Ralls

iTrader: (32)

Car is a 383ci, 8.5:1, T76 Turbo, 10PSI

I'm trying to trace down what seems to be an ignition problem. The car has been under the knife for a while, replacing stuff other than engine related parts. It's back together and runs like crap even though it ran good before. It feels like it will miss every once in a while on cold start idle. Feels ok with hot idle. Cuts up when accelerating light throttle around 2k-3k RPM. It doesn't feel that bad when it cuts up but you mostly hear the exhaust tone changing and RPM's will fluctuate. At WOT it's seems to clear up and accelerate smoothly but feels very weak. Like down 150hp. My A/F gauge is steady at WOT.

I found a spark plug wire touching the header and arching. I replace that one wire and another one that was starting to melt with some extra wires I had. It ran much better but still had the symptoms I described. Then I put brand new ACDelco wires on it with no change. Mind you I have always used Taylor wires but I decided to try ACDelco. I'm wondering if it fouled out a plug from the misfires. I'm using Autolite 3922's. I think I'm just going to replace all the plugs and do a compression test. What are the symptoms of too cold of a spark plug? I have hotter 3923's but I've been using the 3922's with no issues before.

One thing I'm hoping someone might know. With the engine running in the dark, I can see the ignition coil and ignition coil wire giving off EMI. It's not exactly arcing, but you can see the spark through the wire and an "aura" around it. The ignition coil sparks to the metal bracket that houses it. (MSD coil) You cannot see this in the light. Is this normal??

Ralls

iTrader: (32)

Who's good at reading plugs? I just pulled these out after a long drive of cruising and WOT.
These are plugs 1,2,4,5, and 6. Number 6 has the whitest insulator tip which is the same cylinder that had the burnt up wire.


Plugs 3,8, and 7 are black

guppymech

iTrader: (7)

The coil leaking electricity is not good. Stock plug wires are just carbon core and you'd probably do better going back to a spiral wound conductor type of wire. The boost puts a big load on your ignition system. With those 3 plugs looking dark, I'd look at the wires for those cylinders or could be the conductive tracings in the distributor cap.

Boosted Firehawk

iTrader: (11)

change those plugs, i ran them and had the same issue. went back to ngks and immediately noticed the difference and solved the issue

Ralls

iTrader: (32)

Dang, maybe I shouldn't have bought OEM wires. They should still be able to handle at least mid-rpm cruising. I'm using an OEM vented optispark with about 2k miles on it. The MSD coil is a bit older with maybe 5k miles. So the coil leaking out some electricity isn't normal? Like I said, it's not a heavy arc like a bad wire does. But maybe it gets worse under load.

Which NGK plug is the equivalent heat range as 3922's? Using AFR heads with gasket type plug. Really though, I've been using these plugs for about 2K miles. It definitely wasn't doing this before. Is there a point of no return when plugs start to misfire (bad wires) and they simply need replaced?

I'm trying to backtrack when this issue started. Last time it ran I was on the dyno and the transmission wouldn't hold anymore. I limped it home with it slipping badly. It MAY of got hurt on the dyno and I couldn't tell over the trans slip. 6 months later I had a new 4L80E in it. During that time I pulled the headers off and valvetrain to re-torque the heads. There was an incident where the trans harness got ripped up because someone started the engine with the harness still zip-tied to the flexplate. I noticed a TPS wire yanked out of the plug probably cause it pulled the whole harness with it. Fixed that and my tuner didn't notice any other sensors reading incorrectly. Basically that's the story so far.

AChotrod

iTrader: (17)

If your MAF is bad or dirty it could cause your issues. Also put a stock coil back in. MSD coils fail all the time or just dont work as good as the factory coil.

Ralls

iTrader: (32)

Agree, but I switched to speed density. I will buy an OEM coil then. I don't want to be a sucker for "aftermarket automatically means better," but can the OEM ignition system support 700hp under boost?

I'm in the middle of doing a compression check. I need to find different adapters to get to cylinders 6 and 8. So far all the other cylinders have 135psi.

guppymech

iTrader: (7)

I bought stock plug wires cause I figured the originals lasted better than 100k with the stock manifolds. Up till recently I liked the stock wires and recommended them when asked. I ripped a plug boot while changing plugs the other day and when I pulled the ripped boot off the wire to swap it out the wire just fell apart where it was inside the boot. This wire is the one that is closest to the headers so I can only think the heat got to it. For comparison I pulled a boot off the 100k mile wires and the wire looked perfect. Both sets where OEM ACDelco and Delphi made by Packard. I have a spare new set of ACDelco wires on the shelf but I'm not sure I'll use them.
I'm running a BWD Select coil from the auto parts store, it's got a brass terminal and works good on my NA setup. I tried twice to get a ACDelco coil from RockAuto but they kept sending me the wrong one so I gave up on that one.

Ralls

iTrader: (32)

Compression readings are around 135psi. I put new plugs and new redesigned MSD coil. Now it's worse! Once I start to put a load on it at ~50% throttle at 3k RPM, it spits and sputters out the exhaust or intake (hard to tell with open wastegate). If I ride out 2nd gear with little load and low boost and it doesn't backfire.

Does this sound like the opti? Really isn't much more to the equation. Besides an ICM but don't those usually quit all together?

robsquikz28

iTrader: (246)

what does your wideband show?

any codes?

rich5368

iTrader: (2)

Dude I'm currently having the same problem on my car. I can't figure it out. Some boards say the ECT could cause this kind of problem. I'm going to try that tomorrow. My car runs great in open loop and like doodoo in closed.

Jr.Samples

Here goes another low rpm stumble thread.

You can dump parts in it hoping to get lucky or take it somewhere and put it on a machine to see it while running.

I changed

Plugs
wires
Opti
O2s
coil
ICM
TCS

Cause? Fuel pressure.

Put in a new fuel pump and filter.

Ralls

iTrader: (32)

Lol this one had me chuckling. The end of the rotor flew off and embedded into the cap. It's amazing this thing still ran.

TimmyZ28

Yeah, that'll do it.

Boosted Firehawk

iTrader: (11)

Yup, seen that too many times