Electronic Ignition ID & Rough Idle ?s

Platonic Solid · May 25, 2009

Engine = 351C 2V (unknown specs/assumed stock) . Has good compression and no significant oil burning issues. Auto FMX trans.

I'm having a hard time getting it to run smoothly at the factory specified 575 RPM. Starts up strong and seems to run fine at 700+ RPM. It stays running at 575 in gear, but just barely. So far I've rebuilt the carb (2100), replaced plugs/wires, replaced some vacuum lines, and checked timing - which is set to factory spec (6B).

I don't have a vacuum gage, nor do I know what/where/why to get one.

Could it be the electronic ignition?
It has an electronic ignition of some variety which I can't define. Maybe Accel, as the coil is the only item with a label on it. Here's a picture of the guts and the gold mystery box:

The power steering pump bearings are shot too, but I doubt that has any effect on a smooth idle.

2nd Mustang · May 26, 2009

That "gold mystery box" looks like a voltage regulator. Looks like a converted non-points conversion only.

An idle speed of 575 seems really low, but then again all of my Mustangs have been the three pedal variety. Even my present 2003 Toyota Tacoma slushbox idles at 750 in gear.

A good vacuum gauge is very handy to tune and troubleshoot. Do a web search on how to interpret the readings. You hook it up to a manifold vacuum source, not a port source on a carb. You won't regret getting one.

bnickel · May 26, 2009

i can tell you exactly what ignition system you have and amazingly enough you've even called it by it's proper nickname....."Gold Box".....LOL NOT to be confused with the much less popular Mr Gasket "Gold Spark" ignition, however.

anyway it's actually a Motorola/Prestolite ignition system. back in the day everyone sold these systems, Mr Gasket, Accel, Mallory, Montgomery Wards, Sears, JC Penney, Prestolite, and even Ford, Chrysler and GM marketed these systems under their own names, plus lots of other companies you've never even heard of before.....

when they work they actually work pretty well though parts for them are fairly hard to find, but you can canibalize other things to replace the parts if need be. the box itself would be from an early-mid 70's AMC before they started using the ford duraspark, NAPA part number ECHTP75. the pickup/stator/reluctor stuff can be replaced with a complete duraspark dizzy but you'll have to cannibalize the connectors to make them work, you might be able to find an AMC/jeep with the correct parts for the dizzy but i'm not really sure. at that point, though, it's really best to just replace the entire system.

as for your problem with the car not wanting to idle at the specified RPM, you might just either bump the idle up a bit or advance the timing a bit, most ford engines actually like at least 10 degrees of initial timing or more. mine is currently set at about 14 degrees initial timing.

i also would recommend getting yourself a nice vacuum gauge and set your timing and idle mixture with it. what you want to do is set your curb idle at the specified 575 rpm and then connect the vacuum gauge to a manifold vacuum source. next you'll want to set your timing so you get the highest vacuum reading and snug the dizzy hold down bolt. now, your curb idle speed will have gone up considerably so you will need to readjust that back to the specified RPM. next adjust your idle mixture screws to get the highest vacuum reading as well and readjust your curb idle speed again. you will need to repeat this process several times to get everything set just right and eventually it will get where you won't have to adjust the curb idle speed much, if at all, as you zero on the correct tune. once you have everything set properly you should be able to put in gear and have the car run very well with no bogging or hesitation at all.

keep in mind though that as you do this the initial timing may be advanced far enough to ping a little under light load, this doesn't always happen but it is a possibility. if it does happen you'll need to back the timing off one or two degrees at a time until the pinging goes away, then you'll need to reset the idle mixture screws with the vacuum gauge, the same as before and adjust the curb idle speed to the desired rpm, again, as before but you won't need to adjust the timing again this time. like i said though, you won't always run into the ignition pinging issue and on a low compression 351c you probably won't so don't sweat it just be aware that it could happen and it's not the end of the world if it does, you just have a little more tuning to do is all. worst case scenario this will take you most of a saturday or sunday to do, but probably quite a bit less than that.

NOTE: DO NOT set your curb idle speed with the vacuum gauge because the higher the car idles the more vacuum it makes, so if you set your idle speed with the vacuum gauge you'll end up with about a 2000 rpm or more curb idle speed.......

also make sure that all other components in the ignition and fuel system are in good shape before you start this project IE; plugs, wires, cap, rotor, coil, PCV valve, fuel filter(s), fuel pump, carburetor, choke, air filter, etc., etc. we already know the electronic ignition conversion itself is in good shape because the engine does run, if it wasn't working properly the engine wouldn't run at all, so you're in good shape there.

bnickel · May 26, 2009

bnickel said:
i can tell you exactly what ignition system you have and amazingly enough you've even called it by it's proper nickname....."Gold Box".....LOL NOT to be confused with the much less popular Mr Gasket "Gold Spark" ignition, however.

anyway it's actually a Motorola/Prestolite ignition system. back in the day everyone sold these systems, Mr Gasket, Accel, Mallory, Montgomery Wards, Sears, JC Penney, Prestolite, and even Ford, Chrysler and GM marketed these systems under their own names, plus other companies you've never even heard of before.....

when they work they actually work pretty well but parts for them are fairly to find, but you can canibalize other things to replace the parts if need be. the box itself would be from an early-mid 70's AMC before they started using the ford duraspark, NAPA part number ECHTP75. and the pickup/stator/reluctor stuff can be replaced with a complete duraspark dizzy but you'll have to cannibalize the connectors to make them work, though at that point it's really best to just replace the entire system. you might be able to find an AMC/jeep with the correct parts for the dizzy but i'm not really sure.

as for your problem with the car not wanting to idle at the specified RPM, you might just either bump the idle up a bit or advance the timing a bit, most ford engines actually like at least 10 degrees of initial timing or more. mine is currently set at about 14 degrees initial timing.

i also would recommend getting yourself a nice vacuum gauge and set your timing and idle mixture with it. what you want to do is set your curb idle at the specified 575 rpm and then connect the vacuum gauge to a manifold vacuum source. next you'll want to set your timing so you get the highest vacuum reading and snug the dizzy hold down bolt. now, your curb idle speed will have gone up considerably so you will need to readjust that back to the specified RPM. next adjust your idle mixture screws to get the highest vacuum reading as well and readjust your curb idle speed again. you will need to repeat this process several times to get everything set just right and eventually it will get where you won't have to adjust the curb idle speed much, if at all, as you zero on the correct tune. once you have everything set properly you should be able to put in gear and have the car run very well with no bogging or hesitation at all.

keep in mind though that as you do this the initial timing may be advanced far enough to ping a little under light load, this doesn't always happen but it is a possibility. if it does happen you'll need to back the timing off one or two degrees at a time until the pinging goes away, then you'll need to reset the idle mixture screws with the vacuum gauge, the same as before and adjust the curb idle speed to the desired rpm, again, as before but you won't need to adjust the timing again this time. like i said though, you won't always run into the ignition pinging issue and on a low compression 351c you probably won't so don't sweat it just be aware that it could happen and it's not the end of the world if it does, you just have a little more tuning to do is all. worst case scenario this will take you most of a saturday or sunday to do, but probably quite a bit less than that.

NOTE: DO NOT set your curb idle speed with the vacuum gauge because the higher the car idles the more vacuum it makes, so if you set your idle speed with the vacuum gauge you'll end up with about a 2000 rpm or more curb idle speed.......

also make sure that all other components in the ignition and fuel system are in good shape before you start this project IE; plugs, wires, cap, rotor, coil, PCV valve, fuel filter(s), fuel pump, carburetor, choke, air filter, etc., etc. we already know the electronic ignition conversion itself is in good shape because the engine does run, if it wasn't working properly the engine wouldn't run at all, so you're in good shape there.

EDIT: also make sure your vacuum advance is working properly as well and is hooked up to a PORTED vacuum source. some people will tell you to hook it up to a manifold vacuum source but all fords are setup to run ported vacuum for the vacuum advance...period. if the engine is in proper tune then a ported vacuum source is all it needs, especially on a bone stock engine. some performance engines with a big cam might like a manifold vauum source for the vacuum advance but stock engine don't.

BTW, i have a nice little collection of various 70's electronic ignition conversions and i have 2 or 3 of this style, so if you do find you need some parts, other than the box itself, i might have what you need, but honestly at that point you might be better just changing to something else if your system takes a crap, but i wouldn't worry about it until that happens.

Platonic Solid · May 26, 2009

YOU RULE BNICKEL!

My search for a vacuum tester seems to come up with the same result everywhere I go, so I assume this is adequate:

Actron Vacuum Tester #CP7803, $20

VACUUM TESTER by Actron - Part 9090006 - Advance Auto Parts

IOU a six pack

Edit: Could a defective "Gold Box" be a potential source of my battery drainage issue? To date, I've been pulling the positive cable and keeping the battery charged via a "Battery Tender" trickle charger.

bnickel · May 26, 2009

Platonic Solid said:
YOU RULE BNICKEL!

My search for a vacuum tester seems to come up with the same result everywhere I go, so I assume this is adequate:

Actron Vacuum Tester #CP7803, $20

VACUUM TESTER by Actron - Part 9090006 - Advance Auto Parts

IOU a six pack

Edit: Could a defective "Gold Box" be a potential source of my battery drainage issue? To date, I've been pulling the positive cable and keeping the battery charged via a "Battery Tender" trickle charger.

that tester should be adequate, yes. as for your battery drain, the ignition isn't causing that unless it is hooked up way wrong. more likely would be a bad alternator, voltage regulator or battery. autozone or advance should be able to test the charging system on the car and tell you what's wrong

Platonic Solid · May 26, 2009

bnickel said:
that tester should be adequate, yes. as for your battery drain, the ignition isn't causing that unless it is hooked up way wrong. more likely would be a bad alternator, voltage regulator or battery. autozone or advance should be able to test the charging system on the car and tell you what's wrong

Outside of the potential incorrect wiring of the "Gold Box" (which I have no way of verifying), the only thing I haven't changed is the alternator. Can a bad alternator cause drainage when the engine isn't running?

bnickel · May 26, 2009

Platonic Solid said:
Outside of the potential incorrect wiring of the "Gold Box" (which I have no way of verifying), the only thing I haven't changed is the alternator. Can a bad alternator cause drainage when the engine isn't running?

a bad alternator can't cause a drain when the engine isn't running but if it's not charging enough it could very well be discharging the battery driving down the road. if the ignition box was on all the time it would very, very likely have burned up long ago

Platonic Solid · Aug 2, 2009

Update

I followed bnickel's tuning advice along with 2+2GT's vacuum routing assistance from this thread. I replaced the broken distributor vacuum control valve (aka: PVS). Used the 1970 351C vacuum diagram. Removed the EGR temperature controlled vacuum valve (located in the heater coolant lines). Capped off the EGR valve and any other remaining open manifold and carb vacuum sources.

Above actions along with rebuilding the carb, (plus new alternator, power steering pump, thermostat, radiator & heater hoses, plugs and cables) and this old engine runs very smooth at low idle and in gear.

Thanks all

Electronic Ignition ID & Rough Idle ?s

Similar threads

Privacy & Transparency

Privacy & Transparency