ok well a while back i bought this used lt1 to put in my vette. its all in and it runs but runs really wierd. when the car idles under 1k and i rev it real quick it revs fine, when it idles above 1k and i do the same it stumbles and backfires like crazy. its also running really rich (burning my eyes rich).

another thing when the car is running and i pull the maf off of the intake elbow it doesnt do any difference. ive tried 2 different maf's and it does the same thing. (doesnt seem to be reading the MAF).i thought it should change?

things that have been checked or changed:

plugs/wires
cap/rotor
coil
MAP sensor
knock sensor
engine temp sensor
o2 sensors
vacuums seemed fine

PCM/ECU or whatever had the VATS and EGR tuned out and was tuned for long tube headers (installed on the car).

i do not have a obd1 connector and check engine light hooked up to the car (since it was a swap) so i dont know what codes its throwing. i havent been able to check the fuel pressure yet either.


i just need to know what to buy or fix so i can drive the damn thing. ive owned this car for 2 years, been through 3 different motor setups and only driven the damn thing maybe 3 months total.

i can get videos or whatever if that will help anything.

 

anyone?

 

Disconnecting the MAF makes it default into another mode, depending on the computer your using.

You need to get the diagnostics port hooked up, otherwise it's just going to be a guessing game.

 

Agreed

Top priority should be getting a diagnostic port on your setup. I believe the 94 was the cross over year for corvettes as far as OBD1 and OBD2 go.

I know on my buddies 94 I can put of AutoXray scanner on it (using a OBD2 connecter) and I can read all of his ECM data just fine (my AutoXray is a OBD1 scanner) go figure.

Anyway, once you have a port and a scanner hooked up you will be able to see all of your engines sensors and figure out what is going on.

Could be alot of things, 02 sensors , vaccum leaks, exhaust leaks (which will screw over your 02 sensor readings if its in front of them) ect ect.

 

I'd first get any stored codes, but I don't see that you've checked you IAC valve. If it's not closing completely, you'll get a rich mix.

 

I recently went thru some of the same things with mine when I put it back together after sitting over a year in some pieces engine wise. I added a MSD distributor but cannot say that has ever been a part of the issue. There was an issue with my O2 sensor, due to the exhaust hanging on one of the wires when we went to remove it. That got fixed but I learned to triple check wires since they are so hard to see if they have stock routing, make sure your vacuum lines to the Opticspark are correct, and if those O2 connectors are on backwards (possible with broken connector housing) then make sure they line up like the other side. (If they are on backwards, even one, it will blow and O2 sensor fuse) and cause a MASSIVE rich, backfire, sputtering condition. I have a great son-in-law(SIL), I can thank for that one but I refuse to go there. Leaking injectors can cause some rich issues and but I had those taken out and cleaned and they said after cleaning I was fine.

So I did what you did, but I found several issues that I thought was good. I kept getting an O2 issue with one sensor (little to no voltage change). When one checks it, it looks good. But when on the lift and a light brought to it and compared to the other side, the broken connector was reconnected backwards. I can't really blame him, he's young, Stooopid, and knows little about cars, but wanted to show me what he could do. I was at fault for thinking he couldn't mess it up. I also labeled the plug wires, that doesn't help if one puts them on the distributor wrong as you'd swear by looking at the numbers on the wires by the plug end that Albert (Einstein, like in my SIL) couldn't mess up. Again, me bad for believing pictures and numbers are easy to follow. So on my detailed time consuming looking at feeling and dragging wires discovered two crossed on the distributor. He doesn't get to help me on the car anymore. Did I mention that? While it runs well now, I'm chasing a fuel pressure issue and will have that resolved shortly, but basically I had backfiring, spitting, sputtering, running on like 6 cylinders (those other two plugs were clean as new from the swapped wires. Have you checked the burn on your plugs to see if they match or if there is an issue there?) Also, a bud showed me where trash on the MAF sensor wires had trash against them that they would cause huge issues. Cleaning that debris off that got past a bent air cleaner mounting, solved everything. Best of luck. They can be a pain.

Ken