1989 Chrysler Fifth Avenue still idling rough/stalling after carburetor work?

Even the most basic tests will have the inspector pop the hood and take a quick look, from what I understand. But I don’t realistically see the inspector removing the complete air cleaner housing to make sure the carb is in fact the “correct” one

Nashville area emission testing NEVER opened the hood on any vehicles, only tail pipped pre OBDII and looked for the cat converter and of course plugged up to the OBDII vehicles to make sure no codes and the monitors were complete and checked gas caps…

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I’m with tester. Danged if I can remember what year it was, maybe 78, but mom had a Plymouth she bought new. It was about 5 miles from her house to the first stop and it would stall and run terrible every time. I went over the carb twice and still did it. Finally my bil looked at it and there was a coin shaped heat sensor or something on the manifold that evidently controlled the choke. He disconnected it and all was fine.

So I’m of the opinion to at least look over that choke mechanism and that heat tube. It will not run right if the choke is half closed. Some people even go back to a manual choke.

The choke was calibrated to open prematurely for clean tailpipe emissions, common on many vehicles in the late '70’s/early '80’s, I thought it was normal for any car of that period to stall. Your brother-in-law disconnected the choke heater to delay the opening of the choke.

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Well that makes sense, to delay the choke instead of opening it.

Yep, my TR6 needs to have it’s carbs rebuilt sooner rather than later, the enthanol has eaten up the seals and the carbs leak air. Have to use the choke as sort of a mixture control constantly now. Choke closed = idles great, but falls on it’s face around 3k RPM, Choke open= idles at 2k RPM, but will pull strongly above 3k RPM.

Here in Calif the emissions inspectors do look under the hood. To make sure all the emissions parts that are supposed to be there, actually are. They look under the car too, especially at the exhaust system. I doubt they would check the carb’s mixture screws position. Leaning those out could improve HC, but might cause over the limit NOX, so would have be be cautious about adjusting mixture towards lean… They measure the ignition timing but pass/fail has a reasonable tolerance, 2 degrees retarded will still pass I think. So retarding the timing 2 degrees seems a good idea. Blocking off the EGR? Not sure about OP’s Chrysler, but my Corolla’s computer would flag that.

I’ve mentioned here before that my experiments on the Corolla have shown the most effect on emissions testing is the engine air filter. A little on the clogged side results in lower emissions than a new air filter.

Once you do the ignition conversion it eliminates the lean burn system which was the worthless computer for the car… OP’s vehicle is closer to your truck then your Corolla… The EGR most likely has been clogged since the 90’s anyway… Blocking off the EGR is the 1st thing a Mopar guy does if not doing a OEM build or swapping to an Eddy intake… The EGR adds a lot of heat to the bottom of the intake through the cross over and causing less dense air causing a loss of power…

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RE: George wrote

I doubt they would check the carb’s mixture screws position. Leaning those out could improve HC, but might cause over the limit NOX,

A carb’s idle mixture screws affect CO and HC. NOx forms at higher cylinder combustion temperatures, which doesn’t occur at idle.


Remember those plastic caps on the mixture screws so that you were prevented from adjusting the mixture to rich. Their game was to lean out the carb then increase the throttle to compensate for any engine that wouldn’t run. Then the shut down solenoid to stop the dieseling. Thanks to fuel injection, that nonsense was replaced. I’m sure there was a fine or jail time for breaking those caps off. Show me the man and I’ll show you the crime.

My 83 colt with Mikuni? carb had a hot wax pellet choke. Went haywire 1 day and smoked the cat. Had orange glow from under car. I took off air cleaner and watched choke go off/on/off in 5 min. Never did figure out what exactly was issue. Oh, and my mileage dropped 10 mpg after cat incident.

I worked in a new car dealership back in ~75 when a number of new emission controls showed up on the ~75 models. Driveability problems were very common.

To avoid those problems and customer complaints, we quickly learned to:
- Break the plastic and set the carb’s idle mixture screws for the smoothest idle.
- Disable the EGR valve
- Advance the ignition timing several degrees beyond spec.

The above solved most of the problems. In a few cases we learned to raise the metering rods in the carbs a notch, or to drill out the main carb jets about 2 thousands of an inch to restore the richer fuel mixture ratios used in prior years. Doing that always provided a really nice boost in both power and improved gas mileage.

In many ways it was the wild west. Dealerships did what they had to in order to keep customers happy. The complaints were brutal and the car manufacturer was not in a position to help.