Misfiring while cruising

[siteunseen]

3 minutes ago, Patcon said:

What are you doing up or have you been up all night?

I open up a restaurant at 5:30a.m.  Leave at 11 a.m. when they "open"

Pretty sweet job as I'm a morning person.

Edited October 12, 2018 by siteunseen

[siteunseen]

20 years ago I'd be trying to go to sleep, staring at the ceiling fan.

[Patcon]

4 minutes ago, siteunseen said:

I open up a restaurant at 5:30a.m.  Leave at 11 a.m. when they "open"

Pretty sweet job as I'm a morning person.

I am up to go look for Bambi's big brother...?

[AK260]

what kind of gearing are you running? Im seeing an issue on my Z where the car falls flat on its face in 4th gear, running a 3.36 and close ratio gearbox. It used to occur in 3rd gear @4k rpm, but I was able to tune that issue out, im starting to thing its the gearing thats "bogging" down the car if thats possible. 

 

 

Think of your gearing as a torque amplifier - it merely amplifies your engine's characteristics. So if you are bogging down @4K you have a power flat-spot that a long diff will make more prominent.

 

L24s were renowned for having a flat spot at or just before 4K rpm - one way to "tune"' it out is to have a 6-3-2 exhaust header with long primaries and long collectors (the 2 bit) as per the Nismo or Janspeed design. The theoretical ideal (rule of thumb) is around 90cm primaries and 50cm collectors. See this fine bit of engineering ...

 

http://www.datsun-zstory.com/echappements/headers/headers-race-sport/

 

Changing your diff will surely reduce the effect but the flat spot is still there. I just realised why you guys are getting such low revs, you are using an auto 'box, right?

 

Apologies to the OP for taking the thread off track.

 

 

[jalexquijano]

1 hour ago, AK260 said:

 

 

Think of your gearing as a torque amplifier - it merely amplifies your engine's characteristics. So if you are bogging down @4K you have a power flat-spot that a long diff will make more prominent.

 

L24s were renowned for having a flat spot at or just before 4K rpm - one way to "tune"' it out is to have a 6-3-2 exhaust header with long primaries and long collectors (the 2 bit) as per the Nismo or Janspeed design. The theoretical ideal (rule of thumb) is around 90cm primaries and 50cm collectors. See this fine bit of engineering ...

 

http://www.datsun-zstory.com/echappements/headers/headers-race-sport/

 

Changing your diff will surely reduce the effect but the flat spot is still there. I just realised why you guys are getting such low revs, you are using an auto 'box, right?

 

Apologies to the OP for taking the thread off track.

 

 

I need to solve my black fouling at idle issue first before getting into this kind of stuff. I was thinking if using ngk bp5es plugs which are hotter will avoid the fouling at idle. 

[jalexquijano]

On 10/5/2018 at 2:31 AM, AK260 said:

 

Spot on!

Also try it on the coil to dizzy cap cable - which is where the majority of my issues lay.

It looks like your engine earth strap is next to your oil dipstick. Thick black wire goes from block to body.

Your coil has positive and negative low tension connectors. One is 12v from your ignition switch and the other is the 0v that the dizzy breaks / makes as it operates. Also you have low tension connectors at your distributor - look at those too. These connectors tend to corrode. Especially in the UK where we are constantly humid.

IMHO plug fouling at idle is a red herring here and given your photos they look OK. I had an L series that drank a lot of oil and the plugs were not just sooty but also wet and black - it never backfired or missed when cruising or on power. So your plugs for the sake of trouble shooting this issue look fine.
 

 

Would swapping to bp5es which is hotter plug solve the fouling issue at idle?

[Dave WM]

22 minutes ago, jalexquijano said:

Would swapping to bp5es which is hotter plug solve the fouling issue at idle?

it would mask it, but not solve the underlying problem.

[Mark Maras]

  @jalexquijano I don't think you need hotter plugs yet. Some of the plugs are looking good. Let's figure out what's wrong with the others. Have you installed the new wires yet?

[jalexquijano]

Waiting for them

[AK260]

  [mention=28721]jalexquijano[/mention] I don't think you need hotter plugs yet. Some of the plugs are looking good. Let's figure out what's wrong with the others. Have you installed the new wires yet?

Agreed! Plug fouling at idle could be caused by other things like mix, lack of vac advance, etc. Get her firing well first and then sweat the other stuff later. ;)

Is it safe to assume you've already changed your cap and rotor?

[Mark Maras]

@AK260 Jalex installed a new Bosch cap and rotor a few weeks ago.

[jalexquijano]

5 hours ago, AK260 said:

 

Agreed! Plug fouling at idle could be caused by other things like mix, lack of vac advance, etc. Get her firing well first and then sweat the other stuff later. ?

Is it safe to assume you've already changed your cap and rotor?

 

Thats done already.