I have a 1985 L98 from a Corvette. It has been swapped to Speed Density, running the '730 ECU and a TPI chip from Larry's Electronics. I recently had some issues where the engine wouldn't idle and through trouble shooting have found that it's running very rich. The engine is currently in my Jeep after sitting for a couple years well protected in my garage. As far as I know, the engine is all stock.

The plugs are all fouled. The exhaust smells like gas and most recently, I was getting black smoke on startup.

After letting the engine warm up and hooking it up to TunerPro at idle I get the following info:

Throttle Position - .78
TPS % - 0
Coolant Temp - 87.5* C
Startup Coolant Temp - 20.75* C
Battery Voltage - 13.7 V
Fuel Pump Voltage - 13.5 V
Vehicle Speed - 0 MPH
Engine Speed - 700 RPM
Map Volts - 1.6 V
Map kPa - 40.24 kPa
Manifold Air Temp - 65.24* C

Target AFR - 14.73
O2 Sensor - Sweeping up and down
Integrator - 129
BLM - 156 (read as high was 160, as low as 144)
Block Learn Cell - 4 (this changes while driving)
Injector Pulse Width - 2.55 ms

I ohmed out all the injectors with them all ranging from 23 - 29 and one at 42. From what I've read that is pretty high.

The opinion I've gotten from a few people is that I've got leaking injectors. I pressured the system, clamped off the fuel and return lines and it does leak down to around 10 psi in 15-20 minutes. I used a thermometer to measure the exhaust manifold at each cylinder and there weren't any huge differences.

Does anyone have any insight? Does this sound like bad injectors?

 

The fuel pressure shouldn't drop below 30 psi even overnight.
Make sure the map senser is hooked up to manifold vacuum, not ported vacuum. Hook a vacuum gauge up to it, should be over 17 inches at idle, smooth needle. Check all grounds, I've seen GMs act funny w/ poor grounds. Olhm the coolant temp. senser too, & double check your ign. timing, make sure it advances when you rev it. Good luck.

 

MAP sensor is hooked to manifold vacuum. The engine is making about 18 inches of vacuum at idle.

I'll ohm out the coolant sensor if I can find out what it should be. The grounds should all be good, I just put this thing together and the harness is grounded at the same spot I grounded the batter to on the block.

It's running fine (except for a day), just rich.

 

tps reading of .78 at idle? Too high my friend, get it down to .54. It may not completly solve your problem, but it will help.

 

Google "GM engine coolant senser resistance" I found a chart right away.
90*C or 212*F = 241 ohms
10*C or 59*F = 5670 ohms
Thats basic room temp & fully warmed up values.
Vacuum is very good, I'd check fuel pressure, maybe an adjustable fuel press. regulator was installed, make sure the return line is unrestricted.

 

injectors should ohm out around 16...they're all high. Jon @ FIC will help you out