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I hope I'm in the correct forum. I recently acquired a 1984 Corvette, you know, the one with all the fuel injection problems. When you first start the car in the morning, the water temperature has to get to about 190 degrees before it will run right. Otherwise, it will spit and sputter down the road. Also, once you drive it for any distance, once you turn it off, it won't crank again until it cools back down. Any thoughts?
This is not quite accurate. People like to hate on systems that were not used for very long. (Crossfire/optispark being 2 good examples)
Originally Posted by John Gayle
I hope I'm in the correct forum. I recently acquired a 1984 Corvette, you know, the one with all the fuel injection problems. When you first start the car in the morning, the water temperature has to get to about 190 degrees before it will run right. Otherwise, it will spit and sputter down the road. Also, once you drive it for any distance, once you turn it off, it won't crank again until it cools back down. Any thoughts?
I'm not sure why the car would run badly when cold as it's running in open loop and not using many of the sensors. It's running off a pre-programmed mode before it enters closed loop and starts using all of the sensors. I'm not saying it's not using any sensors until closed loop but it relies on the sensors MUCH more when in closed loop.
Sounds like you have issues when cold and when hot. That's quite interesting. Usually issues running rough when cold is related to fuel metering. Is the car missing? Or just running weak? Backfiring? etc.
The Crossfire injection is actually a pretty reliable setup. First off, you need to make sure you're getting good spark and check the fuel flow from each throttle body. The throttle bodies need to be balanced as this is part of the maintenance needed on the Crossfire injection system. This is done with a manometer.
You should be sure that you do not have any vacuum leaks and make sure that the plugs, wires, cap, and rotor are all in good condition. It may be a good idea to measure fuel pressure to see if there's any drop in pressure at any time when hot or cold. I've seen the pickup hose on the fuel pump develop cracks and cause fuel pressure to drop and it takes some time when running to supply adequate fuel pressure to the engine.
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20-'21-'22-'23-'24
NCM Sinkhole Donor
If your car doesn't start till it cools, down, here is my question to you, does it crank and not start, or turn the key, and nothing happens till it cools down.
If it doesn't crank, it's the starter, seize up, and when it cools it will crank.
That is known problem with early C4, replace the starter and put blanket around it to protect it.
Happen to my car years ago.
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-'19-'20-'21-'22-'23-'24
NCM Sinkhole Donor
Car not running right, till it's warmed up, my best advice is get it diagnose, instead of throwing parts into the car.
There will be lot of advice, but get it properly looked at, it could be anything from fuel injector seals leaking when cold, and once it's warmed up they seal themselves.
Don't guess, it will cost you more in the end.
Car not running right, till it's warmed up, my best advice is get it diagnose, instead of throwing parts into the car.
There will be lot of advice, but get it properly looked at, it could be anything from fuel injector seals leaking when cold, and once it's warmed up they seal themselves.
Don't guess, it will cost you more in the end.
Excellent Suggestions with the exception that the 84 with crossfire does not have your typical injectors with seals and whatnot.
Welcome John and I just got rid of my 84. Good luck with yours. I did unfortunately have a bad example of a c4 of any year with my 84 and did not fully get to realize it's potential. Excited to see how yours does.
It is telling your car that the engine is hot when it is cold and signaling the computer to lean out the fuel. Plus, the wrong reading are making your IAC inoperative.
I'm not sure why the car would run badly when cold as it's running in open loop and not using many of the sensors. It's running off a pre-programmed mode before it enters closed loop and starts using all of the sensors. I'm not saying it's not using any sensors until closed loop but it relies on the sensors MUCH more when in closed loop.
The only sensor not used during warm up is the O2 sensor...all others are used as normal.
I agree we nee more info. Help us, help you. People often misuse the term "crank". "Crank" means that the starter is turning the crank shaft. "fire" means combustion is occurring in the cylinders, and "run" means that the combustion is sustaining and the engine isn't "firing" one or a few times and failing to stay..."running".
So....when you're car is hot, what is it not doing?
Cranking?
Firing?
If it cranks when hot, but doesn't fire, have you checked to see if you have fuel injection during this symptom? Spark? Those are the basic, first steps in diagnosis.
My first GUESS is that I would check the Coolant temp sensor...but a better description of the symptoms would help.
First off, you need to make sure you're getting good spark and check the fuel flow from each throttle body. The throttle bodies need to be balanced as this is part of the maintenance needed on the Crossfire injection system.
mazdaverx, I guess I need to ask for your advice. How do I check the fuel flow from each throttle body? And how often do I need to balance my throttle bodies? I've never done this on my '84, but then it only has 240,000 miles on it, and it starts runs perfect! Maybe when I hit 250,000 miles?
Also never balanced the injectors despite drilling/installing butterfly bushings in both TBs, that had worn, allowing unmetered air in. In 100k, my only issues with the Xfire was the teensy intake ports that delivered great low end torque, but starved the engine about 4200 RPM or so. Roy ported his and runs with the devils now & his antique PASSES SMOG W/no problem!
In addition to the ignition checks, I'd recommend vacuum reading diagnoses.
I throw parts as a desperate, last ditch measure and KNOW a few here are way more capable than the supposed 'experts' around the corner.
Last edited by whalepirot; 07-30-2017 at 12:57 PM.
mazdaverx, I guess I need to ask for your advice. How do I check the fuel flow from each throttle body? And how often do I need to balance my throttle bodies? I've never done this on my '84, but then it only has 240,000 miles on it, and it starts runs perfect! Maybe when I hit 250,000 miles?
I saw that exact weld on mine and was pretty sure Bubba did that....
I saw that exact weld on mine and was pretty sure Bubba did that....
That's a pretty hi-tech TIG weld for a "Bubba"! That's a factory weld, after the tech's got thing dialed in, and they're trying to keep the "Bubba's" from messing things up! I'm taking the hint!! Hand's off!! I've come to the conclusion they knew what they were doing!
To check your CFI injectors, point your ignition timing light at the fuel spray. You should see a nice even spray pattern:
Here's me (with my CFI) chasing a couple of ZR-1's and "Whalepirot", thru a nice curvy canyon! This much fun shouldn't be legal!
07-27-2017, 11:21 AM
1984 Corvette
