Miss under load 2.4 w/ webers

berettafan · 06:32 AM

Here are the facts:

2.4 w/ webers

been running great for past few thousand miles

rebuilt webers (bushings and all)

3k miles on rotor, cap & plugs

plug wires look good

plugs all gapped to .030; all are sooty black

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Three or four weeks ago i converted my stock Leistritz to a two-out sport muffler. Car ran fine, some change in power delivery but no popping, spitting, etc. Believe car had been quite rich prior to exhaust change.

Shortly after this the car would die at idle. Determined points gap was down to zero and adjusted. This fixed problem and i reset timing.

Two Sundays ago i attended my second autox. Drove 2.5hrs to the event and did 4 runs with no problems. Towards the end of my last run i noticed some roughness and popping. This happened to start just after the skidpad section of the course. On the ride home the car was a relative mess; popping and rough on acceleration, slightly jerky at certain rpms. The popping was excessive and had NOT been present at all before.

Stopped on the way home and checked idle jets (clean) and timing (hadn't changed). At that time i noticed the accelerator pump on the psgr side would squirt fuel out the top when actuated. took tap and die to nut and stud but still have a small leak at top.

Went for a drive again yesterday and the popping seems to generally only be there under load and i believe it increases in frequency when car warms up. i could be wrong but i thought the car warmed up a touch quicker than usual yesterday.

At rest even when cold you can feel the 'miss' around 2-3k as the car shakes a bit. no popping under those conditions.

So in summary i'd say the popping shows up more when warmed up and under load but the 'miss' seems to be there even in neutral and cold.

Oh, if you stand directly behind the outlets you'll get a black circle on your pants or legs. Some black smoke when revved but not an enourmous amount.

I've looked through a LOT of 'miss under load' threads but very often they are not carb'd cars.

Appreciate any assistance here....

Ron.G · 10-27-2008, 07:34 AM

Don't know if this is the problem but I had a similar problem.
Check your coil wire and see if it is slowly working it's way off the coil.

Mine ran fine but under acceleration it would miss. Pushed the coil wire back up on the coil about a sixteenth of a inch and all was good.

berettafan · 10-27-2008, 08:44 AM

thanks Ron; just went home and tried that but no change.

berettafan · 10-28-2008, 07:50 AM

okay; put new NGK BP7ES plugs in last night and in the process check the plug wires. i noticed that two of them had ends that didn't seem to be screwed on that well and corrected (that is they took 2 or 3 more rotations to 'seat'.

fired it up and immediately heard a loud pop then idled very nicely in spite of 45deg. temps. went for a 20 minute ride (took a while to get it up to temp so i could really get on it) and it definitely was not popping. seemed smoother as well but i'm not convinced i've got 100% power. i figure maybe that loud pop was unburned fuel lighting off after having accumulated from a non-firing cylinder.

so i'll hold judgement for a warmer day but i might be out of the woods.