Rough Idle, '84 Caprice, 305

[DWCaprice2017]

Hi, Everybody!
I got the car almost five years ago. About a year-and-a-half ago, I had the carb (electronic Quadrajet) rebuilt. It ran fine for about four days, then it could barely stay on. Back at the carb shop, he rebuilt it again, finding some small particle had lodged into something. Fixing that, the car ran well...until about two months ago, when it barely stayed on to get me to work. Back to the carb shop, he told me it was dirty--sucking up the junk in the tank--I wasn't keeping much gas in the tank, now I am. He cleaned it, put in a new filter, this time he mentioned that he thought something might be off in the distributor--without specifically testing it. I drove the car for a few days, it was actually running a bit rougher now than before the third rebuild. Doing research, I discovered that a faulty Ignition Control Module could cause rough idling, a bad/clogged EGR could cause it, and of course, the spark plugs, which I replaced about two years ago. I'm taking the bus to work now, so I only drive it a short distance to keep the battery charged once a week, the engine sounds great!

I've replaced the spark plug wires, cap, coil, and rotor when I did the spark plugs. For all these, when possible, I use AC-Delco.
I know the left (passenger side) valve cover gasket needs to be replaced, I did the easier right one a couple years ago. I know it's seeping oil, causing smoke.

Questions:
1. Wouldn't a fuel filter--the one that goes into the carb--filter out all the junk in the gas tank?
2. Is there another component that I hadn't listed that could cause a rough idle--presuming there's no vacuum leaks?
3. Could the carb just be beyond rebuilding, and just get a replacement?
4. I was told to only use Shell or Chevron gas--I'd been using Arco, big mistake I now know!
I took the car to a smog check (California), he gave a preliminary check, it was on the border of not passing,
he suggested I use CRC's Guaranteed to Pass, which I plan to use after getting the idle fixed--does this
stuff work?

Thank you, all!
Be safe out there!

 

[78Delta88]

#1: if the debris is large enough to be caught. If the filter got clogged, fuel will bypass the filter and get into the float bowl.

#2: Yes and Major problem on Q-Jet, primary throttle plate is worn or egg shape. Need new bushing put in.

#3: Typically no, unless you shot it with a .45 or put an axe to it. On the Q-Jet; the only thing renders them useless is bad throttle plate or hot idle compensator port or mounting damage. Bad plate..., install new bushings. Hot Idle Comp., is a non issue GM got rid of that late 60s. The cast is still there on the carb body, but none drilled since about 1971.

#4: Unknown. Shell is know as being a little cleaner, but most Pennsylvania Crude is higher sulfur, same for Pennzoil motor oil. At least going back to the 80's and 90's. I worked ARCO station in HS and noticed my Trans Am ran better with ARCO. During EMT days I was driving the 82 Impala about 8 hours a day to include sporadic lights and siren runs. For the most part filled up at Shell off of SR 37 South of Indy. Never had a problem, never noticed a radical change or greatness either

As far as rebuilding yours or getting a new one, it's 50/50. A good carb guy can have yours singing and smoking tires in no time. A properly remanned one will do the same. Cost is going to be about the same.

Rebuild yourself for about $80... Kit, tools, carb cleaner, plastic tub to soak it in, etc

Buy remanufactured unit for about $250

Have yours built by shop that knows how,... For About $250

So up to you

 

[DWCaprice2017]

#1: if the debris is large enough to be caught. If the filter got clogged, fuel will bypass the filter and get into the float bowl.

#2: Yes and Major problem on Q-Jet, primary throttle plate is worn or egg shape. Need new bushing put in.

#3: Typically no, unless you shot it with a .45 or put an axe to it. On the Q-Jet; the only thing renders them useless is bad throttle plate or hot idle compensator port or mounting damage. Bad plate..., install new bushings. Hot Idle Comp., is a non issue GM got rid of that late 60s. The cast is still there on the carb body, but none drilled since about 1971.

#4: Unknown. Shell is know as being a little cleaner, but most Pennsylvania Crude is higher sulfur, same for Pennzoil motor oil. At least going back to the 80's and 90's. I worked ARCO station in HS and noticed my Trans Am ran better with ARCO. During EMT days I was driving the 82 Impala about 8 hours a day to include sporadic lights and siren runs. For the most part filled up at Shell off of SR 37 South of Indy. Never had a problem, never noticed a radical change or greatness either

As far as rebuilding yours or getting a new one, it's 50/50. A good carb guy can have yours singing and smoking tires in no time. A properly remanned one will do the same. Cost is going to be about the same.

Rebuild yourself for about $80... Kit, tools, carb cleaner, plastic tub to soak it in, etc

Buy remanufactured unit for about $250

Have yours built by shop that knows how,... For About $250

So up to you

78Delta88,
Thank you very much for all of your answers!
I found a shop that will rebuild it for about $200.
I found a company in Florida, Guaranteed Carburetor, that sells rebuilt units for $226, which I think I'd rather do,
but the guy near me is...near me, and he'll take it off the car and make the adjustments--I've heard fine tuning
Q-Jets takes some skill.

I'd like rebuild it myself, but in an apartment with no work space, makes it impractical.

Thank you for being an EMT!
Bye,
Daniel

 

[78Delta88]

Good deal. 226 for a good rebuild is not bad price.

Yes EMT days were fun some times. I took the fire chief signal-10 out to child poisoning 911 call in my 82 Impala. He refused to ever run code 3 with me again.

 

[spongbob]

Some of the quadrajet carbs if not most"... have a vent on top that when you remove the breather and/ then " you rake it against this vent that's all it takes if the old crusty air horn gasket is stuck to the breather hole there will be this debrise in the boul following this happening and it will make your car miss and loose power ..
...significantly....may not be your case', ? ...but I'm mentioning it so everyone knows : clean the bottom edge of the breather wear it meets the sealing area..leave no trace of dirt rotton gaskets there...I'm going to mention driving these old motors and depending on them to perform smoothly its important to grind your valves no amount of carburetor expense will substitute for efficient valve sealing .As far as the rebuild since you' had it dune recently ,I'm mentioning its generally is possible to remove the top and clean the bowl ( and reuse gasket once) and spray gumout though the jets with float removed use a lent free cloth if you do any wiping maybe tape a gas line to a vacuum cleaner hose and vacume the bottom of the bowl . Why do this il tell you why( in short) pressurized air and carbs in general do not get along if you spray the jets out remove the gasket from the top of the bowl body pick it up at front and back it will be sticking near the power valve just be carefull and work that gasket loose no power valve ?new carb? I guess be careful period ...newer carb with cycle parts remove them or use brake cleaner not gumout thanks hope you get it smoothed out ps: they used to sell the top gaskets for quadrajets on ebay by themselves but you have to know whitch one probly:also proubly 70% of a quadrajets troubles may be fixed from the top on the car but one must be carefull not to drop small parts period...editing dune lol

 

[78Delta88]

Darn, and I used to pour the old coffee grounds in mine.

Just love the smell of coffee in the morning.

 

[spongbob]

I've cleaned the coffee grounds ? (Rust)out of every carb you can think of carter asan hitachi rochestor webber mikunni you name it...those cleaning fumes havnt dune me much good...but I can still pronounce" Cresnick acid...