Possible purchase of a 1984 C4 Corvette.

[Dennisch]

A friend of mine is on the verge of buying a C4. He wants me to come with him to checl the car out, and since America has a lot more of them than the Dutchy lands, I request some tips what to look for.

So, those with the knowledge, tell me the stuff.

 

[Cano]

tell me the stuff.

Here's all you need to know:

 

[Dennisch]

While awesome, that didn't help at all.

 

[Heldenzeit]

84 is the worst year of C4. Awful injection system, low power, and fussy electronics. If possible, try and find at least an L98 powered car, if not an LT1.

 

[playnthru]

First year C4's are notorious for problems with their Cross fire injection units.

 

[Tornado]

I always found it amusing that GM took a year off to make the changeover smooth and still completely biffed it.


Gotta love Roger Smith.





Also:

I request some tips what to look for.

A different year.

 

[JMoney]

The C4 is my favorite generation Corvette, but as already explained I'd look for a newer one.

 

[Blood Eagle]

Crossfire injection? No thanks.

 

[Zenith]

I have a friend who has a C4 Vette. Even with the LT1 the Crossfire injection broke literally two days ago. Stranded the car and made him have to get a tow.

If you can work out the fuel issue then you've got an awesome machine with tons of potential for serious builds. What's your friend trying to do with it?

 

[AnthonyD1993]

Yeah, avoid the Crossfire injection powered cars. Crossfire injection cars are dubbed "Ceasefires" for a reason.

 

[Tornado]

Also, I don't know what the roads are like in Dutchy Lands, but 1984 was the year where all Corvettes essentially had the wheels bolted to the frame directly to get better lateral handling numbers.

 

[Heldenzeit]

I have a friend who has a C4 Vette. Even with the LT1 the Crossfire injection broke literally two days ago. Stranded the car and made him have to get a tow.

If you can work out the fuel issue then you've got an awesome machine with tons of potential for serious builds. What's your friend trying to do with it?

LT1 wasn't available with crossfire...

 

[Zenith]

LT1 wasn't available with crossfire...

My bad. It was the Optispark that failed on the LT1.

 

[Heldenzeit]

My bad. It was the Optispark that failed on the LT1.

Yeah thats common. Mine did too on my old 93.

That's a fun service job to do alone.

 

[Dennisch]

What's your friend trying to do with it?

He'll be treating it as a classic car.

Are the issues with crossfire failing parts or just bad design issues, like ground problems?

Also, I don't know what the roads are like in Dutchy Lands, but 1984 was the year where all Corvettes essentially had the wheels bolted to the frame directly to get better lateral handling numbers.

Mostly smooth so that shouldn't be an issue.

 

[Tornado]

Are the issues with crossfire failing parts or just bad design issues, like ground problems?

Yes.

 

[Dennisch]

Dammit.

I've been googling my ass off, and it seems most problems come from either a failing magnetic pickup coil, seen that plenty of times on various GM products, and crappy connectors.

I do remember that GM has that problem identify system where the check engine light flashes and you count them, does the Corvette has that system too? Because if so, I'm gonna check the connections on the car and if they look good, I'm not scared to give him the thumbs up. As I said, it's supposed to be a low milage car, 40k or something.

 

[Grandea GTR]

C4 Corvettes, while better than the C3, were still of "huegh" quality. Especially the early models for that gen.

 

[Dennisch]

So, turns out the reliability stories are true.

The car died twice during the testdrive. After the first it fired right up, after the second it needed auxiliary power input, or in layman's terms a tow cable.

So, the friendly advice I wanted to give wasn't necessary.

Edit.

It was a really nice car, 60000 km. Full service history, not a dent or a scratch. Interior brand new.

 

[Ibonibo]

^

Optispark

Transformers much?

 

[Heldenzeit]

Optispark has a mind of its own. Optispark is self aware.

 

[wfooshee]

Well, I guess it's too late to offer advice, but the Crossfire system was so named because it's barely real fuel injection. The intake was basically a carburetor system, 2 spots on the manifold for carbs, each one feeding runners to the opposite side of the engine ("Crossfire") to get good runner length. Intead of a carb, though, they stuck a throttle body injector, basically a fuel injector in a carb venturi. It could be controlled electronically, so emissions needs were able to be handled better.

So instead of a modern port fuel injection system, with an injector above each intake valve, you had an injector way back at the beginning of the intake path, top of the manifold, feeding four cylinders, and you did that twice.

It was a stop-gap at best, a way to meet emissions regs while the "real" system was still being developed.

So they skipped a year, still couldn't get it right, but finally the '85s had a decent system on the motor.

Nobody actually wants an '84 Corvette!

 

[Heldenzeit]

Cool in theory, it was like a crossram on a 69 Z/28.Crossfire top pic, crossram bottom pic.

 

[playnthru]

Slightly off topic but…Chevrolet produced some Z/28's with Crossfire injection in 1982-83ish. They didn't run any better than the 1984 C4 though.

 

[Zenith]

The rule of American cars remains true.

In general, you don't want a Ford from the 70's, a Chevy from the 80's, or a Chrysler from the 90's.

 

[wfooshee]

And you NEVER want ANYTHING from the first year it was available!!!

 

[Dennisch]

Cool in theory, it was like a crossram on a 69 Z/28.Crossfire top pic, crossram bottom pic.

It looks like they took a TBI throttle body, made it single injector, and then stuck two of them on it. Would have been wiser to just use a larger flow throttle body, me thinks.

Edit. Sure looks like it:

 

[Heldenzeit]

Thats exactly what they did!

 

[wfooshee]

Um.... a TBI throttle body IS a single injector..... usually. If you put two throats on it you put a second injector on it, like the one you pictured. But that's what TBI stands for: throttle body injector. (So you described a throttle body injector throttle body..... ) A throttle body is really nothing but the bottom half of a carburetor, so they were just mixing fuel into the air with big injector instead of a carb venturi. Easier to control electronically than a carb, and a stop-gap to get better emissions control. Bolts on to a manifold they may have even already had.

But by having the two of them they could have all eight intake runners a bit longer than a standard manifold with a single center-mounted throttle body would have allowed (without going way up through the hood) and the longer runners gave them a bit of intake tuning.

 

[Dennisch]

I've only seen the dual injector tbi so far, those crossfire 'carbs' are new to me. So I figured the tbi was dual injector. But hey, learn something new every day.

The tbi systems themselves aren't all that bad, right? I find them quite easy to work on thanks to that diagnosis system with the flashing light on the dash.