Zola

Hey guys,
I've been lurking/learning for a month or so on the form while reviving a 79 L82 barn/garage find that had been sitting for 4 to 5+ years.

I've got her running pretty good except... After shes good and hot (7-10 minutes of driving, I'm in FL its 90* out), she stumbles/bogs with aggressive acceleration. If you let her work threw it or just hold your foot in it, she'll eventually perk up and take off. if you pull on the road easy/normal you can hardly notice but you can tell shes not perfect.

When shes not hot, shes a beast, more so than I expected. I made a turn rolling about 10-15 mph stomped it and got her sideways left, still spinning back right, slid back left a little, straightened her out and took off like a rocket. My son was in the passenger seat, we both looked at each-other and started grinning. He said holy **** I didn't expect that! Me either!

She idles high all the time 1,000-1,300 but with no consistency, sometimes she drops down between 7-900 but that's rare.

I did plugs, wires and purchased a rebuilt carb from National Carburetor (Honestly, fuel systems are my weak point so I haven't messed with it at all). I've been chasing down vacuum leaks like a fat kid after candy. Also, things I assume to be unrelated: gaskets, thermostat, all fluids, u-joints and more but I cant remember right now.

I'm thinking I still have vacuum leaks??? or do you guys think this could be something different?

Any help is greatly appreciated
Rick G

JimLentz

Most rebuilt Quadrajets run poorly. I went through 2 of them before I had mine professionally rebuilt.

AzMotorhead

We need to know basic stuff.
All smog equip installed? properly routed vac lines? Timing set at?

Zola

I had read that on here meany times but National Carb came highly recommended to me but I have my doubts. But with a project like this I cant say for sure yet it's a carb issue...

Yes, sorry, that info would be helpful...
Smog: EGR has been deleted, that's about it
Vac Lines: Fairly certain all is properly routed. Not 100% sure I don't have any leaks still to find coming off the backside port that runs the breaks/headlights/etc...
Timing: That is something I have been meaning to check. I'll do that after work tomorrow... Yes, I know, should have done that already. Keep getting distracted by fixing one thing and going for a burn, fix the next thing and go for a burn...

Thanks for the replies and help so far. I'll report back tomorrow with timing.

Zola

Sorry it took me so long to get back...

Anyhow the timing, with vac advance off, is set at:
19 degrees @ idle
29-30 degrees all in (2,500 - 3000 rpms)

454Luvr

Is that while the motor is idling at 1000-1300 RPM like you mentioned earlier? If so, you need to dial the idle down and check again. Mechanical advance is probably already partially in at that speed.

Zola

Yes, sitting at idle it was right around 1,200 rpms... okay, so I'll back the idle down and check again.

Thanks for the help.

billschroeder5842

Have you checked your Choke? Sounds like you might have a choke issue as it run well cold and pukes out warm.

Zola

454Luver, I think you are correct...
I dropped the idle speed down to 700rpms and the timing fell off to 11*.
Bumped the timing back up to 18* and made a world of difference.

Now I just cant get any consistency in idle. On start up I have to have the high idle screw all the way in just to keep it running (about 500-550 rpms). Take it for a drive and runs pretty good. In gear foot on brake idles right at 650. Put it in park and it runs back up to 1,200. If I turn it off and back on the idle will drop down to 850-900rpms.

Do I just need to keep tweaking and messing with idle high and low and mixture now until I can get it right? Or do you think I am missing something?

As for the choke, it's the automatic choke. It seams to be working correctly; closed when cold open when hot?

You all have been a great help so far.
Thank you
Z

CiCiC3

Sounds like mine in hot weather, it goes into vapor lock because the fuel is actually boiling. I think that is when the fuel line gets filled with vapor partially and with a mechanical fuel pump it's worse. I'm just looking into it now on this forum. No clear solutions yet though.

MajD

Before tearing into the carburetor, I would make sure those old vacuum lines aren't leaking. You may have multiple leaks, so its probably best to plug as many lines as you can. Since they can leak around the nipple connection, I would recommend either testing with fresh hose or buying a plug kit. There are some vacuum circuits controlled by thermal switches on the thermostat housing. Since it acts up after its hot, there could be a leak down stream of one of the switches so you may want to check there first.

Of course, if you're interested in rebuilding the car, many of the vendors sell a correct emissions hose kit for your year and engine. When I purchased the kit, it did not contain the hoses to the charcoal canister. I had to source those locally. My canister hoses were in really bad shape because they pass so close to the exhaust. After installing the kit and canister lines, my 79 ran like a whole new car.

MajD

Zola

MaiD, I think that will be my next step. I've been chasing vacuum leaks fire weeks now. Replacing as many as possible, needed or not, sounds like the smart play. It will fix the problem or at least I'll be able to eliminate that entire system.

Unless anyone has a better suggestion, I think my next purchase will be new vacuum lines and test equipment. Then try more tuning. After that I'll move on to fuel supply???




CiCiC3, you may be on to something as well. Just today I was toying with the idea of swiping out the mechanical for an electric fuel pump... not sure if that will do anything or not. I hate throwing parts/money at problems hoping to find a cure...

DaveL82

The HEI module fails in limp home mode. It will run fine at start up until heat causes it to run rough. Change the module in the dulistributor and rotor as the rotor will have signs of arcing through to advance weights and the module. You'll see rust like deposits on the weights. Common problem and I've changed out a few over the years

REELAV8R

Check that your accelerator pump is working.

Zola

REELAV8R, I thought for sure you were onto something there because it was starting with just 2 pumps on the accelerator and bump the starter. Now its a few revolutions on the starter before she fires off. However, I checked the accelerator pump and it is working correctly.

This thing is driving me crazy... I did get most of the stumbling/hesitation out of her (thank you 454Luvr) but now I cant get a consistent idle to save my life. I'm gonna swap out all the vacuum lines and try again.

One thing I haven't messed with is the mixture... Just don't know enough about it. I've got a suspicion that shes running a little lean but again... I only know enough to know, I don't know enough.

Zola

DaveL82, This also sounds like a possibility. I'll pull this apart tomorrow and look for the "rust like deposits". Thanks for the tip, I'll let you know what I find.

454Luvr

1. "She idles high all the time 1,000-1,300 but with no consistency, sometimes she drops down between 7-900 but that's rare."

2. "On start up I have to have the high idle screw all the way in just to keep it running (about 500-550 rpms). Take it for a drive and runs pretty good. In gear foot on brake idles right at 650. Put it in park and it runs back up to 1,200. "

Well, the problem could be the HEI as someone else suggested, but those symptoms sound like a vacuum leak. You need to plug all the vacuum ports on the intake manifold and carb, then see if it idles better. If not, then with everything still plugged, spray WD-40 (or anything similar that won't eat paint) around the flanges of the intake manifold to see if an intake gasket might be leaking. You also should check to be sure the intake/carb/carb gasket are all compatible. A wrong gasket or carb-intake mismatch can cause a leak.

"I dropped the idle speed down to 700rpms and the timing fell off to 11*.
Bumped the timing back up to 18* and made a world of difference. "

18* is too much. It should run fine with 8-10* initial advance. At this point, it's worth checking to be sure the harmonic balancer hasn't slipped, and that the TDC mark on the outer ring really is TDC. You'll need to drop the pan or get into the no. 1 spark plug hole with a dial indicator to confirm this. There may be other methods; do a Google search for options.

Zola

Maybe a silly question... Could a bad torque converter cause erratic idle? Especialy big jumps from "in-gear to out of gear" and 'hot vs cold"???

Reason I ask is because I have an annoying "eeeeeeeaaaak!" or "waaaang!" noise on hard, off the line, acceleration. I didn't think it was related before. I thought it was the differential carrier bushing or fan/shroud from the torque but my son had it up on a lift today and couldn't find any signs of rubbing. So I'm thinking maybe the torque converter is bad?

Zola

Update: Don't send a boy to do a mans job.... I knew it was the fan hitting the shroud. Broken motor mount letting the motor torque over and fan to hit the shroud. Noise issue solved, torque converter is fine.

As for the idle: She's much better with some fiddling. I think I'm getting close. Only thing I have to figure out now is: In gear idle is perfect, just under 600 rpms and sounds awesome. In park or neutral she runs up to around 1100 if shes hot. But turn off the ignition and back on and she drops to 7-800... Not sure about that yet.

Thanks for the help.

bluedawg

Sounds like a vaccum leak to me as well, but what camshaft and stall converter? Are they stock or are they aftermarket? Sounds like it could also be a camshaft and to tight of a converter, can you get the idle in park down to 750 and if so when you put it in gear does it die, would be symptoms of either a vaccum leak or to tight of a coverter with needing 19* at idle, it might have an aftermarket cam shaft.