Hey everyone, I've been having some problems with misfire when under boost and high rpm. It is intermittent, so sometimes i'll get a good pull, and others it'll break up once it gets to 6k rpm or sometimes higher. I've gone through some trouble shooting with Electromotive (I have the TEC GT) and have changed some grounds and nothing they have recommended changing has fixed the problem.

Then I was thinking, could a fouled plug(s) be causing this? It runs fine normally around town, but when i do a pull it will sometimes misfire, and its happening more and more often, and almost always if i downshift and gun it. I know I should start with the easy stuff first (plugs) but they are relatively new (1500 miles, but they were used during tuning) It first started breaking up during the tune, so we had to stop at 18lbs of boost, under that it was fine so we called it a day. Could they have gotten fouled on the dyno and now have just continued to get worse? It makes sense to me that that could be it, but I'm not sure if thats how fouled plugs would cause the car to act.

And since it almost always does misses when i down shift and gun it, could i be running a bit rich and then there is too much gas when i downshift causing it to miss more consistently when downshifting?

Any thoughts?

 

I have yet to see a TEC GT that works flawlessly. Put PFC on it and be done.

 

Haha, thats kind of what I've been seeing. but maybe i'll get lucky with new plugs, i'm thinking about going with R6725-10's instead of the BUREQ-9's. I found a few posts about the 9's burning up when pushing 450+whp. So maybe (hopefully) thats the problem.

Any other plug recommendations besides full out race plugs? I found the ones mentioned above for $30 a piece. Anyone know where to get cheaper ones?

 

I guess the last resort is to switch out the ECU to something else. I not looking forward to wiring in a different system.

 

www.sparkplugs.com

BR10EGV

 

Aren't those the non resistor type plugs though?

 

http://www.sparkplugs.com/results_cross.asp?pid=3830

BR10EG NGK# 3830

Used them with my GT. I got mine from Rockauto.com

 

I definitely would stick with a resistor type plug.

I agree with Ray, kinda sucks but might be a good idea to install a PFC.

 

So I just ordered some BR10EG NGK# 3830 - what do you recommend gapping these to?

If this doesn't work out I'll probably look to switch over to a different computer. I guess it shouldn't be that hard, just label the wires going into the TEC GT and crimp them onto the new computer's harness. Do most computers use the same types of sensors?

 

And is the PFC a full stand alone?

 

PROBLEM SOLVED: So tonight I get home and my new BR10EG NGK# 3830's are sitting in front of my door. I dremelled down the end of my spark plug socket to make it work with the new plugs (that took a while), and gapped the new plugs to .022, I also noticed the old ones were quite black and had some build up on them. That got my hopes up. So I started it up around 8:00 and took it for a spin. I could notice a bit of a difference while just putting to I-95 while it warmed up.

I rolled onto it pretty good in fourth, pulled hard all the way to 7K rpm and I let off. So then I dropped into third from fifth going about 65 and gunned it. Pulled hard and smooth all the way to 8k rpm when I left off. Did about 15 more pulls, all at about 17psi, a few up to 8.5k rpm and it was smooth as can be. This was the first time i took it that high, i've always been scared to push it because of the occasional misfires, then they became so common i couldnt even push it past 5k rpm. Now its fast as a **** haha and it felt so good. I can't believe it was spark plugs from the beginning.

Now all i can think about is turning up the boost haha - 500whp Club here I come!!!

And the 3rd fast and furious just popped into my head, the part when they are tuning the mustang with the rb26, and he spins out while drifting, pulls the spark plugs, and says "that's why she's spittin". haha.

However, there is a downside, my lumpy idle is a little more lumpy now. Definitely time to smooth out the bottom of the map. No need for a new ECU, can't believe I wasted so much time trying to figure out what it was when i could have just changed the plugs.

Here are some pics of the old plugs, I apologize in advance for the quality, I'm not good at the close up kind.

 

When those plugs wear out look into some greddy [GR-13000150] race plugs. They are the same as the NGK r7420's. These seem to be about the best plug you can run, and last like 20 times longer then the $6/each plugs.

The NGK 6725's aren't much of an improvement over the b10egvs and cost way more. Resistor plugs seem to work well for everyone, non resistor plugs seem hit or miss. Sometimes they mess with electronics and cause quirks and sometimes burned up equipment.
The greddy plugs are resistor style.