Rough idle low throttle surge

[timo22]

Ok, I had the exact same problem. Rough idle, surging when doing 35-40 mph. My brakes also felt hard. So, of course , checked for vacuum leaks. Replaced brake booster, helped brakes but not surging. Tried to find a vacuum leak , but couldn't locate one. Bought a rebuild kit for my edelbrock carb. When I tore it apart, I couldn't see anything obvious . Went ahead with the rebuild and it cured my issues. Engine runs smooth with a good idle and no more surge.. Hope this helps...timo22

 

[Dinosport]

Ok, I had the exact same problem. Rough idle, surging when doing 35-40 mph. My brakes also felt hard. So, of course , checked for vacuum leaks. Replaced brake booster, helped brakes but not surging. Tried to find a vacuum leak , but couldn't locate one. Bought a rebuild kit for my edelbrock carb. When I tore it apart, I couldn't see anything obvious . Went ahead with the rebuild and it cured my issues. Engine runs smooth with a good idle and no more surge.. Hope this helps...timo22

That does help, I also have an edlebrock carb and thats kind of what Im leaning toward as being the problem, If not the carb but something fuel/air related. I know the timing isnt exactly right either but it wasnt doing that till last weekend. Im hoping not to spend alot of money or time right now on it because I would rather put the money toward my LS swap. Ive been slowly gathering little things here and there for it.

 

[pontiacgp]

to adjust the vaccum advance if you turn the adjustment all the way in and back it our 5 turns it'll be in the middle. The you set your timing with the vacuum advance plugged. The you can turn out the allen screw in small incrememts till you get spark knock when your driving and then you turn it in to the prvious position. For now till the problem is solved I'd just leave it turned out 5 turns

 

[Dinosport]

Sounds good. I'll do that. With the vacuum. May just leave there period. Unless I decide I can't do the swap for now then I'll toy with it till I got it right. Thanks

 

[Dinosport]

Well the verdict is there must be something wrong with the carb internally, or something clogged internally.
Fuel pressure checks in at 6psi, that hasn't changed, I didnt mess with timing at all because its the way it has been since before it started surging.
I unplugged each vacuum one at a time and capped it, no change, I sprayed carb cleaner around the gasket, I got it to stay on by raising the idle screw. I toyed with the air mixture screws in front I started at 1 1/2 turns out from all the way tight. I was able to get it to idle better. I put my hands over the carb blocking it, and I could feel the suction and it turned shut off.
Well Im going to see what itll take to rebuild it, I dont know if I will because it seems like a waste to spend to much time or money on that set just to drive it a couple of times before I pull it out.

 

[64nailhead]

Well the verdict is there must be something wrong with the carb internally, or something clogged internally.
Fuel pressure checks in at 6psi, that hasn't changed, I didnt mess with timing at all because its the way it has been since before it started surging.
I unplugged each vacuum one at a time and capped it, no change, I sprayed carb cleaner around the gasket, I got it to stay on by raising the idle screw. I toyed with the air mixture screws in front I started at 1 1/2 turns out from all the way tight. I was able to get it to idle better. I put my hands over the carb blocking it, and I could feel the suction and it turned shut off.
Well Im going to see what itll take to rebuild it, I dont know if I will because it seems like a waste to spend to much time or money on that set just to drive it a couple of times before I pull it out.

You haven't checked the timing or the vacuum, but 'the verdict is in'? Incorrect, if you'd like some help in determining the cause of your issue, then PM me as I'm not going to repeat myself for the third time.

Sincerely good luck - Jim

 

[Dinosport]

Hey guys. So I know I said I was absolutely sure it was the carb. 64nailhead pointed out a few things that I should double check. Also Pontiacgp mentioned how the advance should be set at 5turns out to start.
Here's what I found. The advance was screwed in all the way tight. Dum asses. So I pulled it out 5 turns out and set the timing. I'm about to go for drive in it. I still think there's an issue with the carb. On the pass side if you tighten the adjusting the car almost died till I back it out. On the drivers side the screw makes almost no difference. I saw a video where the guy pulled the screw out checked it and blew air through the hole. I don't have air so i tried to blast a little carb lean through it. But it didn't make any difference.
Another thing I noticed, not sure if I'm over thinking it but if I blip the throttle I don't see anything come out of the rear of the carb?
I'm gonna to run an errand in it. It's an hour out and an hour. I have some bg fuel additive that works really well. I'm gonna give it a shot. There's nothing to lose. Then I'll pull the carb and bring it to a friend.

 

[64nailhead]

Sounds like it's time for a carb rebuild/cleaning. Once that is straightened out, then dial in the timing. Keep in mind that every degree of all in timng that you can add, without detonating, is worth another 5-10hp.

If 93 octane means you can run another 2 degrees, then you'll know why you spent the extra money or know what is left in it if you decide to buy 87.

 

[Dinosport]

Sounds like it's time for a carb rebuild/cleaning. Once that is straightened out, then dial in the timing. Keep in mind that every degree of all in timng that you can add, without detonating, is worth another 5-10hp.

If 93 octane means you can run another 2 degrees, then you'll know why you spent the extra money or know what is left in it if you decide to buy 87.

Wow i didnt know every degree was that much hp. Nice. Thanks for all the help guys.

 

[soma]

the adjustment screw on the passenger side is the hot idle adjustment,it usually drops off after the cam folower drops completely and thats when you adjust the curb idle which is the screw on the drivers side.you only really get adjustment from that after the car has warmed up.if its not dropping off the hot idle you have a choke issue that needs to be looked at.basic adjustments for most of the odds and ends are about 3 to 4 screws out on the apt(same with the m/c solenoid if yours is electric),choke pull off set to have the throttle blades open enough to fit a 1/8 drill bit between the airhorn wall and choke blade when the pull off is depressed,set the choke housing to its notch which is generally right around the front most screw or rivet,turn the idle screws on the base plate out to about 5 turns to start off with each,tune the hot idle(passenger side screw under choke)to about 1100 to 1200 rpm on the second step of the fast idle cam,you can tell this by feel pretty much if you use your finger to cycle through the steps.after warm up and its off its hot idle cam all together then adjust curb idle screw(driver sides) to obtain a good idle at about 1100 in park,900 to 950 in drive and fine tune with the idle bypass screw up top.now is is for the ccc set up for a conventional one its pretty much the same just lower the rpm for hot idle and curb to whatever works best and they lack the idle bypass screw.this is also just a base setting to get it running still would need to be fine tuned to your particular application

oh and no gas immediately comes out of the back of the carb to my knowledge,not till your on the pedal and vacuum is pulling it out after the car has been warmed up and the lock out tang is unlocked