Fireslash

Okay so finally got the car to start today. Many times but I cannot keep it running more than a couple of seconds.






I am not sure where to go from here but does anyone have some suggestions. I'm sure many things have been posted before but I can't find anything that is helping my current situation.


Car has cold air intake, bigger cam, and long tube headers as the upgrades for now. Every monitor is plugged in except for the incoming air temperature or the one that goes to the intake which I have no place to plug it into my cold air intake.
The car only has headers on it right now, was trying to get it running before I spent my time throwing the rest of it on. Could this cause any problems?


The computer is a 411 computer with a tune in by Frost
I cut the starter enable relay wires and connected them both at the relay and the part going to the car. Should I unconnect one of these.
I can hear the fuel pump prime when turning the key. Tightened all of the gas lines down as I had a leak and figured that may be part of the problem. Didn't do much but resolve losing gas.
I bought a 255 retrofit fuel pump. Wired it to my old fuel pump harness. Do I need a hotwire kit to keep gas pressure up after starting?


Thanks in advance, it sounded great for those couple of seconds wish it would just idle for my though.

Fireslash

Also its an automatic that used to be a manual. Not sure if that's going to make any difference keeping it running, but I do have to press in the clutch peddle to get the starter working. Nothing has been wired to the automatic neutral safety switch as of yet as I wanted to get it running before I made matters worse or more confusing.

QwkTrip

iTrader: (22)

I'm not sure how the GM engine management works, but with my Holley HP EFI the air temp will default to -40C if the air temp sensor is not plugged in. This causes the engine to run super rich and die.

This is how I installed air temp sensor in my car.
https://www.thirdgen.org/forums/ltx-...ml#post5968331

Fireslash

Thank you ill go pick one up today and see if that fixes it.

cypris09

iTrader: (1)

Just to clarify. No mass airflow sensor plugged in? And you have open headers? If you have open headers the o2 sensors will pick up the extra air and make the car dump fuel and it'll run super rich. Also with no maf sensor plugged in and if it's tuned to have one, then tall only make things worse.
Are you able to get the car to idle of you give it gas?
This is a mail order tune from frost?

I ask only because I had a mail order tune and it was good for the most part but I have since had several data logs to fine tune it. My biggest thing was getting it to idle on startup. I always had to give it a little bit of gas to get it to idle on its own for the first little bit.

Fireslash

Maf is plugged in so is the rear o2 sensors. Will start putting on the rest of the exhaust if it quits raining tomorrow.

Got the IAT sensor but need it to quit raining before I can do much today

Tried playing with the throttle to keep it going but it doesn't run long enough to do much good

cypris09

iTrader: (1)

Just some things you can double check. Fuel pressure and if injectors are firing. ( use noid lights or a test light). Double check on vats.

Fireslash

Fuel pressure doesn't cut out. It's around 50 psi with prime then hops up to 55psi when it attempts to run.

IAT sensor didn't fix the problem but it sure starts easier so that's good.

Tried to throttle it with my buddies help and sometimes it revs up other times it doesn't. So I'm gonna get a new tps sensor and see if that helps. When looking up functions or problems with bad sensors it seems a lot can make the engine stall so may be replacing one at a time till I find the problem.

cypris09

iTrader: (1)

Tps was gonna be mask next question. Do you have access to a computer at all? Could help narrow down sensors if that is indeed the problem.

redmaroz

iTrader: (4)

I had a similar issue when I first put mine together and it was caused by a vacuum leak. Double check the openings on the throttle body, and the ones on the intake right behind the tb. They should be capped or routed as part of the pcv system. It would run for just a couple seconds then die off. Then I realized that the port on the drivers side of the intake was open. I put a vacuum cap on it and it solved the problem. Good luck.

Fireslash

I've capped all the vacuum lines that I can find as I was hoping it was the same kind of deal. It runs longer but still dies after a few seconds.

The speartech harness came with an obd2 and I picked up a cheap scanner today. I got 4 codes.

P0117 x 2. engine coolant sensor 1 circuit high. No clue but I doubt it would stop the engine.

P0122 throttle position sensor switch A circuit low. I was messing with the idle set screw as it has a decent size cam, and doing the tps relearn so that could have caused it.

P0336 crankshaft position sensor A circuit range performance.

Plan in getting a new crank position sensor and putting it in next week. Will also scour over it again and make sure all the vacuum lines are capped and capped well.

I'm at the point were I need to get it running on my own without too much more cost or take it to a shop. I won't be able to afford both if I slam too much more money on it. Though I would love to get it going all the way without taking it to a shop. Sort of torn over it as it's so damn close.

Fireslash

So I switched out of a bunch of sensors. No go.

Took it to a tuning. They looked at it and refused to touch it for 5 weeks saying I needed a new harness.

Proud owner of hp tuners now. It seems vats was not removed from the computer. Two clicks and she runs great.

five7kid

iTrader: (14)

Sometimes it's the little things in life...

cypris09

iTrader: (1)

Glad you figured it out. Time to go enjoy it!