Stuttering at 1500rpm, then fine...ignition or fuel?

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65Valiant310

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Started the car after a few weeks. Run STABIL in my fuel when it sits for long periods. Car is idling odd, so I let it warm up for a few minutes, and take it for a spin. Car stutters at 1500rpm, then jumps up in rpm and is fine. I put it in park, and rev it up to 1500rpm...feels almost like its missing, then it jumps up in rpm quickly and all is well...
Fuel bad or fuel filter clogged? Ignition maybe?
318 small block, filters are all within a few months old, and all ignition was replaced last year...car runs perfectly most of the time yet this is odd.
Ideas?
thanks
 
I'd start with a new filter, and add some fresh gas. Cheap and easy. Well easy anyway LOL.
 
Gotcha, I will try those. The other day I was messing with converting my open breather to a closed system where the breather hose goes right back into the air cleaner. That is the only other thing I can remember doing, yet plugged the lower outlet on the air cleaner and kept it an open breather for now.
 
Pull the pulgs and take a gander at them. Like Wild said... Take some carb clean with the little tube on the can and blast down into the air bleeds.
 
Started by cleaning out the carb, and shot a video of how when I hold the rpms exactly at 1500, the rpms jump up a few, then back down to 1500, then up a few again.
What to look for when pulling the plugs?
 
am leaning towards a carb issue - I have a few Edelbrok 600's that do something like
that. Forgot exactly how the carb works but think it switches over from idle circuit to
something else around that rpm. If it's an Edellbrok(Carter), look inside and see if one of the sides is dribbling gas.
 
Not a carb expert, but it does sound as if it is pulling gas out of one of the idle or off-idle ports when at that particular RPM/vacuum. Like berlins said, watch for fuel purts down the bowl when at that range

Grant
 
Gotcha, thanks all. I cleaned out the air bleed circuits on both sides. Its an edelbrock 1406 carb. Berlins, have you fixed it or just lived with it?
 
Is it electronic ignition? I just thad the same problem with my 69 340. I put in the Mopar performance electronic distributor and it ran just like you describe.

I removed the distributor and disassembled it and found an extra lock washer was stuck to the magnet on the pick-up. Also.....The silicone block sourrounding the reluctor pick-up was not pushed back far enough onto the mount so the teeth on the reluctor wheel were hitting the block, messing up the gap.

I reassembled it and set the gap at .008 and it runs perfectly now. Smooth from idle right up to 6500 rpm.

The instructions say to set the reluctor gap between .008 and .018, but I found that anything more than .010 causes it to run rough and erratic.

hope this helps.
 
Yes, its got an electronic ignition conversion kit (ignitor kit I think).
 
I have an extra electronic ignition unit, yet need to borrow/buy a chrome/orange box to install it and see if thats the problem.
 
I was messing with the carb before it happened, so I am going to rebuild the carb. Hopefully not too hard, and clean out everything well.
 
Um, Have you checked your vacuum advance.

If you are not getting any vacuum then your car will stumble right out of idle and then run fine.

easy enough to check with a timing light.
 
No, I haven't, no timing light unfortunately. I dunno how to check the vacuum advance so I will read up on it and try to borrow a timing light.
thanks
 
Well if you disconnect the vacuum line while your engine is idling the idle should go lower.
If there is no change then it isn't working.
 
Had a 2.2 Reliant that sat around. Had crappy throttle response and ran poorly. Gave it a massive dose of Lucas fuel treatment, and sprayed the carb vents, etc with cleaner. Ran good after the plugs cleaned themselves off.
 
Timing adjusted, carb rebuilt (by me) and car runs great. No more surging at cruise as well.
thanks all!
 
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