Too rich Quadrajet

Hello I need some help. My 1990 Buick estate wagon has had the following replaced, Carb, A/C compressor, Power steering pump & lines, Alternator Water Pump, radiator & hoses. Now beside I can't any one to paint her body. The check engine light comes on for a rich condition. The Quadrajet is un adjustable. I have blown several discs out in my back from hanging over the engine bay trying to get the engine to run right. I checked & replace all the vacuum lines & repaired any questionable parts with new. I replaced the ECM & several relays and sensors including the O2 sensor. Same problem. The carburetor is under warranty from Auto zone. I called the help line & the person on the phone told me to return the carb for credit. I was hoping that some one had a idea of what is happening. I was told it may be Catalytic converters? I have a pair on my Chevrolet truck I am replacing. Pipes same size. Should I change them? Take to a repair garage to have the ECM checked & maybe they can find source of problem? HELP!

 

Why did you decide on replacing the carburetor, instead of determining what could have been wrong with it? It wouldn't have been such a big deal, in 1966. But, once O² sensors and ECMs are added, everything becomes a nightmare. Fuel injection eventually had to take over, in order to cope with all the added gadgetry.
Quadrajets were manufactured in several different types of which you'd have to keep a close eye on, in order to not install one with a visibly minor difference which becomes an elephant when running.
Do you still have the original or did you have to give it up as a core?

 

First off, find a reputable shop that can hook up an older scan tool (my old shop, like a lot of others, still has a Snap-On MT2500) and read the exact trouble codes. With my small knowledge of CCC systems, I have a few questions to ask which may lead to other questions.
1) When you turn the key on, do you hear a rapid metallic "CLICKACLICKACLICKACLICKA?"
2) If not, are the electronic connections damaged on the carb?

What you should hear, when you turn the key on, but before you crank the engine, is the clatter of the mixture control solenoid. After the engine starts, at idle, it should continue to clatter, and the scan tool's data stream should show a MC solenoid dwell of 30*, when correctly adjusted. Now, in addition to that, at idle, the scan tool should show the oxygen sensor in a .01 to .99 volt full range, and should be swinging rapidly between .05 and .95 volt if everything is correctly running. SO, if the MC solenoid is not clattering, and the O2 sensor is pegged at 1 volt, then either the solenoid is not working, the coolant temp sensor is shorted, the MAP sensor is unplugged or has a heavy vacuum leak, and a few other things. If we were nearby, I at least could do some basic checks, but this does require someone who has done these CCC systems in-depth, and you do need at least an older scan tool to do the work. With these cars, replacing parts without full diagnosis is an exercise in futility.

 

Interesting reply. I replaced the Quadrajet with one I bought rebuilt from Auto zone. Has a limited life time warranty? No shops will work on Carburated vehicles. My Dad & I both have be told this. Dealer will not touch my Dad's 84 Caprice or my 90 Buick. Something to do with emissions & not GM parts. Been kind of bed ridden with my Cancer. First this old Buick wagon came to me as a Old couples car. But found many problems with electrical. I tore into the problems with the first engine check codes for TPS & float sensor. Tore down carb to replace them & never got it to run right. The check engine light only comes on when cruising at a constant speed. Running rich & terrible performance. Have to see if a scan tool is for sale some were. Thanks for your response & I will work on finding what to do? For Sale sounds like my only option with the Ohio law on Salvage vehicles.

 

That carb you got from Autozone is likely garbage. The jobber carbs have been awful for years, a mishmash of parts rarely calibrated for the engine you are requesting they go on.

Listen to STH. He's got it right. This is a feedback carb system and it requires all of the components functioning correctly to work properly. Just throwing parts at it is going to waste time and money. If you have a factory service manual for the car, it details how to troubleshoot the entire system in easy to read flow charts. No shops will work on this system as its been out of production for almost 30 years and most techs in the shops haven't even seen one much less spent any time on one.

 

Tell you what you can try: put up an ad in Craigslist, in search of a shop that has handled GM CCC carbs in the past, and might still have a tech who worked on them, or a shop owner who worked on them back when they were getting started. As for a scan tool, look first for an older GM Tech II tool, and if you can't find one, then an MT2500 or equivalent, on ePay. I know there are a bunch of 2500's for sale, so you only need one that has the oldest cartridges for domestic cars.

 

Holy crap, never mind about the Tech IIs! Even well-used ones are very expensive on ePay!

 

The first MT2500 listed is very complete and only $100

https://m.ebay.com/itm/Snap-on-MT25...799459?hash=item2864152623:g:cisAAOSwvWtbdwi~

Note: no reserve is mentioned, and there's 1 day and 14 hours left for bidding.

 

Everybody take a breath.

First, do not even think about adjusting the CCC Qjet unless you have read and thoroughly understand the adjustment process in the factory Chassis Service Manual. I've had four of these cars now. You MUST follow the factory adjustment process EXACTLY. Failure to do so will not end well.

Second, good luck finding anyone who has a clue about the CCC system anymore. There are no mechanics these days, just parts replacers who are only capable of replacing the part that the computer tells them to change. None of these clowns can diagnose their way out of a paper bag.

Third, you do NOT need any special test equipment to adjust the CCC Qjet, just a dwell meter and a vacuum gauge. Again, READ the factory manual.

Fourth, the OBD I CCC system is pretty stupid. It monitors very few parameters. There are far more failure modes that will not set a code than ones that will. You must be intimately familiar with the theory behind the system to understand these failure modes. For example, if the A.I.R. system (smog pump) valves go bad, you can get fresh air being blown directly at the O2 sensor. The sensor interprets this as a severe lean condition and runs the carb full rich. No amount of adjusting will fix this - you must correct the problem with the A.I.R. system. Usually, one of the check valves in the A.I.R. lines goes bad, allowing hot exhaust gas to reach the switching valve, which then fails open and allows this to happen.

Fifth, you MUST ensure that every single inch of the miles of vacuum lines under the hood are in good shape and connected properly. This is by far the most common cause of CCC problems, and again this will not set a code.

Sixth, even a brand new CCC Qjet must be adjusted per the factory process once bolted to the engine. You cannot simply install the carb and expect it to run right.

 

I will admit, I am lacking in the experience to go making carb adjustments on a CCC carb, but I do know that you do have to start somewhere, and that starts with checking the computer for codes (and make damned sure the 'CEL' light bulb works, as some of the GM cars' data link circuit was tied in to that very bulb) and reading any data, along with a thorough inspection underhood. What the OP's problem is, is that he has a physical limitation, and can't do most of the inspection, let alone know what to inspect. But you have given us some things to work on, starting with disconnecting the AIR output hoses to see if the one-way valves are burned out. And if there was a scan tool handy, the oxygen sensor could be checked to see if any change occured.

 

You can check the O2 sensor and TPS outputs with a voltmeter. Yes, a scan tool makes it easier (I've got an OTC Genisys). I'll also agree with elB - the rebuilt versions of these carbs are crap. One came on my 1985 Delta 88 and when I rebuilt it, I found a complete cluster f**k of incorrect parts inside. More importantly, there are very specific (and fussy) adjustments inside the carb when you rebuild it. The manual calls for special gauge tools, however you can make a copy from dimensions in the manual and a piece of wire (although this kit sold for $10 on ebay).

 

Yeah, I remember my boss from the early 2000's rebuilding these, and having the complete GM kit for it. He was a part-time instructor at Bates Voc-Tech in Tacoma, and his brother was the head instructor for automotive there. If my finances hadn't been so lacking, I was supposed to use my G.I. Bill to attend there, but in the 4 years I worked for Randy, I learned a lot about older cars.

 

Here is the Carburetor I bought to replace the one that did not work after changing both electrical sensors to ECM. It is sealed & not adjustable due to warranty. I spoke with Auto Zone & when I feel up to it? I will take back for a refund. All auto parts stores in my area use the same company. Yes, I have replace all the vacuum lines & the hoses. along with the AIR pipe that was rusted off at catalytic converter. It is after the O2 sensor. I do have the GM repair manual for Buick, Chevy Olds etc station wagons. I do not own any tools to check what you said needed to be with in parameters. So? I guess I am screwed? To top it all off. Many parts are just too old? The headliner fell out after days of above 100 degree temperatures. Along with I pushed the windshield out re-gluing mirror attachment. Thanks for all your input. Anybody want a 1990 Buick Estate wagon? 59000 miles in fairly good shape if not looking at paint & Quadrajet. 20/20 hind sight? Never buy unseen cars trucks electronics etc. on ebay. Third time this past year I got screwed. Plus never buy TV's anymore. If you do not have wifi & want it to work? One I bought kept coming on a 2 am searching for wifi. Scary as hell to hear voices & the TV being on. Thanks again

 

That pipe is EXACTLY the problem. The A.I.R. system has a switching valve. When the engine is cold and in open loop mode, air from the air pump is directed to the pipes that go to the exhaust ports. Once the engine warms up and the ECU switches to closed loop mode, air from the pump is directed to that pipe to the catalytic converter. If the check valve at the top of the pipe goes bad, hot exhaust gas can reach the switching valve. If the switching valve goes bad, air from the pump is ALWAYS sent to the exhaust ports. When the engine is in closed loop mode, the O2 sensor sees this fresh air and incorrectly assumes the engine is running lean, thus the over-rich carb. I had exactly this problem on one of mine.

One easy test is to temporarily disconnect the outlet hose from the A.I.R. pump. If the engine runs better (ASSUMING the carb has been properly adjusted per the factory procedure) then you've found your problem.

 

After a 4 hour marathon to get grass cut & clean up my yard. I check for click sounds? I heard the heater, Air ride compressor, Antenna going up & down, Seat re adjusting it's self, Heater fan, A/C compressor cycling & not staying enaged & lots of other sounds. I checked what I could. Set out for a trip to grocery store. Running ok? I came out of grocery store & attempted to start my 90 Buick. Nothing. cranked & cranked no start. Shut everything off. Only starter to draw on battery. Tried again? Nothing. Waited as I was being stalked by a group in a white Pick up truck. Well after 20 minutes. She started. BUT? A terrible screeching sound. Afraid to shut it off. Out of no where. Another horrid sound. The belts all came off the pulleys. Now was over heating. No more check engine light or screeching. Got home to see my radiator was empty & belts were shredded & ?? I am going to place the belt to alternator on, leave the rest off. See if a Compressor? Power steering? AIR pump? Seems all the new replaced parts have failed? Thanks to Rock Auto Parts , Advance & Auto Zone, O'riley's, NAPA selling replacement parts that are not compatible? Like I said first $4500 can have it. Tired of working on it. Send your interests? Located just off I-280 in Toledo Ohio. JUNK!!