Misfiring while cruising

[Mark Maras]

2 hours ago, jalexquijano said:

Okay. We know that the compression is good and the cap and rotor are also new. So what remains? Should i clean all the 6 plugs and cranked the car leaving it to idle for 20 mins to see if those plug foul to black?

NO.

[jalexquijano]

Just remember i already cleaned those fouled plugs with carb cleaner.

[Mark Maras]

@jalexquijano 

 It seems to me that you're kind of walking up and kicking fate in the shins by letting the engine idle for long periods of time. Especially an engine with a performance cam. Performance cams do wonderful things to engines but as a rule they don't idle well and if you idle them too long the rpms start to drop and you've got to blip the throttle a few times to get the idle back to normal. In that ten minutes of idling did your rpms change at all? Perhaps you're asking too much of the engine to idle that long. And I still want to know if all the plugs were black.

[jalexquijano]

Mark,

This is what my engine has inside with the exception of the far 311 camshaft. I replaced with a schneider 274f camshaft

[Mark Maras]

12 hours ago, Mark Maras said:

@jalexquijano 

 It seems to me that you're kind of walking up and kicking fate in the shins by letting the engine idle for long periods of time. Especially an engine with a performance cam. Performance cams do wonderful things to engines but as a rule they don't idle well and if you idle them too long the rpms start to drop and you've got to blip the throttle a few times to get the idle back to normal. In that ten minutes of idling did your rpms change at all? Perhaps you're asking too much of the engine to idle that long. And I still want to know if all the plugs were black.

 

[jalexquijano]

20 minutes ago, Mark Maras said:

 

The idle did drop and got rough during those 10 minutes even with the hood wide opened on direct sunlight

[jalexquijano]

On 9/24/2018 at 9:59 PM, Mark Maras said:

@jalexquijano 

 It seems to me that you're kind of walking up and kicking fate in the shins by letting the engine idle for long periods of time. Especially an engine with a performance cam. Performance cams do wonderful things to engines but as a rule they don't idle well and if you idle them too long the rpms start to drop and you've got to blip the throttle a few times to get the idle back to normal. In that ten minutes of idling did your rpms change at all? Perhaps you're asking too much of the engine to idle that long. And I still want to know if all the plugs were black.

I checked the choke cables and they did not leave the jets down when pushed back once the engine got warm. I crank the engine and left the car to idle at the parking lot for 10 to 12 mins. Pulled spark plug 3, 4 and 5. 3 and 4 were fouled 5 (first picture) was clean. Maybe i should run the car for 20 to 25 minutes and then leave it to idle. Do you agree?

[Mark Maras]

 No, don't let it idle. You'll only end up buying new plugs. The fact that only a couple of plugs are fouled narrows the problem down to, what I believe is, poor spark plug wire connections at one end or the other. Compression is good, new ignition parts, there's not much left to blame it on. Try re-seating the spark plug wires onto the plugs and into the cap. They all should snap into place. If you have a volt-ohm meter, you could pull the cap with the wires connected (leave the wires in the loom), pull the plugs, reconnect the wires to the plugs and measure the resistance from the terminals inside the cap to the center pole of the plugs. The resistance should be nearly identical on all six.

 Btw, congrats on the dist removal and replacement. Success is sweet.

 

[jalexquijano]

Should i buy a set of brand new spark plugs before doing the test?

[Mark Maras]

You'll need another set but not for the test. When you Z is sitting and idling does the idle sound smooth and even or does it sound like it's missing on a cylinder or two. My guess is in the beginning it sounds ok but gets worse the longer it idles.

[jalexquijano]

Just guide me on this. Do you recommend to race the car for 20 to 25 minutes and then leave it to idle for 10 to 15 minutes with the hood closed? Your assumption is correct. It idles okay for the first few minutes and then it starts getting sloppy tending to fail. I guess i will need to pay you to fix my car as all the mechanics that have diagnosed the engine just ask me to change this, buy that, get a msd ignition, remove the fan clutch and get electric fans, etc.

[Mark Maras]

 Do the test with the engine stone cold. We're looking for a poor electrical connection, or a bad wire or two. I know all the ignition parts are nearly new that's why I think it's a poor connection. When you installed the plug wires into the cap were you sure they all went in all the way? Same question applies to the plug wires onto the plugs.