C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Need help - stranded and not really running.

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Old Aug 2, 2023 | 08:41 AM
  #41  
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Originally Posted by ajp01
What type/brand injectors exactly were those that failed? Were they new or rebuilt/cleaned? Just curious. Thanks -
Pm'ed you

Update - we'll there is some badness internally. Changed the oil and filter, left the original spark plugs, it fires right up and idles easy. Fuel pressure and starting issue seems resolved - but - it is now puffing white smoke. It isn't coolant as coolant levels are holding stable with no loss. It's possible it's blue tinged but my garage walls are blue-gray so hard to tell.

I ordered a compression tester that will be here tomorrow. I truly don't understand what caused all this.

Last edited by JT1911; Aug 2, 2023 at 03:19 PM.
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Old Aug 2, 2023 | 08:26 PM
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In all this I don’t see the FPR being replaced. A ruptured FPR diaphragm would dump gas into the motor and if running, extremely rich. May be worth at least checking out.

you also could have nuked/clogged the cats or have residual crud in them.

gas bathing the cylinders washing off the oil will kill compression and allow oil past the rings…

you may just want to try an Italian tune up…get it good and hot and romp in it to make sure everything is blown out etc…

If it’s truly white (and not bluish) it would be coolant
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Old Aug 3, 2023 | 09:52 AM
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Originally Posted by pedricd
In all this I don’t see the FPR being replaced. A ruptured FPR diaphragm would dump gas into the motor and if running, extremely rich. May be worth at least checking out.
If you mean the fuel pressure regulator, I pulled the vacuum line and it's not leaking fuel. It looks like the fuel issue was due to stuck injectors which have now been replaced.

you also could have nuked/clogged the cats or have residual crud in them.
I thought of this but I didn't think that would yield consistent smoke.


gas bathing the cylinders washing off the oil will kill compression and allow oil past the rings…
If that's the case what's the play? I've not heard of an Italian tuneup.

you may just want to try an Italian tune up…get it good and hot and romp in it to make sure everything is blown out etc…

If it’s truly white (and not bluish) it would be coolant
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Old Aug 11, 2023 | 10:29 AM
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Update - 08-11

Finally had a chance to work on it again. Since the new injectors it fires up and runs fine but we definitely have a oil problem. I pulled it out of the garage and the smoke is definitely blue oil smoke. I let it idle in the driveway for about 20-30 minutes and I could watch the oil pressure gauge slowly but visibly getting lower.

To my mind this points to either bad piston rings or a bad head gasket. If head gasket then that's good news as I know I can fix that. What do y'all think?
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Old Aug 11, 2023 | 10:34 AM
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Originally Posted by JT1911
Update - 08-11

Finally had a chance to work on it again. Since the new injectors it fires up and runs fine but we definitely have a oil problem. I pulled it out of the garage and the smoke is definitely blue oil smoke. I let it idle in the driveway for about 20-30 minutes and I could watch the oil pressure gauge slowly but visibly getting lower.

To my mind this points to either bad piston rings or a bad head gasket. If head gasket then that's good news as I know I can fix that. What do y'all think?
Not sure where the oil smoke is coming from, but the oil pressure gradually decreasing as the motor warms up is normal. The viscosity of the oil decreases with increasing temperature.
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Old Aug 11, 2023 | 11:12 AM
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Drive it. You probably have a bunch of oil in the intake from when fuel overfilled the crankcase. You are also burning off oil in the cats. Idling in the driveway is asking them to overheat.
just check the oil level now and then.
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Old Aug 11, 2023 | 11:24 AM
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Originally Posted by Talfryyn
Drive it. You probably have a bunch of oil in the intake from when fuel overfilled the crankcase. You are also burning off oil in the cats. Idling in the driveway is asking them to overheat.
just check the oil level now and then.
Exactly - get out and after warmup romp on it a bit... = Italian tune up. Drive it around a bunch and check oil level as stated...

After this you will hopefully have cleaned everything out....if it is STILL smoking you MIGHT have a valve seal or ring issue....

Oil pressure going down is not a problem...happens as oil heats up. It is not like a fuel gauge...if you actually run down on oil it would not gradually go down...it's measuring pressure and it would be "fine" until it started to cavitate pull air. I.e. it would suddenly drop to 0/spike and that is VERY BAD because that means the engine is starving of oil RIGHT NOW...which means shut it off NOW.
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Old Aug 11, 2023 | 08:17 PM
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Originally Posted by Talfryyn
Drive it. You probably have a bunch of oil in the intake from when fuel overfilled the crankcase. You are also burning off oil in the cats. Idling in the driveway is asking them to overheat.
just check the oil level now and then.
Originally Posted by pedricd
Exactly - get out and after warmup romp on it a bit...
Thanks for the advice guys. I did like you said. The wife and I went for about a 45 minute drive and it purred like a kitten through the Pennsylvania hill country. Smoke was minimal while driving and it doesn't seem to be smoking now back at home. BUT about half way through the drive oil pressure gauge started varying heavily (heavily = one whole quarter of the gauge) dependant on throttle position. By the time I got home it was holding below the first (20psi?) mark on the gauge. It also seems to be idling at a lower rpm than normal but maybe I don't remember. Picture is at idle in my driveway after the drive. You can see both the pressure gauge and tach.



After shutting her down I checked the oil level on the dipstick and it's right where I left it.
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Old Aug 11, 2023 | 08:58 PM
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What you are describing is perfect oil pressure!!! You are good!

around 20 psi at idle is completely normal when hot. oil pressure varies with RPM, the higher the RPM the higher the pressure. Someone will chime in and tell you exactly what PSI to expect per additional 1k rpm.

Also when nice and hot the idle will settle lower.
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Old Aug 11, 2023 | 09:50 PM
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My analog gauge sits right where your picture shows at idle after warmup. You have no worries.
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Old Aug 12, 2023 | 04:31 AM
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I'd suggest another oil and filter change soon(ish), doesn't cost much and makes sure there aren't any contaminants left in the oil. The lower idle is probably because the ECM is now able to better control the amount of fuel. Picture shows perfect gauges, you're good!
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Old Aug 13, 2023 | 10:03 PM
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Originally Posted by pedricd
What you are describing is perfect oil pressure!!! You are good!

around 20 psi at idle is completely normal when hot. oil pressure varies with RPM, the higher the RPM the higher the pressure. Someone will chime in and tell you exactly what PSI to expect per additional 1k rpm.

Also when nice and hot the idle will settle lower.
Originally Posted by CorvetteRules
My analog gauge sits right where your picture shows at idle after warmup. You have no worries.
Originally Posted by frosted
I'd suggest another oil and filter change soon(ish), doesn't cost much and makes sure there aren't any contaminants left in the oil. The lower idle is probably because the ECM is now able to better control the amount of fuel. Picture shows perfect gauges, you're good!

Everybody - God is good - y'all seem to be right. Put about 150 miles on it in the last 2 days and it is a happy corvette!

I plan to do another oil change after this tank of gas just to be safe. So... Who am I going to see at corvettes at Carlisle?
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