94 LT1 V8 - Fourth Generation Pontiac Firebird (1993 - 2002) - Firebird Nation

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94 LT1 V8


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13 replies to this topic

#1 Flyman

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Posted A week ago

Hey guys Im not mechanically savvy but I have a couple questions. I have a 94 bird v8 with 63k miles and its very well taken care of from the looks of it. So my oil gauge fluctuates when I drive (is it normal ?) also the car revs up when in park and when at a red light it wants to accelerate by itself so I have to really press on the brake hard. Car has a new alternator by the way. Also the car runs good but when I step on it hard it hesitates a bit. Should I do a tune up and a trans flush ??? Or just a tune up ? Again thanks again guys Im a new bird owner and have no idea what was serviced on this bird so Im a little confused on what steps to take to make this car run even better. Thank you

#2 Injuneer

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  • Model: Firebird Formula
  • Engine: 381ci LT1 stroker
  • Transmission: TH400 + GV O/D

Posted A week ago

Have you scanned the PCM for codes?

 

Is the Service Engine Soon (SES) light on while driving?  If not, does the SES light come on for a few seconds, like many other instrument panel warning lights, when you turn the key to “RUN”?  Been helping someone on another site with a recently purchased car,   He was pulling codes from the PCM but no SES light - codes that should have turned it on - but no SES light.  I told him someone might have pulled the bulb or put tape over it, to cover up problems with the car.   Sure enough, tape over the SES light.

 

Is the engine totally stock, or has it been modified?  


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#3 Injuneer

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  • Engine: 381ci LT1 stroker
  • Transmission: TH400 + GV O/D

Posted A week ago

It's normal for oil pressure to vary with RPM.... say 20-30 PSI at idle, rising to 45-55 PSI at high RPM.  Is that what you are seeing?  Ot is the needle jumping around at steady RPM.

 

At idle, engine should hold programmed idle speed +/- 25 RPM.  Programmed idle RPM for the auto trans, engine fully warmed up, is 550 RPM in gear, 650 RPM in neutral.  How high does yours go?



#4 Flyman

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  • Transmission: Automatic

Posted A week ago

The car is an automatic with two older previous owners who took very good care of the car from the looks of it. The car is fully stock. The oil gauge moves when I accelerate but not all the way towards the end and then when I stop it goes down but not all the way down. The SES light is not on and nothing on the dashboard comes on but the lights do work on all gauges. I had a mechanic drive it and he said it feels very good, the suspension and everything aside from the car pulling a little bit when stepping on it hard. He mentioned it probably needs a tune up. Im actually getting a full inspection this week. I just dont feel like its normal for the car to rev up so much when in park or when Im at a stop light it Seems to accelerate so I have to press on the brake harder than I think I should.

#5 Flyman

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Posted A week ago

One more thing, again I feel weird asking all these questions but Im new to older cars. I notice the car get very hot in the engine bay when I drive it for over 30min and above. Just curious if an aftermarket cold air intake can help the engine cool of a bit. Its probably normal for these types of cars but again Im just asking because I want to really enjoy this car and drive it a bit hard when possible.

#6 ZumpTA

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Posted A week ago

All that matters is how hot the engine actually is.  You won't get that from feeling engine bay temps, you get it from the gauge or scanning the PCM while it's running.  Assuming the sensor that feeds the temp gauge is OK, the needle should hover about mid-gauge while driving. The LT1 is designed to run "hot", 220F to 240F is absolutely normal.  You can do a visual inspection of the air dam under the front end, it should exist. That little piece of plastic forces air up to the radiator, if it is missing or broken, that can seriously affect running temperatures.  As can air in the cooling system, or a plastic bag sucked up in front of the radiator.   If the engine isn't getting sluggish once warm, the temp needle isn't approaching the red zone, temperatures aren't fluctuating greatly between cruising and sitting at a light, i wouldn't worry about it.

 

...and a CAI lowers the intake air temperatures producing slightly more horsepower, having one does not impact the under-hood temperature.


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#7 Injuneer

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  • Transmission: TH400 + GV O/D

Posted A week ago

We all want to help you.  But to help you, you need to carefully read what we post, and answer any questions we ask.  That is the only way we can help you solve your problems with the car.

 

You stated "previous owners who took very good care of the car from the looks of it. ".  If they did, you wouldn't be having the problems you describe.

 

And you acknowledge "(I)....have no idea what was serviced on this bird."

 

The car is 25 years old.  At this point, you should replace all fluids, and all critical maintenance items:

 

Replace all fluids:

- engine oil

- coolant

- transmission fluid

- rear axle lubricant

- brake fluid

- power steering fluid

 

Replace maintenance items:

- oil filer

- fuel filter

- trans filter

- air filter

- PCV valve

- spark plugs

- spark plug wires

- O2 sensors

 

Test and replace if necessary:

- ignition control module

- battery

 

Inspect and replace if necessary:

- tires

- suspension bushings

- shock absorbers

- fuel lines

- brake lines

- brake pads

- brake rotors

- windshield washer blades

- signs of front suspension misalignment

- signs of tire/wheel imbalance

 

Use premium fuel (91-octane minimum) for maximum performance.

 

Use fluids and components that meet the standards outlined in the Owner's Manual.

 

OBTAIN A COPY OF THE 1994 OWNER'S MANUAL IF YOU DO NOT ALREADY HAVE ONE.  Read it and ask questions about things that are unclear.  Download a copy at the GM Owner Center website.

 

I may have missed a few things - others can fill in the blanks.



#8 Flyman

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Posted A week ago

Thanks so much fellas ! Ill start doing all of that slowly but surely ! Also for a transmission service should I get a trans flush or change ?

#9 Injuneer

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Posted A week ago

QUESTION:  Have you scanned the PCM for codes?

 

ANSWER:  No answer

 

= = = = = = = =

 

QUESTION:  Is the Service Engine Soon (SES) light on while driving?  If not, does the SES light come on for a few seconds, like many other instrument panel warning lights, when you turn the key to “RUN”? 

 

ANSWER:  The SES light is not on and nothing on the dashboard comes on but the lights do work on all gauges.

 

When you first turn the ignition key to start the engine, the dashboard should light up like a Christmas tree, so you know that the critical warning lights (like the SES) are working.  From the  Owner's Manual:

 

 


Warning Lights, Gages and Indicators - ".... some warning lights come on briefly when you turn the ignition key just to let you know they are working."

 

 

The lights that should illuminate for a few second include:

- BRAKE

- ABS INOP

- TCS OFF (if equipped with optional traction control)

- LOW TRAC

- SERVICE ENGINE SOON

- CHECK GAUGES

- LOW OIL

- LOW COOLANT

 

You indicate that none of these lights come on when you turn the key to start the engine.  If this is correct, you have a problem with the dash and it needs to be repaired.  Having these lights come on for a brief period when you start the engine is not something unique to this car.  It is common with even the most modern vehicles.  Doubt that you and the mechanic wouldn't have noticed this.

 

= = = = = = = = = =

 

COMMENT:  It's normal for oil pressure to vary with RPM.... say 20-30 PSI at idle, rising to 45-55 PSI at high RPM.  Is that what you are seeing?  OR is the needle jumping around at steady RPM.

 

RESPONSE: The oil gauge moves when I accelerate but not all the way towards the end and then when I stop it goes down but not all the way down.

 

My comment indicates the oil pressure at idle is typically in the range of 20-30 PSI.  That is not "all the way down".  At high RPM it is typically 45-55 PSI.  That is not "not all the way towards the end".  Is that what you are seeing?  What is the numerical pressure in each of those cases?  We're lucky the Firebird actually has numbers on the gauges.  The Camaro doesn't have these.

 

And, is the needle steady or jumping around?

 

= = = = = = = = =

 

COMMENT:  At idle, engine should hold programmed idle speed +/- 25 RPM.  Programmed idle RPM for the auto trans, engine fully warmed up, is 550 RPM in gear, 650 RPM in neutral.  How high does yours go?

 

RESPONSE:  The car is an automatic ...... I just dont feel like its normal for the car to rev up so much when in park or when Im at a stop light it Seems to accelerate so I have to press on the brake harder than I think I should.

 

That's why I gave you the programmed idle values for a stock 1994 Firebird LT! with automatic transmission, both in gear and in neutral.  What does the RPM increase to when the trans is in neutral.... A NUMBER OFF THE TACH?  What does the RPM increase to when you are at a stoplight, in gear, holding the car with the brake?  NUMBERS.

 

And to add a question, is the elevated RPM a steady number, or does it surge up and down?



#10 Flyman

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Posted A week ago

I have not scanned it for pcm codes. Friday my mechanic will do a full inspection on the car and check for pcm codes.

When I turn the ignition all of the warning lights on the dashboard light up like a Xmas tree including the ses one.

My oil gauge goes from 20 when Im stationary to like 50/60 when driving and no higher.

My RPM is at 550 when the car is idling In the beginning but when I drive it for over 15 min it will go all the way up to 1000 rpm and then up to 1500rpm, it does this when in neutral. When at a stop light and Im stepping on the brake, it wants to accelerate so the rpm wants to go up to what I mentioned above so I step on the brake harder to keep it from moving. When I really want to step on it the car feels good but it does hesitate a bit. If that makes any sense.

I apologize as I am not mechanically savvy. Just trying to learn as I go and to take care of whatever problems the car might possibly have.

#11 Injuneer

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  • Engine: 381ci LT1 stroker
  • Transmission: TH400 + GV O/D

Posted A week ago

OK.... the warning lights, including the SES light come on when they are supposed to.  Definitely isn’t what your original answer indicated.

 

There's a pressure relief spring in the oil pump that limits pressure to 60 PSI.  Oil pressure sounds OK.

 

Appears you may have a serious vacuum leak that allows the engine to idle at an excessively high RPM.  The PCM has the ability to control the idle speed quite precisely.  It does this by continuously opening and closing a small valve (IAC = idle air control) in the throttle body.  It will shut down to reduce the idle RPM.  But once it closes all the way, if there is a vacuum leak, it can’t shut down any further to control RPM.  Or, the IAC is not working correctly. And oddly, the PCM targets a higher idle RPM when the engine is cold, yet yours only idles at 550 RPM.  Possibly indication an IAC problem.

 

One of our members (GarDoug) has written PCM Scanning software, specifically for the 1993-1995 LT1.  That produces a data log, in spreadsheet form, that reports on the values for 50+ sensors and PCM parameters.  It is often possible to identify problems and determine the health of the engine from the data log, and I can review it for you.

 

Scan9495 is available as a free download.  You need a Windows laptop, and have to buy a cable to connect the laptop to the data link connector under the dash by the driver's right knee.  You post the data log .csv file here, I (and possibly others) can download it and analyze the data.  I have a guide available describing the best way to drive the car while recording the data log.

https://www.firebird...9495-lt1-obd-1/

 

 



#12 Flyman

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Posted A week ago

Thank you so much !!! I really appreciated !! I had a feeling it might be a vacuum leak.

Also My gas gauge doesnt work so I just reset the trip meter so I know when to pump gas. The car was inspected underneath and no leaks were found. From doing research I thought it could be the fuel sending unit needing to be replaced.

Again thank you !! Youre very knowledgeable. Ill look into The info you gave me.

#13 Injuneer

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Posted A week ago

How to check the fuel gauge:

 

http://shbox.com/1/4...html#fuel_gauge



#14 sea dog

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Posted A week ago

Common place for a vacuum leak on a lt1 engine is where rubber intake air elbow goes into the throttle body.






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