Hard misfire, have spark & fuel

MNcarbturbo

What's Fuel Injection?
Just finished my swap and dealing with a dead miss on cyl 1& 5.

4.1 with a 86/87 setup in a G body cutlass. I had pieced the setup together out of boxes that I bought from the guys widow. I had the engine in another G body running for 2 years with about 8k miles on the setup and pulled the engine and sold the roller. Just got it installed in another G body.

All this stuff was new in 19
MAF translator and LT1 MAF
Dynamic LS coil near plug conversion
Casper's cam sensor cap LED
O2 sensor

The engine ran great for 2 years and the only change I made was what car it's in, it sat on a pallet for 18 months.

The wideband (new last fall) located in the downpipe reads dead lean (18 afr+) while the narrowband reads 350-450mv at idle

Scanmaster shows no codes

Compression check shows 125-140 psi on all cylinders. Cyl 1 & 5 are cool when checked with a heat gun.

I can unplug coil #1 and #5 and it makes no change to how the engine runs. It will backfire hard and die if I unplug coils 2, 3, 4, and 6.

I swapped plugs between cylinders and the problem stays on 1 & 5. I have nice hot spark on both. Plugs don't look wet but have a good amount of black soot on them.

I checked the injector plugs with a noid light and I get pulse. I checked fuel pressure and it's good. I swapped injector 1 & 5 with another pair (car runs 37lb GTP white injectors) and no change. I pulled the fuel rail out of the manifold and blipped the injectors with 12v and the pattern looks good.

I swapped ignition modules with another one I had on the shelf and no change.

I checked and reset my cam sensor position and it didn't move from before.

Unplugged the MAF and it made no difference.

The car will die immediately if I unplug the cam sensor after it is running. It doesn't like batch fire mode?

Any thoughts? I'm stumped, it feels like the fuel timing is wrong. I'd rather not parts cannon it. I just don't know where else to look.
PXL_20220515_023519367.jpg
 

TireFryer

The new kid..
My ignition module just died randomly and left me stranded. Sent to Steve V’s automotive. He tested. And the module would just die at like 1200 rpm. But looks like you have an aftermarket coil setup. If that’s fine, you might have to check the wiring for the injectors or coil harness. Maybe get a different injector harness? Sounds like it would be a spark issue with those cylinders sharing a coil. Not sure how that coil near plug thing works but for me 1&5 share a coil I think

I like the LC2 in the cutlass
 

HalfDozIN2

New Member
I can't tell what ignition setup you're running. It's not a tr6 with the remote coils is it? I run one with the truck coil pack, and I had the casper's led cap give me a couple misses/hiccups on the highway after only a couple hundred miles with the tr6. They seem not to agree. TireFryer warned me of it, so when that happened it came off immediately.
 

TireFryer

The new kid..
I can't tell what ignition setup you're running. It's not a tr6 with the remote coils is it? I run one with the truck coil pack, and I had the casper's led cap give me a couple misses/hiccups on the highway after only a couple hundred miles with the tr6. They seem not to agree. TireFryer warned me of it, so when that happened it came off immediately.
Mine was fine for about 20 mile segments. It then would backfire and die. The last time it did it, it blew the downpipe out the test pipe and blew the pipes out the mufflers. I’d recommend a stock cap and try again. Something easy to check. I’d link you the thread with halfdozlin2 but I think the thread was lost in the site attack.
 

MNcarbturbo

What's Fuel Injection?
Those LED cam sensors suck. Put a stocker on it. Known good coil pack if you have one.

I unfortunately don't have a stock cam sensor. I ended up with the LED cap because my OEM one was bad when I pieced the engine together and needed a replacement.

What's the go-to cap? I don't see GM offered anymore, highway stars is out of stock.

I see Casper's has a non LED version, are those any better?

The cam sensor does make sense as it dies when I unplug the sensor so whatever batch fire mode it's going into must be mis informed?
 
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MNcarbturbo

What's Fuel Injection?
I can't tell what ignition setup you're running. It's not a tr6 with the remote coils is it? I run one with the truck coil pack, and I had the casper's led cap give me a couple misses/hiccups on the highway after only a couple hundred miles with the tr6. They seem not to agree. TireFryer warned me of it, so when that happened it came off immediately.

Its a Dynamic EFI kit, same premise as the TR6 individual coil kit kinda. There's a board that plugs into the OEM style ICM and there's an output harness that goes to LS style coils.

Interesting that the LED sensor has so many issues. Never heard that before.

I've kinda ruled out the coils or LS conversion driver board being bad mentally at least. This board still runs waste spark and 1&4 and 2&5 share a driver and 2 and 4 have no spark issues. I don't know how 2&4 would be great and 1&5 would be dead?

Anything is possible I guess.
 
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TurboTGuy

Gray Beard Member
There's a guy that rebuilds cam sensors on here. Can't remember who though. Someone will chime in with it I'm sure.

Maybe he can give you some direction.
 

SCOOBY DOO

I'M NOT A MONSTER, I'M JUST AHEAD OF THE CURVE!!!
Its a Dynamic EFI kit, same premise as the TR6 individual coil kit kinda. There's a board that plugs into the OEM style ICM and there's an output harness that goes to LS style coils.

Interesting that the LED sensor has so many issues. Never heard that before.

I've kinda ruled out the coils or LS conversion driver board being bad mentally at least. This board still runs waste spark and 1&4 and 2&5 share a driver and 2 and 4 have no spark issues. I don't know how 2&4 would be great and 1&5 would be dead?

Anything is possible I guess.
Might wanna disconnect the EFI kit...and see what happens.
 

blackazz

Not a Gn
X2 on replacing the cap.that is great for setting the cam sensor but not for everyday use.
Remember the cap tells the brain where #1 injector is.
 

MNcarbturbo

What's Fuel Injection?
I ran through the last of the no start flow chart last night and it told me the ICM is bad so I'll swap that when it shows up in the mail. The ICM didn't pass the injector pulse when the cam and crank sensor were disconnected and cranking or blipping terminal B and C on the harness test so that makes sense why the car won't run in batch fire mode.

I'll hunt down a new cap in the meantime.

I noticed the crank sensor was really dirty, it had a lot of iron filings/powder on it when I pulled it. I cleaned it off well and reinstalled and adjusted it with no change. The engine sat for 18 months at a chassis/turbo fab shop and in my garage where I do some iron working so it's possible it gummed up from iron dust floating in the air but it didn't solve anything.

Also did a leakdown check, cyl 1 is around 25%, 3 is 2% and 5 is 12%. Cyl 1 had some air coming out of there intake so I think the valve might be hung slightly hung open from sitting. Combined with screwed up ignition might be why I'm getting backfires, spark is working into the manifold. Cyl 5 was just out the crankcase. I need to try to blast the #1 intake valve with some air and tap the valve to see if it's sticky or if the seat is actually shot. The heads looked good when I swapped springs in 17 when I put the engine together but I had 8k on it since so there's a chance a new issue came up or I missed when I inspected everything.
 
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