missing under boost!

[David Knoff]

ok Guys see if someone knows
car runs great no missing But as soon as you put anymore that 6p boot it starts to miss ?
I have put new plugs all the old ones look good burning nice.
Lots of fuel psi
dont know where to go from here this is a new one for me
Anyone?

[Sheela krasnuik]

Have you checked if it's throwing any codes? Might want to check that first.
There have been a few threads on this in the garage, do a search on the forum to help you diagnose the problem.

[daniel Dee]

Any black smoke?? 
Boost leak test.
Check plug gap and wires!

[David Knoff]

Changed the leads and its fixed lol wow who new

[Mike Schmid]

Sounds like you got it but new NGK plugs and wires was the first place to start even way back in the Talon Digest days. 

Electricity will take the path of least resistance and it gets harder and harder to make that jump across the plug electrodes as the engine load (boost) increase.  You can get a weak spot in the insulation somewhere (plug wire, side of the coil, broken plug ceramic, etc) and it can show up when the load gets high enough where the hole in the insulation is an easier path than the jump across the plug. 

Misses like this tend to get worse as they continue because you get carbon deposits along the short which makes it easier and easier to short out again.  I had a coil pack go bad where it got to the point that at night you could see sparks jumping out the side of the coil pack and grounding on the manifold. 

[John Hartman]

also make sure you use the correct plugs.  NGK BPR7ES.  Thats it.  No platinum, no irridium, no triple electrode, no anything fancy.

Its been proven again and again and again.  Just use those.  They are cheap and they work best at high boost in these engines.

That and gap em low.  Coming from domestic hot rodding, the first thing I did when I got mine was to open the gap up to like 40thou.  Then it missed under boost all the way to work...\


28-30thou, thats it.  Boost blows out sparks with big gapped plugs.

[KevinBuckham]

I finally made the switch to NGK Iridium BPR7EIX after avoiding them like the plague for years.   Well for my car they work slightly better than NGK BPR7ES and don't seem to foul so very quickly.  I used to switch out BPR7ES at every oil change, but these seem to be going strong. 

With the waste spark system we have two of them should foul quicker than expected, so we'll see how they are after a year.

[David Knoff]

also make sure you use the correct plugs.  NGK BPR7ES.  Thats it.  No platinum, no irridium, no triple electrode, no anything fancy.

Its been proven again and again and again.  Just use those.  They are cheap and they work best at high boost in these engines.

That and gap em low.  Coming from domestic hot rodding, the first thing I did when I got mine was to open the gap up to like 40thou.  Then it missed under boost all the way to work...\


28-30thou, thats it.  Boost blows out sparks with big gapped plugs.

The Wires where the prob Just found it strange that Steel core wires would only last a couple weeks but i guess there was something wong when they where made.
I use BPR9ES just safer in the our setup But ya i will never use anything other then the NGK VG or Autolite 10s at 28thou

[John Hartman]

no fouling problems with a 9 heat range plug?  I have 8s I use sometimes at the track or dyno kinda thing(well I used to, now that I have the pre turbo water injection nozzle, I don't need them), and if the car was subject to lots of idling and stop and go it would foul up the plugs a bit quicker than I liked. 7s are no problem.

[David Knoff]

no fouling problems with a 9 heat range plug?  I have 8s I use sometimes at the track or dyno kinda thing(well I used to, now that I have the pre turbo water injection nozzle, I don't need them), and if the car was subject to lots of idling and stop and go it would foul up the plugs a bit quicker than I liked. 7s are no problem.

No fouling at all. I just like a colder plug with the setup. On the bottle it's just safer I could prob us an 8 but just a pease of mind thing and plugs look really good. So just sticking with it

[Brett Haviland]

[John Hartman]

LOL!!

I want two of those, the big ones!

[kevin derhouson]

sorry john, but theres only one vin diesel.

[John Hartman]

Hahahaha!  I shoulda seen that coming.  Still punch drunk from my huge road trip.

on a side note, there was a Vinny lookalike in the Wally World parking lot today..  I'da laffed at him, but I was really sleepy and tired, no mood for a scrap.  He looked serious about his serious look

[daniel Dee]

also make sure you use the correct plugs.  NGK BPR7ES.  Thats it.  No platinum, no irridium, no triple electrode, no anything fancy.

Its been proven again and again and again.  Just use those.  They are cheap and they work best at high boost in these engines.

That and gap em low.  Coming from domestic hot rodding, the first thing I did when I got mine was to open the gap up to like 40thou.  Then it missed under boost all the way to work...\


28-30thou, thats it.  Boost blows out sparks with big gapped plugs.

+1  My NGK gapped 26 thou, good at 39PSI and good for everyday driving.
You could use Non-projected nose plugs BR7ES

I used to melt BP type plugs on Nitrous.(V8 power). Problem was poor nitrous and fuel distribution ..
(common in all NOS kits, all garbage everybody just melts their pistons ).

With proper setup (more power with less nitrous I ran street plugs (at the track) 13 to 1 compression +nitrous (SBC).