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

Working on my '95 Corvette

 
Old 04-10-2019, 01:38 AM
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Jaime-Corvette
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Default Working on my '95 Corvette

Hello C4 family!

1995 C4 Lt1 106,00 miles, A4 tranny

I will be posting my progress here on my journey for the corvette. it has its problems but i think it is very fun to work on. I have owned this car now since i was 18, slowly bringing it back to life and now more then ever. Im 24 now and i recently gave it to my brother about a year ago. He will mod it with his own taste (trust me not ugly). We are both working on it as of now. Engine stuff first though before we do new paint job, wheels, stance, small bolt ons and what not.

While i think working with car is very very fun! it is a stressful sometimes, especially because i am limited in skills, tools and straight knowledge of how these things work. i do research and do my best.

After we get the car up and running, i do want to get another c4 vette preferably in BAM color auto or stick i dont care. i just kind of miss the ugly c4 and its one of my favorite corvettes of all time!!! Best rear end thats for sure!

Do take it easy on me if you would like to help and give a hand, this is not my strong suit. Thanks in advanced!!!

When i first bought the car, it was poorly taken care of, no one cared for it, 5 owner and leased, stored outside at a barn, covered in dirt. UGLY.

About 3 years ago i got the car repaired at a mechanic from overheating. I will list the fixes and fairly new parts more or less.

.Warped Heads were Re-Machined
.Cracked Radiator was replaced with NEW unit
.New Water Pump
.New Thermostat
.New Spark Plugs and Wires (read on post #5 for this)
.Starter
.Battery
.Other Stuff i cant remember



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Old 04-10-2019, 02:02 AM
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Firstly I will say that we recently cleaned the engine bay with Gunk engine degreaser and flat spray hose down (covering the opti with 10,000 rags and bags). i know this is still bad and i regret it but oh well, new probable damage has been done.

The engine was running ok until recently. It surges very badly when it gets warm and as of now has a rough start and backfires a few times. It pops and seems to be miss-firing.

This past weekend i checked the codes within the digital dash by jumping the ob11.

i got codes:
module 1: c12 (all good)
module 4: h48 (mass airflow circuit)
h22: (throttle position sensor low voltage)
module 9: h64 (bank 2, right front 02 sensor (lean exhaust)

These codes were present before engine bay cleaning.


We first cleaned the MAF with cleaner. and got rid of the MAF code. We bought a new TPS sensor. the old one did not read well with volt meter. the new one reads about .7 on 0% idle; 4.2 at 100% throttle.

I installed a new 02 sensor on the right side before the cats, near the starter. the wire connector of the 02 sensor (both male and female) were wet. not oil. not fuel. Maybe degreaser water run down from our recent engine bay cleaning. It also wasnt completely snapped together.
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Old 04-10-2019, 02:24 AM
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This is a list all of the things i have replaced or fixed as of now;

.Cleaned MAF with CRC MAF cleaner
.New Throttle Position sensor TPS
.New 02 Sensor Right Front
.New Fuel FIlter
.New IAC (idle air control) valve
.Cleaned up and tested Ignition Control Module and installed with heat thermal paste
.FIxed Ambient Air Temperature sensor wiring.
.Fixed the Whole HVAC thing and everything beyond that! (you know what im talking about)
.PVC valve tee (3/8, 3/8 with rubber cap, 1/4 from charcoal canister purge valve to throttle body)
.Vacuum Check Valve NEW hoses and rubber cap... lines are good
.EVAC Purge Line is good (dont know if its good all the way down)
.1/2 hard curved hose from Throttle Body to Valve Cover was loose, clamped down FOR NOW

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Old 04-10-2019, 02:48 AM
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With all of this, ALL codes are gone except for Module 9: H64 (02 sensor). Not sure why, i cleaned the connector very well nothing should be wrong, unless i changed the wrong one? Maybe i need computer restart? Connector is bad?

I got a new code..

Module 9: H67 (A/C Pressure Sensor or A/C Clutch)

I dont even know...


With all of this, the car still needs to be cranked about 3 sometimes 4 times. it starts very roughly like it doesnt want to start, still backfires very black smoke and shakes the car. when i Rev the car, right side Passenger exhaust (the side with new 02 sensor) throws A LOT of water. Not fuel or oil or milky anything. Maybe that is normal condensation and i should change the left side driver side 02 sensor as well?

Car idles at 925 rpm or so. When warmed up it will still surge and idle funny as if it is missfiring. It doesnt stall though.

Our plans for tomorrow:

Our next move is to get a new MAP Sensor tomorrow as my current one may be bad from engine cleaning... I may check how to test it tomorrow as well.
Planning on Cleaning the EGR Valve or replace it as a whole. I will try to test it with pressure pump used for carburetors, but no promises.

If anyone would like to give a hand Thanks in advanced!
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Old 04-10-2019, 03:00 AM
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I Just took off a couple of Spark Plugs on passenger side. they seem fairly burned but not bad. i need to check the gap on them to see if they went above .50. They did not have fuel on the tips but the threads had a lot of oil.
Is that normal? i heard oem valve covers leak. I assume they come from there.

I am pretty unhappy as to finding out that this car has those CRAPPY conventional ACDELCO R44LTS spark plugs that cost 2 dollars each! that is worst than NGK platium and those suck. I guess these are stock but still.

All wires are brand new maybe 3 years old.

These were installed by the mechanic who worked on the car those 3 years ago.

I will replace all spark plugs with NGK Iridium. hopefully tomorrow as well.




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Old 04-10-2019, 11:37 PM
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Just took off the 3 year old conventional spark plugs. None of them had any anti-seizure on them. Half of them smelled like fuel and the other half had a good amount of carbon build up. Maybe 3 of them were gapped at .48, the rest were at .36 and around that lower mark.

I ended up getting AcDelco platinum 41906 plugs. Maybe these are good maybe they are not. I will see.

I also cleaned the EGR valve. I havent tested it.. Just a clean. I broke one of the hard plastic vacuum line from it. It was brittle. Got some new lines at the parts store.

Right after this I will start the car and see what it runs like.
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Old 04-11-2019, 12:54 AM
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No start

Will continue tomorrow.
Car also wouldnt turn on in open loop (default mode) with maf disconnected. I took the cap off of the check valve and a good amount of air came out. So it is holding pressure. I know I need to smoke the system. I also heard the throttle bodies on these cars leaked a lot of air and was a common thing.
Many things come to play... but not turning on?

I'll look about fuel relay and coolant temperature sensor tomorrow.

Still have not tested MAP sensor.

Distributor going bad?

I wonder what it can be
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Old 04-11-2019, 08:12 PM
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Get a fuel pressure gauge, see if that's up to spec.
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Old 04-11-2019, 09:17 PM
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I just checked the spark on the spark plugs. They light up well, so distributer is out of question.

The funny thing is that these plugs are only a few hours old and the car never turned on with them... just burps farts and nasty cranks. The plugs all have carbon build up... this kind of tells me the cats might be plugged up pushing all the nasty stuff back. I'm taking the cats off right now. It's a pain in the ***!

Going to run open headers.

This could also be why the car doesnt turn on.

Even if the car does start after this I will be doing fuel stuff.

Thanks for the tip thatguy427 I didnt even thi k about that!

If the pressure is too low does that mean my fuel pump is old and doesnt charge well anymore or pumps well enough to start? Im not sure if it has ever been changed.
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Old 04-12-2019, 05:15 AM
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Low pressure could mean the fuel pump is old and isn't charging well enough, or a tube inside is broken allowing air to get in the system. Could be a problem with the fuel pressure regulator, not keeping the pressure high enough or clogged up fuel filter. All have symptoms of possible hard starting.

My '95 has like 190K miles with original CATs. Doesn't seem right yours would be fouled. They aren't too bad getting off. The hard part can just be getting the car on four stands.
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Old 04-12-2019, 03:58 PM
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Took the cats off from manifold well at least the bolts. We couldnt get the front y pipe off that holds the drivers side with the tranny bracket. No matter how much pb blaster and cheater bars we used... it's just not gonna happen.

Its impossible to take the cats off of the car without taking the whole exhaust system off. We couldnt even do that because of that driver side bracket.

Either way the cats were unbolted from the exhaust manifold headers, so there was enough to have an exhaust leak i supposed.

We cranked it and boom it fired up with ease! There was definately an exhaust leak, really loud where the cats and manifold bolt on.

We just ordered new cats.

We will take car to a good exhaust shop to fit the new cats in and we will get rid of the mid pipe resonator. All this will have to be done by cutting, welding and extra piping to be retro fitted.

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Old 04-12-2019, 03:59 PM
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Originally Posted by thatguy427 View Post
Low pressure could mean the fuel pump is old and isn't charging well enough, or a tube inside is broken allowing air to get in the system. Could be a problem with the fuel pressure regulator, not keeping the pressure high enough or clogged up fuel filter. All have symptoms of possible hard starting.

My '95 has like 190K miles with original CATs. Doesn't seem right yours would be fouled. They aren't too bad getting off. The hard part can just be getting the car on four stands.
I will still be taking a look at a new fuel pump and everything that has to do with that.
Just because the car turns on doesnt mean it's all done.

I know that old fuel pumps dont get enough charge and this car did always needed 2-3 cranks to finally go.
That is something to look at.

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Old 04-12-2019, 08:06 PM
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I've only taken off the passenger side CAT without removing the entire exhaust system. Sucks your bolt is so stuck, and you had to order new CATs. From my limited research, I've heard the stock CAT flow much better than most aftermarket options.

Keep us updated. Have safe and happy wrenching
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Old 04-14-2019, 01:32 AM
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We were just checking measurements of the new cats. We saw that all of the tranny oil pan bolts were hand loose and that red oil was leaking out from them. We tightened them for now. Huhh... gonna need new fresh oil for that.

Also, I'm not a expert like some of you but the block says 327 on it. Right near the knock sensor. Took the heat shield off to get a better view.

Lt1 is a 350... but the block says 327. It also has a 6 under it. Is this normal? What do you guys think?



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Old 04-14-2019, 02:03 AM
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327 is the casting code!

The more I know

What a coincidence
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Old 04-16-2019, 08:38 PM
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Got a fuel pressure gauge.
Wow.. we put the car on run and the guage immediately went to 45 and quickly went down. Maybe in 10 seconds back down to 25 until 0.
Initially thought it was the fuel pump... until I took the vaccum line off of the fuel regulator.

A bunch of gas spewed out of the regulator! Time to replace!! That is not supposed to happen!

Going to replace right now. I'll post results right after.

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Old 04-16-2019, 09:11 PM
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Yes it's always better to diagnose than to just throw parts at the C4. Understand that if you remove that central resonator ...... the exhaust system is going to drone.
Also when starting the car; turn the key to "on" wait 10 seconds until the fuel pump has a chance to pressurize the system (you should actually be able to hear the fuel pump) and then turn the key to start. Should then start right up. Always works on my 95 (136K)
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Old 04-16-2019, 10:12 PM
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We changed the part. The old regulator was in fact leaking from the nipple. The new one does not at all. The lines are in there pretty good. Takes some muscle. Pressure holds at 36 and does not go down at all even after 5 minutes.

The car does not turn on. Every time we charge the fuel pump I can hear an air noise coming from the return fuel rail (drivers side). Not sure of that is normal. Honestly can not remember if the car ever made that sound upon fuel pump charging.

When we tried cranking it only 2 times, the motor made a loud noise internally. Nothing crazy. Maybe it wanting to turn on but not turning over?

I dont try cranking it over too many as I dont want to flood the cylinders either.

Trying to think here.

I'll need to do homework on how to check injectors.
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Old 04-17-2019, 02:27 AM
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One very important peice of information I forgot to throw out there!

While cranking up the car the car would make a ticking sound. Fairly loud and not too fast. It did this ticking sound a few times before the engine just stopped wanting to turn on.

This was actually right after the engine bay cleaning. After that, the motor no longer wanted to turn on anymore. It turned on only 1 time right after the wash. It was fine until like 1 minute later it started idling very very badly. We turned it off. Never turned on again. We managed to get it on only 1 time ever since then but ran so bad I didnt want to leave it on and damage anything.the ticking sound is no longer there, and definately no starting engine ever since.

I didn't want to rule the optispark out yet... but is that the optispark taking a crap?

I would think not. I get a nice spark. At least on cylinder 1.

Maybe rule it out for now.

Just throwing this out there

Last edited by Jaime-Corvette; 04-17-2019 at 02:36 AM.
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Old 04-17-2019, 11:21 AM
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Originally Posted by Mr. Peabody View Post
. Understand that if you remove that central resonator ...... the exhaust system is going to drone.
would an X-pipe alleviate that (vs straight pipe)
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