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Engine Missing Above 5K RPM


jackboxxx

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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

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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

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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..

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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.

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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

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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?

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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,

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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. LOL

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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 [email protected]

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

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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

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Did you check your fuel filter?

Ive got the clear glass filter, that has a replacable element inside, which i like for seeing whats coming from the tank, and yea once they start clogging you get a similiar miss. I just replaced the element a couple hundred miles ago

shortly after this problem started thinking the same thing you did.

thanks,

JacK

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Next time you try it with sub standard componets

email me at [email protected]

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

Was your Flux Capacitor fully charged at the time? and what rating resistors

were you using? most people screwup and use the 720 ohm.

JacK

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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. LOL

Sorry, Im using 50mm SU's, stock pump at the moment, what does a stock fuel pump put out in pressure anyway? no I havent checked the floats,

I did just richen the carbs a couple days ago by 1/2 turn because it did seem to be running a bit lean. as for my distributor its been professionally re curved

and is nice and tight maybe moves 10 1000ths. its pretty straight.

But besides all that stuff, I went out yesterday, and found out this misfiring is only happening when my headlights are turned on....see I usually only drive my car late in the day, becasue its so dammed hot out here..im about 40 miles or so from palm springs. point is, half the time im out driving, it gets dark enough for lights, and it never occured to me turning the lights on was related till yesterday. So,, I tired tearing out all my front lighting, refurbished all the harness's looking for maybe some wire intermittinly grounding or something. once all was reinstalled, the same thing was happening,the instant i turn the lights on above 5k rpm. feels like the lighting is robbing the ignition system of needed power to fire properly. what do you think?

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When you ask about the stock pump , are you talking of the electric or manual ? No matter they pump under 5psi. Question , are you still running seald beam head lights or H-4 s ? What condition is the battery in , full charged , some what discharged ? This may sound like stupid questions but we need to eliminate a few things here. Check the tention on the v-belt to the alt. If loose it could be slipping under load . Where I live the daylight hours are deminishing to the point that more and more driving is with the lights on. A loose belt could cause the battery to be discharged to the point that the miss could be from a weak spark. You did say that you had the ignition coil tested , right? O , I started to ask about the h-4 s . If you havent up graded the wireing to the head lights and are running H-4 s this could be part of the problem . But not likely all of it. Just for the heck of it , if you have a batt charger , hook it up and let it charge for a few hours or over night . Then drive it and turn on the lights and see what happens . No more shooting ducks ! then you found the problem . Still does it , we keep checking. Doing this is free so try it before throwing money at it. Another thing if the float chambers run dry or just starting to . This also will cause this high end missing. Did you feel the quakes today ? I received notices of 9 seprate shakers since yesterday in your area. all around 4.5 Gary

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Interesting the the problem seems to be headlight related. Sounds like a simple drain on the ignition system. H4 or not, I'd look at every connection and ground ...every one! Remove, clean and replace. To test, prior to this PMS (preventative maintenance service), you could run a wire, with a switch, between the ballast resistor and battery (disconnect the hot lead to the ballast, from the ignition, and tape it off the prevent a short). Double check the wiring to the coil and distributor (clean these connections good). Ensure the chassis to ground and/or battery - to engine block is clean and tight. Turn the switch to 'on' and start the car. Take it for a spin with the lights on and pushing the rpm's. If the miss is gone then you've got your answer. You'll have to use the switch to kill the engine after the run. The plugs wires breaking down could cause this as well but you'd probably feel this at lower rpm'stoo. On that note, open the hood in pitch darkness and look for the blue aura down the spark plug wires. If you see a glow anywhere but at the base of the plugs the insulation is failing causing crossfire or reduced spark at the given plug(s). If so, replace the wires.

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When you ask about the stock pump , are you talking of the electric or manual ? No matter they pump under 5psi. Question , are you still running seald beam head lights or H-4 s ? What condition is the battery in , full charged , some what discharged ? This may sound like stupid questions but we need to eliminate a few things here. Check the tention on the v-belt to the alt. If loose it could be slipping under load . Where I live the daylight hours are deminishing to the point that more and more driving is with the lights on. A loose belt could cause the battery to be discharged to the point that the miss could be from a weak spark. You did say that you had the ignition coil tested , right? O , I started to ask about the h-4 s . If you havent up graded the wireing to the head lights and are running H-4 s this could be part of the problem . But not likely all of it. Just for the heck of it , if you have a batt charger , hook it up and let it charge for a few hours or over night . Then drive it and turn on the lights and see what happens . No more shooting ducks ! then you found the problem . Still does it , we keep checking. Doing this is free so try it before throwing money at it. Another thing if the float chambers run dry or just starting to . This also will cause this high end missing. Did you feel the quakes today ? I received notices of 9 seprate shakers since yesterday in your area. all around 4.5 Gary

*I meant the mechanical one.

*Im running sealed beams sylvania "performance" from kragen auto.

*the battery is about a year old, its a die hard, its never stranded me, always cranks strong has never given me any reason to think its not holding a charge I drive the car 10-20 miles daily.

*new cables as well.

* 1500 miles ago, i replaced the belt, then this week i replaced the alternator

which required me to readjust the belt, and i did check it today, its nice and tight.

*I replaced the ign coil because the one i had is not rated for over 6500 rpm

so i bought a MSD blaster coil. its only a couple weeks old.

*I dont think its the float chambers only because of the uphill testing I did,

I sprinted up a long grade of at least 2 miles, the car pulls hard all the way to 5k rpm, then sputters...but if i keep it under 5k, itll go up hill all day. ((i was told by a good mechanic that if you are not getting enough fuel once it begins to sputter or die from lack of fuel itll keep doing it through the gears

i can race up to 5k, shift race up to 5k...etc etc no problem. the uphill part creates much more load on the engine thus using more gas.

im going to focus on the headlight issue i think..perhaps ill do the rewiring

thing so they get thier power directly from the battery...

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Interesting the the problem seems to be headlight related. Sounds like a simple drain on the ignition system. H4 or not, I'd look at every connection and ground ...every one! Remove, clean and replace. To test, prior to this PMS (preventative maintenance service), you could run a wire, with a switch, between the ballast resistor and battery (disconnect the hot lead to the ballast, from the ignition, and tape it off the prevent a short). Double check the wiring to the coil and distributor (clean these connections good). Ensure the chassis to ground and/or battery - to engine block is clean and tight. Turn the switch to 'on' and start the car. Take it for a spin with the lights on and pushing the rpm's. If the miss is gone then you've got your answer. You'll have to use the switch to kill the engine after the run. The plugs wires breaking down could cause this as well but you'd probably feel this at lower rpm'stoo. On that note, open the hood in pitch darkness and look for the blue aura down the spark plug wires. If you see a glow anywhere but at the base of the plugs the insulation is failing causing crossfire or reduced spark at the given plug(s). If so, replace the wires.

Ahhh i like this test :) good idea. but i started doing the headlight rewire thing tonight before I read this so...i gotta finish that up 1st.

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