1/4 - 1/8 inch open.

I have tried choking it with throttling it as you mentioned countless times as well as seafoam in the carb but not in the gas. Ive considered todays ethenol gas and its short shelf life and gave up and added some stabilizer tonight to the quarter tank.

when a vacuum leak was introduced, its rpms strangly increased.... although with the choke opened even the slightest past a 1/4 inch causes it to die. Very puzzling results indeed.

 

Are there any wires a mouse could have chewed that would cause it to idle smoothly for an hour with the choke propped closed but cause it to die like this? There are plenty of mice out here.. ive gone over it in the pitch black and could see no issues or sparks.. just a thought

 

The gasoline and ethanol additive that we are forced to use becomes unstable after two weeks in your fuel tank. Over a short period of time it evaporates from the fuel bowl in the carburetor leaving gum, varnish, and finally attacking the metal leaving a white powdery deposit through out the carburetor. The correct repair entails removal, disassembly, and cleaning of the carburator.
To prevent this from recurring I suggest using the additive Sta-Bul as written on the bottle.

 

Did you check the slow-idle screw adjustment position? It's possible the slow-idle screw has backed off and it won't slow-idle. Adjust the slow-idle screw adjustment position.

 

The 307 has about a million miles of vacuum hoses. If any one of them is cracked, loose, or mis-connected, the CCC system goes apoplectic. If any of the sensors go bad, similar things occur. The ECU is pretty stupid, so most of these failures do not set a code. And do not try to adjust anything without following the adjustment process in the Chassis Service Manual to the letter.

 

Is the distributor loose, can you turn it by hand? Wondering if the ignition timing is off.

Can you get it to rev at all? Is the carb throat or the air cleaner overly dirty, a sign of a blocked converter?

Good luck!!!
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It is responsive and throttles all the way up smoothly, it sounds like it should run fine then just dies as soon as i let off the gas or dont have the carb very choked. Ive checked distributer it is tight. Cant even get it in gear without stalling

 

Is the problem that the idle speed is too low, or that there's a vacuum leak? And how, exactly, are you "choking" the carb? Are you physically holding the choke plate closed under the hood?

 

It is acting like a vacuum leak, but when i introduce another vacuum leak it increases in rpms. I am physically holding the choke closed. If i dont it will die immediately. If i hold it completely closed it will die.

 

Since your sense is that it is a vacuum leak if it has a vacuum brake booster (I'm remembering that is hydra boost though) disconnect and plug it. Remove the EGR valve and temporarily block it. Try misting carb cleaner into the oil fill tube to see if there is an intake manifold and/or intake gasket leak, if there is it should rev up.

I re-read original post, am I correct it ran fairly well when parked but not on restart? It was a sudden onset?

Getting reasonable air flow from the exhaust, doesn't seem restricted?

Good luck!!!

 

If you turn the ignition on but dont start the engine you should be able to hear the mixture control solenoid on the top of the carb clicking ? To me it sounds like something is sticking or gummed up in the carb. Try revving it up to a good rpm and putting your hand over the carb real quick. I have had that method clear them up once in a while.

Also, I know everyone wants to bad mouth the ethanol fuel but I just have not seen a big problem with it unless something sits for a few years. When i did the engine and trans in my Wife's Riviera a couple of years ago it was off the road for about 14 months. It had 87 octane Shell with 10% ethanol in it when parked and when I was done it started up and ran just fine.

Thats my 2 cents

 

Correct it ran fine when parked, i can hear something clicking which i supossed is that MC solenoid and ill try plugging up everything as you suggested and see about the intake leaking.

this is not acting like some normal vacuum leak, the choke had to be held almost closed to keep it running. Ive tried choking it after throttling it to no avail and am thinking i may have to tear apart the carb..

 

The MC solenoid should make a steady clicking sound. In front of the carb is a test lead to measure the duty cycle of the MC solenoid it should have a green plastic plug not connected to anything. If you connect a dwell meter on the SIX cylinder scale to that lead with the car running warm it should read 30°. If you don't have a dwell meter use a duty cycle meter, reading should be around 50%. Moving the choke blade to richen or lean the mixture must make the MC duty cycle vary, if it doesn't something is hung up inside the carb.

If you have to go inside that carb I suggest getting a factory service manual in advance and reading it several times. Those carbs can be set-up to run well but only with precise methodical adjustments.

Good luck!!!!
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Pretty sure the A/F solenoid pulses to lean the mixture and a lack of pulses or clicking would leave the mix rich. That is probably a fail safe if the thing quits. The idle passages can't be plugged because closing the choke is activating them. Wouldn't a vacuum leak be the problem here? Are the secondaries fully closed?

 

This is correct. You can pull the plug on the ECU and the engine will still run, it will just be pig rich at low speeds. Been there, done that. The mixture control solenoid is a low probability cause for an idle problem. I'd suggest looking in the more likely places first. Put a vacuum gauge on the engine and see what the vacuum level is. Use a scan tool or volt meter to read the O2 sensor and see you're overly lean or not. Pull the plugs and see if they look lean or not.

 

Yeah, it would have to run for a while to get closed loop, but I wonder what the oxygen sensor is saying. Look real good for vacuum leaks and disconnect and plug the fitting to the power brake booster.

 

Its been raining here so i havent been able to do too much yet, but i did get a vacuum gauge hooked up and upon startup it has 21-22 inch pounds of pressure regardless of whether its in high idle or ive kicked it down and am holding the choke plate so that it wont die. The needle stayed fairly steady.

it actually idled for a minute by itself so i figured id try adjusting the choke just to see how itd respond. I tapped the choke with a screwdriver and it immediately died.. does that mean anything to you guys?

 

What does it mean that you "tapped the choke"? Holding the choke closed richens the mix and opening the choke leans the mix.

 

[QUOTE=Goodoldsreliable;1282898] it has 21-22 inch pounds of pressure regardless of whether its in high idle or ive kicked it down and am holding the choke plate so that it wont die.
It is inches of vacuum, the opposite of pounds of pressure.
Is the engine fully warmed up when it won't idle unless the choke is held almost closed? How fast does it have to idle before it will run with the choke fully open? Is the secondary choke and throttle plate fully closed? It sounds like either a vacuum leak or a plugged idle circuit. You could try running a fairly strong concentration of Sea Foam in the gas, maybe that will help if it is gunk in the carb.

 

im sorry i was vauge, i meant that i tapped the thermostatic choke housing as i tried to turn the choke to jar it as i have it lightly seated so that it wont turn on its own but i can still fiddle with it.

the engine will not run with the choke plate open, at all, ever. Not even after idling for an hour with a screwdriver gingerly placed on top of the choke plate to hold it just an 1/8 of an inch or so from being completely closed. I have ran seafoam and a fuel stabilizer just in case as mentioned above.

im going to take the choke housing off tomorrow and run a coat hanger down the passage underneath as recommended, but have little hope that it will accomplish anything.

this car ran fine when parked a month ago, so none of this seems to make sense.

 

I wouldn't take the whole choke housing off the carb unless the carb is on a bench. That is not the problem. What are the trouble codes in the ECM? If the engine ran for an hour there should be some. Did you disconnect and plug the vac hose to brake booster? Did the pcv hose fall off the carb? You better look real hard for a vacuum leak.