96 LT1 bogging issues
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96 LT1 bogging issues
I drove my car in the rain for the first time since a new motor was put in and was doing fine until I hit some accumulated water, ran rough at the light (5-600 rpm) had to put it in N and give it gas so it wouldnt stall- drove for about 2 miles and it cleared up, went out for lunch and instantlly had the same issue but never cleared up- if I give it gas the power is back but with a light or no pedal it seems like its starving for fuel or something is blocked- any ideas? I did also put a new opti spark and water pump in but I did notice even before the opti swap that when I punch it it bogs with no power, I was told it was the opti and that was not it- so actually have 2 issues if anyone can help- I figured the punching of the pedal with hesitant power could be a fouled plug? any help I would really appreciate it- Ive got more into this car then it will ever be worth so I need to figure it out. Thank you for your help.
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Evan if you have low miles they are 20 years old. Let us know. 
might want see if your cat is plugged too
Last edited by antfarmer2; Jul 22, 2015 at 08:52 AM.
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The car has 90k but the engine is brand new. I don't have any maint history on it. I've owned it for a year n only put 2k on the old motor before it blew. I've replaced the opti already. The 02 are on the exhaust correct? Would you happen to have a diagram on were they are? I really appreciate your time and following this through. Thanks again
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The car has 90k but the engine is brand new. I don't have any maint history on it. I've owned it for a year n only put 2k on the old motor before it blew. I've replaced the opti already. The 02 are on the exhaust correct? Would you happen to have a diagram on were they are? I really appreciate your time and following this through. Thanks again
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Le Mans Master
Joined: Dec 2006
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From: H-Town Texas
Hitting the water may or may not have anything to do with it. Could be just one of those things.
From your description, pre opti and post opti, I'm thinking about fuel pump. I know mine would act up sort of like this intermittantly, until one day it just gave out. Need to pressure test the fuel, running, not running, and warm. Of course, if it's not acting up, it won't show.
If the water did have anything to do with it, my first suspicion would be ground wires. It's really difficult for street water to hit the opti. The water has to get over/across the frame rail, past the PS cooler, the damper, and the serp belt. Then the water pump covers the top half. Even then, the unit is sealed, so a splash of water isn't going to get in it.
Other than this, just double check all the connections, and look for vacuum leaks.
O2 sensors are pretty quick to throw codes.
From your description, pre opti and post opti, I'm thinking about fuel pump. I know mine would act up sort of like this intermittantly, until one day it just gave out. Need to pressure test the fuel, running, not running, and warm. Of course, if it's not acting up, it won't show.
If the water did have anything to do with it, my first suspicion would be ground wires. It's really difficult for street water to hit the opti. The water has to get over/across the frame rail, past the PS cooler, the damper, and the serp belt. Then the water pump covers the top half. Even then, the unit is sealed, so a splash of water isn't going to get in it.
Other than this, just double check all the connections, and look for vacuum leaks.
O2 sensors are pretty quick to throw codes.
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When i first put the engine in prior to hitting the water I had punched it n it sounded like a loud bang n the car was done changed the opti n harness n everything else on the way back out, water pump idlers etc. Car runs great until i get on it, the issue with hitting the water has stopped but still when hitting the gas she wants to go but pops n lerches, if i slowly press down she gets going. Fuel pressure is good but I'm thinking my plugs are fouled would this issue cause the plugs to do this? Thanks for any info. I appreciate it
Le Mans Master
Joined: Dec 2006
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From: H-Town Texas
When i first put the engine in prior to hitting the water I had punched it n it sounded like a loud bang n the car was done changed the opti n harness n everything else on the way back out, water pump idlers etc. Car runs great until i get on it, the issue with hitting the water has stopped but still when hitting the gas she wants to go but pops n lerches, if i slowly press down she gets going. Fuel pressure is good but I'm thinking my plugs are fouled would this issue cause the plugs to do this? Thanks for any info. I appreciate it
Of course plugs being fouled could do this, but the real question would be what's fouling the plugs? If they were old, that's one thing, but new is something else. You should probably pull them and see if they are fuel soaked. Do a spark check as well. Though, if the car idles fine, and gradually accelerates fine, then spark is probably not the issue. It sounds like the issue is that instant demand for fuel on hard acceleration, which has me thinking that the fuel pump may be weak, of course I could be wrong. Maybe revisit the FPR and check for fuel in the vacuum line.
Other thoughts are the MAF, grounds, and of course the new timing set (I hope very much for you that this is not the case)
I'm just throwing out some ideas. I keep going to that old fuel pump because that seems to be the one thing that isn't new, but again, if pressure is good, it's good.
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When i first put the engine in prior to hitting the water I had punched it n it sounded like a loud bang n the car was done changed the opti n harness n everything else on the way back out, water pump idlers etc. Car runs great until i get on it, the issue with hitting the water has stopped but still when hitting the gas she wants to go but pops n lerches, if i slowly press down she gets going. Fuel pressure is good but I'm thinking my plugs are fouled would this issue cause the plugs to do this? Thanks for any info. I appreciate it
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I'm going to guess that when you checked the FP, you rev'd it quickly as well and had no big drop in pressure.
Of course plugs being fouled could do this, but the real question would be what's fouling the plugs? If they were old, that's one thing, but new is something else. You should probably pull them and see if they are fuel soaked. Do a spark check as well. Though, if the car idles fine, and gradually accelerates fine, then spark is probably not the issue. It sounds like the issue is that instant demand for fuel on hard acceleration, which has me thinking that the fuel pump may be weak, of course I could be wrong. Maybe revisit the FPR and check for fuel in the vacuum line.
Other thoughts are the MAF, grounds, and of course the new timing set (I hope very much for you that this is not the case)
I'm just throwing out some ideas. I keep going to that old fuel pump because that seems to be the one thing that isn't new, but again, if pressure is good, it's good.
Of course plugs being fouled could do this, but the real question would be what's fouling the plugs? If they were old, that's one thing, but new is something else. You should probably pull them and see if they are fuel soaked. Do a spark check as well. Though, if the car idles fine, and gradually accelerates fine, then spark is probably not the issue. It sounds like the issue is that instant demand for fuel on hard acceleration, which has me thinking that the fuel pump may be weak, of course I could be wrong. Maybe revisit the FPR and check for fuel in the vacuum line.
Other thoughts are the MAF, grounds, and of course the new timing set (I hope very much for you that this is not the case)
I'm just throwing out some ideas. I keep going to that old fuel pump because that seems to be the one thing that isn't new, but again, if pressure is good, it's good.
Le Mans Master
Joined: Dec 2006
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From: H-Town Texas
Forgive me for snooping, but I looked up some previous threads about your car. You replaced an LT4 with a crate LT1. In one post you said that they took some parts off the LT4 and put them on the LT1. Which parts specifically? Heads, cam, intake? Was this a short block or a long block?
I ask, because of it was the LT1 long block, and you have the LT1 heads,cam,intake but the LT4 ECM, that may be your issue. There are some substantial differences between the two. Grandsportregistry.com has some good info on these differences. Point is the ECM is tuned for the LT4 and could be causing some driveability issues. Might be a good idea to find a tuner and do a wideband base line and see what the ECM is doing, if this has not already been done.
I ask, because of it was the LT1 long block, and you have the LT1 heads,cam,intake but the LT4 ECM, that may be your issue. There are some substantial differences between the two. Grandsportregistry.com has some good info on these differences. Point is the ECM is tuned for the LT4 and could be causing some driveability issues. Might be a good idea to find a tuner and do a wideband base line and see what the ECM is doing, if this has not already been done.
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Actually found out they changed nothing and left all the LT1 stuff on except for my throttle body which I'm assuming is from the original lt1 this is the 3rd motor in 90k miles. I'm not sure what happened to the first motor but i bought it with an lt4 that blew n put back a new lt1 crate motor.
Le Mans Master
Joined: Dec 2006
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From: H-Town Texas
Actually found out they changed nothing and left all the LT1 stuff on except for my throttle body which I'm assuming is from the original lt1 this is the 3rd motor in 90k miles. I'm not sure what happened to the first motor but i bought it with an lt4 that blew n put back a new lt1 crate motor.
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Now that your telling me this when i brought the car back 200 miles after the new engine from the opti dieing they said had a fuel leak n that's when all that stuff got changed, he told me after the repair my fuel pressure was good now it was 40lbs? Obviously too much correct? How would i lower that? I refuse to bring it back because they Hebe gotten 14k out of me from the start plus the original 11k for buying the car they broke my tilt, my shifter my head light cover n it never had a fuel issue until after the motor. They don't want to take responsibility n they lied n said they were Chevy certified and they were not. Probably going to find a good speed shop but i appreciate your help.
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Fuel pressue should be around 40#
Did the new engine come with new knock sensors? If not I would replace them fifty bucks and
For a hundred bucks from rock auto you can get the o2's and enjoy your car.
Did the new engine come with new knock sensors? If not I would replace them fifty bucks and
For a hundred bucks from rock auto you can get the o2's and enjoy your car.
Last edited by antfarmer2; Jul 26, 2015 at 03:57 PM.