Hope someone here may be able to help. My 86 Vette began stalling a while back so I decided to change a bunch of things in the hopes the problem would go away. The original problem was the car would run ok but then after in was driven for a while and the engine reached a high temp; 225, the car would start running rough and eventually stall. The car would start right back up but I would have to keep engine revved up so it wouldn't stall again. I replaced the thermostat with lower degree thermostat. I did everything possible to get rid of the problem. Full tune-up; plugs wires cap and rotor and fuel filter. I even replaced all 8 fuel injectors after engine failed fuel pressure test.I even installed larger capacity radiator, making sure to burp cooling system and also replaced all vacuum line hoses. The car didn't run as rough before I did everything I just mentioned, cept for one thing. When I replaced the fuel injectors, I had to remove the distributor and when I remounted it, engine began running rougher than before, but this time after running engine for a few minutes, rpm's would start fluctuating from 800 down to 700 to 600 and engine eventually stalls. I thought I may have reinstalled the distributor 180 degrees off so I pulled it out and reinstalled it 180 from previous spot. At that point car wouldn't start at all, So I figured distributor was initially mounted correctly. I rechecked timing to make sure it was properly set. Still engine runs rough and stalls. Oh! there are no check engine codes popping up, what am I missing?

 

Can you keep the engine running with throttle pressure?
When you set ign. timing did you open the connector in the Tan/Blk wire coming from the Dist?
Did you use a new gasket set after opening the intake system?

Check fuel pressure at the Schrader valve and manifold vacuum with a "T" coupling at the plenum side port.

 

As I stated in original post, engine will run if I keep engine revved up, but once I let off the gas pedal, engine will fluctuate from 800 down to low of 600 and then will eventually stall. When I reset timing, I did disconnect the EST plug wire when setting the timing. After timing was set, I did reconnect the EST plug wire. What do you mean when you said did I open the connector in the Tan/Blk wire coming from the Dist?
I also installed all new gaskets for intake system, including one for the throttle body. I also replaced the vacuum control valve when I replaced all the vacuum lines. I'll recheck fuel pressure.

 

The connector referred to is the one in the blk/tan EST wire.

With good manifold vacuum, if fuel pressure checks out as stable I would think to perhaps clean/reset the IAC control, located below the TB. Connector is on the right side.

 

sounds like a stupid question but.. are you sure the distributor is down all the way and touching the block? it is possible to not have the gears lined up properly so it will not fit down all the way essentially allowing the timing to be off a tooth or more. i know it is unlikely but i have seen it done before, might wanna just make sure it is actually down all the way and touching the engine block at the flange there. . other than that. the iac like someone else said or even fuel pump pressure would be good places to look probably you said it failed fuel pressure test..... it's more than likely needing a new fuel pump then

 

Hi just wondering if you ever solved this issue or found out more about it. I'm having an almost exact problem on my 90 but even though when i press the gas the rpms go up, after about 30 seconds or so it will start to lower rpms and stall out within a minute.

 

Sorry to hear you are having same problem. I've not found the cause as I've stopped driving the car a while back and have it in storage in my garage. I don't know what the actual cause is but after doing some research back when I first made this post, I did read somewhere that it could be a problem with vapor lock or something like that. I did notice at the time that the engine temp would reach over 24o degrees so it could be a engine cooling problem or one of those heat sensors that work along with the computer and orders the engine to shut down as a safety measure. If you ever find out what the cause is I would appreciate it if you would send me a note, thanks.

 

For sure I will come back if I can figure it out. I also want to throw out there something I had almost forgotten and that is that the day before it did that, I had disconnected the battery to take out a taillight bulb that had broken and had left the metal base of the bulb stuck. I read some stuff yesterday about how disconnecting the battery is not a good idea, and one guy even had the same problem after he disconnected his battery. This doesn't make sense to me because why would it affect it the way it does, seems like a mechanical defect, and also one should be able to disconnect the battery anytime without bad things happening how else could we work on certain things. Anyway, still it was mentioned so I bring it up too in case it's significant. I just had mine towed into the driveway this morning but I won't be able to check it out until the weekend. Hope we can figure it out that's two more c4 on the road.

 

It clears the codes and the "learned" info so it defaults to what the tables from the factory say. No biggie. That guy is probably high on the gasoline fumes. I'd get a scanner before throwing more parts at it. One that can read data and not just the trouble codes.

 

check the tps sensor and fuel pressure regulator

 

Another thing i would check is the coolant temp sensor... the one that tells the ECM what the coolant temp is.. not the one for the gauge.