Engine Missing Above 5K RPM

[jackboxxx]

I only drive this car for pleasure, usually a late afternoon / dusk cruise thru the canyons, and noticed something while out testing new front springs today..the old headlight harness thread prompted me to check out my lighting and sure enough the problem only happens when the lights are on...

So i came home, pulled the tires, then the headlights, running lights and turn signal lights to inspect, all the harness covers are old of course, so i cleaned & re covered them, cleaned and lubed the plugs etc.. but when I got to the side marker lights, both were in bad shape...looking as if they were filling up with water at least 1/2 way..based on the rust marks..which coroded the bulb sockets etc...I found 2 good spares off my parts car, rebuilt those and installed them..now to go for a drive..and see what happens, though I still want one of those headlight power harness's because im sure its robbing power needed for the ignition system.

I have an issue im trying to resolve,

My engine starts acting like its out of time or missing when I hit RPMs above 5000, this is a recent thing, only for the last couple hundred miles, prior to that, it ran fine up to 7k RPM no problems, It is also intermittent, meaning today it runs good, but tomarrow it may do it again. the motor runs great until 5k..no signs of ign or timing problems. Heres what ive already checked:

*plugs: replaced with new NGK BP7ES

*wires: are new Taylor 8mm, and have been tested for resistence & inspected for damage. none found.

*replaced existing Crane coil for MSD Blaster (the crane i didnt know is not recomended beyond 6500rpm.

*tried bypassing the ballast resistor, all that did was make my tach bounce around...

*replaced said resistor above with a new stock one..it was aftermarket b4.

*replaced connectors at the coil, resistor, and distributor.

*tested alternator, battery & regulator all seemed good but I replaced

the regulator and alternator just for goood measure. system runs anywhere from 12.5 to mid 14's depending on load...IE: lights on blower motor on at an idle, the volts are in the 12's...then go to the 14's when I dirve..rpms go up..

*checked all the fuses/fusebox..I had an issue where the fuse prongs for the left headlight were "stretched" and loose around the fuse. thus causing my left headlight to be Dim.

*checked my electronic ign, pertronix..all the wires, and the magnetic contact and connections seem good.

*distributor is tight, no excess play in the shaft, no adjustment bolts loose.

*battery cables are tight at battery and starter.

* i run premium gas, w octaine boost so that shouldnt be an issue..

Im using the stock fuel pump at this time, I wonder about this..but im told that if this was a fuel delivery issue, once the lack of fuel started it would continue thru the gears, especially going uphill..so i tried that, on a 2 mile road, that has a decent grade to it, ran it up to the problem above 5k, shifted, keeping the acceleration going hard, but by shifting, the rpms went down, problem went away untill above 5k again...etc..so i ruled out lack of fuel.

on the other hand, I have a nice Holley electronic pump i tried using when i first did the engine swap, and I think it ran better with the holley...but i didnt have a regulator inline, so after a couple days, the pressure of the holley started forcing excess gas thru the vents in the float bowls. (anyone know where I can get a decent regulator??) id like to go back to the holley.

anyone have any ideas? im pulling my hair out trying to find this problem.

Thanks,

Jack

[smokingwheels]

Try 100 mm of stainlessteel wire wraped around each of the plugs at the end pull back the boots and twist it on

go for a drive, note wires should have sharp ends and not be near any metal

if it works good

if no improvment drain fuel tank and sniff fuel try to get high, compare color with old degreaser fluid.

test new fuel out in another car etc before buying any more.

PS ill have to get my video tape transcribed to dvd oneday

then i can show what i got in my tank oneday in september 2002

[jackboxxx]

Try 100 mm of stainlessteel wire wraped around each of the plugs at the end pull back the boots and twist it on

go for a drive, note wires should have sharp ends and not be near any metal

if it works good

if no improvment drain fuel tank and sniff fuel try to get high, compare color with old degreaser fluid.

test new fuel out in another car etc before buying any more.

PS ill have to get my video tape transcribed to dvd oneday

then i can show what i got in my tank oneday in september 2002

Thanks Brother,

I didnt have any stainless steel available so i used this Zinc/Lead wire i found in my junk drawer which seemed to work well for about 30 seconds... after which it melted and bonded my plugs to my plug wires. I tried using the degreaser as a lubricant to free the wires from the plugs, but all it did was catch on fire...luckily I had a bag of marshmallows handy!

(the trick is to humor the "gifted" ones)

**********************************************************

Now does anyone else have any ideas? seriously..

[240ZX]

What type of distributor are you running. If it is a stock points type unit, the points may be floating at 5K and above. Just a thought!

[jackboxxx]

What type of distributor are you running. If it is a stock points type unit, the points may be floating at 5K and above. Just a thought!

Im running a stock distributor thats been recurved, with a pertronix "ignitor" electronic ignition. no points to float

but you know point float is a good way to describe the feeling im getting when this happens.

[smokingwheels]

Thanks Brother,

I didnt have any stainless steel available so i used this Zinc/Lead wire i found in my junk drawer which seemed to work well for about 30 seconds... after which it melted and bonded my plugs to my plug wires. I tried using the degreaser as a lubricant to free the wires from the plugs, but all it did was catch on fire...luckily I had a bag of marshmallows handy!

(the trick is to humor the "gifted" ones)

**********************************************************

Now does anyone else have any ideas? seriously..

oh so the wires burnt up hmmm and it worked for 30 seconds!

you can find sum stainless steel mig wire .9 mm from a hardware store

only this will do they wont eat that up not like your zinc/lead or was it tin/lead (solder)

this is no trick my granfather had a 2 strock slasher (victor)

it used to backfire and unscrew the plug

i got sick and really pissed off this so i tried somthing the wire worked

never had a bother with it for the rest of the day

cheers brother

[240ZX]

Here's an additional thought. I learned this years ago with a 289 mustang I had. What I'm talking about is the routing of the plug wires! On the mustang, if plug wires were routed next to each other, that in the firing sequence fired right after the adjacent wire, it would cause a miss fire. So, if the firing order is 153624, you dont want 1&5, 5&3, 3&6, 6&2, 2&4, and 4&1 next to eachother. Does this make any cents?

[Sean240Z]

A few months ago, I had a similar miss. Just prior to getting the miss, I had been fiddling with the carb mixture and pulling the plugs out frequently to see if they had become carbon fouled. It turns out that during all of the installing and removing the plugs, I had inadvertantly unthreaded the screw in receiver at the top of one of the plugs (i.e. the part where the plug wire connects to the plug) and bent it over while trying to force the plug wire on. I replaced the plug and I no longer had the miss.

This may not be your problem as you recently replaced all of your plugs, but I thought I'd through it out there.

Cheers,

[Curtis240Z]

Did you check your fuel filter?

[beandip]

Unless I misread you dident say what carbs you are using . I tried a RX-7 fuel pump on a stroker with tripples, Mikunis , no regulater needed and it supplied with no problem all the way to redline. I am running the same pump on my Z running a pair of SUs again no regulater. Also the pump is quiet and pumps 4psi. Have you checked the float levels , if you are running SUs. For other carbs I can't be of any help. Shooting ducks at 5K and above could be caused by running lean , however if he float levels check out , see if any of your friends have a '79-80 ZXdist and coil . I have one and have never experienced any missfire at speed . In my openion counting on a 30+ dist having a true running shaft is expecting a lot , at the Rs you are turning . Thats my 5c . Gary It was 2c but with the cost of gas I have to charge more.

[smokingwheels]

Thanks Brother,

I didnt have any stainless steel available so i used this Zinc/Lead wire i found in my junk drawer which seemed to work well for about 30 seconds... after which it melted and bonded my plugs to my plug wires. I tried using the degreaser as a lubricant to free the wires from the plugs, but all it did was catch on fire...luckily I had a bag of marshmallows handy!

(the trick is to humor the "gifted" ones)

**********************************************************

Now does anyone else have any ideas? seriously..

Next time you try it with sub standard componets

email me at smokingwheels@yahoo.com

well because i ended up with 2 flat batteries in 2 cars

the time frame is too close

PS I have a 40 amp charger home made hmmm 2000 va transformer

was rated 20 volt 20 amp until i removed a few windings

hmmm 2000 va @10 volts ~199.2 amps is this correct?

no wonder i can arc weld the jumper leads

however blows the rectifiers up, out of sum old altnator

[jackboxxx]

A few months ago, I had a similar miss. Just prior to getting the miss, I had been fiddling with the carb mixture and pulling the plugs out frequently to see if they had become carbon fouled. It turns out that during all of the installing and removing the plugs, I had inadvertantly unthreaded the screw in receiver at the top of one of the plugs (i.e. the part where the plug wire connects to the plug) and bent it over while trying to force the plug wire on. I replaced the plug and I no longer had the miss.

This may not be your problem as you recently replaced all of your plugs, but I thought I'd through it out there.

Cheers,

Nope not that...sure woulda been an easy fix..thanks though!

JacK