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

Is This Normal?

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Old Apr 13, 2010 | 11:02 PM
  #1  
L98RedVette's Avatar
L98RedVette
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Default Is This Normal?

I'm a new user to Corvetteforum, and I am not that great on knowledge with engines...

My 1990 L98 Corvette's Oil Pressure goes crazy! The oil pressure gauge shows 0 to 80, my car reads 75, then jumps down to about 40 and then jumps back up to 75 and repeats when I am braking or idling. My vette sometimes shuts down, especially when braking.

Does anybody know what could be wrong?

Please let me know, and do not use abbreviations on anything because I don't know what they mean...please keep in mind that I'm not that knowledgable on Engines.:o

any information helps! I have a C4 Haynes Repair manual(doesnt help) but could be used to refer to parts mentioned
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Old Apr 13, 2010 | 11:13 PM
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Describe more about how you are driving when the oil pressure goes up and down.

For instance....when you give it full throttle does it increase? When you come to a stop in gear what does it read? What does it read when you are going down the road in top gear at 55-60mph?

It shuts off when you hit the brakes? If it is a manual tranny car you need to push in the clutch when coming to a stop or it will stop completely....lol j/k dude

Seriously though. How many miles, what tranny, any modifications to the car....etc
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Old Apr 13, 2010 | 11:40 PM
  #3  
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Default Wow

damn it feels great when someone responds to my problems...

well its an automatic...
the only mods i have are simple, Flowmasters exhaust system, K&N AirFilter, K&N Oil Filter and Royal Purple Synthetic oil...its mostly Stock...

My engine is pushing 98,000 miles...I bought it used, and I am a 3rd owner. The first two owners raped the c4...they abused it and drove it on a beach!!! i found sand under the hood the first week i had it! I bought it about 2 years ago and this problem just about started 5 months ago..

ANOTHER PROBLEM....MY speedometer doesnt work...it seems "burned" from the LED. I can only read it when the lights are on and the when i squint...sometimes it just shows a ZERO and i dont know how fast im going.
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Old Apr 13, 2010 | 11:50 PM
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Could be a bunch of things but its likely either the gauge itself or the oil pressure sending unit thats found on your engine...
When you start the car it should read at about 60psi on a cold startup and under 20 when its fully warmed up at idle. When you give it gas it should increase to 40-60ish depending on how much gas you are giving it.
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Old Apr 14, 2010 | 12:22 AM
  #5  
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^Almost exactly what mine is to a T!
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Old Apr 14, 2010 | 01:49 AM
  #6  
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THANK YOUZ!...will check up on those parts
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Old Apr 14, 2010 | 12:26 PM
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I think you have two separate problems.

1) The oil pressure problem sounds like a bad sender. If the '90 is like my '86 the good news is that the sender is not that expensive. The bad news is that the sender is a pain to get at as it is buried at the back of the engine, on the driver's side, by the distributor.

2) Does the check engine light turn on? If so, read the codes as they may indicate a problem area causing the stalling.

Steve
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Old Apr 14, 2010 | 01:45 PM
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the light comes on...then turns off before i can scan anything and get information on it....well, i dont scan it, but a friend of mine that knows better than i do does. it wont say whats wrong, unless the light stays on while i take it to him(which it usually turns off)....
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Old Apr 14, 2010 | 02:21 PM
  #9  
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Check the engine oil level to ensure that it is not under or over filled (getting bubble churn from the crank if over).

If your lucky: just your pressure sender just has a problem. Replacing the sender is not that big of a deal so it would be a great place to start if you can't nail down a trouble code.

If your unlucky: oil pump/pickup has problems or you have multiple issues.

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Old Apr 14, 2010 | 02:52 PM
  #10  
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Yes, Sounds like the sending unit.

http://shop.advanceautoparts.com/web...S_575807881___
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Old Apr 14, 2010 | 05:39 PM
  #11  
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Originally Posted by L98RedVette
the light comes on...then turns off before i can scan anything and get information on it....well, i dont scan it, but a friend of mine that knows better than i do does. it wont say whats wrong, unless the light stays on while i take it to him(which it usually turns off)....
The ECM stores codes whether the light is on or off. Next time it has a problem read the code. You do not need a special scanner, just a paper clip or jumper wire to bridge two contacts on the diagnostic connector. The check engine light flashes out the malfunction code. There are multiple threads in this forum on how to do it.

Steve
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Old Apr 14, 2010 | 06:51 PM
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If your car was driven on the beach....in Texas ? lets assume it was also exposed to salt water. There are a dozen different things that could be wrong, but the one single thing that could be common to all your issues would be a bad ground, or series of bad grounds. Look around your car; there will be a number of braided wires without insulation; these are ground cables, clean and tighten where they connect to the frame, block, etc. Good luck.
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Old Apr 15, 2010 | 02:33 AM
  #13  
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the car was originally from florida.
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