fast89stang

iTrader: (2)

I have my car up and running. At first I had a oil pressure issue, I got that ironed out and now I have this. You crank the car and it may or may not idle right. Might idle for 10-20 seconds fine or it may start backfiring right away. I have tried all the timing curves in my 6012 box. The only way it ran "ok" was with a timing curve programmed in of "0" across the board. It was sluggish of course, but it didnt backfire. I have it set where it is roughly 20 degrees at 2000 rpms now and it will backfire. It has a vic jr intake, L92 heads, 6012 box, 4x cam gear with a ls2 front cover. I first thought it was my rigged up intake gaskets sucking air causing a lean condition, but changed them and didnt help. Talked to a friend, he said swap the outside wires on cam sensor connector. I had called him and told him it was being hard to start and was giving me a cam sensor failure. I swapped the wires, it was easier to start and quit failing cam sensor, but still pops out both sides on the exhaust and will occasionally backfire thru the carb. I may have one problem, not sure if this will cause it, but I am running the stock spark plugs from the ly6. I wanted to just use them to get it running and change them later. The motor was running fine in the truck it was pulled from, it just had low oil pressure, so i wouldnt think the crank sensor was damaged. It has a brand new 950 holley ultra hp carb on it. I thought maybe it was bad, tried another 950 I had that ran good last time out and the same thing. The plug wires are new. I am not sure what coils I have. I think they came off of about a 04 chevy truck, so not sure if they are considered LS1 or LS2 style coils. I am not running a map sensor with my box. I am about to give up hope on this thing. Oh, I have the box grounded to the back of the block by the valley cover. Not on the cover but on a spare hole in the block. It might not be a super clean ground, but I thought it was sufficient. I havent monitored the voltage on the switched power wire yet because my meter is at work, but I may need to do that. Is there any way you guys might can steer me in the right direction? Any help would be greatly appreciated and may also prevent me from selling this project before its finished. thanks.

fast89stang

iTrader: (2)

updated. I installed 7.35 pushrods last night, thinking maybe the valves were being held open much causing a valve to not seal good. No change at all. You can change the pop by turning the 4 corner idle screws out about 2.5 turns and idling engine on 1100rpms. but it idles worse with screws like that. It idles best with them 1 turn out, but then it pops.

89gmcs15

iTrader: (7)

Did you install a cam and have it degrees

fast89stang

iTrader: (2)

cam is installed, and yes has been degree'd. I havent checked to see if my ignition feed wire to msd is 12 volts yet, but I need to. I have checked and double checked grounds, moved timing around. I have a leakdown tester now, may try installing correct plugs first, then probably gonna do a leakdown test. I have tried another carb with same result. I installed a 3 bolt cam and ls2 cover to do away with vvt. The cam gear is a 4x gear. everyone says it will be worth it when I am done, but its gonna have to be pretty fast to be worth all this hassle. LOL

UrSmked

iTrader: (15)

I was having a the exact same issues as you with my 6.0, l92 heads, vic jr., holley 950, msd 6010 box. We put the motor in the car and got it running and it ran and sounded great. Took it for a test drive, found a minor oil leak at the fitting for my oil pressure gauge, fixed that and the car wouldn't run right again. It would idle like **** and thats if we could even get it started. It was back firing through the carb and out the exhaust. Took the front of the motor back off to see if everything was dialed in right and it was. Dropped my oil pan to check the reluctor wheel and they was good too. I called MSD and they claimed I had a bad box. They sent me another one and same problem except even worse. Called them again and they said I had another bad box, sent me another and the same issues. I replaced the cam sensor 3 times, crank sensor 2 times, new plug wires, different coil packs, basically anything you can think of. I was getting ready to sell the whole thing because I was getting so pissed off.
I then took the motor to Jason and F-Body Central in Baltimore, MD. It was out of my car on an engine stand. He hooked it up to a 16 V system and put new NGK TR6 plugs in and it fired right up. It originally had TR5's in it.
I got home and put the motor back in the car, but I didn't want to buy a 16 V. system so I just figured my starter wasn't cranking the motor over fast enough to create a good spark, so I bought a powermaster. After I installed that, the car still would backfire. We tested the battery and it was good, so I jump started the car off my friends truck and it fired right up. Drove it around for about 10 miles and now I can get the car started without jump starting it.
It still spits a little through the carb on the first initial attempt to start, but it doesn't backfire. It is very tempermental on how much fuel I give it during the cranking process. It is something that I am still trying to figure out to get it to start up everytime. What I have learned is that I let the motor crank over about 2-3 times before I start to give it any fuel for start up. It's really weird but maybe the computer takes a couple of revolutions to find top dead center.
Sorry for the long post, but this was a gremlin I was fighting for a long time and I hope it helps you out with your problem. It sounds just like mine.

UrSmked

iTrader: (15)

One other thing about my timing...I changed my timing to 14* at start up and ramped it up to 29* by 3000 rpms. I am also not running a MAP sensor. When I did this, I couldn't even jump start my car. It would back fire out the exhaust and through the carb. I then bumped the timing up to 18* at start up and at that point, I was able to get the car jumped. That is when I drove it around for about 10 miles.

speedtigger

iTrader: (16)

Try putting some brand new plugs in it and see if that helps. When I first put mine together the carb was too rich out of the box and it fouled the plugs. It backfired like crazy. I replaced the plugs and it was all better.

Prorac1

iTrader: (4)

Stupid question. Did you zero out the map table. The programing comes with a map table already installed. Even without a map sensor hooked up it will show 1.1 map and add timing to your base maping. That would explain why it ran with 0 base timing. I would change the plugs also as Tigger suggested. Eric L

fast89stang

iTrader: (2)

I havent zero'd the map reading out. I knew I read something on this and didnt think of it. I will go in and try and find that and see if it helps. I knew even when it was idling it would show about 23 degrees or so of timing when it was set to only have like 10 or so. I went in to the map sensor selection, but only seen the option to change to 1 bar,2 bar etc,. Thanks for all youre input, all of you. My god I am about ready to sell it. LOL I am at the point right now I regret getting rid of my 302. the bad part about all this is, I am a ASE master tech and have been for 20 years. But this goes to show, no matter how good you are, someone elses input always helps. Its so easy to overlook simple stuff. Thanks again guys. New plugs and ZERO map will be next on the list.

fast89stang

iTrader: (2)

question, do I zero the map table just by clicking on the graph and selecting "zero curve"? If so, then yes i did that, but I have a chip back in it now, so maybe it automatically puts a map curve back in???? So just leave the chip out, zero map curve and start a timing curve at??? lay a good base line to start at for me and maybe I can work from there.

Pop N Wood

iTrader: (1)

Do you have a wideband? Perhaps your mixture is just way off. Fuel pressure? Float levels? Check for vac leaks with a can of starter fluid or propane?

If you hook the lap top to the MSD box when it is running the display will show you the actual timing being used. No need to guess at MAP advance.

89gmcs15

iTrader: (7)

12 @ 0, 18 @ idle, all in by 3k. Idk what your all in should be tho, start low and add until you lose mph at the track or (I hate to say it) until you hear detonation, if ya can, then back off a few. (FYI I had detonation @ 31 after 5500 rpm but we've got crappy 90 octane e10 premium gas and my dcr is alittle higher than ideal) maybe someone can chime in on a better curve but it should run with this one

fast89stang

iTrader: (2)

Ok. Thanks for all input. I dont have a wideband. Fuel pressure is 8psi. Float levels are middle of sight glass. Already checked vac leaks. Tonight i went out and cranked it. Then remembered the old trick. Front 2 header tubes on passenger side cool to touch. Others hot.so i know my problem is there. Gonna swap coils around tomorrow and if it doesnt change then gonna do comp test. So at least im making progress

fast89stang

iTrader: (2)

well, dont the simple test last night. I felt all the header tubes after 5 min of run time. #2 nd 4 were cool. so, gonna swap all plugs, if that dont work, swap coils, then......run comp test, and i say i probably bent 2 intake valves during ptv check. No big deal since that head is super easy to pull. I think I have it definitely narrowed down now.

331camaro

iTrader: (1)

start with the plugs, i had the same problem at first start up. had a bad cam sensor, soaked the plugs, you can clean them up with a wire brush, and a small propane torch to dry all the gas out but nothing is like new. good luck. my opinion, and most guys would probably agree that stock inch ls engines like a lean idle, compared to gen1 sbc's where a little fatter on idle didnt hurt anything except your eyes. good luck!

fast89stang

iTrader: (2)

you wouldnt believe what I found wrong!!!! gotta love MSD quality control!

89gmcs15

iTrader: (7)

Bad box? Wires crossed? Anything mass produced I'd believe there's issues.

fast89stang

iTrader: (2)

wiring from box to coil was mixed up in box I guess. Connector wiring looks right, but 2 and 4 cylinders are swapped. I put a whole different coil pack on that side and still did it. I swapped the coil pigtails (had to unbolt cylinder 2 coil) and ran perfect!