Modified lt1 issues! Help!!
Modified lt1 issues! Help!! Ok guys, so I got a 96 z28 (383 stroker, 30# injectors, larger fuel pump (can't remember off the top of my head what it is)) and the list goes on and on. Problem is it's running extremely rich, like will choke you out if you stand behind it. A lot of fuel in the oil and when I come to a stop or let it idle for a few minutes, it will drop oil pressure and try and die. Can keep it running but it's not right. I've used a fuel pressure gauge already and tested good. Held a consistent pressure and didn't drop any. Where should I go next?? Fuel pressure regulator? Any sensors?
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as Caprice notes, if you have not had a tune for the mods, especially with the larger injectors, it will run pig rich.
if it has been tuned correctly...check for pre 02 exhaust leaks
if you smell gas in oil...find the problem. continued operation will cause engine damage
if it has been tuned correctly...check for pre 02 exhaust leaks
if you smell gas in oil...find the problem. continued operation will cause engine damage
I was told it was a mail order tune from pcm for less by the previous owner, but there is no telling really. That was my original plan but can't find anyone to check the tune and re-tune it! Seems like no one will touch an lt anymore
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I don't use PCM4Less but if they are like other tuners there is likely a sticker they put on the PCM with some form of code/number identifying the file. This doesn't mean that tune could have been flashed over but you could at least contact PCM4less with any ?;s if you did find some form of ID
you have a 96 so you could go buy a OBD2 code reader (assuming you are not running a obd1 tune)
data log would help the most to see wtf fuel, 02, etc. 411 is.
you bought a modded car with little background on what exactly is done and was it done right.
could your tune be wrong for the injector size you have, yes
could a injector(s) be puking fuel, yes
could you have exhaust leaks pre-02, yes
at the very least you need to turn the above to confirmed "no"
you have a 96 so you could go buy a OBD2 code reader (assuming you are not running a obd1 tune)
data log would help the most to see wtf fuel, 02, etc. 411 is.
you bought a modded car with little background on what exactly is done and was it done right.
could your tune be wrong for the injector size you have, yes
could a injector(s) be puking fuel, yes
could you have exhaust leaks pre-02, yes
at the very least you need to turn the above to confirmed "no"
I did buy the car already built 
but it has good suspension for a start. Going to ls swap this winter and the car already had a small cage and every option BMR Suspension offers... I really just need to get this thing back running good so I can pull it out and sell it! I do have every recipe for the car though so that helps. I also don't have 02 sensors, so that eliminates that
but it has good suspension for a start. Going to ls swap this winter and the car already had a small cage and every option BMR Suspension offers... I really just need to get this thing back running good so I can pull it out and sell it! I do have every recipe for the car though so that helps. I also don't have 02 sensors, so that eliminates that How do you test the regulator ? I believe it was start the car then pull the vaccum line off of the regulator and if fuel comes out of it at idle it's bad? Someone correct me if I wrong ?
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Verdad Gallardo TECH Veteran
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from this side of the internet, as you give further details, we can guess based on that new tid bit...
no 02's...
you need to confirm the tune you have is for the current mods
beyond that, possible mechanical issues in fuel delivery.
you say you checked FP....what was it and is it with vac line on or off?
what is FP under sustained WOT driving?
No 02s , and I'll check on the tune when I get home to check the FPR. Maybe there is a model number or something where they could tell me what I got. And the FP, I only test at idle and a quick throttle snap. Idle was around 38psi and was told it dropped to low 30s when throttle was snapped( my grandfather was watching the gauge and not so sure if that was correct or not) but I can re-do it to get exact numbers... I'll test the FPR when I get home in a few hours and post my results
Believe me I already have. Changed it three times last month. I just drove it a few times and did do 2 autocross events. Since the oil pressure has started to drop from it, I haven't drove it other than moving it around on and off my lift.
Also have fouled 2 sets of plugs since I've had it... It's just the rear 4 are really black and the front 4 seem to be running lean? Really white looking . Any idea?
Hope I am wrong but from what you are saying about this car and if actually put together with O2 delete I would be afraid it was built by an utter incompetent with more money than brains.
I would go a step further and say if you can sort this out you should not even consider an LS swap.
Test the fuel pressure with the engine off, cycle the key to on a few times and it should come up to 43-45psi, maybe slightly less due to no alternator output. 38 at idle is reasonable. Run it as little as possible because if it really is polluting the oil, that rich can hurt the motor. If you really want to start it check it with the vac. line disconnected and plugged.
The 30psi was hopefully a high vacuum spike when the throttle was closed.
The LT1 IS CAPABLE and the LS swap a bandwagon too quickly jumped on.
A halfassed 383 LS1 should be better than a stockish LS1 and starting with what you have should be cheaper to get to a serious result than starting all over.
On the fuel pressure it might help to understand the regulator actually does NOT change fuel pressure, but rather keeps it steady in relation to manifold pressure otherwise at times of high vacuum which is low load the vacuum would suck extra fuel. What we measure is pressure relative to atmospheric pressure.
I would go a step further and say if you can sort this out you should not even consider an LS swap.
Test the fuel pressure with the engine off, cycle the key to on a few times and it should come up to 43-45psi, maybe slightly less due to no alternator output. 38 at idle is reasonable. Run it as little as possible because if it really is polluting the oil, that rich can hurt the motor. If you really want to start it check it with the vac. line disconnected and plugged.
The 30psi was hopefully a high vacuum spike when the throttle was closed.
The LT1 IS CAPABLE and the LS swap a bandwagon too quickly jumped on.
A halfassed 383 LS1 should be better than a stockish LS1 and starting with what you have should be cheaper to get to a serious result than starting all over.
On the fuel pressure it might help to understand the regulator actually does NOT change fuel pressure, but rather keeps it steady in relation to manifold pressure otherwise at times of high vacuum which is low load the vacuum would suck extra fuel. What we measure is pressure relative to atmospheric pressure.
Does it have a Monoblade TB on it or an aftermarket one with the blades opened to set idle? If the TB is opened or in the case of a monoblade the IAC distribution system cut out this is the result.
Guys thanks for all the help! As soon as I get home from work here I'm gonna get straight to checking everything and give exact numbers so hopefully we can figure this out. Later on tonight I can also give I full build list to you all so you can Help me sort through what all I have and what all I need
Ok, so tested the regulator, checked fuel pressure again, and checked injectors.
Fuel pressure:
Idle: 34
Throttle snap(wot): 40
After snap it would drop to low 20s for a sec the come back?
Regulator tested good, didn't leak any fuel and had a good vaccum.
Injector test I did after I started it and had to move it to another garage bay for some other stuff, so I'm going to re do it tomorrow.. Just to make sure. I did test them all and they all read about 14.5 ohms with the car off.. Good or bad??
Fuel pressure:
Idle: 34
Throttle snap(wot): 40
After snap it would drop to low 20s for a sec the come back?
Regulator tested good, didn't leak any fuel and had a good vaccum.
Injector test I did after I started it and had to move it to another garage bay for some other stuff, so I'm going to re do it tomorrow.. Just to make sure. I did test them all and they all read about 14.5 ohms with the car off.. Good or bad??
Are 02s really going to make that big of a difference? I mean, this car will choke you out standing behind it, and even leaning over the motor bay. I know stock injectors are 24#, mine are only 30#. How do I check them properly? They all read the same thing but could it just be they are to big or what?