i have a 88 corvette with 78k miles, just bought car from original owner several weeks ago, he had a ton of receipts showing car has been very well cared for and maintained, when i got car it has what i would call a misfire, i bought and installed new injectors "new version orange from reputable injector company", only complaint they are louder then original "is that normal?", i kept them factory lb settings, all new intake gaskets, new egr, cleaned throttle body and iac motor, new plugs, plug wires, cap and rotor, car still when cold take s a 45 sec to start and when it starts it has slight black smoke coming out exhaust, also when you rev car to an rpm range you can her the missing in the engine, when driving the car and keep accelerator at one rpm range it surges, tired it at 2k, 3k, 4k, all the same surge and slight misfire, its a manual trans, it drives me crazy, i'm very **** about my vehicles running correctly, please anyone with any info would be appreciated....thanks

 

Black smoke out the exhaust is a sign of being too rich. First, pull any error codes. Pull some spark plugs, engine cold, look at their condition. Insulators should not be discolored, dark insulators show too rich condition. Too rich can cause misfires and hard starting. New or not, injectors could be leaking. Measure fuel pressure, it should be 35-42 psi and it should hold up for 1/2 hr after the ign is off. Rapid drop is a sign of leaky injector/s or defective check valve in the fuel pressure regulator. Too rich will also cause long cranking to start.

 

i put gauge on it, was at 41 left hooked up for 1/2 hr went to 39-38 area, is this normal pressure rate drop?

 

also running delco 41-808 platinum professional plugs and napa beldon premium wires "blue color",

 

You have pretty normal fuel pressure and normal leakdown rate. If your plug wires are resistance wires, measure each wire with an ohmeter, they should have the same ohms per foot resistance. GM wires are about 5000 ohms per foot. Another thing you could do this evening is to turn off your underhood lights and when it gets dark start the engine in a dark place and start looking for sparks along each plug wire. None of the wires should be touching metal and you shouldn't see sparks anywhere along their length. Any broken or missing wire looms should be replaced.

 

i did the night deal, no sparks, are the plugs correct 41-808 i don't see anything listed, bought new ones today #5 delco plat, i just put other plugs in and don't want to install these if the others are ok, as they are brand new, wires are brand new also, beldon premium, was going to get accell cap and rotor tomorrow and try that, i reset some earlier stored codes int he system and car ssem to run a little better still have long crank on initial start up, also when i bought tune up stuff i bought a relocation kit for mat sensor, now that i read it was probably a waste of money, but car had same issue before i relocated it so i don't think that is the issue either, just letting everyone know what has been done to car, can you read real time data on obd 1 cars, like o2 reading and such, maybe its worth the $100 to have chevy diagnose the car?

 

What did the old plugs look like you took out?

 

Check the grounds for the ecm, usually on the back of the heads, also do a resistance check on the coolant temp sensor. The resistance changes w/ coolant temp. You can find the listings online for temp/resistence values. Clean your maf sensor, I heard oiled air filters like K&Ns can coat the sensor & give wrong readings.

 

was it missing before you started doing this

 

Biggest problem on these cars is underhood temp. It takes it's toll on wires, hoses, vacuum lines.
The reason your car takes so long to start is the fuel pump relay is bad. THe engine has to wait for the oil pressure to come up to turn on the oil pressure switch that turns on the fuel pump.
The relay is on the firewall next to the wiper motor.
GM put that oil press. switch in there incase the fuel pump relay failed, it would still eventually start.
If the car is actually missing and has black smoke, it would indicate a leaking injector, but if your leak rate is minimal, I would go to the ignition system.
It sounds like you are going to "fix it up" anyway, I would try regrounding the coil in the distributor, or go to a hotter coil and check the distributor grounds, engine grounds, mass air relay, and just unplug the ignition module over by the heater while it is idling, any change indicates a bad module. (other than the computer throws a code)
Also, unplug the mass air connector, and check the pins/sockets in the plug. make sure they are all uniform, and none are bent back.
There are plenty of places for things like this to occur. Just careful inspection might just reveal something.
Go over the last service invoice that the previous owner had performed, it may provide clues as to why the car is like it is today.

Sometimes, the ignition coil can internally short, and cause weak spark, and the distributor module is almost 25 years old. Buy some of the white heat sink compound, and take the dist. module out, and put more compound in there and check all the wires and dist. condition.
Sounds more like a cracked cap, but these seldom crack because of the large diameter of the cap, and the plastic can flex more than a small base dist.

 

I just went thru the surging and missing, not to mention the killer black smoke on start n accel. Change your o2 sensor. $18 at advance it'll save you a $120 dealer charge. Let me know how it runs