63 Fuelie stumbles off idle

[Troy P.]

Went out for a cruise today to enjoy the nice weather and give the car some mileage. Ran fine most of the time then developed a rough idle with a stumble starting up form a stop.

Sometimes one or more of my ignition wires comes loose from the spark plug and I get these symptoms. Checked the wires and all is ok.

Back home readjusted timing and idle speed and mixture. Idles pretty good but still has a stumble coming off idle.

Any suggestions as to what the trouble might be?

BTW while back in my shop I finally took my sloppy exterior rearview mirror apart and tightened it up. Back together and back on the car now. Works great! Should have done this years ago.

[Loren L.]

Re: 63 Fuelie stumbles off idle

Fouled plugs.

[Troy P.]

Re: 63 Fuelie stumbles off idle

I was planning to pull the plugs when the exhaust manifold cool off. We'll see.

Speakling of plugs though, what are recommended. I'm running NOS AC 44s.

[Chuck G.]

Re: 63 Fuelie stumbles off idle

Repro plug wires? I've had a few "bad" out of the box.

Chuck

[Bruce B.]

Re: 63 Fuelie stumbles off idle

Try a hotter plug, such as a AC45 if there are any signs of fouling.

[Troy P.]

Re: 63 Fuelie stumbles off idle

No. Since its a driver I'm using decent wires. Good thought though.

[Troy P.]

Re: 63 Fuelie stumbles off idle

Pulling the plugs this morning. We'll see.

After all these years of development I thought there might be a better plug than the AC44 & 45. Maybe not?

[Bruce B.]

Re: 63 Fuelie stumbles off idle

I use AC45 in my 340 HP 62 Corvette and my 57 FI car and they are great and have never fouled even though both cars run rich.
I believe they are actually AC45R since they are the only ones currently available other then the rediculously priced ones on EBAY.

[Kent S.]

Re: 63 Fuelie stumbles off idle

Are you sure it's not fuel percolation due to today's gas - sounds like it all started after your car got warmed up from driving?

[Troy P.]

Re: 63 Fuelie stumbles off idle

Pulled the plugs. Yikes! They were AC43s. What was I thinking? Road trip? Replaced the plugs with ACR45s with high hopes that was the issue.

NOPE! Still stumbles off idle around 1500 rpm to 2200 rpm. It idles just fine but bucks a bit taking off from a stop and doesn't run smoothly once up to speed.

Put fresh gas in during the test drive. Pertronix in the distributor.

What do you suggest as the next step? Test the ignition wires?

[Paul Y.]

Re: 63 Fuelie stumbles off idle

Pulled the plugs. Yikes! They were AC43s. What was I thinking? Road trip? Replaced the plugs with ACR45s with high hopes that was the issue.

NOPE! Still stumbles off idle around 1500 rpm to 2200 rpm. It idles just fine but bucks a bit taking off from a stop and doesn't run smoothly once up to speed.

Put fresh gas in during the test drive. Pertronix in the distributor.

What do you suggest as the next step? Test the ignition wires?

I would test the Cranking Signal Valve. Just block the hose off with a forcepts or small vice grip. (by squeezing it to shut off engine vacuum)

[Troy P.]

Re: 63 Fuelie stumbles off idle

Doesn't it come into play only during start up (i.e. when cranking)?

[John D.]

Re: 63 Fuelie stumbles off idle

Troy, Sounds like your FI unit may need some TLC. Maybe you can luck out and fix the issue while it's on the car. How are the rubber hoses and rubber elbow under the air meter. Make sure no cracks and make sure they are squeaky tight. That's the idle air circuit.
The main diaphragm cover could be warped. The main diaphragm itself could be bad.
What fuel are you using? Is it fresh or not. Vacuum leaks could be the problem.
Look in the 63 shop manual in the trouble shooting section.
See page 6M-30. It says Check for : Defective main control diaphragm or vacuum leaks (I covered this). Faulty spill pluger operation. That's the accelerator pump.
Check for plugged nozzles. Check for incorrect economy stop setting. Your axle link assembly could be the culprit
And the list goes on.
Want a cheater? Try some good fuel injection cleaner in your ethanol and see if that helps. Step up to some better fuel while you are at it also.
The AC43 plugs were horrible for sure. Try a good ignition coil too. One last thing that bothers me is your distributor.
If you have the fuel injection rebuilt and you still have trouble go to NAPA and buy some good points and condenser and a good 12 volt coil. JD
(dirt could be the culprit)

[Loren L.]

Re: 63 Fuelie stumbles off idle

Timing. The Board cannot cope with less than letters - How STUPID is that?

[Troy P.]

Re: 63 Fuelie stumbles off idle

I pulled out the shop manual and did see the troubleshooting suggestions. First step is to look at the fuel pump cable. Easy to do. Then in several cases the book indicates spill plunger. Could be nozzels too. I'll look into the FI unit methodically tomorrow.

I've had it apart years ago. When I reassembled it I honed all the covers flat on a sheet of glass. So I believe they're OK.