Random misfire at idle

[S13xCrazy]

Alright guys, I'm pretty stumped here. I always try to avoid these topics, as I usually figure them out eventually but this one is really ticking me off!

Short story, bought the car with a damaged valve. Pulled it apart, got a new head and had it rebuilt, threw it together. no big deal. Previous owner was an idiot, I went through 100% of vac lines, fixed FPR setup, shoddy wiring, etc. etc. etc.

THE CAR:
Aermotive FPR Adjusted to proper psi, GT28, Recirc bov, freshly rebuilt head, Z32 maf, eprom tune, 440cc injectors. NO COLD START ACCESSORIES (ALL BLOCKED)

Compression is 150 across the board

Started it up and it was running pig rich. Black smoke.
OK, went ahead and went through the basics.
Checked timing, no problem, spot on. adjusted with a timing light as well.
Replaced plugs, o2 sensor sensor. The car was still running rich and had a dead miss now. After going through, I determined #4 injector was sticking. Got a good injector from a friend, put it in and it ran better but still had a slight miss and running pig rich still.

After this, i figured maybe MAF or another sticky injector. So instead of screwing with the stock tired stuff, I went ahead and got a Z32 maf, rebuilt 440cc injectors, and a tune my buddy used to run (worked great on his, same setup)

boost leaks - fixed a couple. No leaks
Vacuum leaks - Fixed a couple. Around 18hg/in now
TPS - Good and adjusted properly
O2 - brand new
Spark plugs - Brand new
MAF - Brand new
Injectors - Brand new
Coolant temp - Have swapped with others and same results

The car is still running very rich and has an intermittent miss. If you rev it up at all the miss goes away and it runs smooth, still smokes though. Going down the road I get a solid hesitation right before 3-5psi comes on.

Recap: Slight miss, black smoke, gas in oil, black spark plugs

Now, my best guess at this point is going to be old/tired coil packs, ignitor, or drop resistor. Any tips/ideas from the experts of CAs?

I understand you guys will want to blame the tune, but keep in mind this is 100% identical to what was happening with the stock tune and setup. Even tried a different stock ECU.

[sjbsuperman1425]

Did you try grounding the ignitor? Also, make sure all the connections to the ignitor and coilpacks are good and tight. Sometimes the old connectors just dont "click in" all the way and it doesn't get a good connection. But for sure check grounds and connections. Check for a bad connection in wiring as well.

Also, be sure to change the oil. The gas+oil mixture will obviously cause problems. My Buddies RB25 drained 7qts of oil/gas mixture because of a similar issue like this. His problem was a bad connection in the coilpack harness. Mice had gotten to them.

[S13xCrazy]

No worries on the oil, I keep changing it.

What do you mean by grounding the ignitor? As in bolting it to a bare piece of metal on the chassis?

[boost_boy]

Just because your buddy's tune worked for him, doesn't mean it will work for you. You seem to have covered all of the basics which gives us very little to work with. You are also telling this forum that you know what you're doing (per your post), so at this point me telling you to start with your ecu, whatever program you are using (may have improper values) and possibly the type of AFM your program entails, would be insignificant. Not a lot of options here, but the obvious. Running rich means you're either leaking vaccum (you said you corrected most) or again, your management system isn't compatible with the programming of your chip. Good luck with one (sound like fun).

P.S. Did you check the codes on your ecu?

[S13xCrazy]

The only reason I am NOT pointing at the ecu/tune is because it did it with stock injectors and stock ecu. I figured the new injectors/afm/wiring would solve the problem. Unfortunately, it remains the same. I might switch back to stock injectors, ecu, afm for diagnostics purposes but was hoping to nail the problem on the head without that.

code 55 everytime.

I am going to install a wideband/SAFC to do some real numbers, however the random misfire is what really gets me.

Anything is possible, I'm not saying forsure it is not the tune but in the order of the way I did things I'd like to believe it's not. I'm always open to suggestions, just wanted to try to provide as many details as I could.

Thanks for the help guys, I'll keep going through and see if I find anything new.

[float_6969]

Check your cam timing.

[boost_boy]

Check your cam timing.

He said his timing was "spot-on, no problem..checked it with a timing light".

[float_6969]

If his exhaust cam is right, but his intake cam is off, his ignition timing could check out right, but the intake cam being off a tooth would makie it run poorly (If intake came is opening late, it's closing late, the intake charge reversed back into the intake manifold, and then the combustion chamber is too rich. This would stop once the RPMS/& boost level increase to the point that the reversion would stop).

[S13xCrazy]

If his exhaust cam is right, but his intake cam is off, his ignition timing could check out right, but the intake cam being off a tooth would makie it run poorly (If intake came is opening late, it's closing late, the intake charge reversed back into the intake manifold, and then the combustion chamber is too rich. This would stop once the RPMS/& boost level increase to the point that the reversion would stop).

You and boost_boy really are INCREDIBLY knowledgable on this stuff, it actually amazes me. I hope one day to understand things the way you guys do! Both of you are what makes this forum what it is, thank you!

I ended up figuring it out last night. I read the article about the guy using the neon coilpack and realized that they were the same as the 420a eclipse coil packs. My girlfriend blew up a 420a a while ago so I went ahead and pulled the parts off that. Wired it up with a new pigtail and BOOM, problem solved!

As I was doing it, i tested the old harness and figured out the grounding splits were not making very good connection, so the spark was probably that much weaker from poor grounding. I went ahead with the swap and it cleared everything up just the way I had hoped. Still a slight hesitation at higher rpms, but I have to put in new plugs and gap them as I am sure the old ones are fouled out.

I am probably going to order new coil packs and a new harness so I can switch back to the stock stuff and not worry about ignition dwell. Used the other coil pack as more of a diagnostics test than anything I guess.

[sjbsuperman1425]

I have a brand new Wiring Specialties Pre-Made harness I'm willing to part with. never installed it and it includes the coilpack harness as well. PM me if you are interested.