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[slowbuick]

Hi all, some of you might remember me from previous forms from when the car was having trouble starting and was stalling out. Iv gotten many good answers and I'm still referring to the excellent info iv received from there for this current problem. Iv since resolved that by replacing the fuel pump. The car was fine for about 6 months and now I'm having trouble again. Its not stalling and has no trouble starting and cruises fine, however, its still generally boggy when going down the road and hesitates when you accelerate suddenly from a stand still or when you try to accelerate quickly when rolling. Another words, when your maintaining speed, its fine, but when you hit the gas from a stop, it will bog out and you have to either get off the gas and hit it again more gradually, or sometimes at higher speeds you have to mash it to get out of the bog cycle, sounds like a classic accelerator pump issue, except that was replaced 6 months ago.

List of things that have been replaced/checked
-Fuel Pump Replaced
-Carb professionally rebuilt two years ago, then professionally cleaned and had the accelerator pump and filter replaced 6 months ago
-Vacuum lines professionally checked and passed 2 days ago
-Timing on point (Mechanic checked 2 days ago)
-Idle is good (also Mechanic checked 2 days ago)
-New spark plugs/wires/ignition coil/module 2 years ago
-Fluids all changed 2 years ago
-Kickdown cable and throttle all replaced and tuned professionally
-Gas tank lines replaced
-New Battery
-Valve cover gaskets replaced
-Electric wires and plugs for electronic choke replaced
-Pretty much any preventive maintenance/old car maintenance/and broken parts have all been replaced
-Rest of the car is in amazing shape, very solid, and has 0 issues other then that damn buick 3.8

It was at the mechanic 2 days ago, where he played with the timing and checked all the lines/carb/etc, and it only made the bogging more tolerable, not a permanent fix. Many of you will probably say that I had a crappy mechanic, and while I do agree to some extent, he is known to be one of the best mechanics in my area. The mechanic before him I took it to for the fuel pump issue always gets it right, though he's had it twice and his work has never lasted more then a year. Again, it could be the mechanics, but these guys are some of the best around and typically deal with cars like this and always have good reviews. I'm at my wits end with this thing, whether I get rid of it or not, I would like to get it fixed so I can either be able to get to work or be able to sell it for enough money to get another problemed car. I could try to get a good driving video from the hood to hear the engine if that would be of help to anyone.

 

[ck80]

Dumb question, but, when they're working on the carb, are they using modern manufactured, ethanol resistant parts for it and such?

Cause if they're using old stock carb kits and pieces, and, you don't burn ethanol free aka marine gas then you'll keep undoing the repaired work....

Basically if you need to keep having the work redone, there's a few common denominators, especially if it's the recurring problem. One answer is incompatable parts and fuel. Another is that they are getting things close, and, then tolerances continue to get worse and the problem returns - such as if the needle issues with bushing wear and they aren't fixing the bushings, just swapping needle size.... or, float is getting damaged by the ethanol and not working like it should.... so on so forth.

Edit: another would be which fuel lines were done... there's rubber lines hidden atop the gas tank between sending unit and metal lines that were not ethanol safe from the factory. And, not all rubber line sold by parts stores is ethanol safe either. If that line is getting degraded and sending debris to the carb.... or if the tank was never dropped and checked, has the fuel filter ever shown signs of crap being pushed to it...

Edit 2: another question would be if you're still running the efe unit (early fuel evaporation unit) it's like a thick gasket with wires coming off it between the carb and intake. They melt with age. You could have some sealing issue with the e.f.e. or a problem on the intake/carb surfaces that, when freshly put together, everything seals nice. As time goes by, something loosens and you wind up with a massive vacuum leak.

 

[ck80]

I just called up my carb guy, he said that he replaced everything with ethanol safe parts, however I still believe its entirely possible that these problems could be a result of them. Carb was professionally cleaned and rebuilt by the best in the area. Im not quite sure what the efe unit is, but if its related to the carburetor it most likely was replaced. If its part of the engine, then it wasn't replaced and could likely be something to check on.

Fuel Lines- I should have mentioned I did not touch the stock metal lines, I just dropped the tank about 6 months ago and replaced the rubber lines on top of the gas tank (old ones broke when I dropped it lol), from what I saw the metal ones looked fine, but I could be wrong. I shook the empty tank and it didn't feel like any crap was in there. Fuel filter has never looked bad, though it has had a tiny bit of crap in it in the past, as a matter a fact, when I had my guy clean the carb the second time 6 months ago, he said there was a little bit of buildup inside it, though he said it wasn't enough to start trouble. I'm going to take the fuel filter off sometime tonight or tomorrow and get back to you on how it looks, your theory about the gas lines is starting to make more and more sense.

Just for some context, 3 years ago the carb was professionally cleaned, 6 months ago it was cleaned again (when he said there was some buildup but not enough to cause problems) when I was having my starting problem, though that ended up being the fuel pumps fault. I think what we are both thinking now is that since then the fuel lines or whatever is causing the crap to build up has started again over those 6 months. I'm also going to ask my carb guy what he did with the bushings inside it since you brought up a good point about them.

Mechanic- I took it back to the shop today and raised the idle for the hell of it, did nothing. He said that the timing might be a little too fast, and also said similarly to you that the ethanol might have done some damage in the carb, that was when I called the carb guy and he said that shouldn't be the case after his work. To keep myself from blabbing on, its going to go to him again this Thursday and well see what happens when he adjusts the timing again.

Thanks again for the helpful response, it gave me a lot of things to think about vs going in cold.

First and foremost, the e.f.e. unit was a gm attempt to improve cold start/idle issues on the automatic choke computer controlled carbs. It's like I said, it looks like a very thick composite gasket, ~3/16" or so with a pair of wires and plug coming off it. Embedded into it where the openings for the fuel/air mix to pass from carb into intake was a metal grid. On cold starts the computer would activate the grid which acted as a mesh heater to pre-heat the mixture. The grids would, over many years, melt away. Assembly order is intake, then efe, then carb on top. As you can imagine, it can be a source of vacuum leak since you're adding multiple layers of surface sealing instead of just carb direct to intake.

Based on your other info, I'd add two consideration points: 1) was the rubber line you replaced above the gas tank ethanol safe, or, just fuel line? Not all new rubber gas hoses are ethanol safe, although, fuel injection barrier hose usually is. 2) I'd drop the tank, pull the sending unit, and check the fuel sock. It's a $1 part, but, if there's dirt or debris in the tank it'll clog and restrict flow.

It's a cheap labor-only exercise that tells a bunch. When the car is shut off, and suction ends, debris can detached from clinging to the surface and flow is better. Start up again, and, it comes back. Especially if you're seeing stuff in a fuel filter anyways.

I had an 88 cutlass I bought that was so bad, the car would shut off after a few minutes due to starvation. Redid the tank/sock and problem gone. That was much worse than yours, but, I think if you want to narrow things down as cheaply as possible I'd drop tank, check sock, ensure rubber lines ethanol safe. Then unhook the rubber line to the fuel pump, blow out the metal fuel lines. Hook a long rubber line on the back to a glass jar of gas, hook the front line to a cheap HF transfer pump, and pull the gas through and look if it comes clear or is picking up junk. Then you know you've got good gas supply to the pump, and, all it takes is time to see if issues are present in that area.

I'd check the e.f.e. surfaces using some starting fluid sprayed while idling, cold engine. If the idle races, you know it's sucking in.

Then I'd chase my vacuum lines and make sure there isn't something cracked or broken anywhere, just to be safe. But the fact the problem goes away and returns over time steers me away from that.

It really sounds like you've got an issue elsewhere with a reassembly loosening up, or, an ethanol issue.

Fwiw, ethanol free fuel has higher energy content so while it's more per gallon, you use less (depending on driving style.) I only run ethanol free due to it both being much more corrosive, and, it's water introducing properties unless I'm in one of my late model vehicles AND on a road trip where I know the gas will be burned away in the next 48 hours.