Hard misfire, have spark & fuel

[MNcarbturbo]

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.

 

[TireFryer]

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

 

[WarWagon]

Try a third or new ignition module. Wide band O2's read lean on misfires no oxygen burnt.

 

[SCOOBY DOO]

Those LED cam sensors suck. Put a stocker on it. Known good coil pack if you have one.

 

[TireFryer]

Those LED cam sensors suck. Put a stocker on it. Known good coil pack if you have one.

I agree with this. I had the led cap and it caused me issues on top of issues with anything other than the stock ignition system.

 

[HalfDozIN]

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]

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]

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?

 

[MNcarbturbo]

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.

 

[TurboTGuy]

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.

 

[Lockman]

I will. Turbo Nasty rebuild's 'Em.......or he'll sell you the parts to rebuild it yourself . Good Guy.

 

[SCOOBY DOO]

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]

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]

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.

 

[TurboBuRick]

Damn, you have a nasty little gremlin.

If my memory serves me right, there are some modules that will not work in batcfire.

My money in on the injectors. If injectors sit for long periods and are allowed to dry out, they can hang up. Been through it a few times..

Remove those 2 injectors. Using compressed air, blow backwards through the injector.. try to rig it where you have a good seal between your blow gun and injector. Use some lube like wd40 or pb blaster.. The injector is not going to flow constant. It will however open and let a shot through. When you see a shot of air/lube out the top of the injector, it should be good to go. I’ve done some strange things to get stuck injectors to brake free. Tap the side them them on a vice. I e used an air chisel with a flat chisel to shock the injector.
You can actually try the air chisel thing on the side of the injector without removing them.
Just maybe you wil get it to brake free.
Obviously don’t get crazy with the air chisel. Just little shots will do. Super sonic shock.

Good luck

 

[Buick Mark]

Those LED cam sensors suck. Put a stocker on it. Known good coil pack if you have one.

Yep!
Put an LED on something, it will sell, whether it works properly or not.