rfoster23g

I have a 1987 z28 with a 5.7l l98 with aluminum heads from a corvette. Just got the engine in and been trying to get it running right. I can keep it running if I keep it revved up but it seems to want to stumble a bit. The engine will die if it gets below 1500 rpm on the tac. The fuel pressure is a little above 35 psi at idle and jumps up to about 40 ish psi when revved. New ac Delco plugs, new wires, new distributor, and tuned ecu for 350. I cleaned the throttle body and Iac and swapped it out with another. The car still is doing the same thing even after cleaning the maf sensor. There is no check engine light on while running not sure where to go next any help would be much appreciated. Thanks!

Tuned Performance

iTrader: (92)

With the new distributor we’re you able to set the timing with the est disconnected.

Tuned Performance

iTrader: (92)

Any sign of cylinder miss ? Or does it run smooth at 1500 rpm ?

rfoster23g

yes we set the timing with the est but I believe it is a little too high at the moment since it cranks slowly at first. The engine is running pretty rough the lower the rpm goes I am going to check and make sure all the wires are correct for like the fifth time.

Tuned Performance

iTrader: (92)

You might want to start unplugging injector connectors. It could be a few bad injectors.

Tuned Performance

iTrader: (92)

Btw you can test the iac to make sure it’s getting a signal from the ecm. To do this jumper the aldl a to b turn the key to the on position. You will hear the iac moving if it’s getting a command signal.

ULTM8Z

Tuned ECU? Who did the tune? What did they do to it?

have you tried the factory memcal? If all you changed were the heads, it should idle fine with the factory memcal (assuming everything else is set up correctly)

Tuned Performance

iTrader: (92)

Arar is the tune , originally a 305 . Mild timing changes, tb lockup raise, fans on earlier. You can try installing in the stock prom in the dip socket in the memcal. Watch the notch it faces the same direction as the sockets notch. I’m not sure if it’s the tune though. If that engine sat for along time I’d suspect the injectors being clogged.

ULTM8Z

Dumb question, but I assume the cylinder displacement constant was updated?

Tuned Performance

iTrader: (92)

Dumb question, but I assume the cylinder displacement constant was updated?
Is there even a setting for this in $6e ? Or are you kidding !
My TC and tp don’t show this parameter. I know it’s in $8d .
I started with arar and made minor timing changes, disabled egr , tcc lock higher, fans on earlier.

ULTM8Z

Lol! I have no idea!!

maybe since maf cars sample the air directly the engine displacement is irrelevant

Tuned Performance

iTrader: (92)

Me too lol

rfoster23g

so I checked the injectors one by one and the only one that doesn't change is number two all others result in dip in rpm. Anybody have a set of used injectors or any suggestions? I am going to check them again though do you guys have any ideas what else i should check meanwhile.

Tuned Performance

iTrader: (92)

I have a used set but there unknown condition, you might want to contact southbay.

Tootie Pang

iTrader: (2)

Check the simple stuff first.

Check for vacuum leaks (hoses and ether spray)
Check for mixed up plug wires.

rfoster23g

Thanks for the help guys turns out number 2 plug was fouled and number 8 plug wire had slipped off enough that it was missing. The car still would not idle but ran alot smoother so I did the idle reset procedure and now it is idling great. I believe the car still has some bad gas in it because every few seconds it hiccups abit i am going to run some octane booster and drive to see if it clears up. Thanks again for the advice!

Tootie Pang

iTrader: (2)

Thanks for following up and closing the loop! Too many OP's just disappear without letting us know if their problem was resolved. Even if it wasn't.

Tuned Performance

iTrader: (92)

Great news