mopar performance ignition miss

-
lilhows340

lilhows340

Well-Known Member
Joined
Jan 1, 2010
Messages
268
Reaction score
4
Location
Ontario Canada
Hi I have 2 318's Scamp and Aspen also a 340 Demon. All with Mopar performance ignition. All 3 have a low rpm or idle stumble. All have different carbs. Spark plugs on the black side so lean is not the issue. At the moment I am increasing plug gap on 340 from .35 to .45. Anyone else experience this.
 
lilhows340 said:
Hi I have 2 318's Scamp and Aspen also a 340 Demon. All with Mopar performance ignition. All 3 have a low rpm or idle stumble. All have different carbs. Spark plugs on the black side so lean is not the issue. At the moment I am increasing plug gap on 340 from .35 to .45. Anyone else experience this.
Click to expand...


Get the black off the plugs. Being pig fat (black plugs are pig fat) isn’t much better than being screaming lean.
 
The 340 that I'm working on at the moment has 50 miles on since rebuild. I read that you can get a stumble from a lean condition. I was out tuning it, have snap-on timing light and vacuum gauge, when I noticed the same stumble my teens have. Both of them are drivers and ran pretty good other than that stumble/miss at red light or slow city driving so just let it go.
 
lilhows340 said:
The 340 that I'm working on at the moment has 50 miles on since rebuild. I read that you can get a stumble from a lean condition. I was out tuning it, have snap-on timing light and vacuum gauge, when I noticed the same stumble my teens have. Both of them are drivers and ran pretty good other than that stumble/miss at red light or slow city driving so just let it go.
Click to expand...
What carb are you running?
 
lilhows340 said:
The 340 that I'm working on at the moment has 50 miles on since rebuild. I read that you can get a stumble from a lean condition. I was out tuning it, have snap-on timing light and vacuum gauge, when I noticed the same stumble my teens have. Both of them are drivers and ran pretty good other than that stumble/miss at red light or slow city driving so just let it go.
Click to expand...


What carb is it????????????
 
lilhows340 said:
Hi I have 2 318's Scamp and Aspen also a 340 Demon. All with Mopar performance ignition. All 3 have a low rpm or idle stumble. All have different carbs. Spark plugs on the black side so lean is not the issue. At the moment I am increasing plug gap on 340 from .35 to .45. Anyone else experience this.
Click to expand...
How do you know it's ignition? Idling in gear and you matt the gas pedal and it stumbles? Under what conditions?
 
1. Like Yellow Rose wrote above, get the black off the plugs.
Heavily carboned plugs make it more difficult to spark.
Start with clean plugs.
2. A carb is not rich or lean. Begin with the idle circuit. If its fouling at idle, then look at the choke and if not choke, then make adjustments to clean it up. On the other hand if its lean at idle, then look at the choke after making adjusments to hot idle to make stronger. Test by placing in gear if automatic. Only after good idle is established is it useful to look at the 'high speed' circuit, and then pump shot.
 
lilhows340 said:
All 3 have a low rpm or idle stumble.
Click to expand...
I think you might be experiencing what is commonly called a tip-in hesitation.
This is often caused by the primary throttle blades being too far down on the transfer slot, which is a typical occurrence when trying to run too much idle-timing for the carb. It just takes too long for the transfers to come up to speed.
The simple solution is to increase the idle speed,to move the butterflies up the slots,and then take out some idle-timing to slow it back down. Works for me every time.
 
Thanks for the reply's. The 340 and one of the teens has the 650 eddy. The other teen has the 390 holley. All three motors do the same thing and the only thing common to all is the ignition system. The issue is at idle or slow cruise is is seems to die for a split second. I have re-gapped spark plugs on the 340 and will be going out for a test drive this weekend.
 
IMO; if the ignition was weak enough to missfire at tip-in, then it wouldn't recover and take a load either.
In the past, I have run the Chrysler electronic ignition system, with no problems. In fact, I have subbed in multiple factory slanty or SBM,ECUs from several different cars, with no problems in normal driving. That's the way I prove the ECUs for resale.
I'm not saying you don't have an ignition problem.
What I am suggesting is that it is highly unlikely, when a much simpler explanation exists; KISS.
 
lilhows340 said:
Thanks for the reply's. The 340 and one of the teens has the 650 eddy. The other teen has the 390 holley. All three motors do the same thing and the only thing common to all is the ignition system. The issue is at idle or slow cruise is is seems to die for a split second. I have re-gapped spark plugs on the 340 and will be going out for a test drive this weekend.
Click to expand...
I agree with AJ
You in all likelihood have fuel issues.
What do the plugs look like?
This may help
Spark plug reading can be complex and sometimes frustrating task this page will help make it easier and the results rewarding
 
You must log in or register to reply here.
-

Back
Top