900hp lt1 build not going so good need help asap!!!
10-13-2011, 07:13 PM
#1
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900hp lt1 build not going so good need help asap!!! Hey fellas, well i have done everything in my power to try to fix the issue, what im about to post is kinda long but youll need every bit of info to figure this one out.
3 years ago i bought this awesome 97 30th ann z28, it had a 355 and a powerdyne on it, the car ran like a raped ape and i was at the dyno when i saw the car put down 455 and 509 to the wheels on 8 psi. now i talked to the kid that owned it and made him an offer blah blah blah. well he took it. i had the car for all of two weeks ran 11 flat on street tires blah blah blah well one day i decided to step up to 42# injectors and a 12 psi pulley, i called ed write and had him do me up a pcm for plug and play. well i threw the pcm in, along with the injectors and pulley went to start the car up and it had a hard time starting, finally got it to idle and took it for a test drive . . . . i made it 5 feet before it died on me, wouldnt take a load to save its own life.
so i took everything off cuz it was my daily at the time so that i still had a car to drive, and when i put all the old stuff back on it still wouldnt take a load. so i trailered it to LMR in houston to have it dyno tuned thinking i fucked the computer up some how, the thing put down 292 and 309 after 3 hours of trying to figure out the issue!!!!! i lost 300 horse some how and i dont know why. it has been completely redone with a 383 billet stroker and a 80mm turbo. i have done everything possible to get this thing perfect. no cheap parts at all. full fuel system, ignition system, you name it its on the car.
after a week of tuning and diagnostics and replacing every part on the ignition side it still wont take a load, runs great untill closed loop then runs a little rough at idle but when you try to drive it it spits pops and bangs like im holding some kind of two step button. if im making 200 wheel im doing good.
i have replaced the pcm thinking that was fucked and still no luck we have copied other turbo lt1 tunes to see if it would help and nothing wont boost, wont take a load at all. new opti, new coil, new icm, new pcm, new plugs and wires no grounding issues on any wires, it has a versafueler to run my low impedence 95# injectors and i have tested all the connections with noid lights and all injectors are hitting, i dont get any missfire at idle untill it goes under a load.
what the ***** is wrong with this thing??!!!! harness issues, pcm issues???!!!! i have done every test with my DVOM and everything is getting what it should be i need help so badly or im going to hang myself. i have searched a nd searched and searched. no luck. so lets see if any body has any ideas i havent tried.
thanks a ton for all the answers im open for anything.
3 years ago i bought this awesome 97 30th ann z28, it had a 355 and a powerdyne on it, the car ran like a raped ape and i was at the dyno when i saw the car put down 455 and 509 to the wheels on 8 psi. now i talked to the kid that owned it and made him an offer blah blah blah. well he took it. i had the car for all of two weeks ran 11 flat on street tires blah blah blah well one day i decided to step up to 42# injectors and a 12 psi pulley, i called ed write and had him do me up a pcm for plug and play. well i threw the pcm in, along with the injectors and pulley went to start the car up and it had a hard time starting, finally got it to idle and took it for a test drive . . . . i made it 5 feet before it died on me, wouldnt take a load to save its own life.
so i took everything off cuz it was my daily at the time so that i still had a car to drive, and when i put all the old stuff back on it still wouldnt take a load. so i trailered it to LMR in houston to have it dyno tuned thinking i fucked the computer up some how, the thing put down 292 and 309 after 3 hours of trying to figure out the issue!!!!! i lost 300 horse some how and i dont know why. it has been completely redone with a 383 billet stroker and a 80mm turbo. i have done everything possible to get this thing perfect. no cheap parts at all. full fuel system, ignition system, you name it its on the car.
after a week of tuning and diagnostics and replacing every part on the ignition side it still wont take a load, runs great untill closed loop then runs a little rough at idle but when you try to drive it it spits pops and bangs like im holding some kind of two step button. if im making 200 wheel im doing good.
i have replaced the pcm thinking that was fucked and still no luck we have copied other turbo lt1 tunes to see if it would help and nothing wont boost, wont take a load at all. new opti, new coil, new icm, new pcm, new plugs and wires no grounding issues on any wires, it has a versafueler to run my low impedence 95# injectors and i have tested all the connections with noid lights and all injectors are hitting, i dont get any missfire at idle untill it goes under a load.
what the ***** is wrong with this thing??!!!! harness issues, pcm issues???!!!! i have done every test with my DVOM and everything is getting what it should be i need help so badly or im going to hang myself. i have searched a nd searched and searched. no luck. so lets see if any body has any ideas i havent tried.
thanks a ton for all the answers im open for anything.
10-13-2011, 07:56 PM
#3
Scan the o2's. Sounds like they are going way lean, causing the car to dump fuel. When is the last time they were replaced? How does it run in open loop? You can unplug the o2's for the time being if you need it to get you around.
10-13-2011, 08:05 PM
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brand new o2's, i have replaced them at least 8 times since this problem started, something when i plugged in the the pcm and injectors back when i first got it is the reason its fucked up. the car was a beast before i did anything to it
10-13-2011, 08:23 PM
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nope coil was tested an another lt1 camaro and ran perfect, and my icm has been tested 100 times and tests perfect, we get it hot durring the test and it passes every time
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10-13-2011, 08:59 PM
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free revs great in open loop, once it goes to closed loop you can barley tell its acting funny but still free revs fine just not as good, its a tranzilla t56. and it sputters under load no matter what, sometimes at 2000 rpm and up or sometimes not until 4000 rpm. its so frustrating. it hasnt always popped and spit, it used to just act like it had no power then just recently started popping. thats why i went threw the entire ignition, replaced everything. starts up like new so wtf is that about? ha ha ha im going nuts!!!
10-13-2011, 09:32 PM
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free revs great in open loop, once it goes to closed loop you can barley tell its acting funny but still free revs fine just not as good, its a tranzilla t56. and it sputters under load no matter what, sometimes at 2000 rpm and up or sometimes not until 4000 rpm. its so frustrating. it hasnt always popped and spit, it used to just act like it had no power then just recently started popping. thats why i went threw the entire ignition, replaced everything. starts up like new so wtf is that about? ha ha ha im going nuts!!!
10-13-2011, 09:34 PM
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What are your IAT, MAP, IAC readings? Bad MAP can cause this.
What is your computer data spitting out/seeing? This should help you diagnose it. It sounds most likely a wiring or sensor issue. Plug the car into a computer and monitor it as it's running and look for anomalies.
What is your computer data spitting out/seeing? This should help you diagnose it. It sounds most likely a wiring or sensor issue. Plug the car into a computer and monitor it as it's running and look for anomalies.
10-13-2011, 10:36 PM
#13
The good news is it sounds electrical/ignition related under load since it revs freely on it's own, now we just have to run it down. sounds like you have another lt1 car around to test with. Take the TPS sensor and the map sensor from that lt1 car and put them on yours and see if that changes anything. and do a data log and see what changes, assuming you have something to look at all the parameters.
10-13-2011, 10:53 PM
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well i did have a test car, it was at the shop my car WAS at, i had to take it home cuz his shop is busy and my turd is in the way. and yes it revs freely but not like it did when i first got the car, you know how you can tell from the sound that its just not running right? yea i can just tell even though it revs freely that its not quite right. anyways if i need to i can just throw new parts at it i work at ed bozarth chevy dealership so i can get them on hand and test it out without buying parts 
ill test the map but the tps is the third one so im pretty damn sure its not that. id like to know if there is any electrical testing i can do on the harness at all at the plugs? my gut tells me its in the wiring somehow, just dont want to rip the car apart when i dont know where to start. i have done all the shoebox thread testing and all my readings are fine no funny business at the opti, coil, icm, or injector connections, i have not tested the maf connection nor any other connections. this pin drag test they are talking about how do i perform this test?
ill test the map but the tps is the third one so im pretty damn sure its not that. id like to know if there is any electrical testing i can do on the harness at all at the plugs? my gut tells me its in the wiring somehow, just dont want to rip the car apart when i dont know where to start. i have done all the shoebox thread testing and all my readings are fine no funny business at the opti, coil, icm, or injector connections, i have not tested the maf connection nor any other connections. this pin drag test they are talking about how do i perform this test?
10-13-2011, 10:56 PM
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and as for data logging all i have is a live data scanner it tells me pretty much everything, open loop closed loop, all o2's, maf, map, iat. how about the IAC? its the factory one, never had any problems with it before, what would cause any sensors to go bad when i plug in a new pcm? short them out or something?
10-13-2011, 11:00 PM
#16
I don't know what the pin drag test is, so can't help there.
Some of this stuff may be a good waste of time, but if you don't want to try another harness and still want to test yours then you can at least test for continuity (to make sure the wires aren't broken) You do that with a multi meter set on continuity. Then you take let's say your TPS sensor unplug it, then find the corresponding terminal on the PCM and when you touch the two ends for that corresponding wire , if the wire is good, you'll hear a beep. you can test all the major sensors that way.
are you getting any codes at all?
Some of this stuff may be a good waste of time, but if you don't want to try another harness and still want to test yours then you can at least test for continuity (to make sure the wires aren't broken) You do that with a multi meter set on continuity. Then you take let's say your TPS sensor unplug it, then find the corresponding terminal on the PCM and when you touch the two ends for that corresponding wire , if the wire is good, you'll hear a beep. you can test all the major sensors that way.
are you getting any codes at all?
10-13-2011, 11:06 PM
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the only ones that pop up so far are evap purge too low, but its because i recently took off all the smog ****. but other than that nothing, we were getting missfire random but we fixed that after we found a bad wire on the opti harness, i replaced the harness and the car idled and rev'ed way better. down low its as smooth as can be but once ya drive it **** hits the fan, ill check all the connections and see if any of them are bad. where are all the ground wires in the engine bay? i know of the main one that grounds the motor to the body, and then the one that is over by the pcm, any more?
and are there any major power and ground wires to check? inside the car, under the dash, in the engine bay?
and are there any major power and ground wires to check? inside the car, under the dash, in the engine bay?
10-13-2011, 11:15 PM
#18
grounds:
=pcm ground - on block by starter and knock sensor (btw-you do have the right knock sensor for obd2, right?)
=grounds on drivers side head - icm, etc.. and the strap that goes to the frame
= battery ground to block
= grounds inside car that go to the bottom driver and passenger side screws that hold the dash on.
=pcm ground - on block by starter and knock sensor (btw-you do have the right knock sensor for obd2, right?)
=grounds on drivers side head - icm, etc.. and the strap that goes to the frame
= battery ground to block
= grounds inside car that go to the bottom driver and passenger side screws that hold the dash on.
10-13-2011, 11:25 PM
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it has the factory knock sensor never had an issue there, now as for the one on the block for the pcm, i noticed its grounded to the body not the block, i remember it on my oil pan, dont remember how it got grounded to the frame!!! could that be it??
all other grounds are where they were when i got the car, coil and icm grounds are still on the head, the main strap is old but still where it is goes from the side of the water pump to the frame/body, i might replace that and see if that helps.
battery ground is the factory one i think, it is mounted to the motormount i think if i remember correctly, its been there since i got the car.
maybe its the pcm ground, now that i think of it when we were trying to start the car it wouldnt fire just cranked and cranked, and i remembered there was that ground but totaly spaced the original spot, so i grounded it to body above the k member, is that ok??
all other grounds are where they were when i got the car, coil and icm grounds are still on the head, the main strap is old but still where it is goes from the side of the water pump to the frame/body, i might replace that and see if that helps.
battery ground is the factory one i think, it is mounted to the motormount i think if i remember correctly, its been there since i got the car.
maybe its the pcm ground, now that i think of it when we were trying to start the car it wouldnt fire just cranked and cranked, and i remembered there was that ground but totaly spaced the original spot, so i grounded it to body above the k member, is that ok??