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84 Engine Troubles, Please help!!!



I have a 1984 vette with the beloved crossfire. The car runs bad! It has a bad rough idle, and has loss of power (engine cutout) when applying the gas. The engine dies under any kind of load. You have to feather the gas just to keep it running, but will idle for a brief period at times. I have changed the plugs, wires, coil, module, cap, rotor, temp sensor, O2 sensor, but nothing seems to help. No engine codes set. Engine runs (when it does run) like it's only hitting on 5 or 6 cyclinders, but everything looked fine as far as the old plugs, and the new plugs and other parts did not make a difference.
I am at my wits end here!! Has anyone ran into this problem, or can anyone direct me in the right direction?

No engine mods, 85,000 miles.

Thanks, Gary
This may sound strange but have you changed you fuel filter and / or checked the injectors.

I was told by a mechanic that I needed a valve job at the tune of $700 .
I forgot to tell him there was a new filter in the console, he changed it and the truck ran great.

hope this turns out to be your problem as it's an easy and cheap fix.


First of all, welcome to the CAC. You and your vettes will love it here.
Second, as an owner of the "beloved xfire" I feel your pain, brother. I've never had your kind of problem, but I have read tons about our car. Have you synchronized your throttle bodies? It sounds like with all that you have replaced that synch might be your problem. Keep us informed. There are lots of people here that are wizards, we'll have you hunting mustangs in no time.:D
As RalleyRed suggested, I would look at the fuel delivery. The injectors on the crossfire are easy to test for proper operation or leakage and a new fuel filter along with fuel pump pressure test may be an inexpensive way out. Also check the Thermac temp. sensor for damper operation. Keep us posted. I would also take a look at base timing. When I replaced my coil,plugs,rotor on the 82 it needed timing advance to run properly.
Good Luck.:)
84 Nightmare

Thanks for the help and suggestions!
The fuel filter has been changed, and the fuel pressure is within specs so far. Can't seem to figure this one out!!
Here We go

Does the Check engine light come on?
( If it does we need to explore this further)
AND.. when the key is in engine off does the Check engine light .....light?

1) If the fuel filter is ok, remove the air cleaner( Top & Bottom), plug the vac lines going to the engine, that came off. now have some body start the car.. fuel coming out of both injectors?

2) How were the wires coming out of the coil, cruddy, corroded? Make sure these wires are not hanging on by a thread. Better yet..substitute the coil ( If possible )

3) How's the EGR...remove the vac line going to it, Is the egr shaft sitting ALL the way down? AND there should be NO vac on that line @ idle.

4)Remove the battery for a few minutes..let the ECM start fresh.

5) Have you cleaned/replaced the IAC valves?

6)To relearn the IAC valves.. let the car start for a sec then shut it down.. restart within 10 seconds, it will idle high and work it's way back down.

7) Is the tach on the dash working correctly? and when the car is running.. Voltage over 13.5?

8) How is the power connection ( the big red wire going to the BATT on the Distrib?) Make sure it's got 12 volts on it and the connection's not loose.

AND THE GROUNDS..check the frame ground points!

9) How much slop is in the distrib rotor... there should be NONE.. the unit has no mechanical or VAC
advance it Should be rock steady.

10) I had my last rotor self destruct.. it left bits of bronze all over the interior of the distrib, causing massive misfires.. what color is the spark.. nice blue 1" fatty..or 1/2" yellow.

Try these suggestions, It's hard to sus it over the internet.. but we will try.

Never ASSUME anything.

Sounds like a fuel pump problem. Install an 85+ fuel pump. The stock pump can't pump enough when it's old and worn to keep the pressure up when applying full throttle. Because of the series plunbing of the TB's the pressure drops rapidly when on TB squirts. Go to http://www.crossfire.webhop.net and sign up, then look in the techa rticles for the 85 pump install.

This is a very common CFI problem.


What the hell is that? My goodness it looks wicked! Did that start as an L83 engine? Would that fit under my hood? How many horses is that? I'm guessing that is an xram under there somewhere. Mighty impressive.
Hi Drewser.

Indeed that's a modded L83 block under all the stuff. The 2 bolt block is actually pretty good because it's a higher alloy content than the 4 bolts. This block is being machined for splayed 4 bolt moroso billet steel caps, hard blocked, modded here & there for better oil control and so on.

It would fit under your hood, the fuel lines on top of the manifold are no higher than the aircleaner on a CFI. The room on the side for the turbo's is where the problems are but that would be much easier to solve in a C4. This WILL fit my 82.

There's no X-ram under there, no CFI, it's a carbureted engine. Those are 4 dellorto DHLA 45 Tri-Jet (rare!) carbs (according to David Vizard the finest carbs ever made). They're somewhat similar to the Weber DCOE carbs with the difference that these are built for turbocharging (therefore the third jet -> tri-jet)

This is that manifold:

Horses? Don't know yet. The carbs can take 3 bars of boost but I'm not going to run that, it's a straat motor. I think I'll leave it at around 600 in the begin ning, slowly increasing and looking for knock or lean conditions. With a 7500rpm revving engine built like rock 1200Hp would be a breeze if you turn up the boost. That's a little too much if you ask me.

So Harley

Got it sussed out yet?

I just purchased an 84 with simular probs. Mine is hard to start, runs irratic, hessitates, appears to have an intermittant missfire, but no codes TPS measures ok, good spray pattern on the injectors, no drip from the inj. ? Anybody have any ideas?

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