Misfiring while cruising

[jalexquijano]

11 hours ago, AK260 said:

I think your speedo may be a little optimistic - the longest R180 was a 3.364 which means you should get 22 (ish) mph per 1000rpm. Unless of course your gearbox has a super long top gear.

 

Mine is pessimistic around 30mph (i.e. Shows 25mph) then gets accurate at 80 and optimistic above 90! Ahem - All tested on a track of course, officer!

 

Don't always trust your old dials.

 

Other possibility is that your rev counter is being pessimistic and you really are doing 100 in which case your real (not indicated) revs are around 4.5K RPM! And if you think that the max speed of your car is around 120mph and max torque at c.5.5krpm, then the 22mph / 1000 rpm works.

 

Or are you running some super tall tyres!? ?

I have never either the tachometer or the speedometer from the dash to restore them.

[psdenno]

You can do a speedometer accuracy check by driving with a portable GPS navigation unit in the car (Garmin, TomTom, perhaps even your cell phone with mapping app, etc.).  The GPS unit will show your actual speed and you can compare it to your speedometer reading.

Dennis

Edited October 12, 2018 by psdenno

[siteunseen]

Back in the late '90s when I had my boat a friend paid $3,000 for a GPS and we all used it to get the correct speed.  The factory set up was only good to about 70 or 80 mph.  I put that in a pocket on the back of my seat. Made a few passes and it showed 101. I lost interest soon after that and sold the boat. Why do I spend all my time and money getting something to the top then lose interest?  As bad as i hate to say it I'm scared to drive the 240. Still enjoy talking with my friends on here but the car sits all alone. How much does Mrs Dennis charge per hour?  

[Patcon]

I have an app on my phone "speed cast" I believe that will give GPS speeds and acceleration numbers

[siteunseen]

Thank you Charles!  I'll have to read up on that.

Mine runs around 75mph @2,200rpm.  80 @ 2,500.  I changed out the speedo cog and have 15" tires.  Seems steady compared to traffic on the interstate but that app would let me know for sure.

[psdenno]

1 hour ago, siteunseen said:

Why do I spend all my time and money getting something to the top then lose interest?  As bad as i hate to say it I'm scared to drive the 240. Still enjoy talking with my friends on here but the car sits all alone. How much does Mrs Dennis charge per hour?  

I'm sure you would get the "friends and family" rate.  This week, she's been an expert witness at the murder trial of someone she worked with several years ago.  You would be a nice break for her.

Dennis

[Patcon]

43 minutes ago, psdenno said:

I'm sure you would get the "friends and family" rate.  This week, she's been an expert witness at the murder trial of someone she worked with several years ago.  You would be a nice break for her.

Dennis

We hope...

[Stanley]

Would one of these help?

https://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6

 

[AK260]

I've used similar things before but the the cheapest way to see if you are getting spark is to get the engine running, set the fast idle to around 1.1krpm - take a plug lead off at a time and point it to something metal on the block - you will soon see/hear the spark. BTW did you get the new leads?

Remember the old ones can have a break inside and give intermittent spark / intensity when vibrating under normal conditions.

As a rule of thumb you should be sitting somewhere between 2.8-3.1k rpm at 70mph depending on which variation of diff ratios/gearbox / wheels you have. The typical range is somewhere between 21.5-22.5 mph per 1000rpm.

Use a free app on your phone like track addict and you will have a better view of your speedo accuracy.

[heyitsrama]

6 hours ago, siteunseen said:

Thank you Charles!  I'll have to read up on that.

Mine runs around 75mph @2,200rpm.  80 @ 2,500.  I changed out the speedo cog and have 15" tires.  Seems steady compared to traffic on the interstate but that app would let me know for sure.

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. 

[siteunseen]

OE R180 with the wide B 5 speed.

Mine does well in fourth gear.  That's where it stays unless I'm on an interstate.

Edited October 12, 2018 by siteunseen

[Patcon]

1 minute ago, siteunseen said:

OE R180 with the wide B 5 speed.

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