HELP HELP HELP! Still have a missfire

[Racingki]

OK, here is the deal, I have a 99 lightning with 63k on it. I started to get a missfire in one of the cylinders, I took it to the dealership and they said it was a #? cylinder misfire. They said it was the coilpack and would have to replace that one and the plug, they wanted $375!!! well i decided i would do it myself since i do have pretty good mechanical skills. Well i bought MotoBlue performance coilpacks plugs and 44lb injectors (just in case it was an injector) Well, I got it ALL done today, and guess what!! still not running right, Here is the symptoms. At idle, at first it will run PERFECT! no miss no nothing, i take it out and am easy on the throttle and it runs great, once i get into 1/4 throttle or more it misses HORRIBLY! and no matter how far on the throttle you go it still misses, as it gets warmer and warmer it will start to miss as it's just sitting at idle at a light. I have NOOOO idea what could be left, posisbly a burnt valve? any ideas?!?!?!? please help please

[L8 APEX]

We have found most aftermarket coil packs to be junk. You can't replace injectors without a custom tune to their flow rate. I have never heard of 44lb injectors, stock is 42 by Ford standard which are 50 something by Chevy standards. Anytime someone upgrades they go with 60# because they are about 400 a set and that is pretty cheap. It sounds like your combo is all wrong for the tune. You haven't mentioned what you have to a tune..

[Racingki]

I got accell 44lb from rpmoutlet.com, i was told the stock was 39lb, well i pulled the front (closest to the bumper) injector and it runs the same, all others i can tell it's not firing, so it's the front right, now i took my volt meter to the plug to check if it was getting voltage, any idea what the voltage is suppose to be? one of the others was reading .22 this was only .12, any more ideas, yea i have a custom tune from the place here in garland.

[Mark #2]

Did you pull the plugs?
A misfire is often due to a burned or detonated plug IMHO.

[Racingki]

Just put in new plugs, so thats not it.... anyone know how to check if the correct voltage is getting to the coilpack? with a digital voltmeter?

[L8 APEX]

All of the coils should have constant positive voltage and the PCM should pulse a ground to fire it. Or something like that.

[slick-svt]

Just touch it to your tongue while truck is running and if you piss your pants you can rule that one out....:icon_mrgreen:

[L8 APEX]

PS" The pulse probably occurs faster than a multimeter can respond or display. You would likely need a scope meter to catch this ****.
edit: don't censor my shat biatch!

[Beaudee]

O2 sensor!!! They do go bad without a code,had same problem with mine and found bad O2 sensor.

[mikelemoine]

Just put in new plugs, so thats not it.... anyone know how to check if the correct voltage is getting to the coilpack? with a digital voltmeter?
Did you check the gap on your plugs? They aren't always right out of the box and a bad gap can cause misfires...

[Racingki]

you had a single cylinder not firing and it was a bad o2 censor?? and yes i checked all the gaps on the plugs, gapped them to .38 on all of them. i'll go get a scope meter today, any idea what the voltage should be to the coilpack?

[Racingki]

And when it's just running with the coilpack plugged in and suck i DO NOT get a check engine light, but when i unplug the coil pack and injector for the cylinder I do get a check engine light.

[Racingki]

Ok, i switched out that one coilpack for one of the stock coil packs and no difference, still not firing on that cylinder, don't know if it is fuel related or ignition related, no matter if i unplug the coilpack or the injector while it's running it doesn't change anything on the way it's idling, so i know its that cylinder. any ideas? im getting frustrated.

[charlie]

The way I tested mine to see if it was firing. I used the L-cheapo light with a clamp on one end, and a needle on the other. I stuck it in both wires (one @ a time) to see how fast the light was flashing. Then I tested one I knew was good. In my case I was getting a steady light because of back feed from the other cylinders feeding back from the radio suppression capacitor. In other words I was not getting fire form the computer due to a loose connection in the wiring harness.

Charlie

[Racingki]

Well i pulled out the cop and left in plugged in with the coltmeter into the plug end and gounded the gound wire, i got a constant 12v when on and then when running of course it jumped, so i'm sure i'm getting a spark, is there a way to check the injector or the connector to the injector? more and more i'm worried i have a burnt valve.

[charlie]

I used a stethoscope to check the injectors.. You can hear a faint tick.

Charlie

[Beaudee]

you had a single cylinder not firing and it was a bad o2 censor?? and yes i checked all the gaps on the plugs, gapped them to .38 on all of them. i'll go get a scope meter today, any idea what the voltage should be to the coilpack?My truck was dropping 4 cyl.,a miss like u are describing sounds like more than one cyl..Best thing to do is let Terry look @ it.

[Racingki]

well i did a compression check and here is what i found, dunno if i dropped the plug before i put it in, well i got 60-90lbs of pressure when i did the compression check. it idles fine now but still stumbles when you get on it and it has boost. u think o2 sensors?

[Mark #2]

well i did a compression check and here is what i found, dunno if i dropped the plug before i put it in, well i got 60-90lbs of pressure when i did the compression check. it idles fine now but still stumbles when you get on it and it has boost. u think o2 sensors?

Did you check any of the other cylinders?
Would think you should get around 125 for a 8.5 compression ratio.

[Racingki]

ok, i guess i'll check another...

[Racingki]

checked it on the other side and got 130, so i checked the problem cylinder again, and gt 120 the first time and 110 the second. i think i'm ok on the heads, it now idles fine and drives normal fine but with boost it stumbles bad, the plugs are a lil white, so i got new o2 sensors and gonna see if that helps. any other ideas?

[Mark #2]

checked it on the other side and got 130, so i checked the problem cylinder again, and gt 120 the first time and 110 the second. i think i'm ok on the heads, it now idles fine and drives normal fine but with boost it stumbles bad, the plugs are a lil white, so i got new o2 sensors and gonna see if that helps. any other ideas?

If they are white, Lean, detonation or spark blow out?
What plugs and gap?

[Racingki]

they are tr6's and have a .038 gap. just put in today!

[Racingki]

ok, replaced the o2 sensors and still same thing, once i get to 0 boost/vacuum i get the bad miss and stumble. I had this tune on the truck before and was running fine, just one day while i was cruising at 45 it started this. so the tune was ok then, why not now? anyone think maybe my MAF went bad? I get my Sniper Tuner in next week, try flashing a new tune, but i can't think of anything else.... i'm stumped, btw cehcked compression again and i guess it was too loose i got 115-120 when i check that cylinder again, i don't know which one is missing when i'm on it, anyone have a real time datalogger they wanna come help me and use?

[charlie]

Are you reading any codes, or pending codes? Pending code may not turn on the check engine light.

After reading all of this again.... It sounds a lot like you have a vac. leak. (White plugs)

Charlie

[jmlay]

How long has it been since you replaced your fuel filter?

Mike

[diablolightning]

Have you checked your Fuel presure?

[Racingki]

i changed the fuel filter about a week or two ago cause i thought maybe that was the problem. didn't check fuel pressure, any easy way to do it and what should it be?

[L8 APEX]

There is a test port on the passenger idle fuel rail and Vatozone sells a test gauge for 35 bucks or so. It should be 35 at idle and 50-55 at WOT.

[tiffo60]

i would by a set of stock coil packs and go from there:tu:

[Racingki]

Ok, checked the fuel pressure, i get between 30 and 35 at idle and about 50 when i go wot. So i got good fuel pressure, it doesn't miss when i sit there and rev it, no matter how hard i rev it or how high, just when it is underload and boost gets to about 1-2psi or higher.

[BC Lightning]

Ok, checked the fuel pressure, i get between 30 and 35 at idle and about 50 when i go wot. So i got good fuel pressure, it doesn't miss when i sit there and rev it, no matter how hard i rev it or how high, just when it is underload and boost gets to about 1-2psi or higher.

my vote is for vac leak

[Racingki]

where all should i check for this vac leak?

[Racingki]

i've gone through and tried to look at anything that looked like a vac line and everything seems to look hooked up all the way and no leaks. any certain line i should be paying attention to more than others that would cause this problem?

[L8 APEX]

You put the stock coils back on? Aftermarket coils are usually junk, but several folks have posted that here already:icon_eek:

[99WhiteBeast]

This looks like nice tool to have for checking the COP's
http://www.sjdiscounttools.com/wae76560.html

[charlie]

This looks like nice tool to have for checking the COP's
http://www.sjdiscounttools.com/wae76560.html

We will see. I just ordered it.

Charlie

[charlie]

where all should i check for this vac leak?

Look behind the lower intake, in the middle @ the bottom. It is part of the PCV system. If it is there, it will most likely be a cracked line in the bend. (if that is it)

Charlie

[02REDSVT]

Thats how my truck has been acting up for about 4 or 5 months now. Do not drive it anymore. It wont miss when I sit there and rev it. Just when its under load or boost also. When I put the fuel pressure gauge and drove it. The needle goes to 50psi but shakes up and down like crazy between 40 and 50 psi right when its starts to miss.

[Racingki]

I found it, it was a single bad COP, one of the brand new Motoblue ones, i'me sending it back since it is lifetime warranty. i put a stock on in there for now.

[Sinic]

This is a common problem for the 5.4l motors s/c or not. The best way I found to locate the problem coil is to unplug the injector if the motor stumbles a little thats not it. Most of the time your computer will not recognize the miss till its to late. If you drive while your truck is missing like that it could run rich on that cylinder and bang.

You ask what makes coils go bad? Water, moisture. Never pressure wash your motor.

You can get a kit of 8 coils from ebay for 100 bucks and more than likely you will get 7 that work great (I'm not saying this is the best place to go but it's a quick fix to calm your nerves). Replace the one/s that are no good and you have more for the next time.

[charlie]

This looks like nice tool to have for checking the COP's
http://www.sjdiscounttools.com/wae76560.html

It works!

Charlie