Issues Starting
Rule #1 Corvettes are not "usually" suitable for Daily Drivers unless it is either new or in very very good shape. They are not as bad as the British cars of the 60's but close in some ways. Do you have access to any OBD1 scanner or code reader thru all your buddies?
There are Factory Service Manuals made for each particular year of the C4's. You will NEED one of these to work on your Corvette. They are critical to have if you own a C4! They are available in Hard copy for about $85 and on DVD in PDF format for about $35 so you choose which works better for you. Be sure to get one made for the 1985 like your Corvette is as they are year specific.
When I first read your post I kept thinking are the spark plug wires on the right cylinders? This can cause symptoms like you describe above. Check the vacuum lines on your engine, if you have a vacuum leak all sorts of things could happen affecting the engine and it's idle speed.
I would start by performing a basic tune up on the engine and replace if needed the distributor cap, rotor, Spark Plugs, Spark Plug Wires. A good way to test to see if the wires are bad is to run the engine with the hood open at night-time when it is real dark. If you see sparks jumping around then your spark plug wires become suspect. If they are old they should probably be replaced. Inside the distributor cap look for carbon tracking that forms inside the caps and can cause misfiring. You can check each wire to see that it is getting a spark as that would be helpful to know. Just put a timing light pickup on each wire and see if it is flashing when sparking on all 8 cylinders.
This is only applicable IF your C4 has a MAF or it might have the MAP sensor instead. I am not that personally familiar with the 1985 Model so I have to ask. If you have a MAF then get a can of spray MAF cleaner and be very careful cleaning the sensor wires on the MAF. The tiny wires that measure the air flow are about 1/10 the diameter of a hair and very breakable. Your Mass Air Flow sensor measures the volume of air flowing into your Combustion chambers and if it is not accurate the car will not run very well if at all. Try and unplugging the MAF and see what the engine does when you start it up. IF you have a MAF sensor it will be on the tube that connects to the throttle body. There can be absolutely NO air leaking in between the MAF and the throttle body or it hurts the output signal.
Are you familiar with the Throttle Position Sensor and the Idle Air Control devices? The TPS needs to be set at a precise number to work properly and the IAC is a "controlled air leak" that should hold your idle speed where you set it. IAC's can and do go bad and if you do have to replace it be sure to get one with the same shape Pintle on the tip. The pintle goes into the throttle body and controls the idle speed for the Engine Control Module. I bought one and they gave me one with a different pintle altogether so I learned about these devices the hard way. I would imagine that your engine just needs a little love and a few new parts.
Is it displaying any Codes or warning lights currently? Another tool that you might need is a Fuel Pressure Gauge with a long discharge hose on it. Your engine has basic fuel pressure requirements and needs around 42 psi at idle, the fuel pressure being off will cause all kinds of drive-ability issues. We attach the FPG to the Schrader Valve on the passengers side fuel rail. There is a Fuel Pressure Regulator under the plenum connected to a rubber vacuum line. Pull the vacuum line off the FPR and smell inside the hose. IF there is a strong smell of raw gasoline then it might indicate a bad FPR Diaphragm which would then need to be replaced.
How good are you with working on engines? Do you know the OBD1 versus the OBD2 worlds? Are you familiar with the process that occur when you start up your Corvette? Are most of the problems after warm-up or before? When does the car act up on you? The more details you can give us the better we can help you.
As you try these various test be sure to tell us what happens and when you fix your Corvette we ask that you tell us what was the cause of your issues. We all want to learn so this way it helps everybody involved. Putting details on the Profile page also helps from getting hit with the same questions over and over.
As far as the Fuel pressure gauge you might be able to borrow one from a local auto parts store if you don't have one. I personally bought one as I like to play with my cars. Be very careful as pressurized gasoline can vaporize extremely quickly making it a Huge Fire hazard. Any time you work on the fuel system be sure to have a fire extinguisher handy just in case. If the rails are pressurized I would suggest that you don't push the center pin or gas will squirt out everywhere potentially even under 40+ PSI. A really bad idea if you are smoking at the time.....
Waiting for your answers here, Good Luck and be Safe!
Chris
Rule #1 Corvettes are not "usually" suitable for Daily Drivers unless it is either new or in very very good shape. They are not as bad as the British cars of the 60's but close in some ways. Do you have access to any OBD1 scanner or code reader thru all your buddies?
There are Factory Service Manuals made for each particular year of the C4's. You will NEED one of these to work on your Corvette. They are critical to have if you own a C4! They are available in Hard copy for about $85 and on DVD in PDF format for about $35 so you choose which works better for you. Be sure to get one made for the 1985 like your Corvette is as they are year specific.
When I first read your post I kept thinking are the spark plug wires on the right cylinders? This can cause symptoms like you describe above. Check the vacuum lines on your engine, if you have a vacuum leak all sorts of things could happen affecting the engine and it's idle speed.
I would start by performing a basic tune up on the engine and replace if needed the distributor cap, rotor, Spark Plugs, Spark Plug Wires. A good way to test to see if the wires are bad is to run the engine with the hood open at night-time when it is real dark. If you see sparks jumping around then your spark plug wires become suspect. If they are old they should probably be replaced. Inside the distributor cap look for carbon tracking that forms inside the caps and can cause misfiring. You can check each wire to see that it is getting a spark as that would be helpful to know. Just put a timing light pickup on each wire and see if it is flashing when sparking on all 8 cylinders.
This is only applicable IF your C4 has a MAF or it might have the MAP sensor instead. I am not that personally familiar with the 1985 Model so I have to ask. If you have a MAF then get a can of spray MAF cleaner and be very careful cleaning the sensor wires on the MAF. The tiny wires that measure the air flow are about 1/10 the diameter of a hair and very breakable. Your Mass Air Flow sensor measures the volume of air flowing into your Combustion chambers and if it is not accurate the car will not run very well if at all. Try and unplugging the MAF and see what the engine does when you start it up. IF you have a MAF sensor it will be on the tube that connects to the throttle body. There can be absolutely NO air leaking in between the MAF and the throttle body or it hurts the output signal.
Are you familiar with the Throttle Position Sensor and the Idle Air Control devices? The TPS needs to be set at a precise number to work properly and the IAC is a "controlled air leak" that should hold your idle speed where you set it. IAC's can and do go bad and if you do have to replace it be sure to get one with the same shape Pintle on the tip. The pintle goes into the throttle body and controls the idle speed for the Engine Control Module. I bought one and they gave me one with a different pintle altogether so I learned about these devices the hard way. I would imagine that your engine just needs a little love and a few new parts.
Is it displaying any Codes or warning lights currently? Another tool that you might need is a Fuel Pressure Gauge with a long discharge hose on it. Your engine has basic fuel pressure requirements and needs around 42 psi at idle, the fuel pressure being off will cause all kinds of drive-ability issues. We attach the FPG to the Schrader Valve on the passengers side fuel rail. There is a Fuel Pressure Regulator under the plenum connected to a rubber vacuum line. Pull the vacuum line off the FPR and smell inside the hose. IF there is a strong smell of raw gasoline then it might indicate a bad FPR Diaphragm which would then need to be replaced.
How good are you with working on engines? Do you know the OBD1 versus the OBD2 worlds? Are you familiar with the process that occur when you start up your Corvette? Are most of the problems after warm-up or before? When does the car act up on you? The more details you can give us the better we can help you.
As you try these various test be sure to tell us what happens and when you fix your Corvette we ask that you tell us what was the cause of your issues. We all want to learn so this way it helps everybody involved. Putting details on the Profile page also helps from getting hit with the same questions over and over.
As far as the Fuel pressure gauge you might be able to borrow one from a local auto parts store if you don't have one. I personally bought one as I like to play with my cars. Be very careful as pressurized gasoline can vaporize extremely quickly making it a Huge Fire hazard. Any time you work on the fuel system be sure to have a fire extinguisher handy just in case. If the rails are pressurized I would suggest that you don't push the center pin or gas will squirt out everywhere potentially even under 40+ PSI. A really bad idea if you are smoking at the time.....
Waiting for your answers here, Good Luck and be Safe!
Chris
A lot of these terms I'm following to the best of my ability but I will definitely at least check for sparking tonight when I get off of work. Just to clarify the FSM is not the owners manual? I got the original one with the car. I can provide some more background. It hit 51500 miles in 2011 and wasnt driven again except to a dealer in early 2021. The dealer was a good gig nothing shady, they said that they serviced it a bit. After purchase I took it to a specialist shop in Chicago, they only work with Corvettes. They quoted me for $2100 of work a lot of which included things such as flushing every system and what not. I didnt have the time so I had to take it 1000 miles down to GA. I couldnt drive manual initially so my dad drove for 400 miles, he rode the clutch for the majority of it
We were having issues with the gas gauge reading properly and if we started the car on an incline it stalled (Restaurant parking lot had some elevation to it) Gas gauge hasnt read properly since we bought it. Took it to a small place called Earl's Garage over here. He has a lot of Corvettes that he works on. Showed me that someone accessed the fuel system as the rubber or plastic cover was missing, so my cap area just has wires and everything exposed. I thought that was normal
When he has an opening he is going to check the wiring in that area and if its not that he said I should get a whole new pump system cause the sensor in there is probably bad. A specific scenario where this would happen; I went ab 20 miles and stopped, went in the store for ab 30 minutes, came out and went to start the car, kinda sounded weird like it was struggling went to 1300 revs then just kept going down and down around 500-400 it started shaking really bad and i thought the engine was going to die so i feathered it gas to keep it alive which worked. My interior was also abnormally hot and the coolant temp was at 227 degrees. Took it 5 more minutes to another store, only spent about 10 minutes there. Similar coolant temp, same bad noises when starting, died even faster before I could give it gas. Thats about all I remember other than it just sometimes sounds bad sorry I cant do better than that (There was a time when I ran out of gas driving it so I track my miles now, still think that one is on me trying to save money on gas. This was after the story I mentioned though)
As for Rule #1 I dont have another option yet but I only put about 200 miles a month on it. There are no codes or warning lights at all. I should be able to find an OBD1 scanner somewhere, there is a community garage on base where you can rent a lift I just dont know what their tool spread is like. No clue the difference between OBD1 and OBD2 or the starting process. I do have some problems with gearing but thats probably a different topic, short story, if im in a parking spot, I have to shift to 1st then neutral then reverse. If i go straight to reverse my gears bang. I hope I covered as much as I could let me know if I can provide anything else!


if upu take more than one off, thrre is a fiagram of the hoses on yop left of the radiator cover.
slso look at the hoses on the cruise control just above the battery on the left side behind left wheel well.
In a single post to this thread mention as much as you can regarding the build. If the SPID (Service Parts Identification) Label is still in the rear compartment you might take a 'snapshot' of it and post it!!
CHECK YOUR PM's my email is there!
Last edited by WVZR-1; Feb 5, 2022 at 11:32 AM.
The Best of Corvette for Corvette Enthusiasts
if upu take more than one off, thrre is a fiagram of the hoses on yop left of the radiator cover.
slso look at the hoses on the cruise control just above the battery on the left side behind left wheel well.
Ok.....I'll try to answer this....A C4 isn't really an investment. If you have some money, maybe sell this car and buy a better C4, if this is the body style you like. You will probably spend 5 times more than this car is worth. I pulled my 86 out of a junk yard waiting to be parted. Sometimes, in the beginning I wish I left it there!!! As far the videos, just search on line and anything you want to see will be there. As for the tools I would take one job at a time in buying. I would suggest a good socket set, open ended wrenches, various pliers, various screw drivers, a HAMMER!!
A good corvette shop that still works on C4's is hard to find. If you find one the labor rate is usually very high. Just any mechanic cannot work on these. They usually do more harm than good. I'm not saying you can't find one, just hard.
Where are you located??
In a single post to this thread mention as much as you can regarding the build. If the SPID (Service Parts Identification) Label is still in the rear compartment you might take a 'snapshot' of it and post it!!
CHECK YOUR PM's my email is there!
A good corvette shop that still works on C4's is hard to find. If you find one the labor rate is usually very high. Just any mechanic cannot work on these. They usually do more harm than good. I'm not saying you can't find one, just hard.
Where are you located??
Failed: https://drive.google.com/file/d/1VKY...ew?usp=sharing
One last addition and the reason why I think my pump might be toast, when I was adding gas it wasnt gradual pressure on the pedal, that was pedal to the floor, and there was some bad lag so I dont know.

















