Hey Everyone-

I am a new C3 owner and have a problem I would like some help on. I've been searching alot on the site and cant seem to find my exact problem, so just need a little guidance.

On Friday my car started missing on the highway. I could feel power reduction for a second every few second. I would describe it as missing, but it still was running.

Once I got off the highway, it died at a stop light. It fired right up when I gave it some gas and I was on my way again. Everytime I would let off the gas and almost come to a stop, the car would either cut off, or almost cut off.

I replaced my ignition coil, because my resistance was off slightly, but that did nothing. The car starts every time, but only stays running if I keep my foot on the throttle. If I tap the gas lightly every second, it will stay running. Once I let it try to idle, the idle become slow and sounds rough, and then it dies. Usually it cuts off quickly, one time it idled rough for about 15 seconds then died

I was wondering if I may have a vacuum leak, but since it doesnt idle at all I was thinking this could be ruled out. My headlights still work, (the right one is a little slower but was when I got it too)

I am thinking I may have a bad distributor. It is an original or orginal replacement for a 74, and so I was planning on going to an HEI unit with the tach drive as a replacement.

Any advise would help, thanks!

 

First, COngrats on the new toy
2nd, the distributor isn't bad, points and condensor maybe.
I would start off with a full on tune to make sure everything is right. Check all the vac hoses end to end, all the vac fittings, advance module etc..
Good way to learn the car too.
The coil resistance being a little off is nothing, you pull 2 new ones out of the box and they will be a little different.
Check the distributor cap, plug wires and boots, rotor.
Take a few engine pics and post them

 

I will get some photos up this evening. Is there a good writeup on how to check the the vacuum lines?

 

Pulling each vacuum line at the source... carb base or manifold port... one at a time and plugging the source one at a time will help locate the system you'll need to follow if it's vacuum you need to fix. Plug a single port and fire it up... if it's the leaker the car will run much better. Repeat as required until you've done them all.

 

my 74 was doing the very every same thing, plus my head light would not come up. I plugged all the vacuum lines but the one going to the brake booster and the dist, and headlights. Engine now runs smooth, no hiccups lights both go up together. I started replacing all the vacuum hoses BIG diff. But after all my toy, she's 38 years old, been sitting in a barn for almost seven years.
P.S. Love this Form, You all ROCK

 

Here are a few engine photos.

I will follow the vacuum lines tomorrow and can hopefully find the leak. I only had a few minutes to look today and couldnt figure them out even with the service manual so I am going to reread it tonight and take a closer look tomorrow when I have the time. Am I going to be doing the line blocking in the driver side area towards firewall? That seems to be where most the lines run through?

I did notice my PCV Grommet is 3/4 torn and so it is not sealed at all. It almost ripped apart when I took it out. Would this have anything to do with it? I have a new one on the way.

Thanks for the support so far! Hopefully Ill have this fixed soon. I've already replaced my saggy rear spring, replaced my brakes, fixed my rear lights, and my oil pressure gauge. All simple stuff but its always fun learning new things.

 

Doesn't look bad at all. What your looking for on the vac hoses is cracks or holes. Replace anything that is obviously dammaged. Go through the ignition step by step, the Lars Sticky is good for that. Eliminating the basics will save you a lot of frustrating time farting around chasing ghosts on an old car. You ignition wire routing could use some thought, tieing them together like they are isn't a very good idea.

 

Thanks, I just printed it out. You are talking about the sticky by 69427 in this sub forum?

Do you think the torn PCV grommet could cause an issue?

 

If you still have a q-jet, check that the fuel filter's not blocked. My 74 did what you describe, and that was the issue.

 

In the top photo, in front of the intake runner for the number 6 cylinder, there is a reddish stain in the corner of the runner and the manifold base. Is that from a gasoline leak?

 

Im pretty its coming up from the bolt on the intake, its never wet there when running and I havent seen any gas there since i've owned it

 

Is it rusty antifreeze? I'd pull that bolt and put some ARP teflon thread sealer (or similar product) on the bolt threads and stop the leak if that's what it is? Might not hurt to get the manifold bolt torque and torque sequence and go around the manifold as a preventative measure. Seems like you're already dealing with a possible vacuum leak.

I would remove the hose that goes from the manifold to the vacuum tank and plug the connection on the intake. That isolates the engine from the rest of the vacuum system in one shot. Then run the car and see it it's runs better. If better, then there is a leak in the vacuum system somewhere. If no improvement, then you know not to waste any more time on the vacuum system.

I thinking that this is more a carb issue than an ignition problem from your description, although the rule of thumb is that 90% of the time it is ignition. Do you have an inline fuel filter? Have you checked the fuel sock on the pick-up in the tank, they deteriorate over time.

Did you check for a vacuum leak at the carb base and around the intake? Did you make any changes to anything shortly before the problem developed?

 

I will plug the intake vacuum line first and see what that does.

I am unsure if the car has an in line fuel filter. If so I'll replace it. Friday, when this started I had done my most spirited driving before getting on the highway and noticing the issue. I also don't have much gas in the tank. I wonder if I stirred something up.

No recent changes to anything else.

 

Well, I took the vacuum line from the intake and plugged it with my finger and tried the car. It had the same symtoms exactly. I felt alot of suction in my finger. This would mean I can rule out a vacuum leak? Please take a look at the picture and make sure I am plugging the right tube. I plugged the end of the small black tube that goes up then right immediately.

Next will be a new fuel filter. Sorry for a lame question, but how do I keep fuel from going everywhere when I take off the fuel filter? I thought the fuel pump would keep it from flowing, but when I did my rear spring I had the back end way up in the air and the front on the ground, and the carb was loading with gas. I pinched the line for that, but is that the best way?

If its not the fuel filter, I have a new HEI distributor on the way so hopefully its one of the two.

Any way its the fuel pump? I feel like it would not rev up if the fuel pump was bad. When I rev, it runs better, but still misses.

 

There are more than one vacuum ports on the carburetor and intake manifold. A big one goes direct from the rear of the carb to your power brake booster. There are also "timed" vacuum ports, probably at the carb base plate, and also elsewhere on the intake manifold. Anywhere on the intake/carburetor you see a port sporting that black tubing you have a possible vacuum leak. Run the test on ALL of them before you spend any more money on parts you might not need.

 

You should look at your rubber fuel lines as well!
Cheers

 

Check your plugs, and make sure none of the plug wires are resting on those headers...

 

I checked the remainder of the lines coming from the intake/carb. None made a difference. I also installed a new fuel filter, and an HEI distributor and wires. I still have the same problem. I wanted a new distrubtor anyway to fix my tach, so it wasnt a waste.

What is left? A carb rebuild? That I do not know how to do, nor do I want to tackle that. My carb is pretty dirty looking, inside and out.

 

It sounds to me like the carb might be flooding. of corse with out being their its just a guess. I'm also guessing from post # 14 that its a holley carb. I't might be time to rebuild it. You can try taking out and flogging the living daylights out of it @ wide open throttle to try and maybe was any trash or debree out of the needle and seat. If one of your needles aren't seated it could allow the bowl to overfill and flood out the carburator. Do you have to hold the throttle open a little in order to start it or do you have to pump it in order to start it.

 

Its a holley. Yes I have to hold the throttle open to start, it wont start with no thottle, and dies with no throttle.

The clear plastic part in the first picture has some seapage. What is this?

The others show my carb, it looks pretty nasty to me, I have a local shop that does rebuilds, or should I send it somewhere?

Thanks