View Full Version : lt1 headache

04-30-2012, 10:37 PM
LT1 i finished and put back together, the car had a no start problem that was me adjusting my valves to tight, re adjust got it to start with WOT. The vehicle reved freely but as soon as i let off the throttle it died. I figured since i got it to start it probably died do to the sensors all not being hooked up so i threw it all back together. Go for a start and it reved freeley again but did not idle stil let off throttle and bam died. Got out of the car looked the engine over and such and was puzzled went to try a start again and this is what i got

that was all with WOT, anyways i tinkered with it some more and readjusted valves changed out the bigger fuel injectors i put on the car, since the computer still isn't tuned for the mods. Fired the car up after adjusting lifters again under WOT it starts revs a bit but not freely kind of chose were it wanted to rev to capping at like 4500 rpms knew this wasn't right so i let off the throttle and it stalled out like usual, looked stuff over and am just down right confused, try to start it again WOT and it starts holding throttle down it revs to like 700rpms and then a second later up to 1500 and held it there. Still confused get out check spark plugs wires firing order on opti and just sit there with no idea. Now it only somewhat starts with the throttle 1/4 to 1/2 way down depends and then i'm lucky if i can keep it alive at 500rpms

car is a 96 with the m6

The new build is
LE2 heads with patriot extreme gold springs
comp cams xfi280 230/236 113lsa
pacesetter longtube headers with ORY
ported lt1 intake
professional products 58mm throttle body
scorpion 1.6 nsa rr
trickflow chromoly pushrods
guide plates
took off air pump, a/c system except the box in the firewall, evap system, egr and replaced the traction control module on the valve cover with a non traction control throttle cable
new aluminum intake elbow

replaced water pump
fuel filter
fuel pump
new wires
spark plugs
sensor in waterpump
coolant sensor in the head
oil level sensor
oil pressure sensor

I know i have spark
I know i have fuel not sure if its enough though could be bad pump even though its new gonna get a fuel pressure test tomorrow
Gonna get a compression tester tomorrrow to make sure i have that also

just curious on what everyone else thinks like i said it doesn't even start under WOT anymore and i need to feather the throttle about 1/4 to 1/2 way to get it to start, if compression is good again tomorrow i guess i'm gonna rip down the front and check the new opti because at this point the only think new on it is the back housing.....thats another story though

04-30-2012, 10:48 PM
Double check and make sure your maf is hooked up. Double check the plug wires. Mine didn't want to start after the H/C swap and I found that 2 of my plug wires weren't on all the way. I'd double check your fuel pressure too and see if something went wrong installing the new one. Are you absolutely positive you got the cam in just right. It kinda sounds in the video like a miss or timing being off. Hope I was able to help at least a little. Good luck.

04-30-2012, 10:52 PM
the opti should be on right, like stated though i'm going to get my hands on comression and fuel tester try them tomorrow i had a fuel pressure gauge hooked up when i did the pump it read 0... figured it was just busted, autozone rental but i heard the pump kick on and prime i know that fuel got to the fuel rails cause when i swapped injectors fuel came out, just not sure if its the right pressure, if compression and everything else checks out fine i'm taking opti off probably timing cover also just to make sure it didn't become a tooth off also i've been messing with this for like a week and a half now and am just over it

thanks for the help though just curious as to why it only startsunder certain throttle conditions thats what gets me and makes me curious if its really timing

05-01-2012, 02:04 PM
fuel pressure isn't right when cranking it stays at where it needs to be but let off the fuel pressure drops... and key on it only goes up to about 30 psi and then drops

edit: went and played with it a couple time set the fuel pump primer it held pressure with the primer hooked up and even after i took it off it still held pressure. tryed with keep after that and it still seems to be holding a decent amount of pressure, also tryed a start with the fuel pump primer in and its a no go

if i just crank it without touching the throttle i also realized its got a pattern to it
crank crank crank crank crank little pop little pop and then repeat not sure if that sounds like timing is off or not?

05-01-2012, 02:44 PM
Could be a couple of reasons. Either when you installed it one of the suction lines has a leak, The check valve is bad or may be a bad regulator. Key on with no start it should prime to 41 to 45 PSI. When the engine fires it may drop down to 39 to 34 PSI. After engine shut off it should still be in the 41 to 34 PSI range and hold for at least 15 to 20 min.

05-01-2012, 03:03 PM
first few times i tryed it the pressure jumped to 30 some and then just dropped went for a start pressure jumped to were it needs to be but then dropped when i let off, after i bypassed everything it primed right and has held a decent pressure not the best, i still don't think this is the issue though, gonna do a pressure test as soon as i get motivated to take spark plug wires out haha. Will test fuel pressure again though see were it sits this time

05-01-2012, 04:50 PM
Personally it sounds like your regulator is F'd. Rather it be broke or miswired. It's not happy. But that's me.

05-01-2012, 05:18 PM
well like i said its holing fuel pressure now out of now were but even with constant pressure why would that prevent start and only let it crank over and start and die with throttle pressed partially

05-01-2012, 06:27 PM
well got a live scanner on it not sure if i really like it should of just forked out money for a datalogger but, map sensor reads 23.x, ignition timing fluxuates while cranking from -11 to i've seen pos 3.0 but its normally in the negatives. I don't quite know what these values read but figured i'd share them lt and sh term fuel trim read 0.0 MAF wasn't hooked up so that didn't read anything

05-01-2012, 06:28 PM
also all 4 O2 sensors read something even though i deleted the rear ones

05-01-2012, 06:31 PM
also had someone else try to start it for me while i took a look and when all was said and done openin the throttlebody resulted in a slight bit of white smoke coming out...

05-01-2012, 08:02 PM

05-01-2012, 10:16 PM
which ground i can check them tomorrow but i haven't undone any of them

05-01-2012, 10:41 PM
put your stock TB on and try to start it.. if it fires right up, you know where to go from there...

05-02-2012, 12:27 AM
stock throttle body broke have no way to fix it... Any reason particualar that you say to put the stock throttle body on?

05-02-2012, 01:01 AM
On the live scan what does your TPS read? Are ALL of your sensors hooked up?

05-02-2012, 01:36 AM
live scan tps read 0 when not touched and 100% when to the floor i also tested the it with a multimeter also so thats right, only things not hooked up to connectors are the emissions i got rid of. I was hoping the scanner would show IAC but aparently not....

05-02-2012, 11:40 AM
stock throttle body broke have no way to fix it... Any reason particualar that you say to put the stock throttle body on?

The XFI280 is still a decent sized cam for a 350/355. idle issues will still occur. An aftermarket TB that does have the idle air passages correct will only increase the headache of tuning the idle. Unless you fix the issue and determine nothing has changed, the idle BLMs and ability to idle stably will be hampered.

05-02-2012, 12:51 PM
Dose the white smoke coming out of the exhaust smell at all? Does it smell like coolant or Raw fuel? Have you tried removing the radiator cap after you try to start it and make it run for a few minutes to see if the cooling system is pressurized? Not like pressurized because of heat but because of compressed air.

05-02-2012, 02:28 PM
white smoke only comes out sometimes its fuel smell, i'm just at a lost right now fuel pressure gauge shows 43.5 like its suppose to but it drops quickly no leaking injectors but it seems like the gauge itself is leaking at the shrader valve so imma take the gauge off and take a look at it

05-02-2012, 06:55 PM

I got the car "running" long enough to take this video of some readings, i feel like the map sensor is high, also my plugs are still fouling out even after swapping to the stock injectors that don't leak

and yes i have spark, now i'm not sure if its strong enough though?

05-02-2012, 09:39 PM
anyone? I've read that the MAP with car not running is around the outside pressure but even then its low outdoor pressure was almost 30"hg today, The whole time i had it "running" it read about the same thing, which seems like it would cause my excessive fuel i think.... My new plugs are already fouled with gas and my oil... yeah thats a different story drained it don't wanna throw in new oil until i figure out why i'm having excessive gas

05-02-2012, 10:55 PM
come on can anyone make sense of any of this?