1984 Corvette: She lives!

[bartric]

Well, I got 'er started up today. She sounds so beautiful. The starter was bad, so I replaced it and she fired right up. Now to the problem that I'm needing some feedback on.

It runs for so long and then just dies. It's spraying gas all the way up until it dies. Could timing be the problem because I'm sure it's not timed 100% correctly, we just kind of guesstimated it.

Please leave all possible ideas of what could be causing it to randomly shut off after running for a short bit of time. Also, there was a vacuum hose off could that be the problem?

 

[warren s]

How long does it run before dying out? Does it restart right away after it dies out? What do you mean by "spraying gas?" Does die out if you leave it to idle or are you trying to give it more gas and it stalls no matter what you do?

A vac hose off could cause a bad idle, but if it starts in the first place you should be able to keep it running by working the throttle. How old is the gas in it? Its been sitting for a while since it last ran? How are the plugs and wires? Cap and rotor?

 

[boomdriver]

How long does it run before dying out? Does it restart right away after it dies out? What do you mean by "spraying gas?" Does die out if you leave it to idle or are you trying to give it more gas and it stalls no matter what you do?

A vac hose off could cause a bad idle, but if it starts in the first place you should be able to keep it running by working the throttle. How old is the gas in it? Its been sitting for a while since it last ran? How are the plugs and wires? Cap and rotor?

I'd say once again its poor fuel flow. filters or the intank pump and its screen.
Find where the Vac hose lives...its needed somewhere and many other systems are totally dependent on good vac. That could be causing it to die as ECM shifts without good vac control;.

 

[bartric]

@ Warren S, it runs for maybe about 15 seconds, at idle, and it'll die. But yes it does start right back up. By spraying gas, I mean there is a healthy cone of fuel being sprayed from the injectors up until the point that it dies. It isn't losing fuel pressure, I'm sure. It won't die if you give it gas, you can keep it running if you're giving it a bit of throttle, even the minimum amount that is noticable.

It doesn't just have "a" vacuum hose off, it has about 3, that I'm aware of. One coming off the front TBI that leads to the Air Input Valve, one of the hoses that runs from the rear TBI to the three way that leads to the air cleaner, and then another one running from that three way vacuum thing to one of the vac motors. Also one of them on the Air Input Valve is completely not there. So that actually makes 4 hoses. The gas in it is new, bought some to put in it. Plugs are what was in it, as are wires, the cap is one my dad had sitting around but it looked good on the contacts. The rotor, I'm not sure.



Drove it at least a good foot today, Had a decent idle in park and neutral, but in gear it was very rough feeling.

 

[boomdriver]

@ Warren S, it runs for maybe about 15 seconds, at idle, and it'll die. But yes it does start right back up. By spraying gas, I mean there is a healthy cone of fuel being sprayed from the injectors up until the point that it dies. It isn't losing fuel pressure, I'm sure. It won't die if you give it gas, you can keep it running if you're giving it a bit of throttle, even the minimum amount that is noticable.

It doesn't just have "a" vacuum hose off, it has about 3, that I'm aware of. One coming off the front TBI that leads to the Air Input Valve, one of the hoses that runs from the rear TBI to the three way that leads to the air cleaner, and then another one running from that three way vacuum thing to one of the vac motors. Also one of them on the Air Input Valve is completely not there. So that actually makes 4 hoses. The gas in it is new, bought some to put in it. Plugs are what was in it, as are wires, the cap is one my dad had sitting around but it looked good on the contacts. The rotor, I'm not sure.



Drove it at least a good foot today, Had a decent idle in park and neutral, but in gear it was very rough feeling.

Yeah, you gotta chase down all the vac leaks. With several possible vac leaks, fuel is less suspect.

ECM controlled engines are very precise in the fuel delivery, even in cold start and a small vac leak can screw up the ability to run especially at idle where the fuel metering has to be richer in order to run when cold. Just above idle the metering returns to normal, where the ECM constantly adjust to the changing operating conditions. Idle is the toughest rpm range for a motor to maintain.

In computer controlled cars, the duty of the choke is taken over by an automatic system that richens the fuel/air mix when cold. Thats initiated by temp sensors.
To minimize emissions and other negetive aspects of a rich mix, the cold start system is usually on timer switches (about 8-10 seconds or just during cranking) and related to temp or some other indicator that tells the ECM that its running and the richer or extra fuel is no longer needed. The extra fuel is very limited for many reasons, and its unnecessary. Old carbed motors would run for several minutes with the choke on, wasting gas and slowly destroying themselves in the process. Now we get precision thru the electronics and that means longer life and better economy. It also means that it likes to have everything "right"...

Have you got your Factory Service Manual?
In case nobody mentioned it, they are worth their weight in gold, and will have pics and drawings of the vac line routes, what and where they go and ALL the diagnostic info. The FSM is an absolute "gotta have".
I got mine on Flea-Bay for $75 used, for the 2 book set.

 

[bartric]

@boomdriver, thanks for the reply. There is currently only one vacuum hose that isn't connected. It is the one running from the Canister by the driver side light. The smaller hose. Not 100% sure what it runs to, but we think it runs to the PCV, although in the diagram it shows the smallest hose running to the Purge Control Solenoid which I'm not sure what it is or where it's located. we already have one hose running to the PCV but it looks like two are supposed to run to it and one was filled up with sealant or something.

I do have a Factory Service Manual with it, there is actually someone on Ebay selling copies of it that he burned onto a CD in .pdf format including the shop manual, the electric trouble shooting manual and the parts catalog for $10.

The book may be worth it, but I don't exactly make top dollar at my job and currently just spent a good $80 on some tune up stuff for it, rotor button, plugs, wires, fuel filter, air filter, gaskets that sit on top the TBI's. And after I get everything running right I plan on changing the oil in it too. Only reason I didn't buy a cap is cause there was already a new one with it along with a new coil pack. Rotor button was only thing that wasn't new.

Tomorrow is a busy day for me and my fuel/air filters and wires are supposed to come in at Advance, so I'm going to try to make some time to get all that stuff put on tomorrow and probably going to try to find that connector piece for the PCV to see if it's supposed to have another hose go into it along with buying some vacuum hose so that I can replace the broken one on the cannister.

 

[Schrade]

A vacuum leak means air is moving in somewhere BESIDES through the TB, and one result is less vaporization of the fuel.

A vacuum leak will make ANY internal combustion engine lope idle - a 30-year old lawnmower, or a new vehicle with no miles yet.

Is this built to spec, or are you just 'resurrecting' a broken one?

 

[bartric]

I'm ressurecting one suffering from "Idiot gone 'electrician' done tried to install a radio and clipped some wires" along with missing a few hoses and a partially broken PCV Valve that I'm replacing tomorrow.

Okay, a few questions for all you C4 owners, help me get some stuff plugged back up!

1. I found a red electrical hook up next to the canister close to the driver side front light, I can't quite see what it goes too, anyone that minds looking and telling me what theirs plugs into, I'd be thankful.

2. AC compressor: there is no vacuum hose attached to the back of it, and there is no plug attached to the front of it. Please trace these down and let me know where the plugs and hoses are coming from and going to.

Pictures would probably be very helpful too. Thank you.

This thing is like a 500 piece puzzle... except the owner before me seemed to have left about 300 of them at the auto parts store...

 

[Schrade]

It doesn't just have "a" vacuum hose off, it has about 3, that I'm aware of. .

Start here. You can find air leaks without tools. Get the vacuum ports capped, unless you can get the proper, UNcracked, hose that goes on EVERY vacuum port which is open. An air leak will make it run as rough as a fuel leak will.

Lets get the air right, then check fuel (pressure) afterwards, and then fire. You can do a static timing check too, without tools.

 

[bartric]

Okay, I've uploaded a video on YouTube of the car running, the audio is definitely not the best, but if you listen well toward the end you can hear it starting the 'almost die, rev, repeat' sequence until I turn it off.

YouTube - 1984 Corvette running problems.

I still think it may be the timing, because when we finally got it to hold a somewhat okay idle, my dad said it was reading 40 degree BTDC. And it's supposed to be 6.

 

[tcolyer]

Bartric, where are you located in Tennessee - I am outside NAshville and have worked with the crossfire a lot

 

[bartric]

Bartric, where are you located in Tennessee - I am outside NAshville and have worked with the crossfire a lot

About an hour and 10 minutes east on 40 to Cookeville then 20 minutes north on 111 to Livingston. So, it's a decent drive from Nashville.

 

[tcolyer]

AFter listening to the youtube video - it seems like a vacuum leak - have you checked the top intake plate for leaks or just replaced the gasket? It also could be very badly balanced TBs or injector issues.

This is a list of thing I did to mine:
82 Corvette Engine / performance modifications

1) CompCams XE256H camshaft 256/268 duration, 447 / 454 lift, 110 lobe Center angle. 106 Intake Centerline. Advanced 3degrees with crank gear
2) CompCams valve springs, Melling anti-pump up lifters, Melling push rods and CompCams 1.6 ratio roller rockers increasing lift by .030
3) Cloyes True Roller Double timing chain with multiple keyway crank gear
4) 1985 Monte Carlo SS 305HO Heads – (10 – 10 1/5 to 1) compression - gasket matched ported and polished
5) 1984 Corvette intake – new style ports are joined in 84 not 82
6) Intake mods: remove EGR tunnel, gasket match & port / polish runners, run two gaskets on upper plate, remove swirl plates
7) TBs were modified for adjustable fuel pressure – set at 14lbs
8) TBs spacers were added under the TBs and under the Injector riser
9) Factory exhaust headers had pollution tubes shortened and smoothed then gasket match ported / polish
10) Catalytic converter gutted and Walker Dynaflow mufflers installed
11) 1986 Corvette fuel pump installed for more pressure and flow
12) 1984 Corvette computer with Hypertech 160 degree chip

 

[warren s]

What does it run?

 

[tcolyer]

What does it run?

Never had on the strip but it pulls hard all the way to 6000 - guessing i would think it is around 300hp

 

[bartric]

We just checked for leaks with starter fluid earlier today, and found out the diamond shaped seal in between the intake and crossfire is letting in air almost all the way around. Just ordered the seal earlier to replace it.

 

[vetteboy86]

Is the cooling fan running in this video?

 

[bartric]

Is the cooling fan running in this video?

Yes, that's the terrible over tone that covers up the engine sound.