My car has started to 'surge' when driving. I'm not even sure if that is the right word. It goes alot, mostly noticeable at very light throttle, but I didn't try anything else, and it feels like it gets a very quick momentary shot of gas or throttle, and blips forward and then goes back.
Its never done this before, and it just dosen't feel right.
Where should I start looking?

Matt

whats the problem, not enough information

I just re-read the post and I must have been in outer space when I wrote it.
When driving at light throttle, (well I haven't really tried much else) the car gets an unsual surge. It feels as if the throttle blades opened a bit more very quick, then went back to where I had them. Its bizarre. It feels like the car rocks forward, then back. I can't quite finger it.

Hope that helps..
Matt

Try changing your gas filter.

Are you running vac. advance? Too much vac. advance will cause a condition like this at cruise, you will feel a real slight surging / bucking but not off the line or at WOT. Just a thought, had to share cause I dont have many of them. smile.gif

Fuel filter looks ok. I run all mechanical advance, no vacuum.
Could dirt in the carb cause this? I hope not, because just about everything else in the world makes more sense to me than those things..

Matt

i'm with these guys, i think some type of leak, intake maybe. get some carb. cleaner. while at idle, spray around bottom of carb. and intake manifold. see if idle changes. if filter is clean, then carb.should be ok unless something mechanical has let loose. if idle changes while spraying cleaner, then you've narrowed it down. also, this may not be a fuel problem. it could be a coil going bad or cracked dist. cap. good luck, keep us informed.

Have you readjusted the idle mixture yet? If not, do so. It does affect part throttle operation. If that doesn't help, you want to start looking for a vacuum leak, or some other cause for a lean mixture.

This is great..

This morning (and its my birthday today, I guess this is my present) I decided to take the carb off, and retorque all the manifold bolts.
I did this after I rechecked the timing, after someone was telling me that 20* initial is too much and causing the surge, but it never did before-- so I won't look there, unless someone here tells me otherwise.
I ended up stripping a carb stud hole. I was remvoing the carb, and a stud came out. I couldn't get the nut off, so I assumed it was jammed. I went to the store and bought 4 new carb studs and a new carb gasket.
Came back home, reinstalled the carb, ended up turning the nut down and the whole thing just turned and metal shavings came out.
The car starts and runs fine, the surge is still there. It may be now exaggerated by running one less carb stud until I figure out what to do-- ?
One more question, well two. Say I was clumsy and dirt got stuck in the fuel line past the filter and got into the carb. Could this cause the surge?
Second, is this surge dangerous? Is the engine more likely to grenade with this if I get on it without resolving it satisfactorily?
What other things could cause a lean condition, assuming I have tried to narrow down any possible vacuum leaks?

Thanks..
Matt

One more question, well two. Say I was clumsy and dirt got stuck in the fuel line past the filter and got into the carb. Could this cause the surge?

Absolutely, especially if this is a Q-jet! A large enough piece of trash can lodge in one of the main jets, causing that side of the engine to run lean. It can happen to Holleys too, but Q-jets are more susceptible to this because of the jets being in the bottom of the float bowl.

A heli-coil will take care of the problem with the stripped stud.

I'm doing the helicoil tomorrow morning, I'll see how the engine is running afterwards. Its a holley 4bbl carb, so I'm hoping dirt isn't the cause. I'm just dumbfounded because it appeared all the sudden..

Matt

Say I was clumsy and dirt got stuck in the fuel line past the filter and got into the carb. Could this cause the surge? Sounds like you are running a inline filter. Is it possible that you still have a filter stone in the carb inlet? At best this would be a unnecessary restriction in the fuel line, if partially clogged it could really starve the motor.

Matt, it's simple enough to pop the bowls off, use an air can ( computer/electronics cleaner ) and blow through every hole you see.

Next time, don't pop the carb off, just blow some carb cleaner, chased by compressed air ( from the can not a bigass compressor) down the air bleeds. That's likley where the problem lies. Just a little fleck will do it.

While you have the carb off, ensure the needle/seats are clean. Use a wet Qtip or just air.

You'll find it here, although when it happened to me, it was a bit more severe than you describe.

If you run through the whole carb drill and it still happens, then you HAVE to have a wire that's bad or a spark plug.

Either way, it'll be iron ed out. Then you can enjoy this thing and STOP wrenching on it.

Happy Birthday Dude!

Ok.. did alot of fumbling today. All indications now point to either a bad coil or bad coil wire..
New one on the way.. too bad stores around me don't sell MSD or performance stuff.

If not, back to square 1.

Thanks everyone!
Matt

I'm interested to know, what was it that makes you think it is your coil?


Rocky

Rocky,

Its sort of a hard-press guess but it dosen't appear to be dirt in the carb unless we didn't look hard enough. We tried to track down any and every possible vacuum leak. The distributor housing is new. Idle mixture has been readjusted, (4 corners ahh!).
And someone who hadn't been around the problem keenly noticed that it dosen't start until the engine is at its high operating temp of 200-210 F.
So unless the brand-new distrib cap is cracked, I can't imagine what else it is..

Matt