Rough Idle (170)

[Junior64]

I have a '64 Falcon with a 170. I have a rough idle while in park or just sitting at a light. I have an automatic transmission and set the RPM at the factory 525-550 setting and it shakes quite a bit and put puts out the tailpipe. Nothing fixes this except when I give it gas or increase the idle RPM above 700. Below is a list of work I have just completed on it.

- Resurface Head/Complete valve job (valves, springs, guides, seals, seats)
- New lifters and push-rods (hydraulic)
- New plugs
- New wires
- New coil
- New distributor cap, rotor, points, and condenser.
- Timing checked (Does not fluctuate at idle)
- New fuel filter
- Re-built/adjusted carburetor


I did notice some wear on the distributor gear when I pulled it out, which makes me think that may be causing it. I am just hoping that someone out there has experienced the same issue and can point me in the right direction. Right now I am thinking about getting a re-manufactured distributor and then maybe checking the timing chain if that doesn't work. The engine doesn't make any abnormal noises, just shakes a bit. Please help!

[FalconSedanDelivery]

If you advance the timing does it go away , also keep in mind Specs are starting points NOT absolutes , set things where it runs best NOT by a book , You do need to know where your at ( verifying starting points , such as has your Dampner slipped ) and adjust accordingly

[Junior64]

Advancing the timing does not help. I've taken it 20+ TDC with no joy. One strange thing I noticed is that when I set TDC on the number one cylinder and install the distributor with the rotor facing right on the number one plug, the timing reads 10 BTDC with the light.

[bubba22349]

Sounds like you are dropping a cylinder. Do you still have the old lifters?

[Junior64]

I tossed the old ones. There was no unusual wear on them. I forgot to mention that I did a compression check and it was good on all cylinders. About 180 psi each.

[bubba22349]

Okay If the distrib is well used you need to check for shaft play in top bushing (side to side movement) push on and pull straight back to you at 90 degrees to shaft. If you feel much slop in this bushing its time to get a rebuilt.

[Junior64]

There's not any play that I can tell, just the wear on the gear.

[69.5Mav]

I would suggest verifying your timing mark. These damper/ballencers are known to slip as they age. Trying to set timing on a motor with an unverified slip damper is frustrateing. Bring the number one piston up to TDP by looking in the spark plug hole then see where your timing mark is.

Some other thing you could check are

Dwell

condition of the spark plugs i.e. are they black (rich) or white (lean).

How does the exhaust smell

Good luck

[Junior64]

Timing mark is right on TDC when the #1 is up at the top. Just installed new plugs. Dwell is right on. The exhaust smells fine (after replacing the valve stem seals) and the plugs are a nice brown.

[mugsy]

My '65 with a '69 Carter YF carb has a very similar problem you discribe (I didn't watch the clip). I took the Idle Jet out and drilled out the jet part. The engine idles a lot better. Its still not solved but at least I can drive it and stop at lights and such and not have the thing shake me to death. And with the carb off idle it runs fine; she runs purrs right along. I'd play with the idle mixture screw and such on yours.

[Junior64]

Well after messing with it all night, I am finally satisfied...for now. I set the timing to about 17BTDC and the idle at 700 while in drive. It is smooth and runs fine this way. With the idle set at the factory setting (500) there was no vacuum advance at idle. Is this normal? I also noticed that the mechanical advance is not working. Will this affect idle?

[bubba22349]

With the idle set at the factory setting (500) there was no vacuum advance at idle. Is this normal?

Yes, there is little or none at idle.

I also noticed that the mechanical advance is not working. Will this affect idle?

If this engine is still org. with all the stock parts you have an LOD system. Many people have trouble with this system because it works totally different than other vacuum advance systems. You need to check the SCV on the carb. If you don't have a good repair manual check this link for very good info on how they work. http://classicinlines.com/Loadomatic.asp

After you read that you will know why the idle setting needs to be close to factory spec. I suspect that the SCV needs replacement. Good Luck

[Junior64]

I replaced it when I rebuilt the carb. Do you know how to op check it?

[69.5Mav]

I also noticed that the mechanical advance is not working. Will this affect idle?

If you've got mechanical advance then you have the wrong distributer. The SVC valve and distributer are made to work as a pair and will be difficult at best to tune if they are mixed up with newer systems. Make sure you have the right components.

[Junior64]

I have the Load-O-Matic distributor with the SCV equipped carb. I wasn't aware that these distributors did not have a mechanical advance.

[ozconv]

My 67 started doing something similar on the way home from a cruise in last week. It would only keep running under throttle and would start to run rough at cruise and stall at every light. The other weird thing is that when I put it in neutral while coasting and gave the engine gas to keep it running, it acted as if it was still in drive (C4 automatic). I haven't confirmed it yet but I am suspecting that the vacuum modulator diaphram on the transmission may have ruptured on the way home and created a large vacuum leak as well as sucking AT fluid into the engine. Sounds like your condition isn't as bad as mine but my understanding is that a rough idle is often caused by a vacuum leak and if the modulator is ruptured or there is a leak in the hose from the modulator to the metal line on the transmission, it wouldn't be obvious when checking for vacuum leaks. How old is your C4?

[Junior64]

Good call on the modulator. I have an original Ford-O-Matic 2 speed. When I pulled the hose off the modulator, I saw that the previous owner plugged the line with tape. The rubber hose that connects to the modulator is leaking, but when it is plugged, it still runs rough. I will try changing the modulator when I get back from travel for work. I hope that works. I also change the distributor today with no joy. If a new modulator/line doesn't fix it, I'm thinking about replacing the timing chain/gears. Any other ideas before doing that? Thanks for everyone's help!

[MPGmustang]

IIRC on my old stock engine... I pinged under load if I went above 12 TDC, drive ur hills at WOT and make sure you don't ping, if you do back it off 2* until it don't.

My old engine with the autolite 1100 and LOM distrbutor liked idle at no less than 650 rpm with my T5, I have A/C so I bummped it up to 850rpm so the A/C could kick on and be perfect idling. Another suggestion, maybe the alternator is going out, less spark = rough Idle?. I would also try makeing your plug gaps smaller, store is usually .045 i'd try .040 or even .035 and see what's best. it's all trial and error. check your gas/air screw on your carb see if the tip is still intack (with the engine off). stock engines love 20 hg vacum, Confirm that you CAN reach that, what's the rpm? I recomend to stay there. it's happy and it's getting it's way (kinda like women).

Richard

[Junior64]

I'm not pinging when under a load. I was thinking about the generator too. It looks old as dirt. What's the best route to go? Get an alternator/kit, or just rebuild the gen?

[bubba22349]

Plugs on a stock Ford point ign. should never be over .035 they usually like .032! How is the coil output?

[Junior64]

I have the gap set to 0.35. I will try 0.32. I have not tested the coil since I just replaced it.

[Eaglo]

If you want to check your spark control valve, you can do that with a vacuum gauge. If you connect the gauge to the distributor vacuum line you should see little to no vacuum at idle increasing gradually to maybe 5 inches at 2000 RPM and a bit higher at WOT.

It's not the numbers that are important, as they varied with the Loadomatic and carb setup. What's important is that the vacuum starts out low or none and increases gradually to wide open throttle.

If you want to get deeper into it, you can take an adjustable timing light to the car and with the vacuum advance hooked up you can read the number of degrees advanced at different RPM's. You'll see your basic 10 degrees or so at idle, increasing to maybe 20 - 25 degrees as you throttle it up.

With no pinging and the timing set as you mention, it sounds like your advance and spark valve is doing what it should, which is no little accomplishment for these setups.

[Junior64]

The vacuum works as you described. Little to none at idle and a gradual increase. I don't have a gauge to hook up, I just used my calibrated finger When I get back into town, I'm gonna narrow the gaps on the plugs and get that modulator valve replaced. Will ATF leak out after I remove it?