jay_rich

iTrader: (8)

Okay I got my car running a few weeks ago, all was good idle then I took it around the block and it kept backfireing but everything on the efi live seems perfect. AFR etc. So we added 15% more fuel and it went away.

Drove it for like 1 hour straight no issues. Took it out last night for a good highway cruise for about 25min or so and around town and everything was great. Ran smooth no issues.
I leave the "races" (about 60-65* out) we were at and get on the highway and pop pop pop while driving. Accelerate pop pop pop. I had my buddy log the car and everything was fine, afr's were in the 14.xx range the entire time.

I got it home then went to take the GF for her first ride today and the same thing. This time it was like 80-85* outside


My exhaust is a 4-3.5inch fender dump maybe about 2 feet long with 2 90* bends in it then a turn down.
I was wondering if this may be do to not enough backpressure or something? I know when I first got my 383 LT1 in my car and ran open headers it did the same thing. I figured it would be fine since I run the headers to a merge then 2 feet of DP.

Here is a pic of the setup and how the DP routes.

98Z28CobraKiller

iTrader: (17)

Sounds like a non turbo related issue to me. What did the wideband read before and after you added the 15% fuel that you said made the popping go away? Is it popping at steady cruise? Maybe around a certain RPM? If you can catch it with the logger, play it back real slow and watch all your sensors. See if any are glitching from a broken wire in the harness or a loose connection somewhere. Also check the fuel and ign maps in graph view to see if you have any spikes or valleys. Check plugs and make sure you dont have any cracked, broken or burn plug wires. Check to make sure that the grounds on the back of the head are good and tight.

jay_rich

iTrader: (8)

i know the grounds are good, plugs are new but ill pull them all, just seems wierd it was fine, shut it off for 20-30min and then it acted up.

jay_rich

iTrader: (8)

I took it for another cruise, pulled about 4 degrees timing down low and added a bit of fuel...car drove like 14.7-15.4ish made one initial pop when backing outta the drive way. Drove it for about 5-7min all fine.

Decided to test my line lock (no burnout just to see if it was working) then my trans brake (brought it to like 3500ish then let off)

After this it started backfiring like crazy, almost seems like it is loading up.
Plugs are gapped at about .030ish

Jay

jay_rich

iTrader: (8)

Well I pulled the plugs and did the driver side first and was like great all the plugs look nice, little bit of tan colour. I get to the passenger side BLACK!!!

Here is a pic of them! I put all new plugs in and gapped them to .032 (they were at about .029)

Now to find out why, at first when i pulled 8 i was thinking a spark issue, but its the entire bank and I dont get codes.

Jay

jay_rich

iTrader: (8)

I think im gonna try putting in some new O2 sensors tomorrow, the ones im using have unknown miles (from an old setup) and may have been tossed around.

also when we first started tuning the idle when I got the car first started it wasnt logging the voltage of them, seems like sometimes on my datalog my O2's show and sometimes not.

Well see if that cures it!

Jay

Photochop

iTrader: (74)

I had the same issue on my last car. Changed out both 02s, still did it. Ended up being the 02 sensor wiring on the passengers side that had issues. Instead of hunting down the exact source in the wiring mess, I just ran the car in open loop (defeated the 02s) and it didn't have the problem again. Not to say this is the proper way to do it, but if you disable your 02s and the backfiring issue goes away, you found the source without spending money on 02s.

jay_rich

iTrader: (8)

yea that will be my next solution, i read ur post earlier also. I have 2 new o2's comming so im gonna try them then next keep it in open look

Jay

jay_rich

iTrader: (8)

Put 2 brand new bosch o2's in and bam car drives fine, and the tune went from 14.5ish cruise to 11.00afr with the new o2's!
My buddy thought it was strange how his MS3 cammed 6.0 tune needed 15+% more fuel on my motor!

tonight I will be tuning for 2 bar custom OS!

Jay

FasTimeSS

iTrader: (47)

id say def o2s, this happened to me while i had my h/c n20 looks like that bank is way outta wack on the tune as well but this could be from that o2 as well.


that would explain why those plugs are effed on passenger side