1983 LeSabre sputtering underload


Old 01-08-06, 12:05 PM
Jason R's Avatar
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Join Date: Jun 2002
Posts: 261
1983 LeSabre sputtering underload

HI all, I'm trying to help my dad figure out what is wrong with his 83 lesabre with 5.0L (307) engine and quadrajet carb.

It starts and runs fine in neutral and park. It'll idle fine in gear but when you try to accelerate it starts sputtering. When the engine is cold, it's hard to get 'er above 35 MPH. We checked the timing because it felt like a timing issue, and the ignition timing is fine. It got a new timing chain and gears last fall and had been running fine since then until now.

The exhaust does not smell of fuel so I assume it's not an excess of fuel. The fuel filter was replaced already today.

Any ideas?

We did notice during out 'array' of tests that the choke plate on the two back carb barrels never open (well, unless you open them by hand).

Thanks for any help you can offer.
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Old 01-08-06, 12:59 PM
Join Date: Jan 2006
Location: Ontario, Canada
Posts: 759
The 2 rear flaps that you refer to that are not opening, are your secondaries, which will only open up on heavy acceleration. Have you added any additives to the fuel to remove moisture, in case of that. Not knowing where your from, I can only say that ice/moisture in fuel lines here in Canada are a common winter problem, that requires periodically adding gasline antifreeze.
How does the car run when warmed up? If it runs good when warmed up then maybe your choke assy has partially seized or got out of adjustment somehow. That is the front butterfly (flap looking thing) It should be almost, if not closed when starting cold, and should open up fully (straight up )when warmed up. It needs the choke on a cold start to supply extra fuel to engine when cold.
Answer these questions: Did you just experience a temperature change in your area, about the same time this all started? Does it run good when warmed up? When starting cold, is that front flap almost closed, or closer to straight up position? I'll get back to you a.s.a.p.
Old 01-08-06, 05:38 PM
Lugnut's Avatar
Join Date: Jan 2001
Location: Kansas City, Missouri.
Posts: 1,172
Consider that aged spark plugs may be the only problem. Start there, inspect them or just replace them.
Old 01-12-06, 09:12 PM
Jason R's Avatar
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Join Date: Jun 2002
Posts: 261
Thanks for the help.

I do not believe he has added anything to the fuel. Good idea, and cheap.

We were thinking it may be time for a tune up just because it couldn't hurt. The right side of the engine has lots of hoses in the way... fun fun.

We are in southern LP of Michigan.

We did rev the engine pretty good by pressing the accelerator all the way to the floor for about a second. I suppose that would be different from flooring it while driving down the road.

I suggested rebuilding the carb, which I've done quite a few times... on 2 bbl carbs without fuel mixture solenoids that were bolted to 4 cylinders. When I popped the air cleaner's lid I found that he'd been running it with no filter.

I'm starting to wonder about the lack of fuel smell coming out the exhaust. It would seem that if the carb was dumping in enough fuel and the spark plugs weren't getting it burning then I'd smell fuel coming out the exhaust. I think I'll suggest he buy a repair manual and while he's at auto zone he can borrow a fuel pressure gauge. Members of other sites have suggested possibly testing the tps and the fuel mixture solenoid(s).

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