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I have a 94 camaro Z28 5.7 that was running fine then one day the temp light came on and then went off so I did a nomad check and everything was fine. A few days later it started running rough again so i went and got plugs and wires . There was no change in how it was running, still rough . I checked the internet and it said was it was a bad opti spark so I got new one and change it , there was still no change. I started looking further into it and changed the 02 sensors. Someone said it could be the coolant temp sensor so I put a new one in I also changed the water pump and put new heads in right away . I found the plugs, wires ,and sensor to be bad and replaced them all immediately . It also has new alternator ,knock sensor, coil module, intake gasket , fix exhaust leaks ,fuel filter , fuel pressure reg, egr, and the fuel pressure is 43 and holds . So now the car starts and idles rough for about 30 sec. n dies . Also put a different computer into the car and it still runs the same . Could someone please help?! I don't know where to go from here with this LT 1 , Thank you in advance.
If it starts and runs then dies after 30 seconds that strikes me as a fuel issue. If this was spark issue, it would either not start, or it would start and run like crap but at least it would run like crap forever and not die. You say pressure holds at 43psi. Does it hold exactly 43 psi even as the engine is dying or does it slowly bleed off? When you pull the plugs, are any darker than the others or are they all the same color?
Also, I see you have the ability to scan the car, I'm at work so I can't see the log. What is the coolant temp and injector pulse width? What are your IAC counts? What happens when you try to run the car in speed density? You say the plugs, wires, and sensor are bad. What sensor do you mean?
Last edited by AdsoYo; Nov 7, 2015 at 10:36 PM.
Reason: meant to say speed density, not closed loop
If it starts and runs then dies after 30 seconds that strikes me as a fuel issue. If this was spark issue, it would either not start, or it would start and run like crap but at least it would run like crap forever and not die. You say pressure holds at 43psi. Does it hold exactly 43 psi even as the engine is dying or does it slowly bleed off? When you pull the plugs, are any darker than the others or are they all the same color?
I agree fuel issue, check filter and oil pressure sensor or fuel pump. How are you testing the pressure, is it a "test gauge" or a hard mounted gauge - hard mount require that you remove the Schrader valve to operate correctly. The “test gauge” has one built in that will only let you see max pressure. And will not bleed down
30 seconds is the ECU priming the fuel system plus a timed runtime before the oil pressure switch takes over. Look at the pressure switch for sure and the fuelpump relay as well
Also, I see you have the ability to scan the car, I'm at work so I can't see the log. What is the coolant temp and injector pulse width? What are your IAC counts? What happens when you try to run the car in closed loop? You say the plugs, wires, and sensor are bad. What sensor do you mean?
Coolant temp cold start 48 degrees Fahrenheit, Injector pulse width B1 15.38 and B2 15.23 most of the time there all over the place, Iac Position 142
And hear is a list of everything we replaced o2 sensor, alternator, coolant temp sensor head, intake gasket, opti spark, fuel pres reg, egr,
air intake, throttle pos sensor, fix exhast leak, (spark plugs new and wire new ill check them again in the morning),
coolent temp sensor, water pump, plug for temp sensor, knock sensor ,coil moduler
15ms injector pulse is insane if that's at idle. Should be more like 3-5ms. The PCM is holding the injectors open for most of the engine cycle at that amount of time desperately trying to get fuel in. Your injectors either aren't correct for an LT1 or you have no fuel pressure. The IAC is way open, although for a cold start that might not be too crazy. Unplug the PCM for 20 minutes to reset the fuel trims, then hook up a fuel pressure gauge, unplug the MAF to put it in speed density, and fire it up.
Sorry About head things meant to say new temperature sensor in head. Fuel pressure with shrader valve out key on 38 psi key off in about an hour it drops off to 35 psi. The temp sensor in the water pump replaced with new also put new wire and plugs for sensor. free scan said it was at -40 degrees.now back up to. where we have ambient temp. All spark plug are all black no brownish tint.also did unplug pcm n unplug maf n would not start.
Last edited by CorysCamaro; Nov 10, 2015 at 03:43 PM.
The water pump temp sensor is the important one. If it's reading ambient, you're good there. Silly question but you plugged the PCM back in before trying to start it, right? If yes then your plugs must be fouled to the point there is no spark. Fuel pressure is good enough to start, I would still like to know what it is with engine running up to the point it dies on you. Can you tell if the plugs are oil fouled/carbon fouled/wet fouled etc? Could you post a pic? I was thinking this was a pump issue but since your plugs are fouled, we have to start exploring other causes.
The water pump temp sensor is the one the PCM looks at, the one in the head is only for your dash gauge. -40 is essentially open, meaning that sensor is failed or disconnected. Unplug the sensor when the car is sitting cold and hasn't run in a day so the coolant should be ambient outside temp, then get out your multimeter and read the resistance across it, and look at this chart.
If it is reading about 200 to 2000 ohms (I don't know where you live or what temp it is at your house) then it might be ok, if it's reading 100,000 ohms or open loop as in no resistance, it's broken. Sometimes they fail and get a dead spot in them.
If that checks out good, then you need to check the PCM side of the wires. It's a 20 year old car so the wires could be chaffed, cut, or loose. The PCM sends a 5v signal and a ground on the 2 wire. One of the 2 wires (key OFF) should read to ground. With the key on you should have 5v DC to ground on the other wire.
I would change your oil at this point as you have been flooding it with fuel and it's probably diluted with gas and will wipe a bearing when it starts.
Here is your biggest problem: you changed 50 things. You changed the opti, but what opti did you put in? Was it an el cheapo Chinese POS? It could have been bad out of the box. I would take apart your old opti, clean and inspect it, loctite everything as you put it back together, and give it another shot. What O2 sensors did you put in? Should have been AC Delco.
Last edited by bufmatmuslepants; Nov 12, 2015 at 05:54 AM.
All 8 plugs look like that? If so then the PCM is dumping fuel into the combustion chambers just like your injector pulse width was showing. You need to figure out why the engine is running so rich. You said the coolant temp sensor in the water pump is reading ambient so that would imply it is working and not the source of your problem. Although it would be nice to get the car started so we can make sure it's reading correctly all the way up to the engine being fully warm. It also doesn't look like leaky injectors since all 8 would not leak at the same time, that would be like winning the lottery.
When you tried to start the car with the MAF unplugged, did you remember to plug the PCM back in?
Have you checked for vacuum leaks? A good (and fun) way to check is to get a friend then go to your hardware store and buy a t-fitting and about 4 feet of some cheap bulk hoses and smoke a couple cigars into the engine through the brake booster hose, then see if the smoke leaks out anywhere.
You said this happened all of a sudden. So the car was running fine then one day it started running rough. The only other things I can think of that would cause the car to dump fuel suddenly are the MAF (which we've unplugged), wrong tune in the PCM (you said you replaced it, did you get an unmolested stock 94-95 PCM?), and bad wiring to the coolant temp sensor. You don't need to keep throwing money at this. This is a fuel issue and nothing needs to be replaced right now until you figure out what the problem is. Even those fouled out plugs can be reused since they're copper cores. They'll clean right up after some spirited driving
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Could someone please HELP?! 
