A new "my lt1 runs like poo" thread :p
 

Ok, wound up driving the z an hour home in the pouring rain after work Thursday night. Car was running mint but now not so much. It started popping, sputtering, and backfiring randomly on the highway on my way home and now, even after the rain has stopped, is still doing it.
I did a quick look around at all the wires and everything looks ok but it feels like it's down a cylinder or two.
At first anything under 2500 rpm was horrible and almost undriveable. Now, it's cleared up a little, but still not so great under 2000 and downright horrible under 1500. It does however idle great and starts right up fine. It will pull all the way through to redline without too much drama but you can definitely tell it's just not all there. My other half said it best when she drove it, "the gas pedal feels like a spongy brake would react"
Not throwing any codes so could it still be the opti? It really feels just like a plug wire is shorting out but they look fine everywhere. Any ideas before I tear the front of the motor off, AGAIN!!!

opti or coil but you aren't alone not many lt1's have been running right lately :P

Tell me about it. I'm getting ready to either do an ls swap, or eliminate the opti.
Been seriously considering opening up a hole at the back of the intake, dropping in a regular distributor, and just running a megasquirt.

Speaking as the owner of an LT1 that runs like a top, I can tell you that my car has zero issues driving in the rain, ever. Refresh my memory, is your opti vented? And you checked for simple stuff like vacuum leaks and fuel pressure? Connections on the coil are good? And there is definitely not a plug wire touching something hot?

Yes, opti is vented, none of the wires are touching anything hot, triple checked.
Didn't see any vacuum leaks, all of the ignition plugs look good.
Didn't check fuel pressure cause whatever caused it happened after it got wet the other night so I'm pretty sure it's ignition related. You can definitely smell unburned fuel from the exhaust.


I used to love lt1's. My old 9c1 caprice was awesome. I beat the daylights out of that car. Went through 3 transmissions and 2 rear ends but the motor was always strong and trouble free.
I don't want to hate lt1's but this one is making it hard not to. Grr...

Yeah I just realized fuel pressure issue wouldn't make sense. Is there any chance it could be a bad coolant temp sensor causing the computer to see a cold engine and dump fuel? If yours is the same as mine there are separate sensors for the gauge and the PCM so the gauge can read correct and the PCM can still be getting bad info.

I can't believe it's running that bad and not throwing codes. I'm just trying to come up with anything other than the opti that could cause it.

i have heard stories of the vented optis getting water in them and they start running just like that but i dont speak from experence.

i know you said no codes, could an o2 cause a problem.

Mine used to run beautiful. But I did an emissions delete and race headers with ory and now the air fuel ratio is all tweaked.. Still trying to track it down but Now its running good till about 3200rpm goes lean as you all saw on the dyno 17:1!!! WTF So, at least my ignition is good... knock on wood.

17:1 is leeeeean...

haha wow I meant lean I posted too early..

Kevin u can try cleaning the maf first 2nd would be an adjustable fpr to mess with it some

Didn't get the chance to tear into it today. Wound up taking a ride instead. However, today it's a little better. Now it's only breaking up under/around 1500 rpm. Not really backfiring anymore either.
But yeah, still no codes. It seems to be slowly clearing itself up but who knows if it'll go away completely and either way it would be nice to figure it out so I don't have to fear driving the car in the rain :p
Somene on ltxtech asked if my air filter got wet. I do have a cold air intake that has a cone filter down low in front of the tire. He said his does sometimes and screws up his maf. But, I'm not throwing any codes. I would imagine I'd have a code if it were O2's. I know my caprice did when the o2's went bad. So aggravating.

I'm gonna clean the injectors and maf and put a new fuel filter in. If that doesn't help aeromotive fuel pressure regulator time.

I dunno if a wet air filter could cause it or not, but since we're on that topic how big is the filter on your CAI? When I got my car it had a Moroso CAI on it, and it had a K&N cone filter on it that was so long it almost touched the splash panel. I replaced that with one that was a few inches shorter, which I found after some research was the same size as the one the kit came with. I just wanted a few inches of insurance in case I ever hit one of those sneaky puddles that looks 2" deep but it's 12" deep.

as much as I hate to admit it (and I do) The LT1 is a great engine that is hampered by a unreliable ignition system. Chances are it is a coil or opti but I would do the LSX ignition upgrade way before I tried to do an LSX swap on an LT1 car.

Scary lean......

It's a smaller cone type. Cheapy from autozone k&n knockoff. But, the splas shield under it was cut away by a previous owner. I'm assuming to get more cold air to it.

Honestly, if I do get rid of the opti I'm leaning towards a conventional distributor and a megasquirt ecu. Probably cost less than half as much as the efi connections stuff. Unless I decide to try and work a deal with someone who may be selling their set up ;)

Do you remember Rob's setup from new england dyno on the white 96ss?? That was a nice setup and very clean. He is still on Nems if you have ?'s I am sure he would answer them.

Yeah I'm sticking it out with the opti till it is declared toast. Then I will do the efi connections conversion. But no need to upgrade now :) Yep its pretty scary lean but only at the top end like over 3k rpm. Strange, but I've been driving it the past couple days and taking it off the road soon to straighten it all out.. :D :klab:

Yeah I remember checking that car out years ago and it's the one that set me on this train of thought.
Doesn't seem like a huge deal. Just need a nice accurate distributor with a locked out advance so I can control timing with the ecu, then use the conventional cap to distribute the spark just like an old school small block.
Pretty sure you can get a megasquirt to control fuel and spark now. Iirc he used either a fast or a dfi set up. But at the cost of those I'd just go efi connection lol.

Only big issue I see is getting the hole through the intake in the right place for the distributor.

Yeah i think he used a fast but megasquirts are great for the money. I believe there is a template online there is also a place that does them online for the thirdgen people I can't remember the site but it's lt1intakes.com or something it's been awhile.

Yeah, that sounds about right. I knew there was a place online. If the opti is f'ed I'm pretty sure this is the route I'm gonna take.
It's also the route I think I'm gonna look into for my turd gen if I stick with the lt1 I have for it.

Oh, one other thing, since I'm supposed to be filling in for Pizza, I have to add...

He called the shit poo!!!

Calling it poo made me smile lol

If you go rear dizzy you have to drop the motor to remove it. I was going to go that route but after getting a lot og the ls1 stuff cheaper then off there site and really not liking how tight it is to work under the cowl anyway. I sed fuck that. And that's th e reason gm went with a front mounted opti in the first place. They actually have ltq blocks in some early 90's trucks but you can't telll unless you know what to look for because they ran a conventional dizzy setup. Anyway my point is either keep the opti and its issues. Or go efi and have tunability from a know and GREAT tuner. Megasquirt may be good for the price tag. But who will tune it? You'd be stuck tuning it yourself or paying someone more then a regular tune to do it for you. And that would negate the cost of the "cheaper" system as it were. I say check your lower opti vent hose the one soaked in oil and the one that probably fell off.

Trust me, I would have absolutely no issues with tuning it myself and honestly would rather. Tuned a number of carbe'd cars in my day with great success. Doing it with a laptop would be even easier.
Anyhow, if I stop being a pussy or it warms up a little this afternoon I plan to dig into it some today. :)

hahaha!

What can I say, I'll call it like it is lol.

Anyhow, triple checked all the wires and connections. All was good. Also checked the lower vent hose, and while yes, it is covered in oil, it is still firmly in place lol.

Then I crawled under the nose and looked at the air filter. Tough to say if it's still wet but the mesh on it is definitely very rusty like it was soaked. So, I'll take it for a rip tomorrow and if it's still breaking up I'll try pulling the filter and see what happens :)

Ok, so, triple checked every wire connection and hose. Everything looks good.
Cars not throwing any codes whatsoever. Breaks up below 1,500 rpm, smooths out, and now when I wind it out wide open it stays fairly smooth until about 5,000 then starts breaking up again. But it's definitely down on power regardless. Feels like it lost a cylinder.
It also gets a weird burnt sweet smell to it when I wail on it.
Oh, and it's occasionnaly puffing some white smoke out the exhaust here and there, and, lastly, on a whim checked the radiator and it's about a third of the way empty.

Hmmmmm.......

Uh oh...how does the oil look?

That doesn't sound/smell good Matt! :confused5:

Not bad....... Yet :(

If it wasn't such a bitch to do the plugs I'd compression test it.
I'm thinking fuck it, I'll run it for the next couple weeks until the snow flies before I tear into it and see what happens. Once it's apart and I know what's wrong I wont put it back together so I'd rather keep driving it for now. It's not overheating or anything yet. I figure worst I'll do is cost myself a couple o2 sensors.

If it does need to come apart I'm thinking a properly nitrous built 383 may be in order lol.

I smell head gasket.......

Ahyup. That's what I'm starting to think. Yay :p

My car is misfiring at the top of second gear at close to redline ...

Ok, so, the problem went away for a while. And now I'm not smelling or losing anti freeze anymore and the fill cap/dipstick only show clean oil.

However, now the issue is back with a vengeance. Runs good until it gets up to temp then sputters, pops, loads up, backfires (quite spectacularly sometimes lol) and generally runs like a bag of smashed assholes.

So, I've recently replaced both o2 sensors, the iac, and pulled the air filter to make sure that wasn't the issue. When I changed the iac I pulled the throttle body off, removed the bottom plate, and cleaned it thoroughly.
Now, when it's cold it runs like a raped ape, better than ever. As soon as it gets up to temp it's just a mess. Falls all over itself and is almost undriveable.

HELP!!! I have someone just waiting for me to sort it out and I think I have the car sold for a good price. Want to get it resolved before he moves on but don't want to keep throwing parts at it...

I'm sure we've been through the obvious stuff like ECT sensor already, but Adam's car had a similar issue recently, and it was the wiring to the sensor (specifically the ground wire), not the sensor itself. And you must have tried the coil spacer mod already? But the symptoms are such a dead ringer for an ECT issue that I'd be surprised if that isn't somehow the problem. Not to mention the intermittent nature of the problem suggests wiring or ground.

Yeah I was thinking the same thing but autozone doesn't have the one that goes in the head. Only the one in the water pump. Which one is the ecu sensor? Isn't it the head one?
Last year when I had my ignition issues I went through every ground in the car, took them all off and scraped them all clean so I'm pretty confident it's not a ground unless it's in the harness.

And on another note, kid that wants the car just texted me and wants to meet up mid week... The way I feel right now I really think I'd rather have 6 grand in my pocket than the car lol.