I have a 95 Z-28 the car was runnig great one day and the next day it started to struggle to run over 3000 rpm i talked to some friends who have alot of experience with lt-1 engines and they told me it was the opti so i changed it. Still no start here is a list of parts that i have changed but it still won't go

opti
spark plugs
wires
coil
i c m
fuel pump
regulator
filter

the only time it will even try to start is with the intake elbow off and throttle held wide open i also pulled the intake and resealed everything

please help

 

Have you done the basics and checked to see if it was getting spark and fuel?

 

What is the fuel pressure?

Can you hear the fuel pump kick on when you turn the key to on (Dont crank)

Try spraying ( VERY SMALL ) amount of starting fluid into the intake manifold. Crank it. Watch out for it to catch **** on fire though. If it sputters, then you know you have at least some spark and it is likely a fuel issue.

Pull a plug wire off and have someone crank the motor with a plug in it, see that it is infact getting spark.

Get Noid lights and check the injectors to make sure they are pulsing.

 

i have 43 psi fuel pressure and i know i am getting spark at the coil i tried starting fulid and nothing i think the plugs may be fuel fouled even though i just put them in so i am going to try a new set of plugs

 

i have checked all the injectors and the harnesses and they are all working correctly

 

You went from running poorly (struggling to run over 3,000rpm) to "won't start". What was the exact sequence of events.... A) running poorly, then wouldn't start, replaced Opti.... or B) running poorly, replaced Opti, wouldn't start? If its "B", there's a possibility you aligned the Opti incorrectly when you installed it.

If it only shows signs of life when you open the TB, it might be an issue with flooding, since holding the throttle blades open puts it in "clear flood" mode. Might indicate excessive fuel pressure, badly leaking injectors, faulty coolant temp sensor.

Have you scanned it for codes?

 

if the coolant temp sensor is not working the car wont run or it will trigger the check engine light? so then the car shouldnt run without coolant? that seems odd.

 

yeah it was running poorly so i changed the opti i was real carful when reinstalling the opti to get the dow pin in the right location the o-rings did make it rather hard to get it seated in all of the way. Is it possible to still be able to bolt it up if it is not installed right ???

 

well i just put in the new plugs and it fired up and ran kinda as soon as you try to apply any throttle the car bogs down and then dies

 

Yes, the engine will run without the coolant temp sensor. And it should set a code and turn on the SES light. But when you first start the engine, the PCM has to assume the temperature from the CLT sensor is correct. If the sensor is not connected, or the sensor itself has an open circuit, the PCM sees infinite resistance on the circuit, which it interprets as a coolant temperature of -40degF. That means it seriously richens the mixture to compensate for sub-freezing cold start, and could flood the engine to the point where it might not start.

 

Injuneer, wouldnt you expect it to at least sputter some though?

I think he may have put the Opti on wrong. Pull the plugs and make sure they are getting spark all the way to the plug.

Pull the fuel rails off and crank it. Make SURE the injectors are firing.

If it has spark, and has fuel. The only other thing it needs is compression. I dont see you having a lack of compression. I mean anything is possible. But I wouldnt expect it. This would lead you to the next possibility. Incorrect Timing. This is only acheievable by putting the Opti on incorrectly.

What year is the car? If it is OBD II it would have a crankshaft position sensor. That can, on some cars, cause a lack of spark, fuel, etc. I am not sure how the PCM works on a OBD II F-Body, but its something to consider if your a 96-97 car. Someone who knows more about the electrical systems of these cars can chime in and correct me if the CPS doesn't control these functions like it does on many other cars.

Make sure you double check that stuff though.

 

i pulled a plug and checked for spark and it is bright blue
i still feel that i am getting to much fuel it smells real rich i will try to plug that senser back in i have been trying to start the car with the water pump off just to make sure i got everything hooked up right

 

I know this might sound rather stupid, but the other day i had this problem right after i replaced the ICM, turned out the long skinny tube that comes off the intake elbow had came disconnected. i popped it back in and it ran perfect..i dont understand it, but it worked fine with it on, and wouldnt run with it off. Just an idea..

 

i think you are talking about the silencer that comes off the bottom of the elbow but i have had that blocked off since i bought the car. so i am not sure

 

What did the old plugs look like when you pulled them out? Any signs of fuel soaking them?