'98 Lumina won't run

Hi, the other day my cousin's '98 Lumina (3.1, 140,000 miles) died. They had it towed home and I performed a few checks on it, and I can get it restarted, but it just bogs & spits until it kills again. I put a new fuel pressure regulator in, new plugs last week. In august, I put in a new fuel filter and plug wires and a pvc valve. The car has never had any problems, always started well and ran good. I've switched the coil packs/module with another that runs, compression tested (all over 140) and verified that there was spark in all cylinders, fuel pressure is 40 with key on and not running. I'm pretty sure all injectors are firing. The only red flag I've come up with is that every time I pull the front plugs (2,4,6), 2 is black with soot, 4 is normal and 6 is wet. I'm leaning towards the computer melted down, or the timing chain having skipped a tooth or 2. Does anyone have any ideas on checking either of these? I've got a code reader, but that's all it is. The first time it died, there was no code, but since I've been able to get it restarted it comes up with the multiple cylinder misfire code. Any ideas? Thanks.

Hi, the other day my cousin's '98 Lumina (3.1, 140,000 miles) died. They had it towed home and I performed a few checks on it, and I can get it restarted, but it just bogs & spits until it kills again. I put a new fuel pressure regulator in, new plugs last week. In august, I put in a new fuel filter and plug wires and a pvc valve. The car has never had any problems, always started well and ran good. I've switched the coil packs/module with another that runs, compression tested (all over 140) and verified that there was spark in all cylinders, fuel pressure is 40 with key on and not running. I'm pretty sure all injectors are firing. The only red flag I've come up with is that every time I pull the front plugs (2,4,6), 2 is black with soot, 4 is normal and 6 is wet. I'm leaning towards the computer melted down, or the timing chain having skipped a tooth or 2. Does anyone have any ideas on checking either of these? I've got a code reader, but that's all it is. The first time it died, there was no code, but since I've been able to get it restarted it comes up with the multiple cylinder misfire code. Any ideas? Thanks.

I would check for good hot blue spark to all spark plugs.
Is the engine missing when running?
That engine will give also give you a fit if it has bad plug wires.
If timing chain was off it would show up on low compression?
Was the compression test even or some real high or low?

My uncle did the compression test, I'm going to do it again and see how much variance there is. The wires are only a couple of months old and the car never showed any signs of trouble before it just up and shut down. Yes, it's missing while running and it's spitting and it sounds like it's flooded, I thought it may come out of it, but it never does. Only runs with throttle wide open, and even then it's only for 20 seconds or so, and it never cleans out, just sits there and bogs.

My uncle did the compression test, I'm going to do it again and see how much variance there is. The wires are only a couple of months old and the car never showed any signs of trouble before it just up and shut down. Yes, it's missing while running and it's spitting and it sounds like it's flooded, I thought it may come out of it, but it never does. Only runs with throttle wide open, and even then it's only for 20 seconds or so, and it never cleans out, just sits there and bogs.

One other thing you might check is the egr valve or for a clogged cat.

One other thing you might check is the egr valve or for a clogged cat.

On cats, be aware if one or more cylinders arent firing, all that raw gas can go downstream into the cat, mine did that once with one plug not firing, and within a couple minutes, the cat was glowing orange, so hot it melted undercoating off of underside, dripping on cat, looked like car was on fire from all the smoke. Which a fire could happen... just a FYI, be careful.

In case I missed it...no codes?

Sounds like it's overfueling....just for laughs try thumping on the MAF sensor while trying to start it...see if anything telling happens...

In case I missed it...no codes?

Sounds like it's overfueling....just for laughs try thumping on the MAF sensor while trying to start it...see if anything telling happens...
Agreed, could unbolt the engine pipe and see if it runs also. Check if something got sucked up into the air intake also, but not much room under there for that, just take a look

Thanks for the ideas. I re-compression tested here's the results:
1 - 225 lbs
2 - 195 lbs
3 - 0 lbs
4 - 120 lbs
5 - 0 lbs
6 - 120 lbs

So, I removed the timing cover, chain/gears are like brand new and not skipped.
So, I took the heads off last night, bent/stuck exhaust valve in cylinder no. 5, and a dent in the top outside ring of that piston. Also, intake runner in head for cylinder 5 is full of gas, and there's a 1/2 cup on piston no. 6 too.

Dropped heads off this morning at shop, they're going to surface and pressure check my good head, then I'm taking it back home and going to bolt it down and recheck compression to find out if I need to replace the piston (worried it may have smashed the top ring). Wish me luck, I really don't feel like changing out the piston.

If it checks out good, I'm having a valve job done and gonna slap it back together.

Thanks for the ideas. I re-compression tested here's the results:
1 - 225 lbs
2 - 195 lbs
3 - 0 lbs
4 - 120 lbs
5 - 0 lbs
6 - 120 lbs

So, I removed the timing cover, chain/gears are like brand new and not skipped.
So, I took the heads off last night, bent/stuck exhaust valve in cylinder no. 5, and a dent in the top outside ring of that piston. Also, intake runner in head for cylinder 5 is full of gas, and there's a 1/2 cup on piston no. 6 too.

Dropped heads off this morning at shop, they're going to surface and pressure check my good head, then I'm taking it back home and going to bolt it down and recheck compression to find out if I need to replace the piston (worried it may have smashed the top ring). Wish me luck, I really don't feel like changing out the piston.

If it checks out good, I'm having a valve job done and gonna slap it back together.

Eek.

I'd replace the piston anyway...any time a cast piston gets tapped, it usually causes a stress crack that will make it split apart if not sooner, later...

True and it might have pinched the top ring land, question how did this happen!! Sounds like someone wound it up real good, watch the lifters on those cylinders also.

Yeah, I'm hoping to find out why. My cousin drives it, she's 17, and your typical blonde, but she's the kind of girl who puts on her seatbelt, adjusts all of her mirrors, spins around as far to each side as she can to see stray childern, etc., and then dials her phone before she starts driving. I'm guessing she didn't do anything malicious to it, but I'll have to prod her either way.

Update time: Brought the good head home and attempted to compression test the 3 back cylinders and noticed that the last 3 (towards the driver's side) rockers weren't moving. The camshaft was broken in half, thus explaining all of my previous symptoms. So, now I'm swapping engines. I have one out of a '94 Buick Century (vin m), I know there are differences, but if I use the intake and exhaust manifolds and other accessories that are different, will it work? I know the rear Buick head has a temp sensor in the head that the original head doesn't have, and for some reason I'm thinking the rockers are different too, anyone know for sure?