[66Lemanster]

Recently started have some issues my my 66 Lemans. I was driving around town just fine, came to a stop and tried to take off and the car just bogged down on me. Now I have no get up and go from the line or after it shifts into second (automatic). It takes about 5 seconds or so for the engine to catch up and run normally from the line and the same for when it shifts. Checked all the wires and plugs, everything is fine. Replace fuel filter and ensured full is pumping accordingly. Took it to my shop and they tested the vacuum and said it checked out. When the car is in neutral or park the engine revs up just fine, only when in gear down it bog down. Shop also checked timing and rich/lean ratio. Made a couple of adjustments which helped minutely. After checking about on here, I have heard others say it might be the accelerator pump in the carb or maybe the timing chain. Before I go and drop the car off at my shop for a few days, I just wanted to see if anyone on here had any other suggestions. I haven't rebuilt the carb yet, that is next on the list. I'm open to any and all suggestions. This car is my daily driver and really need it to be running right. Let me know if there is anything else you need to know about the car.

[J_JAMNIK]

Sounds like an accelerator pump to me.

[PITTSBURGH 64]

My car did this when the winter gasoline came in. It was like I wasn't getting enough fuel. Try a different brand of gas. I've been having good results with Shell. I was using Sunoco or BP.

[78 GHOST]

You might have a clogged "sock" which is a nylon filter which slides onto the end of the fuel level sending unit. You can diagnose this by buying a length of fuel hose, and connecting a fuel can to the hose, effectively providing another fuel tank.. drive it and see if it's any different. I'd suggest using a fuel tank out of a small outboard powered boat, kinda made to not spill fuel everywhere.

To change the sock, you must drain the fuel from the fuel tank, lower the tank and remove the retaining ring to pull the sending unit.

Once you've got the sending unit out, you can grab the retaining ring which holds the sock on the end of the sending unit and twist it off. You need to replace the sock as it keeps sediment out of the fuel supply.

Other ideas, I recently found a problem with the engine under load only, caused by a faulty coil. Swapped out the coil for a good oil filled unit, and voila' problem solved.

A slipped timing chain will cause major problems.

A vacuum leak.

A debris fouled fuel filter at the carb.

Points old and crapped up.. out of adjustment.

Having a shop tell you "things are fine" doesn't really help us too much. If you can provide some basics such as the actual timing, vacuum you're reading, etc. we can help nail things down.

Personally, I only suspect an accellerator pump if the engine initially stumbles, then catches and runs fine. Your description sounds like a loss of power regardless of how much or how long you hold the pedal down. Is this so?

Typically, an engine will run like crap as a result of a lot of things being just a bit out of whack. Plugs are a little crappy, points are a little funky, filters are a bit dirty, engine suffers a few vacuum leaks, etc.

Personally, I'd suggest starting at the basics and going from there. You might need to borrow or buy a couple of essential troubleshooting tools and try your hand at fixing things yourself.. many shops aren't really good with these old vehicles anymore. You need a timing light, an Ohm meter, a vacuum gauge, a spark plug socket, plug gapping tool, and. These tools will help you determine the basic health of your engine, a compression tester is useful later if you eliminate the basics first.

[66Lemanster]

I appreciate everyone's suggestions.

Ghost, I already did what you suggested about the fuel level sending unit. (Very good idea by the way) It was one of the first things I tried, figured it had something to do with getting fuel to the carb. I also disconnected to the fuel line to the carb, disconnected the distributor cap and turned over the engine a couple of times just to make sure I was getting a steady pattern of fuel coming out. The main reason I suspected the accelerator pump is because it does exactly what you stated "engine initially stumbles, then catches and runs fine". Only difference is is does it in first runs fine then does it when it shifts to second then runs fine. I also suspected maybe I had a worn timing chain since I believe they were nylon back then and may have stretched some since it is the original timing chain. Definitely something I need to have checked. The shop I take my car to only works on 60's and early 70's classic cars and I have been doing business with them for awhile. I will find out from them exactly what the timing is set to and what the vacuum is reading and report back.

Pittsburgh, Not sure if is a coincidence, but I did fill her up that morning at a gas station I have never been to before. It was a little below a quarter today after work so I decided to take your suggestion and found myself a shell station and filled it up. Been driving it around tonight and it sounds a little healthier, but no real performance changes. We'll see how it does over the weekend. I figured what could it hurt to try a tank or two of good gas. So I will let you know once I run it for awhile longer.

After the new year, I still plan on rebuilding the carb since it has never really been touched. 99% of this car is original so a lot of things need some TLC. I am going to just start working my way through it all and see if we can;t figure it out. I truly appreciate all of your help and will keep you up to date until the car is running like it's glorious self.

[RAJNWDY]

I don't know whether you watch NASCAR but they had a problem with water in the fuel and some big wrecks came out of it because some of the cars didn't perform. As far as the timing goes. If the chain has streched that much you would have had a big differance before now. They timed the engine and found no other problems, If your worried about the chain, you should be able to rock the crank back and fourth and watch the rotor in the distributer If you get a lot of movement before the rotor moves then the chain is streched fairly well. Nylon gears.....Chevys yes...not too many pontiacs of our vintage. Carb problems....maybe but Carb problems come on kind of gradually. Not usually all at once. rebuild it though, it probably needs it. Hows the trans shifting??? A trans thats not working right will degrade performance....OK I'm done, just a few ideas.

good luck

[smagnotti]

With that original timing chain and gear you probibly have loads of slop. To check it, remove all of your spark plugs, remove the distributor and the air cleaner so you can see the rotor from the front of the engine, then grab the balancer and by hand turn the crank back and forth as far as you can while viewing the distributor rotor and you will notice that the rotor lags far behind in movement( which it shouldn`t) when you change spin direction on the balancer! If this is the case I would not drive the car again but to get it to a repair shop, as these gears like to fully let go when you need the car the most!

[66Lemanster]

I will definitely check to see if there is any slack i the timing chain with your suggestions. Something else that started happening today is the A.I.R smog pump started making a grinding noise when the car is in park or sitting at idle, but once I accelerate the noise goes away. Not sure if this has anything to do with my current problem, just thought I would throw it out there. I did get a chance to pull the carb off this week, and other than some buildup and dirt it seemed fine. Put on the rebuild kit and and got it back on there with no real change in performance. I really do appreciate everyone's suggestions. I will continue systematically going through everything and see what I find.

[66Lemanster]

One update for anyone who is still following this thread. Although the shop I took my car to said there was no vacuum leak, I found one. I was trying to figure out why my idle was staying high even after the engine was warmed up, and I noticed a noise coming from the drivers side of the engine. After listening very carefully, I found a vacuum leak in the hose that goes to the brake booster. I'm assuming the shop didn't catch it because they used the port on the back of the carb who this line connects to. Either way, I finally decided to make the time and test everything myself. So tomorrow I am going to get a vacuum gauge and timing light and go through the entire engine myself. Pretty new to all of this but I should be able to isolate any vacuum leaks with suggestions in other threads. First thing is definitely fixing the connection to the brake booster. I did notice that putting my hand around the connection, stopping some of the leak, did allow the engine idle to come down and sound a lot better. Hopefully fixing it completely will solve some of my problems. I thank you all again for your suggestions. I guess I learned the hard way not to trust the shop, although I should of listened to Ghost in the first place. I will keep you all up to date with any progress.

[78 GHOST]

I'm glad you have found one of your issues, rough running older cars usually suffer from a combination of numerous factors. A few minor vacuum leaks, plugs a little cruddy, etc. Keep after the small things and you'll soon have a car that runs like a Singer sewing machine.

Personally, I would set about changing all the rubber hoses and belts on your car, including the radiator hoses, heater hoses, all vacuum lines, including the one on the bottom of the vacuum modulator line to the tranny. Some items like radiator hoses and belts will do nothing more than provide peace of mind, and keep the old ones as spares. Other items such as vacuum lines will improve performance.

Good luck and keep dialing it in, you'll be happy you're turning the wrenches. Also, don't sell yourself short, you're asking all the right questions. Finding the right areas to focus is the hardest part, doing the work is usually easy compared to finding where to focus.

[LPete]

Make sure the spark advance is working correctly when you check the timing. I'd be curious if that was checked at the shop.

[66Lemanster]

Finally replaced all the vacuum lines except for the line that runs to the transmission and one other. Having a little trouble locating the transmission line. The other line runs to the back of the engine and connects to something that reminds me of a PCV valve. Not sure, but still researching it. Car is running a little better but still have poor performance from a stop. Will continue to keep you all up to date with my progress. Thanks for the suggestions.