So I recently bought an 89 iroc with the 5.7. I bought it with the plenum and runners removed so I put everything back on, replaced a bad injector. Now when I start it, it turns over and hits and when it finally starts it jumps to 4000rpm and then slowly drops off and dies. Any suggestions?

 

Vacuum leak? Did you mix up the runner gaskets on the lower manifold?

 

The gasket install went smoothly. I've checked and rechecked my vac lines and can't find a leak but I'm going to go ahead and replace all of them anyway. im stumped. I have spark and I have fuel pressure. Maybe check my timing?

 

In my opinion if it is going to 4000 rpm with a closed throttle then it is getting air from somewhere else. Must be a big leak. Can an IAC stick wide open?

 

I've replaced the iac, fuel pump relay, ignition control module, sending unit, fuel pump, fuel filter, checked my tps. It's at .56 volts. Replaced a bad injector. The idle has gotten better and I can sometimes start it without ether. Still climbs to 3500rpm. Sometimes it wants to idle. Fuel pressure is right at 40psi. it's not throwing any codes when it runs, so I suppose I'll tear down the plenum and runners and replace the intake gaskets and coolant temperature senser, and the fuel pressure regulator and egr valve and solinoid and double check to make sure I havent missed a leaking vac line. I really am stumped. But that's what I get for buying someone else's mess. Keep throwing ideas out to me this is my first tpi motor and whatever I'm missing is probably something simple.

 

This is how I set my timing and minimum idle speed and also resets the IACV .
Setting timing =

Disconnect the EST wire, start car and idle until the car is at operating temp., adjust timing, shut off car , reconnect EST wire.




Setting minimum idle speed.

• 1) Jump the A to B terminal under the dash
• 2) Turn the key on but do not start it
• 3) What 45 seconds then unplug the IACV with the ignition still on.
  You should hear a slight ticking coming from the valve.
  Disconnect the EST wire and remove the jumper.
• 4) Start the car.
• 5) It may be necessary to hold the throttle open slightly to prevent the engine from stalling.
• 6) Allow the engine to reach normal operating temperature.
• 7) Connect a tachometer. I used a digital timing gun with RPM feature.
  8) Adjust the minimum idle speed using the throttle stop screw.
  9) My Chilton’s says set it to 700rpm in park on an 89 TBI 5.0 auto.
  10) When done shut the car off and reconnect the EST wire.
• 11) Plug the IACV back in.
  Done
• Also a great investment if you need RPM feature. Overall makes a standard gun look like a rock.
• Amazon.com: INNOVA 3568 Digital Timing Light: Automotive
  Amazon.com: INNOVA 3568 Digital Timing Light: Automotive
  
  
  
  
  

 

Where do I locate the est wire?

 

Passenger side of the engine compartment near the strut tower. It's a tan wire all by itself with a connector in the middle.

 

Looks like this =

 

I unplugged the wire and I could immediately notice a difference when I tried to start it. Had to quit early tho since it's midnight and the woman was irate. I'll try again in the morning and let you know how it goes.

 

Wouldn't start at all with the est unplugged. But actually idled a little longer when I plugged it back in.

 

Still haven't figured out what is going on with the car. Going to remove the plenum and runners. Replace all of the injectors. Replace the gaskets on the intake and put a new distributor cap and rotor. I'm getting 44psi at the rails but I'm going to go ahead and replace the pressure regulator and the egr valve and fully inspect all of my vac lines. Getting kind of fed up with this car.

 

Before you spend a fortune, take the intake apart and double check the runner gaskets. Any time I've seen the problem you have is from a BIG vacuum leak. While it's apart check you can check the egr to make sure it's not stuck open.