Project 96 LT4
#21
Instructor
Thread Starter
History of the car is that it has been sitting for a while. I am going to guess almost 2 years just from looking at the receipts for work done.
Work done.
The opti was supposedly changed a year ago, but I see that the opti vent hose is not hooked up. Plug wires look newer. I need to pull plugs to see how they look.
I was told gas was old. Fuel tank is almost empty.
Plan is to siphon out gas to inspect and pressure test fuel system at shrader valve.
Jack up car and inspect 02 sensor connections, and knock sensors.
Check ICM, do Optispark testing and hope for the best.
She idles a little rough and I need to fix these items to get inspected.
The other thing is I am going to rebuild the steering column since the tilt is broken and may be causing ignition switch to malfunction. Car sometimes has a hard time turning off when key is turned to off position. When I readjust tilt it works.
Washed car last night and can tell it going to need a clay job and good polish and wax!
Any tips/advice are greatly welcomed. I followed Chstitan42 s post on his 96 LT4 and I am hoping it is not the opti but hey you never know.
Current Fault Log
------------------
P0141: O2 Sensor Heater Circuit (Bank 1 Sensor 2)
P0161: O2 Sensor Heater Circuit (Bank 2 Sensor 2)
P0300: Random/Multiple Cylinder Misfire Detected
Wish me luck.
Just took it for a spin and p0300 code came back. I reset it then drove again just around the block and it did not come back. I am almost out of gas so I think I am going to call it a day and then try tomorrow or later this weekend. I need to fix that steering wheel it still comes down and I don't think it will pass inspection.
Last edited by Indio Monk; 10-17-2016 at 07:24 PM. Reason: Pics and new info
#22
Instructor
Thread Starter
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Indio Monk (10-18-2016)
#25
Instructor
Thread Starter
#26
Burning Brakes
Thanks! Kg4fju! I think this maybe the issue. I looked at the lower Timing Cover I think that is what it is called and I can see the Crank Positioning sensor wire/connector. I am going to pull the intake and some hoses to get down there and check it out. I might have to also jack up engine a few inches per others that have had to check this. I hope I don't have to but they say there is only 4 motor mount bolts and that you really don't have to take the bolts completely off just loosen them to lift engine 1/2 inch or so. Hope to get to this Saturday or SUnday!
I would definitely verify the sensor's wire routing as I believe you said the OPTISPARK was replaced on your car.
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Indio Monk (10-18-2016)
#27
#28
Le Mans Master
In your first post you said it had been sitting for a couple of years. You added some Lucas product to the gas. Now the tank is nearly empty. You said you were going to check the fuel pressure and siphon off the gas.
Did you siphon off the gas or do you still have the 2 year old gas in it? At that age you may just be dealing with bad gas. I had a problem with a car that had been sitting and it was not starting very easily and missing and it cleared up as soon as I put new gas in it. It might be worth putting in some new gas to make sure.
Good luck.
Did you siphon off the gas or do you still have the 2 year old gas in it? At that age you may just be dealing with bad gas. I had a problem with a car that had been sitting and it was not starting very easily and missing and it cleared up as soon as I put new gas in it. It might be worth putting in some new gas to make sure.
Good luck.
#29
Instructor
Thread Starter
In your first post you said it had been sitting for a couple of years. You added some Lucas product to the gas. Now the tank is nearly empty. You said you were going to check the fuel pressure and siphon off the gas.
Did you siphon off the gas or do you still have the 2 year old gas in it? At that age you may just be dealing with bad gas. I had a problem with a car that had been sitting and it was not starting very easily and missing and it cleared up as soon as I put new gas in it. It might be worth putting in some new gas to make sure.
Good luck.
Did you siphon off the gas or do you still have the 2 year old gas in it? At that age you may just be dealing with bad gas. I had a problem with a car that had been sitting and it was not starting very easily and missing and it cleared up as soon as I put new gas in it. It might be worth putting in some new gas to make sure.
Good luck.
My steering wheel puller arrived at home but here I am at work .
Oh well hopefully I will get home by 9.
#30
Le Mans Master
The car was almost on empty and hit reserve yesterday, but seems like it ran better the more it was driven. I did a "bandit run" to the nearest gas station that is .5 miles from my house this morning. I put in 10 gallons of premium and ran it hard on some side roads. It seems like it is running better with the new gas. When I say better I mean that I don't feel the idle rumbling or trying to stall and when I get on it it seems like it pulls hard and smooth. I really need to compare with another LT4. I am going to try and hit up CHSTitan42 to see his LT4 in person and get a feel for what one should run like.
My steering wheel puller arrived at home but here I am at work .
Oh well hopefully I will get home by 9.
My steering wheel puller arrived at home but here I am at work .
Oh well hopefully I will get home by 9.
#31
Instructor
Thread Starter
I did have a O Sh@$t moment when I did a pressure test on the cooling system. At 16 psi I saw coolant leaking but I was lucky it was loose hose clamps. I tightened them and no more leaks after pressure test.
I asked my wife who knows how to drive cars fast to listen to the vette while I revved it to at least 4k rpm and then also hold it stead at 2k rpm. She said, "sounds smooth and I don't hear any misfires." No smoke, nada or weird sulfur smells. I think there is a vacuum leak and that I need to track down. I read another LT4 forum where some one crossed two spark plug wires I think 6 and 8 and that caused a p0303 but his car was running ROUGH and mine is not.
The diagnostics continues. I really want to take this out on the highway and just BLOW all this crap out and hopefully that will help!
Last edited by Indio Monk; 10-20-2016 at 08:38 PM. Reason: Pics
#32
It has been sitting two years I would not be hard on it for awile.
#33
Tech Contributor
Did you ohm check the plug wires? Also... #3 passes between the accessory bracket and the PS pump if it's still routed per the factory. It's subject to chaffing.
#34
TheCorvetteBen
Another tip is to get the car inside a dark garage, and with the lights up look for a spark plug arcing against something else. I that is the quickest way to find a problem between the spark plug and the distributor. That is IF the miss is spark related.
#35
Melting Slicks
okay, I just can't take it anymore....I kept hoping that your problems would cure themselves, those are the best problems, the ones that cure themselves....but since they haven't allow me to relate my own experience with a 96 LT4. Draw whatever conclusions you care to.
My steering column was bad too...so these cars may have similar mileage (little north of 100K ?). Pulled that sucker and replaced with a new one ...not that hard...but I digress.
Mine had a rat's *** cheapo... LOUD..."custom" exhaust...so when I pulled the exhaust and peered up the cats, guess what? no matrix in the drivers side...just an empty can. Later I found that one of the multitec injectors on that side leaked and probably melted and blew out that side cat's innards.
So one new exhaust...one new set of Bosch III injectors and one new cat later...
I decide to pull the valve covers for a little inspection....guess what...and this is on an engine with no apparent problems...one rocker was off the valve stem and one was partially off with damaged self alignment ears ...so two...possibly three (my memory fails me) stock LT4 rocker arms ....and yes, stock rocker arms may look like other rocker arms, but trust me, they are a one year, non adjustable pedestal design that interchange with NOTHING and have a price, if you can find them, to match...
So all is well, one would think. Then the OEM opti spark craps out. I found some receipts in the car that lead me to believe it was the original opti with one cap and rotor change. If the serpentine belt hadn't cut one of the ventilation hoses and the other hadn't deteriorated from oil and heat I believe that the opti would have still worked; as it was the brass terminals were green from water intrusion...yeah I know I never should have used a high pressure washer on the engine...
With everything off the front of the engine to access the opti and a repeat of the rocker arm issues, without any damage this time...thank god...further investigation was called for.
Pulled the camshaft. The last three lobes were rounded off, actually grooved by the lifter; so...one Hot Cam and a new set of lifters, new opti, new plug wires and new plugs, new water pump, new main Extreme Duty timing chain, new rod and main bearings and new oil pump and new canton road race pan...I'm back on the road and guess what?
Now I have a P0300 service engine light code "random misfire" and a smog test coming up...Yup I replaced the crank position sensor and in the process I found that I had run the sensor wire through the plug wires, or more accurately had led the plug wires so they surrounded the sensor wire...whatever, the result was the same.
Long story short, the P0300 never went away entirely...but once cleared, it stayed off long enough for the smog test and the Hot Cam (along with a new opti and ignition tune up and one new cat) passed California smog with flying colors.
Sooo....if there's any moral to this story, and I'm not sure there is, I'd consider pulling the valve covers...easy enough on an LT engine and checking for anything amiss there.
My steering column was bad too...so these cars may have similar mileage (little north of 100K ?). Pulled that sucker and replaced with a new one ...not that hard...but I digress.
Mine had a rat's *** cheapo... LOUD..."custom" exhaust...so when I pulled the exhaust and peered up the cats, guess what? no matrix in the drivers side...just an empty can. Later I found that one of the multitec injectors on that side leaked and probably melted and blew out that side cat's innards.
So one new exhaust...one new set of Bosch III injectors and one new cat later...
I decide to pull the valve covers for a little inspection....guess what...and this is on an engine with no apparent problems...one rocker was off the valve stem and one was partially off with damaged self alignment ears ...so two...possibly three (my memory fails me) stock LT4 rocker arms ....and yes, stock rocker arms may look like other rocker arms, but trust me, they are a one year, non adjustable pedestal design that interchange with NOTHING and have a price, if you can find them, to match...
So all is well, one would think. Then the OEM opti spark craps out. I found some receipts in the car that lead me to believe it was the original opti with one cap and rotor change. If the serpentine belt hadn't cut one of the ventilation hoses and the other hadn't deteriorated from oil and heat I believe that the opti would have still worked; as it was the brass terminals were green from water intrusion...yeah I know I never should have used a high pressure washer on the engine...
With everything off the front of the engine to access the opti and a repeat of the rocker arm issues, without any damage this time...thank god...further investigation was called for.
Pulled the camshaft. The last three lobes were rounded off, actually grooved by the lifter; so...one Hot Cam and a new set of lifters, new opti, new plug wires and new plugs, new water pump, new main Extreme Duty timing chain, new rod and main bearings and new oil pump and new canton road race pan...I'm back on the road and guess what?
Now I have a P0300 service engine light code "random misfire" and a smog test coming up...Yup I replaced the crank position sensor and in the process I found that I had run the sensor wire through the plug wires, or more accurately had led the plug wires so they surrounded the sensor wire...whatever, the result was the same.
Long story short, the P0300 never went away entirely...but once cleared, it stayed off long enough for the smog test and the Hot Cam (along with a new opti and ignition tune up and one new cat) passed California smog with flying colors.
Sooo....if there's any moral to this story, and I'm not sure there is, I'd consider pulling the valve covers...easy enough on an LT engine and checking for anything amiss there.
Last edited by mtwoolford; 10-20-2016 at 10:44 PM.
#36
Instructor
Thread Starter
#37
Instructor
Thread Starter
okay, I just can't take it anymore....I kept hoping that your problems would cure themselves, those are the best problems, the ones that cure themselves....but since they haven't allow me to relate my own experience with a 96 LT4. Draw whatever conclusions you care to.
My steering column was bad too...so these cars may have similar mileage (little north of 100K ?). Pulled that sucker and replaced with a new one ...not that hard...but I digress.
Mine had a rat's *** cheapo... LOUD..."custom" exhaust...so when I pulled the exhaust and peered up the cats, guess what? no matrix in the drivers side...just an empty can. Later I found that one of the multitec injectors on that side leaked and probably melted and blew out that side cat's innards.
So one new exhaust...one new set of Bosch III injectors and one new cat later...
I decide to pull the valve covers for a little inspection....guess what...and this is on an engine with no apparent problems...one rocker was off the valve stem and one was partially off with damaged self alignment ears ...so two...possibly three (my memory fails me) stock LT4 rocker arms ....and yes, stock rocker arms may look like other rocker arms, but trust me, they are a one year, non adjustable pedestal design that interchange with NOTHING and have a price, if you can find them, to match...
So all is well, one would think. Then the OEM opti spark craps out. I found some receipts in the car that lead me to believe it was the original opti with one cap and rotor change. If the serpentine belt hadn't cut one of the ventilation hoses and the other hadn't deteriorated from oil and heat I believe that the opti would have still worked; as it was the brass terminals were green from water intrusion...yeah I know I never should have used a high pressure washer on the engine...
With everything off the front of the engine to access the opti and a repeat of the rocker arm issues, without any damage this time...thank god...further investigation was called for.
Pulled the camshaft. The last three lobes were rounded off, actually grooved by the lifter; so...one Hot Cam and a new set of lifters, new opti, new plug wires and new plugs, new water pump, new main Extreme Duty timing chain, new rod and main bearings and new oil pump and new canton road race pan...I'm back on the road and guess what?
Now I have a P0300 service engine light code "random misfire" and a smog test coming up...Yup I replaced the crank position sensor and in the process I found that I had run the sensor wire through the plug wires, or more accurately had led the plug wires so they surrounded the sensor wire...whatever, the result was the same.
Long story short, the P0300 never went away entirely...but once cleared, it stayed off long enough for the smog test and the Hot Cam (along with a new opti and ignition tune up and one new cat) passed California smog with flying colors.
Sooo....if there's any moral to this story, and I'm not sure there is, I'd consider pulling the valve covers...easy enough on an LT engine and checking for anything amiss there.
My steering column was bad too...so these cars may have similar mileage (little north of 100K ?). Pulled that sucker and replaced with a new one ...not that hard...but I digress.
Mine had a rat's *** cheapo... LOUD..."custom" exhaust...so when I pulled the exhaust and peered up the cats, guess what? no matrix in the drivers side...just an empty can. Later I found that one of the multitec injectors on that side leaked and probably melted and blew out that side cat's innards.
So one new exhaust...one new set of Bosch III injectors and one new cat later...
I decide to pull the valve covers for a little inspection....guess what...and this is on an engine with no apparent problems...one rocker was off the valve stem and one was partially off with damaged self alignment ears ...so two...possibly three (my memory fails me) stock LT4 rocker arms ....and yes, stock rocker arms may look like other rocker arms, but trust me, they are a one year, non adjustable pedestal design that interchange with NOTHING and have a price, if you can find them, to match...
So all is well, one would think. Then the OEM opti spark craps out. I found some receipts in the car that lead me to believe it was the original opti with one cap and rotor change. If the serpentine belt hadn't cut one of the ventilation hoses and the other hadn't deteriorated from oil and heat I believe that the opti would have still worked; as it was the brass terminals were green from water intrusion...yeah I know I never should have used a high pressure washer on the engine...
With everything off the front of the engine to access the opti and a repeat of the rocker arm issues, without any damage this time...thank god...further investigation was called for.
Pulled the camshaft. The last three lobes were rounded off, actually grooved by the lifter; so...one Hot Cam and a new set of lifters, new opti, new plug wires and new plugs, new water pump, new main Extreme Duty timing chain, new rod and main bearings and new oil pump and new canton road race pan...I'm back on the road and guess what?
Now I have a P0300 service engine light code "random misfire" and a smog test coming up...Yup I replaced the crank position sensor and in the process I found that I had run the sensor wire through the plug wires, or more accurately had led the plug wires so they surrounded the sensor wire...whatever, the result was the same.
Long story short, the P0300 never went away entirely...but once cleared, it stayed off long enough for the smog test and the Hot Cam (along with a new opti and ignition tune up and one new cat) passed California smog with flying colors.
Sooo....if there's any moral to this story, and I'm not sure there is, I'd consider pulling the valve covers...easy enough on an LT engine and checking for anything amiss there.
There are so many things that can set off this p030X code its just crazy! I guess I should check air filter MAF and double check spark plug wire routing. After I do all that and still a no go I am going to research the best LT4 shop in town (Dallas Tx Area) and let them have at it. This car supposedly has a rebuilt engine but no receipts. Just looking at the engine I think it has been rebuilt. The shop that supposedly did the work is a very reputable (corvette) one in LA
(California). I might also give them a call.
Hours of youtube videos, google searches and all of you nice c4 owners checking in and helping out is great.
I have a garage fridge full of beer so if anyone wants to stop by and supervise come on over.
Thanks!
Last edited by Indio Monk; 10-21-2016 at 07:47 AM. Reason: Pics
#39
TheCorvetteBen
Mis fires are caused by issues with one of three things. Spark, fuel/air mixture, or mechanical failure. I hope it is not the third because that is the pricey fix!
#40
Instructor
Thread Starter
I hope it is not that also, thing is it just runs good in my opinion. Good power no stalling or misfires felt IMHO.