Slight Stutter every 5 seconds at idle, can't figure it out.

ABC123 · Uber Guru

Slight Stutter every 5 seconds at idle, can't figure it out.

4SPEED427 · A Poncho Legend!

If you sit in the car, hold the brake and put it in drive, does it do the same thing?

If you load the engine (still holding the brake, in drive) does it still do the same thing?

ABC123 · Uber Guru

So now the neighbour is wondering why I am doing brake stands in my shop biggrin

Yes, shake is still there under load.

Canadian Poncho · A Poncho Legend!

Is the shake always at the same time interval?

seventy2plus2 · Canadian Poncho Superstar!

When you did the Pertronix conversion, did you run a new +12V line to it? They need a full 12 volts, and the original wiring harness has a resistive wire in it going to the coil. The resistive wire serves the same purpose as the old ballast resistors on the firewall.

cranks38 · Addicted!

- Slop in the timing set should be obvious when you put a timing light on it. (The mark will "walk" noticeably.)

- I am not a fan of ignition conversions... though many persons like and recommend them, many others have problems and complaints about Petronix products. (Only GM's HEI is a true H.E.I. in this context.) Having said that, a conversion is only as good as the components it's mated with. Check the condition of everything and follow Petronix instructions to the letter, including coil resistance, which is critical...

- Assuming you have an otherwise healthy engine, most carburetor problems are ignition related.

Just my knee jerk reactions...

ABC123 · Uber Guru

Canadian Poncho wrote:
Is the shake always at the same time interval?

Like clockwork !

4SPEED427 · A Poncho Legend!

ABC123 wrote:
So now the neighbour is wondering why I am doing brake stands in my shop
Yes, shake is still there under load.

Ok, that rules out a vacuum leak pretty much.

ABC123 · Uber Guru

seventy2plus2 wrote:
When you did the Pertronix conversion, did you run a new +12V line to it? They need a full 12 volts, and the original wiring harness has a resistive wire in it going to the coil. The resistive wire serves the same purpose as the old ballast resistors on the firewall.

Wow,

That was not in the instructions.

It did run fine after the conversion.

I am tempted now to put the points back in to see if that solves the problem.

I am using the pertronix coil but I kept all the old parts.

Trying to figure this out myself first because of what Covid-19 has done to my job,

I have lots of time to play.

Canadian Poncho · A Poncho Legend!

As mentioned full 12V is important for the Pertronix to work properly. Any slop in the distributor shaft? Is your float level set correctly in the carb?

seventy2plus2 · Canadian Poncho Superstar!

ABC123 wrote:
seventy2plus2 wrote:
When you did the Pertronix conversion, did you run a new +12V line to it? They need a full 12 volts, and the original wiring harness has a resistive wire in it going to the coil. The resistive wire serves the same purpose as the old ballast resistors on the firewall.
Wow,
That was not in the instructions.
It did run fine after the conversion.
I am tempted now to put the points back in to see if that solves the problem.
I am using the pertronix coil but I kept all the old parts.
Trying to figure this out myself first because of what Covid-19 has done to my job,
I have lots of time to play.

Was just looking at the Pertonix instructions online. The requirement for +12v is in the Wiring Instructions on page 2, including Recommended Installation which addresses bypassing the resistive wire.

ABC123 · Uber Guru

seventy2plus2 wrote:

Was just looking at the Pertonix instructions online. The requirement for +12v is in the Wiring Instructions on page 2, including Recommended Installation which addresses bypassing the resistive wire.

I must have missed that completely !!!

Clint, I think you are on to something.

I have a plan now for Monday.

I hope it is this simple.

ABC123 · Uber Guru

As a trial, I ran a jumper wire from the fuse box to the coil.

There is a definite difference !

Thanks Clint !

However, the shake is still there.

I'll stop in and see Tiny this week.

My timing gun is very old so I think it's best to have him look at it.

I'm thinking at this point, timing chain.

Canadian Poncho · A Poncho Legend!

Jeff (Tiny) will figure it out. He's one of the best old school techs I know. Say "Hi" to him for me.

4SPEED427 · A Poncho Legend!

I know this may be a dumb (obvious) solution but did you check the gap on all the plugs when you installed them?

ABC123 · Uber Guru

4SPEED427 wrote:
I know this may be a dumb (obvious) solution but did you check the gap on all the plugs when you installed them?

0.035 Gap

The plugs I took out were gapped the same.

Tiny said he would have to have it for a day.

He would start with a compression test.

and go from there.

73SC · A Poncho Legend!

Before I'd be worried about tearing in to the engine for an almost indiscernible shutter, I`d be looking at the ignition wires and making sure there is good contact at coil and plugs, look for cracks and arcing, are the boots good and not soft and cracked or melted. After that I'd be going at that carb, make sure its clean and then set the idle mixture properly followed by curb idle. How about your fuel filter, I mean these are all easy things that cost little or nothing make your baseline right but they eliminate a lot of things too. If you don't trust your timing light its gotta be timed after Petronix switch.

I keep a spray bottle in my garage for ignition misses, have a look:

https://video.search.yahoo.com/yhs/search?fr=yhs-symantec-ext_onb&hsimp=yhs-ext_onb&hspart=symantec&p=spray+bottle+test+of+s%5Bark+plug+wires#id=1&vid=52231d50f249289f46674922fe3a4412&action=click

-- Edited by 73SC on Monday 8th of June 2020 11:36:32 AM

66 ponchoboy · Veteran Member

Number 8 cylinder camshaft lobe is round common occurrence. ps wild guess

timbuk · Canadian Poncho Superstar!

thought this thread was about the PM.....

ABC123 · Uber Guru

timbuk wrote:
thought this thread was about the PM.....

Shhh !

No politics

But,

Haircuts allowed in Ottawa as of Friday.

long stroke · Canadian Poncho Superstar!

ABC123 wrote:
4SPEED427 wrote:
I know this may be a dumb (obvious) solution but did you check the gap on all the plugs when you installed them?
0.035 Gap
The plugs I took out were gapped the same.
Tiny said he would have to have it for a day.
He would start with a compression test.

and go from there.

I am not saying that this will fix your problem but with Pertronix you can run 040 to 045 on your plugs. A wider gap is better with that amazing conversion. I have had Pertronix on all my oldies for over 20 years and swear by it. Never and i mean never had any issues at all with that wonderful system. Good luck fixing your situation there.

SD 396 · Poncho Master!

Did your engine have this issue before the conversion? If not you should be able to rule out everything other than what you swapped. Give the tech working on it as much information as you can to help him with the diagnostics and save him some time.

Good luck.

ABC123 · Uber Guru

SD 396 wrote:
Did your engine have this issue before the conversion? If not you should be able to rule out everything other than what you swapped. Give the tech working on it as much information as you can to help him with the diagnostics and save him some time.
Good luck.

I did the conversion last fall and everything was great.

Sat for 5 months in a body shop with me having the motor out for a few weeks.

It has never really ran right since I got it back.

First dirt in the fuel filter and then a piece of something stuck in the needle.

New filter, fuel lines and float seems fine.

Remanufactured carb last fall.

I'll get Tiny to set the timing.

I'm sure his equipment is better than mine wink