1987-1990 Carburator...replace?
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5.0 and 5.7 Discussion, 1987-1990 Carburator...replace? in Cadillac Engine Technical Discussion; The carb on my 90 Brougham 307 is failing me. I'm losing power (literally creeping out of stop lights), losing ...
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    My_favorite_Brougham's Avatar
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    1987-1990 Carburator...replace?

    The carb on my 90 Brougham 307 is failing me. I'm losing power (literally creeping out of stop lights), losing gas mileage (I'm about 15 mpg on the highway, 12 in town), and occasionally the engine will act as if it were running out of gas even with a tankfull. What can I do. When I bought this car, I thought it was fuel-injected being a 90's Brougham, but I soon found out that my car was the last with a carb (Oh unfortunate me). The 5.7 was injected, and the 91's and 92's were too. I just happened to get one of the few that were not.

    But with that realized what can I do. Is it possible to take the fuel injection system from a 1991 Brougham 5.0L and put it on mine, or have I been cheated out of the durable Chevy engine and stuck with the Olds? Maybe I could get this one re-built, but for how much? Or could I get a good one from another 90 Bro to put on mine, but what's involved with making the switch?

    I am so in the blue.

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    creeker is offline Cadillac Owners Connoisseur
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    Re: 1987-1990 Carburator...replace?

    I'm pretty sure the 307 is the olds. engine, and the 305 is the chev.

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    eldorado99's Avatar
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    Re: 1987-1990 Carburator...replace?

    Yes you can just rebuild your carb, thats what I would do. If you do it yourself its about 30 bucks for the rebuild kit and about 10-20 hours if you've never done it before. If you want someone else to do it it's probably about 100-300 bucks, but you won't be guaranteed they did a great job.

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    creeker is offline Cadillac Owners Connoisseur
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    Re: 1987-1990 Carburator...replace?

    also, forgot to mention,according to one of my books,the 307 was the standard engine that year.

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    Re: 1987-1990 Carburator...replace?

    By the way if the problem is indeed your carb, which it very likely is, then once it's rebuilt you will fall in love with the car all over again. A rebuilt carb makes a HUGE difference in how the car will run.

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    Re: 1987-1990 Carburator...replace?

    Thanks for the info. I think I'll get a rebuild kit, but is it very complex for a first-timer? I just don't want to get over my head, and be stuck w/o a car for too long.

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    Re: 1987-1990 Carburator...replace?

    It is pretty complex compared to other carbs, but if you just think your way through it with a clear head you should be fine. If you get a book called "Rochester Carburators" by Doug Roe (Mine was 5 bucks on ebay) and read through the relevant bits and get a Factory Service manual for your car it will be pretty easy to figure out, but it will still take time and patience.

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    Johnny Bravo is offline Cadillac Owners Fanatic
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    Re: 1987-1990 Carburator...replace?

    Quote Originally Posted by My_favorite_Brougham View Post
    Thanks for the info. I think I'll get a rebuild kit, but is it very complex for a first-timer? I just don't want to get over my head, and be stuck w/o a car for too long.
    No, no, no! Do not attempt rebuilding an electronic controlled Q-jet carb yourself.

    Get a rebuilt Q-jet from professional rebuilder.
    It works like this: They send you a newly rebuilt carb (with a core charge), you (or your mechanic) installs it, you ship them your old carb, they refund the core charge. Bingo, you won't be without a car any longer that it takes to get the carbs swapped out.
    You could also ship them your carb to be rebuilt, but then your car is off the road in the mean time.
    Here are two good rebuilders:

    eBay Motors: 1981-1990 Quadrajet W/Climatic Choke 5 Year Warranty (item 8049066841 end time Jul-07-06 12:27:51 PDT)

    eBay Motors: ROCHESTER QUADRAJET CARB ELEC CHOKE CARBURETOR 4 bbl (item 140039149132 end time Oct-15-06 12:10:53 PDT)

    Call, or e-mail either one with your problem and they can fix you up. The one guy is located down there in Texas so mabey he'll work out better for you

    By the way, you've hardly been "cheated" with the Olds 307. They are super reliable engines that will run forever with a little maintainence, and sometimes even without.

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    N0DIH's Avatar
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    Re: 1987-1990 Carburator...replace?

    I have done 2 rebuilds on E4MC/E4ME carbs. Easy as any others. Get the tools and the FSM. All you need to do it.

    Do NOT go electric choke. Stay with hot air if that is what it came with. I tried it on my 307, and the electric opens too fast, and doesn't at the rate the 307 likes. Stay hot air, it is a good simple choke. Again, a dialed in E4Mx carb is one of the sweetest Q-Jets ever made. Even in -10 to -20F weather, one small tap of the gas and my 350 started better than most EFI cars. (i did a 350 swap in place of my 307)

    Stop by my place and I will go through it with you.

    1. Lost power, is accelerator pump ok? Quick check, pop off air cleaner and depress pump only, it should stall the engine. If not likely bad. If makes it stumble really bad, might be ok too.
    2. Fuel pump working ok? It is up to snuff?
    3. Don't forget ignition, weak ignition will kill power too, HC goes up, O2 interprets this as rich and pulls out fuel.

    I honestly rarely use a rebuild kit unless I need parts like accelerator pump or if I tear a gasket. The can be reused with 100% success if they are in good shape.

    I have mods to do to it if some additional performance and drivability are needed, look into this forum somewhere, I posted them once. Maybe still in the Olds FAQ, some are there too. I am all over in that thing...

    I have a friend who has done wonders for junk shape q-jets. He would do it for a very reasonable fee, I can ask. He is by me in Wisconsin. If you want to ship, I can ask how much he would charge to do it. I have the tools too, so between the two of us, you will have nearly a new carb. Beleive me, the carb I gave him was sad, and he made it run sweet.

    Don't fear a Q-Jet rebuild, but also it isn't the best choice if you have no carb or q-jet experience. I have far more than I ever wanted.... Which is why I ended up with a Edelbrock AFB....

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    Re: 1987-1990 Carburator...replace?

    N0DIH, I like your idea, but with one problem. This happens to be my only car for time being and can't go without it for any length of time. (I'm still a student). But I know of plenty of 307's in a few nearby boneyards. Do you think they would need to be rebuilt? If so, I'd be interested in shipping it to you; then I could just switch mine.

    But I'm still only 90% sure the carb is the problem. You see, my problem was a lot worse. I couldn't get her up to highway speeds in under a whole minute of flooring the gas. Then it was very weak, and nearly rumbled any passengers (and myself) to death. In fact it sounded like a diesel engine, with that distinct sound, when she acted up. So I took her to the mechanic and found out my fuel filter was nearly completely clogged. They replaced it, but said my carb was "underperforming." That's where I stand now. But if there's a chance it could be something else, I'd rather not hand over unnecessary cash.

    What do you suppose could be other possible causes for my symptoms: (poor gas mileage of 12/15, poor acceleration, the occasional 'diesel rumble', occasional stalling) Basically, I creep out of stop lights and signs so slow that everyone honks at me. Sometimes I have to put on my flashers until I finally approach a decent speed.


    **On a different note: What's wrong with electronic choke? After all, I really dislike having to pump and pump and pump, and try the starter three times just to get her going.

  12. #11
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    Re: 1987-1990 Carburator...replace?

    If you EVER have to PUMP, there is a big problem. If you EVER have pump a Q-Jet to get it to start, that is a sign something is messed up. All it does is dump a ton of fuel in the carb. Like I said, my 1982 Q-Jet on a 1977 Olds 350 in a 1985 Olds Cutlass would start like EFI when it was -20F out (yes I live in Wisconsin!).

    1. Get a FSM, you need it, read the carb sections. Read even older ones too. It really helps you understand them. I save all my old FSM's, can't part with them....

    2. It soulds like your float is dead. It will dump fuel like crazy if it is. And when they get really old, they do stop floating. Get a new one.

    3. I bought a 82 junkyard carb for $50 and cleaned it up, reset it all to 1985 442 settings and dropped it on. Did some other mods (learn the carb first, I have put them on this forum somewhere....) and it was a sweet carb.

    4. If it has this symptom, this is the fix. Get in (engine COLD), TAP gas pedal enough to set choke. Pop hood and remove air cleaner, is choke FULLY CLOSED? Correct answer is YES. If not, clean and examine linkage, do not feel the need to screw around with the choke setting, leave it alone. (No electric choke is gonna fix this, the hot air choke is far superior in operation, trust me). Ok, got it working right? It should be FULLY tight closed.

    5. Now, start car. It should start right up and choke should be opened now 0.100 inches. Within around 1 second of start. If it dies right away and restarts, this is likely NOT opened up to 0.100" within 1 second. If not, remove vacuum hose on front vacuum break, depress, plug line with finger, and release. It should take 1 minute to fully extend. This is #1 problem with all Q-Jets I have ever seen. BAR NONE!!! Fix. You will LOVE your carb after that. Set all linkages to factory settings. Also, check rear vacuum break too, it can fail, but doesn't at near the frequency as the front. This is controlled by the ECM from that little black vacuum switch box on the drivers side valve cover.

    6. Ok, got it running? Is the heater hose clipped to the side of the choke housing? Correct answer is YES. If not, fix, this is important to have. Choke rate depends on it.

    You like electric chokes right? So do I, so I modified mine for it, And after a few weeks, changed it back. 1. It opens and warms up too fast, faster than the 307 likes. I tried and tried, I could not get the rate to be right for the 307. It would open, and then cool off too fast, remember that hose? You can't put it on a electric choke. It needs it. So fueling is always wrong with a electric choke. The hot air choke was a staple to Olds V8's. They just plain did well with them. Keep it that way, thank me later... I am a fanatic about good drivability, and know my stuff on these, and I couldn't get it to work worth it, the hot air choke did best by far.

    Check all the vacuum lines, all should be good. If you need help routing them, snap a picture, I can help, I am sick, I still have them all memorized!

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    Johnny Bravo is offline Cadillac Owners Fanatic
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    Re: 1987-1990 Carburator...replace?

    Quote Originally Posted by My_favorite_Brougham View Post
    N0DIH, I like your idea, but with one problem. This happens to be my only car for time being and can't go without it for any length of time. (I'm still a student). But I know of plenty of 307's in a few nearby boneyards. Do you think they would need to be rebuilt?

    What do you suppose could be other possible causes for my symptoms: (poor gas mileage of 12/15, poor acceleration, the occasional 'diesel rumble', occasional stalling) Basically, I creep out of stop lights and signs so slow that everyone honks at me. .
    I really dislike having to pump and pump and pump, and try the starter three times just to get her going.
    Don't be a penny wise and a pound foolish. Who is going to warranty this backyard rebuild? What about the special tools and milling machine necessary for rebushing and resurface the throttle plate? If this was a hobby car I'd say going ahead and tinker with it, but not on your only means of transportation.

    Junkyard carb: You may get lucky and happen upon a usable Q-jet in the J-yard. However, all that I've seen are pretty beat and probably varnished up from sitting for who knows how long.
    Again, what is your time worth: i.e. find a used carb, remove it, clean it up, install, mabey it will work, mabey it won't. How long before it craps out as well and the whole process starts over again.
    I'm all for saving a few bucks when possible, but in this case it just doesn't pay in my opinion.

    With all the pumping, hard starting, engine down on power you're definetly ready for a carb rebuild. It probably has a clogged catalytic converter as well, which would explain the lack of power and poor gas mileage.

    An out of wack carb, running overly rich will do that, and kill the O2 sensor and foul the spark plugs in the process.

    Oh, and you may have damaged the fuel pump with that severely clogged fuel filter.

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    Re: 1987-1990 Carburator...replace?

    Quick. Look at this carb whose auction ends in less than an hour will it fit an Olds 307 on my 1990 Brougham? It looks like a good buy for a rebuilt one.

    eBay Motors: Rochester Quadrojet 4 Barrel - Rebuilt (item 300034166678 end time Oct-11-06 18:37:02 PDT)

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    Re: 1987-1990 Carburator...replace?

    I sent my carb to CARBS UNLIMITED INC. carburetors including Weber Edlebrock Holley Quadrajet to have a the fuel inlet retreaded and a rebuild. They do good work. But I know my wagon is missing some vacuum lines and other things. Even before the rebuild it ran fine, but you had to pump it like 10 times or more to start it when it was cold. Now its like 5 times so it's getting better. I replace the blocked breather today and it starter after 3 pumps.




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    joe_padavano is offline Cadillac Owners Member
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    Re: 1987-1990 Carburator...replace?

    Quote Originally Posted by My_favorite_Brougham View Post
    **On a different note: What's wrong with electronic choke? After all, I really dislike having to pump and pump and pump, and try the starter three times just to get her going.
    That isn't an electric vs. hot air choke issue, that's something not working correctly. My 307 with electronic Q-jet has the factory hot air choke and it starts just fine. Keep in mind that every carbureted car requires a single pump on the gas pedal to set the choke and squirt a little gas in the engine. EFI engines do this automatically, which is why you don't need to touch the gas pedal to start them. It's been over 15 years since the last carbureted car was sold in the US, so most people don't even know this.

    Getting back to your problem, both the starting issue and the lack of power at stoplights sounds like an accelerator pump problem. This is one of the things that gets replaced in a carb rebuild. You may also want to replace the choke coil. The bimetallic spring can lose tension over time. I replaced both the coil and the accelerator pump when I rebuilt my carb, and as I said, it starts like an EFI car.

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