Q-jet won't idle when engine warms up

[Greg Kennedy]

Dear Cliff and friends:

So glad to have discovered this forum.

I love old Oldsmobile Toronados and my 1981, 307 gasoline engine with Quadrajet E4MC is giving me grief.

It ran like a top when I stored it last winter, and now it dies whenever the engine warms up now.

If I feather the gas pedal, it will keep running. Or if I tighten the low idle speed screw like crazy, it will keep idling roughly, but at around 1500 to 2000 RPM. I try to lower this and she dies.

If I step on the gas, it's smooth, but take my foot off the gas and she dies (unless I keep the idle screw tightened as above).

I've replaced the PCV valve, checked and cleaned the EGR valve. Checked vacuum hoses to the best of my ability. The baseplate gasket is new; I don't think I have a vacuum leak there. Sprayed some carb cleaner around it and it didn't affect the engine speed.

I did a rebuild about two years ago, but I confess at the time I didn't know much about how the idle circuit worked, and didn't run any wires, etc, down the idle tubes.

I have bought the special tool that let me play with the idle air mixture, trying two turns out, two and a half, three turns out, and now it's at three-and-a-half turns out on each side.

Bottom line .... could my problem be as simple as just removing the carb again -- and then making for damn sure the idle tubes are clean?

Or am I getting into a timing issue?

Remember, this is a car that never stalled before coming out of storage this spring .... and now it won't idle when warm.

I'm open, and very very grateful, for any expertise you folks can offer. I've already got a bald spot and don't want to pull out the hair I have left. 

I love the challenge of learning more about these amazing carbs, and I best order me a copy of Cliff's book straightaway here for future reference.

Thanks so much,
Greg

[Greg Kennedy]

I just wanted to mention that my carb is not computer-controlled, if that matters,
Greg

[carmantx]

Make sure your float is fully open when engine is warm.

[429bbf]

welcome to chp. lets start simple . is it running out of fuel or does it act like its flooding.if it acts like its flooding the choke pulloff maybe bad . if its running out of fuel I wonder toward the idle tubes . fwiw ps carb no. would be nice

[Greg Kennedy]

It's interesting you mention the choke pulloff -- if I use my finger to hold the choke valve when it's idling I can keep it running easily. So perhaps the idle rods aren't bunged up. The two vacuum breaks front and back seem to work fine and hold vacuum without fading. Thoughts?

[429bbf]

ok theres a lot confusing stuff here . you say you have a e4mc carb but you have no computer to it . how are you controlling the metering rods? second ques. are you holding the choke open ?if your holding the choke open you coil in the choke could be bad if both pull offs are working . you don't need both but the rear one may control the opening of the secondaries. little more info needed. hth

[Greg Kennedy]

I suspect my 1981 Toro  was built at the very beginning of the 1981 production cycle, because it has NO electronics or wiring going to it. I have another 1981 Toro parts car that does have the electronic carb bits, so I do know the difference.

My secondaries are staying firmly shut, no air leaks there. When I last had the carb apart a couple of weeks ago, I made sure the float was properly adjusted, that the metering rods were smooth and not sticking, etc.

Is it possible somebody put an older carb on my car somewhere back in its history?

I will get the carb number and post it here shortly; maybe that will help.

Thanks so much for your help so far; very much appreciated.

[carmantx]

My post said float, but I meant choke.  Make sure choke is full open when engine is warm.  If you have to hold it open, then it is either not set correctly, or element is not functioning properly.

[Greg Kennedy]

Thank you Carmantx. Here are photos of both sides of my carburetor.

Its number is .... 17081282.

I'm suspecting more and more the choke coil is shot, or set incorrectly. I have moved it about with different adjustments, but no success so far in sustaining a low-rpm idle.

[Greg Kennedy]

Now this is getting really bizarre.
I looked up my carb number 17081282 only to be told by one website that it's from an 81-86 Chev/GMC/Truck and should have an electric choke -- which mine does not.
Maybe my carb's a 'transplant' from a truck..... a R4-M4ME.
Hmmmmmm.... any thoughts?

[429bbf]

greg reread the post . first the idle air screws are fuel. in is less fuel ,out is more fuel. if your choke has screws and not rivets loosen the screws and put a screwdriver in the end and turn clockwise (i think thats right )until the choke flap opens all the way.up this should help you make a little head way . i see the front pullout is attached to the secondaries, if it is hooked to the choke you do not need the rear pulloff.hth

[Greg Kennedy]

Thanks 429bbf.
Mine is the kind with 3screws. I have tried loosening the screws and adjusting the choke valve.  But I was turning it until the choke valve closed when the engine was cold.
I can try turning it now till it's totally open,  but should I do it with a cold or warm engine?

[77cruiser]

Does the choke ever open when it warms up?
If the carb originally had an electric choke it might not have the vacuum passage & won't pull in the hot air to heat the coil.

[Greg Kennedy]

Yes, it does have the metal tube that comes up from the engine to deliver heat right to the choke coil.

[carmantx]

The 17081282 should have been an electric choke Quadrajet originally, which would mean that the vacuum port in main body to the choke housing is NOT open.  So even if you have the metal line connected, there is no vacuum to pull the hot air in to the housing.  So you need to put an electric choke element on that carb for it to work properly.

And set the choke, with engine warm, to full open position.

The choke flap is closed in your pictures, and think that may be at least part of your issues.  Fix that first, or at least open choke flap all the way before other diagnosis.