Causes for misfire on Pinto engine

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79Caprigl
Posts: 52
Joined: Tue May 24, 2016 8:28 pm
Car(s): Capri 1.6gl (restoration project)

Causes for misfire on Pinto engine

Post by 79Caprigl »

Hi all,

I recently managed to start my capri for the first time since purchase. There appears to be a misfire which affects the car until it is warm. In addition, there is also a squeal upon start-up.

It's had a brand new dizzy fitted, rotor arm, a carb tune up and a new battery. The revs also seem to drop causing it to cut out.

I'm unsure what the problem could be, was thinking possible idle control valve or a fuel problem?

Any advice appreciated.

Cheers
Paul G
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Re: Causes for misfire on Pinto engine

Post by Paul G »

I assume your car is a 1979 1.6GL.

The squeal on start up would be the fan belt. It either needs tightening up a bit or repacing. The misfire could be several things though. A 1.6GL would not be fitted with an idle control valve, that is usually only fitted to fuel injection cars.

You say that you have replaced the distributor and rotor arm. Have you got the plug leads back on in the correct order? The firing order is cylinder1 then 3,4, and lastly 2 and the rotor arm turns clockwise so find no 1 (fan belt end) lead and then go round the cap checking they all go to their correct cylinders.

If this is OK then remove the spark plugs. Any that have not been firing should show up as wet and or oily. If there is an oily one change it for a new plug and see if that does the trick. if it doesn't try changing the lead that goes to it.

The other thing to look for are split or disconnected vacuum hoses around the carb and under the air filter. Check that all are in good condition, connected to something or, if they have been removed, that they are plugged up securely.

Finally, with the engine running spray some WD40 around the joint where the inlet manifold joins the cylinder head, if the misfiring stops then you may have a suspect gasket.

There are many more things that may need checking if all the above doesn't work but give these a go for now and get back to us if it still isn't working properly.
340truck
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Re: Causes for misfire on Pinto engine

Post by 340truck »

Couple of questions - how can the carb have had a tune up if you've only recently started the engine? Leave the carb for a moment, it is rarely the cause of a misfire anyway. Have you set the ignition timing, with the engine running, with a strobe light? Misfires are more usually caused by ignition problems. Plugs ok? Leads good? Points gap correct? Electronic ignition fitted instead? Cheap units can fail even when new. Sort the ignition then, and only then do you look at the carb. Sort the idle mixture and ensure the choke is working correctly.

Now you're misfire should be sorted. If it's still there, all the time, then on a 1600 I would suspect valve recession Reset the valve clearances and if you still have the misfire then the head is gonna have to come off to find what the problem is.
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