Renault engine misfires

[califkid_66]

Went for a ride was ok then went on the highway higher rpm started having misfires felt like one cylinder on off then it got worst so I turned around made it home but was missing a lot and loss of power
Trying to figure out what it could be
I ordered new rotor distributor cap and new spark plug wires I didn’t check the plugs yet any idea what happened what could cause this
Thanks !

[314159td]

Misfires only at higher RPM is less likely to be a bad coil in my experience, but still good to swap it for troubleshooting.
I've had that caused by partially clogged main jets recently - rapidly pumping the pedal would make things better via the accelerator pump.
Points or electronic ignition?
Running through the entire tune-up procedure from start to finish (static advance, dwell, idle tune, etc) is never a bad idea if it's been a while.

[califkid_66]

Started missing at high rpm but now missing in all range not drivable feels like it’s running on 3 cylinders then 4 fourth starts up once in a while
Starting to think the coil is going bad

[jbcollier]

Rather than replacing parts and hoping for the best, test what you have and eliminate things one at a time.  You can test your ignition wires, coil and rotor (if it has a resistor) with an ohmmeter.  Fuel pressure can be checked with an inexpensive gauge and flow can be checked with a small container.  Ignition caps can be checked visually.  If it is arcing, you can see the carbon tracks.

There are three things that are difficult to diagnose without specialized and rare test equipment: condenser, spark plugs (miss firing under load) and coil (internal short under load or when hot).

I always start with the basics:

- compression
- valve adjust (probably not required in this case)
- timing
- fuel pressure and volume

If everything checks out, then try new plugs (easy and cheap), condenser and coil, one at a time.  Still no go?  You didn't check things carefully enough!

[BDA]

What do your spark plugs look like? Are they all firing?

[califkid_66]

I didn’t have a chance to check yet but this morning I had to move the Europa and it started right up but seems to be running on three
I did not remove the spark plugs yet
I have electronic ignition I was thinking either bad spark plug wire bad plug
I’ll update when I start checking the components
Thanks again for your help

[BDA]

An ignition test pen is your friend (https://www.ebay.com/itm/315379183161).

[califkid_66]

I have one ! Just have to find it

[BDA]

We've all been there!

[califkid_66]

Ok just pulled the plugs out

[jbcollier]

You are burning a lot of oil on that one cylinder.  Fit a set of new plugs and see if that clears the running problem.

[califkid_66]

Not yet JB !! Let start with a compression test
I didn’t open the carb just put my dad’s compression tester cranked a few times  pretty happy with the readings
 140 148 146 140
That’s a 5.4 percent difference between highest and lowest

[jbcollier]

Unfortunately, compression and oil consumption are not related.  You can have great compression and burn oil at a rate to make a Saudi Sheik grin with glee.  You can also burn virtually no oil and have 0 compression.  Fit the new plugs.  Everything running fine?  Good, cancel the new ignition parts and plan on pulling the head to see what is up.

Twice, my former boss built up engines with the rings installed upside down.  Ran great.  Lots of compression.  Burned oil like crazy.  Installed the rings properly and all good again.

[califkid_66]

I changed the plugs adjusted the gap cleaned the idle jet and mixture screw adjusted the carb and idle it run great !
It was running to rich
Now I want to check the timing what would be the timing on Renault 821

[jbcollier]

Disconnect the vacuum advance.  Rev the engine up to 5k and set the timing to 36° - 38° BTDC.  Now check the timing at idle and mark it down for next time.