Rough Idle...

[Anonymous]

I have a '76 Maverick and has a 200 in-line 6 engine. I purchased it at the beginning of the year, it came from Alabama and it's only got 14,000 miles on it. The car was running very rich and sometimes stalling. I pulled the carburetor (a Carter, model YFA carburetor) and had a mechanic install a carb kit. It ran much better, but was still not quite right. I drove the car to the same mechanic to have him fine tune the carb and check the timing. When I picked the car up, he said that he has worked on many of these I-6 engines and they never run completely "smooth". After the adjustment, the car seems to run well at highway speeds, but it idles a bit rough, and when I come to a stop sign, it almost seems like it's going to stall. I had a couple of friends (who know more about engines than I do) listen to it, and they said that it sounded like it was starving for gas when idling. One guy said that he thought perhaps one of the ports may be partially blocked, and the mechanic may not have cleaned/soaked the carb good enough when installing the carb kit.

1.) First, it is a common characteristic that the straight 6 engines idle a bit rough?
2.) Any suggestions as to what I should be checking for? Could the problem be a sloppy carb kit install?

 

[SteveS]

Rough idle is NOT a characteristic to inline 6's. My 82 Cougar Wagon with the same engine idles very very smooth. This was not always the case. When I first got it 4.5 years ago the idle was a little shaky but not bad and didn't feel like a stall was imminant. Mine has EGR and the valve was bad and the manifold was completly plugged with carbon. I had to use my dremel to decarbon it. Decarboned, new EGR, carb adjust, timing adjust and gapped the plugs at .050 instead of .052 did the trick. Totally smooth. Mine has the duraspark II dizzy.

 

[ludwig]

You could have the idle set too low. It should be between 700 and 850 in Drive. The carb is not complex. If the idle is OK, you can fiddle with the air/fuel mix. It's best to use a vaccuum guage with this but you can also just turn the screw in until it starts to stumble, then back it off a quarter turn.
It could be the choke not opening completely. Get some carb cleaner. Put on your shop goggles and spray the carb inside and out while the engine is running. Work the levers and such to free them and blow off the dirt and crud with an air hose once you have cleaned the outside.

You could have a vaccuum leak around the base of the carb. Spray some WD40 around there. If the idle smooths out, there is your leak.

You would do well to get a dwell tach, timing light and a vaccuum guage. All together they will cost about $50-60 at Sears or where ever. They are not hard to use and you can reset the timing and idle to spec on your own according to the shop manual (not the owners handbook). The I6 did not come from the factory running rough.

If you changed out the ignition to Pertronix I or Duraspark, you will notice a definite improvement of idle quality and throttle response.

 

[pedal2themetal45]

I sugest finding a new mechanic that guys a BOZO if he says they all run rough.
sounds like it might be idleing to slow or the Air/fuel mixture isn't right. I'd also check the plugs, plug wires, then take it to a new mech.
Tim

 

[JackFish]

14,000 miles? Brand new, not a rebuild?
If that's original miles I'd look at something like sticky lifters.
Does tick or clatter in the valve train area?
Might just need the crap run out of it.

 

[fb71]

my 69 falcon w/200 sat for nearly 30 years without being started. I changed the oil, added fresh gas and a battery, hit the key, and she fired right up and idled smooth. If its shaking, it still needs work.