Isabella Is Stalling

[Pescado]

Hey All,

Hope everyone has enjoyed the summer with tops dropped...

Need some help with Isabella she's not happy these days...let me explain. When I start her she starts good on fast idle and idles well at 2000rpm, after idling for a few minutes she will just stall out and after this every time i start her she idles for a couple seconds and then stalls. Isabella was born in 1979 and i replaced the carb with a new 32/36 weber 2-3years ago, new dizzy, new starter, new coil, new control module, new plugs/wires. Plugs look good maybe a little lean, car idles at around 900rpm, I had a fuel pressure gauge on the car the last time i went through this and fuel pressure looks good and holds close to 3...what can i do to help her?

[Pescado]

adding in that when she stalls some fuel is burped out the carb.

[Pescado]

So changed back to my old control module and the car is fine now...what's going on with these things? The one I just replaced was a new accel purchased this summer to cure a stumbling issue the car had at 4200rpm when in 4th and 5th gear. I came across a video and the owner had the same stumbling issue he claimed that the new accel ICM cured this problem...not the case for me.

[Pescado]

Hey all,

So the car is running good now...idles nicely, no stalling and drives really good until I push the car in 4th or 5th gear...it continues to stumble around 4300rpm. I fell like timing is set and air/ fuel is good seeing as the car runs stronge in other gears . I did a compression test...150 across all 4 cylinders...what else should I be looking at?

Thanks for any thoughts/help

[18Fiatsandcounting]

Compression is good, and it sounds like the carb is generally set up OK. A couple thoughts:

1) Weak ignition system. It might work OK under idle and part throttle, but at WOT for extended periods of time (such as in 4th or 5th gear), you start losing a good spark. How are your plugs and plug gap? Look OK, and gap around 0.030" for electronic ignition?

2) Weak fuel pump. The fuel delivery can keep up for a short while, but again, at extended times in 4th or 5th gear under load, the fuel delivery falls short and the engine starts losing power.

When you say "stumble", that sounds like the ignition system is cutting out.

One other thought: A partially plugged catalytic converter?

-Bryan

[Pescado]

Thanks Bryan…plugs look good but I’ll check the gap. Not sure how I can check fuel pressure while under load unless I’m on a Dyno or extend the fuel pressure tester so it sits out side of the engine compartment….maybe a camera under the hood…I’ll report back with my findings.

[Pescado]

ok managed to get a camera and light in the engine compartment and captured the "stumble" it's a little hard to see where the needle is on the gauge due to a water mark on the video but you can see that the needle stays between 2 and 3psig and you can clearly hear the "stumble" at the 36sec mark

Link to my you tube channel

https://youtu.be/NC9bbd7xitw?si=gEgzoQLl7Ek8wgET

[18Fiatsandcounting]

Thanks for that video. That doesn't sound like a misfire to me, and it doesn't look like it's a fuel pressure issue. The "stumble" sounds like the engine is seeing an abruptly changing air/fuel mixture, like either the throttle plate is loose, there is an intermittent air leak into the intake manifold that opens and closes rapidly, an extremely touchy gas pedal, partial blockage in the main jets of the carb, etc.

-Bryan

[Pescado]

Thanks for that video. That doesn't sound like a misfire to me, and it doesn't look like it's a fuel pressure issue. The "stumble" sounds like the engine is seeing an abruptly changing air/fuel mixture, like either the throttle plate is loose, there is an intermittent air leak into the intake manifold that opens and closes rapidly, an extremely touchy gas pedal, partial blockage in the main jets of the carb, etc.

-Bryan

Thanks Bryan….those all sound possible but I’m not sure how to troubleshoot those issues , what if the vacuum advance wasn’t working? Would the car act like that?
Also I was thinking maybe the intake cam is off a tooth?

[Pescado]

Hey Bryan...I did a vacuum test and got the following results

with meter in between vacuum advance and carburetor tester was reading 2 to zero Hg

with meter only testing the carburetor I was getting 22 Hg plus raises when rpm raised

gap on plugs is good, sprayed carb cleaner all around and no signs of a leak.

[Yadkin]

some fuel is burped out the carb

That's likely an ignition timing issue.

Verify your timing belt is correctly positioned. Verify correct ignition timing with the vacuum advance hose disconnected and plugged.

If this doesn't correct the stumble, rebuild the carburetor. Kits are inexpensive and it's not a difficult job.

[Pescado]

some fuel is burped out the carb

That's likely an ignition timing issue.

Verify your timing belt is correctly positioned. Verify correct ignition timing with the vacuum advance hose disconnected and plugged.

If this doesn't correct the stumble, rebuild the carburetor. Kits are inexpensive and it's not a difficult job.

Hey thanks Yadkin...I have removed the belt and checked all marks again as I thought maybe the intake cam timing was off, dialed in the ignition timing again and the carb was bought new 2 years ago...weber 32/36

[Pescado]

My next test is to isolate the brake booster in case a leak is happening there...also not sure about the hose on top and the one on the bottom of the black carbon box, these two hoses have just been breathing into the atmosphere after I removed all smog and upgraded the carb and intake...I could never really figure out what to do with them.

[18Fiatsandcounting]

That black carbon box is the activated charcoal filter, part of the EVAP system. Evaporative emission control, used to collect gas vapors from the gas tank and recirculated them to be burned in the engine rather than released to the atmosphere.

There are differences in model years, but the bottom port on the canister is to the metal line that goes back to the gas tank. The port on the side (if you have one) was to the carb float bowl vent, and the top port went to a small calibrated port on the intake manifold.

If you changed your carb and your intake manifold, the charcoal canister isn't doing much so you can leave the ports on the canister disconnected. Not ideal, and you might smell gas occasionally, but it doesn't do any harm. Make sure all the ports on the intake manifold are either connected to something or are sealed off.

-Bryan

[Pescado]

Hey guys...anymore thoughts on the vacuum test I did and mentioned above...I tried sucking on the hose to pull in the vacuum advance and nothing! no movement but feels air tight. This is a new dizzy from Vicks does the advance vacuum need any adjustments?