crookedbowtie

96' LT1. starts right up everytime I turn the key, then dies. If I catch it just right I can keep it going by putting my foot into it and keeping it there, but as soon as I let up...dead. What do I need to check or replace?

OreoLt1

iTrader: (11)

Sounds like an IAC problem(idla air control valve). That is the number one symptom of an IAC fault because it can't open to adjust for the amt. of air to let into the enigne to let it idle.

But if you crack open the throttle your compensating for the faulty valve by allowing air in yourself. Try having someone start the car for you and at the same time tap(TAP moderately but don't haul off and wack the crap out of it) on the IAC with a small hammer or an extension. If it then idles or idles half *** there is you issue.

crookedbowtie

Ok, It will now start and run every time. Forgot to mention this is a swap and the motor has never run with the reprogram and I never saw it run in the first place and I guess the pcm just had to do a lot of learning. It is running extremely rich and surging a little (I believe from running rich can't find any apparent vacuum leaks). The fuel pressure comes in at 43.5psi until it starts running it jumps to 70-90psi. I suspect a bad fuel pressure regulator.

If I hook a vacuum pump up to it and pull 14 hg it bleeds off rather quickly, This leads me to believe that as the motor pushes more voltage through to the fuel pump (255lph Walbro) the pressure increases to maximum 80psi and the leaky vacuum diaphragm in the regulator just plain doesn't control fuel pressure in regards to engine vacuum at all.

Any thoughts or comments helpful, and suggestions on what fuel pressure regulator to get.

BlownEarDrums

iTrader: (2)

What year, motor, and mods are done to it? Do you have all your sensors plugged in and functioning correctly? (oxygen sensors, MAF...) Are you running speed density or mass air, closed, loop open loop?

crookedbowtie

96' Firebird formula motor, Running open loop, no cats or emissions, headers dual 2 1/2in pipes to 50 series flows 3in. out, cold air box w K&N, pcm reworked by CP wire, emissions and rear o2s deleted and re calibrated for the exhaust and intake, still using the MAF sensor and every sensor that is needed is hooked up. I just received a new Aeromotive regulator, and a Trickflow air inlet elbow ( the stocker is questionable). Input welcome and I will update with the results of the regulator for future reference.

crookedbowtie

Ok you can hit me with the stupid stick!! Shiny new Aeromotive fuel pressure regulator....not the solution. I am a dumb *** and did not pay attention to the tiny fuel return line that 80's Toyota 4runners come with. Bigger return line problem solved. At least the Aeromotive piece is a nice unit and am glad I now have adjust ability....the trickflow air inlet elbow looks better too!


How long does it take all your motors to idle down? This one seems to "hang" for a while and then idle kind of high. Haven't let it warm up yet. Should it step down more when warm?

crookedbowtie

Damn this POS. I thought it was solved. Started up several times ran great. Now it will just crank and crank and crank and crank and crank and won't start....not even on starter fluid or with the MAF plugged or unplugged!!! I thought it might be flooded so I pulled a pllug black and sooty, but not wet with gas. I checked for spark, injector pulse, and I have fuel pressure and the motor turns over. I am giving up tonight and am extremely frustrated please help me this LT1 is is kicking my butt!

crookedbowtie

My battery voltage is in the 11's. The alternator wasn't even putting out twelve volts. How sensitive to voltage are these LT1s for starting purposes. It cranks fast, but maybe not enough to fire?

BlownEarDrums

iTrader: (2)

So do you have spark? if it wont start on starter fluid you have no spark. Only take three things to make a engine run. Fuel, compression and spark... I would check your Coil and ICM and see if they are the culprit.

BlownEarDrums

iTrader: (2)

Put a battery charger on it and get the battery back up.

tufflt1

iTrader: (5)

We are in the same situation here crookedbotie, my car will start and just turn off on its own. My car is completely stock though, this problem is driving me CRAZY!!

crookedbowtie

Sorry to hear that TuffLT1 because I am sure you are as frustrated as I am.

BlownEarDrums, I will try to start it on the charger when I get home. Yes it is getting spark, but maybe not enough. Spark is kind of a yellowish maroon. Wondering if the plugs are fouled, although they are not wet, just sooty. I am going to have the alternator tested as well it is not putting out. Easy ways to check the ignition module? The noid light confirms injector pulsing and I have tried low and high fuel pressure, I tested all the injectors with the light and and a 9volt every one lights and clicks. Vats has been removed from the computer so it shouldn't be that.

crookedbowtie

Ok, fresh battery charge. She starts and runs good, but the alternator is only pushing 11.75 volts...not so good. Apparently she just wasn't getting enough spark. I am going down to have my alternator load tested and probably drop another $140 into the LT money pit. This is adding up for sure. What do they say...Make a budget and triple it, make a time goal and double it...yep I'm there! It will all be worth it to have the meanest daily driven convertible Toyota 4runner around. Kind of a waste of an LT1, don't hate me, everything else I drive is a chevy/gmc. I liked everything about the Runner except the anemic 4 banger

BlownEarDrums

iTrader: (2)

Glad to hear you got it running. Maybe look into a junkyard unit.. much cheaper and last a good wile. Some time you might even find a brand new on in a wrecked car....


tufflt1: Is your battery strong?

crookedbowtie

BlownEarDrums, my battery is strong less than 6 months old and a red top Optima. I ran it in a different rig and never had an issue. It starts and seems to run fine now, but my alternator is not charging. It is a brand new today alternator my other one failed on the Autozone tester. The dead one pushed 11.75 volts and the new one...11.5 WTF. I checked the signal wire to it with the key in the run position using a voltmeter, noid light and a test light, no sign of life. Can I just run a switched ignition wire to this or will that harm it?

1995Transamconvert

I am having a similiar problem. Mine just died one day. New optispark,tps, inlet temp. sensor, and plugs, then ran fine. Now it just cuts off whenever it feels like it. Can get it started (sometimes) then put it in gear (auto) and it dies again. It's not reliable, when it runs, its strong...

Does this sound like IAC?

crookedbowtie

Hooked straight battery power to the alternator signal wire. Seems like I have to turn quite a few RPMs to get any kind of voltage above 12volts, but I was seeing 13.6. This may be because I drained the battery from running it to check the voltage earlier and it is having to overcome that before it can reach its full potential ( everything hovers around 11.75v which is just barely enough to start the motor and run it) . I am not getting a signal from the PCM for the alternator in the run position. If that is my only problem I will just bypass it with switched ignition power ( I don't know how to make the PCM send the signal). Also after I revved it for a while the motor was surging a bit....ran fine before. And there is a noise like a squealing/groaning that I couldn't tell whether it was from the PS pump or the alternator, but it is still there with the new alternator so it must be the PS pump GRRRR! Maybe I got a bad new alternator, but how likely is that? Right now I am thinking my old one may have been fine even though it conveniently tested bad at Auto Stoners__Zone:bs:. I am charging my battery again to see if it will all go away with a full charge and a good (maybe), at least new, alternator. I may just drive it off a cliff if I can get it out of my driveway:!

BlownEarDrums

iTrader: (2)

What you want to do to fool the alternator is run a 12v wire from inside the fuse box to the "signal" wire on the alternator. The alternator needs to see a voltage drop to be able to adjust the power to the brushes and thus generate power. If it still is not making power consider the alt dead. LT1's are VERY VERY VERY sensitive to voltage issues. As for the whine, it may be the alternator or another device on the belt drive system. Get your battery back up to voltage and try the above.

BlownEarDrums

iTrader: (2)

If you give it more gas when you put it in gear does it still die?

Is your SES light on?

crookedbowtie

BlownEarDrums, I understand the signal wire turns on the alternator. What I have learned since my last post is that the LT1 cars actually use the generator light in the dash as a resistor. Supposedly this drops the voltage signal wire has to have the resistance to drop the voltage because the alternator needs to see less than 12 volts or it messes with the regulator and ends up putting out too many volts.

I haven't figured out how exactly to make this work to my advantage, but have figured out a 194 or 168 (used in the dash) light bulb has a higher cold resistance than an ignition ballast resistor .5 ohms @20K vs. .2 ohms @ 20K. I was told to wire this light inline as a resistor on the signal wire to a switched ignition circuit. Haven't figured out exactly how to make this work yet. Any switched ignition source should register a voltage drop since it is in the system, right? Do you know how to wire this correctly? Does just wiring it to a fuse box 12 volt source do the same thing?