Technical Misfire on acceleration

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Technical Misfire on acceleration

turbo93

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Hi all, so my barn find panda is almost ready to be put back on the road. Got all the electricals sorted but i still have an engine problem. The engine misfires on acceleration. Its got new plugs, leads, rotor and cap. Carburetor has been overhauled and should be fine. Fuel filter is new and so is the fuel inside the tank. I cant seem to find the cause of this. Also its spitting a black liquid from the exhaust. Any help please cause its driving me mad? Thanks
 
Is your vacuum advance tube free from holes and connected correctly. Most pandas do spit condensate from the exhaust. It’s because the pipe doesn’t get that hot so the moisture from the combusting gases cools. Before it leaves. Not to worry unless it very oily.
 
yeah, the black liquid will be condensate mixing with soot. my panda does it.

as said, that vacuum advance can be a pain. often the rubber diaphragm inside gets a hole in it and stops working. best way to check is to pull the pipe from the back of the carb and suck on it.. if you can just keep sucking air through it, it needs replacing.

also looking down the carb with the engine off and choke open whack it to full throttle. you should see a little jet of fuel squirt down into the carb. if not, the acceleration jet is blocked. though this normally causes the engine to almost cut out before picking up when you blip the throttle.

here i have a video on it so you know what i am on about.
a few mins in..
 
Yeah ive been told that it could be the vacuum advance. I tried sucking on it with the engine started and i can keep pulling air normally. Even though i noted that with the hose removed the engine is worse. Maybe cause with it plugged it still creates a little vacuum? [emoji848]
 
it does sound like its working. the engine will be worse as it is able to pull in air after the carb. while the engine is running, the intake manifold is always under some kind of vacuum especially while at idle.

hmm ok, while the engine is off try having a look down the carb with a torch then quickly open the throttle fully. you should see it squirt fuel down into into it. if not, that jet will be blocked.
 
it does sound like its working. the engine will be worse as it is able to pull in air after the carb. while the engine is running, the intake manifold is always under some kind of vacuum especially while at idle.

hmm ok, while the engine is off try having a look down the carb with a torch then quickly open the throttle fully. you should see it squirt fuel down into into it. if not, that jet will be blocked.



So by removing the hose and the engine is worse means that the vacuum advance is working correctly? Ill try the carb thing tonight and keep you updated. How can the accelerator jet be unblocked? And which one is it?
 
Replaced the vacuum advance unit and still no luck. Engine runs a bit better but is still rough. What I’ve noticed though is that the ceramic part of some of the spark plugs is cracked. Could this be the problem?
 
Yes that will defiantly cause a problem. Your first post said it had new spark plugs- you now need another new set and fit them carefully. Do not over tighten spark plugs.
 
Not the ceramic on the nose but the insulator on the outside. You think thats the problem?
 
hmm it could be, it may mean that the spark plug inside may be very low resistance. on ebay, if you type in the number on the side of the spark plug you should be able to get one single plug to replace it. or for testing, just use one of the old plugs if you have it.

yes, if the engine runs worse with the hose disconnected it means the vac advance is working. also ANY vacuum leaks will cause the engine to run bad.
have you tested the brake vacuum servo if it has one? its not often it happens, but if that is leaking that could be causing the issue. like i say, and atmosphere getting into that intake manifold will cause the engine to run badly. its also one of the top causes for most 90s cars to fail emission tests.

if you watch that video i posted, you can see the jet i am on about. i even squirt mains water pressure through it and it jets quite well.
 
Yes that jet squirts fuel well. Tomorrow ill be getting a new set of plugs and see how it goes. No brake servo for this model as its quite old.
 
This is the condition of the plugs IMG_0001.JPG
 
That plug is one of the worst I have ever seen and should be discarded straight away.
Get 4 new spark plugs .
As previously said.
 
Bought 4 new plugs and a brand new battery since the one it had was done for. Will try it out and keep you updated.
 
Update: so i replaced all 4 plugs and the engine is running much better now. It still has the idle a little rough. What else could it be? Could it be the mixture screw? Its got a small blow in the exhaust from what I’ve noticed. Thanks
 
Before adjusting the carb, check that the timing is set correctly using a strobe light. Once that is correct you can move to adjusting the idle mixture and speed on the carb. Ideally you need a CO meter and tachometer to do this accurately, but it is more than possible to do it by ear.
 
Before adjusting the carb, check that the timing is set correctly using a strobe light. Once that is correct you can move to adjusting the idle mixture and speed on the carb. Ideally you need a CO meter and tachometer to do this accurately, but it is more than possible to do it by ear.



I did not touch the timing. Can timing be lost if a car has sat for a while? Its sat for 5 years so anything is possible.
 
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