1970 Ford Maverick Intermittent Idle Issue

About 9 months ago, my husband and I purchased a mostly restored 1970 Ford Maverick. We redid the interior and have been showing it to rave reviews. Most of the time it runs great. However, periodically it has problems staying running. For instance, this weekend it started, but then when I put it into reverse the idle would drop and it would die. It would start right back up but wouldn’t stay running long enough to get it out of the garage–thought I was going to asphyxiate myself (even with the garage door open)! After about 15 minutes it finally maintained the idle and I got it to the car show. When I left the show, it took about 3-4 attempts to keep it running. Then it died at the first intersection, restarted, and then was fine. When it?s acting up, it idles rough. Our mechanic says it?s not the carburetor (which can?t be adjusted due to stripped screws) but he did replace the bad fuel pump, which did not solve the problem. Then he thought it might be the vacuum canister so he disconnected it. Again it worked fine for a time, and then started acting up again. We asked if it might be the fuel filter. He says no because the problem is intermittent, which is also why he doesn?t believe it is the carburetor. His next best guess is 37 year-old gunk in the fuel tank. I think we should rebuild the carburetor, replace the fuel filter and any icky looking fuel lines. Would this be worthwhile? Any other suggestions?

Is it a 6 or V8? Does it still have points ignition? If it’s a “California car” it might have an EGR valve, which can destroy idleing ability.

The carb has stripped screws but that’s not the problem? WHAT screws? (idle mixture?) Is the choke working correctly?

I think there is a thinging called a dashpot that may have something to do with it, but I’m just guessing

I think we should rebuild the carburetor, replace the fuel filter and any icky looking fuel lines. Would this be worthwhile? Any other suggestions?

I would start there, but skip the fuel lines. Next would be a carburetor rebuild.

What you really need and may even find here, someone who worked on these beasts in the 70's.  The 70's were a hard time for most cars as they were trying to clean up the exhaust, but no one really knew how.

I think there is a thinging called a dashpot that may have something to do with it, but I’m just guessing

Not a bad guess. They did go out and would cause problems idling, but I really don’t think this one sounds like it. But then I did VW’s not Fords.

It sounds like you are having the most trouble right after starting a cold or cool engine. Perhaps the choke is sticking or is inoperative. There should be an electrically operated solenoid to control the idle speed. It closes the throttle plate completely when you shut off the engine to prevent dieseling. Maybe it is working intermittently.

The choke staying closed could make the engine quit. Next time this happens, jam a 6" screwdriver in the throtttle bore to hold the choke open and see what happens. When the engine is warm you can clearly see if the choke opens. The choke thermostat is usually useless if it is so old. If rivets are holding it in then it is probably original.

I had a similar problem on the 1971 Maverick that I owned. In my case, there was a electric throttle stop on the carburetor. When the ignition was on, a plunger would come out and hold the throttle open enough to idle reliably. When one turned off the key, the plunger would retract. This device was on there to prevent the car from “dieseling”, a condition where the fuel mixture is ignited by the heat of the combustion chamber with the ignition off. The one on my Maverick didn’t work reliably, so I bought a replacement and installed it. The replacement was very inexpensive and it took almost no time to install.

The other problem that I had that may be related to your problem is that the valve seals were bad. This would allow oil to seep into the combustion chamber when the car was parked. The oil would eventually foul the spark plugs and cause driveabilty problems. This, too, is not an expensive repair if you find an old time mechanic who knows this trick: Use an adapter to screw into a spark plug hole and keep pumping in air from an air compressor. This supports the valve so that the keeper and spring may be removed without dropping the valve into the combustion chamber. The seal is then replaced and the spring and keeper reassembled. Otherwise, the cylinder head must be removed to do this work.

My Maverick was a 250 cubic inch 6. I’m almost certain that your 1970 would be a 6 cylinder as the V-9 wasn’t offered until later. There were three variations of the 6–a 170 cu inch, a 200 cu inch, and a 250 cubic inch.

A couple of ideas. I am pretty sure that the problem is choke related. As has been said, this is a smog lowering carburator and a lot of features were used to clean up the warmup emissions so the choke has to be clean, the stove has to be working and connected, and everything adjusted to Hoyle. The other thing I have seen with this carburator is that the throttle base to middle body bolts would loosen allowing air to get in the gap. This really caused problems – I don’t remember if it was cold warmup problems. To check for this, remove the air cleaner, grasp the top of the carburator and push lightly back and forth. If there is any motion, those bolts may have loosened up.

Hope that helps

Thanks to all for your input. We found a shop that specializes in classic Mustangs. They agreed it was probably the carb. Replaced the carb, and the spark plugs (the previous owner had put the wrong ones in), and adjusted the points. Runs like a dream.

Mustangs, Falcons, Mavericks, are pretty much identical except for the sheet metal…The engines and transmissions ARE identical as are all the “inside” parts like window regulators and door latches, brakes, all that stuff…Makes parts easy to find.