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 normal 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 sensor in head in right away . I found the plugs, wires ,and sensor to be bad and replaced them all immediately in the water pump. 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 LT1 , Thank you in advance.

 

What "temp light" came on? Do you mean the "Check Gauges" light? Did the coolant temp gauge indicate it was overheating? Was is running rough when this light came on? What "normal checks" we're done?

Is the engine stock, or modified? If modified, what has been done to the engine?

I'll take a look at the scan file in the morning. In the meantime does it show any codes? Did you scan for codes BEFORE replacing all those parts?

 

Downloaded the file, and see is is a compressed for using .rar extension. Please upload the file(s) in it's original .csv format.

 

First is just turned key second is idle

 

Something wrong with the coolant temp sensor (or the wire). Did you replace the sensor in the water pump or the one on the driver side head? The idle log shows the coolant temp sensor at 68*F when the log starts, and at the end of the log it's only 72*F. Impossible after almost 5 minutes of idling.

The coolant temp sensor is causing all kinds of problems. Because the temp is low, the PCM sets the target idle speed as 900 RPM. The PCM has told the the idle air control valve to open up to the max possible value (160 counts) and the engine is still only idling at 500 RPM. Seems like the IAC is screwed up, or may the cat is plugged up, or the air filter is totally clogged.

The low coolant temp is also causing the PCM to set a very rich A/F ratio, because is thinks the engine is still cold, and needs cold start fueling. The low temp also prevents the PCM from going into closed loop, where it controls the A/F ratio based on the O2 sensor readings.

There are no codes shown, but it appears the PCM has been reset, clearing the codes and the long term fuel corrections.

You also need to answer the questions I asked in post #2. What light came on? Did you really replace all those parts, including the HEADS? Something doesn't add up.

 

MAP is up in the 80's too. Fred, is that normal for idling at only 500 rpm? Might confirm a blocked air intake.

 

No, not normal. I didn't have time to go much beyond what I mentioned in the post above. For the barometric pressure near 100kPa, a near-sea level reading, idle MAP would typically be in the range of 30-35 kPa. Might be another sign of a plugged cat.

Or maybe when he replaced the heads, the valves were adjusted wrong.

 

The other thing that stands out is the huge difference in O2 sensor readings. The left O2 is averaging 890 mV with a peak value of 995 mV, while the right O2 is averaging 222 mV with a peak value of 275 mV. With cold start enrichment, and all fuel trims locked at 128, I would expect both sides to be the same, and up in the 900 mV range.

The AIR pump appears to be disconnected, since there is no real change in O2 sensor readings when the relay shuts off.

He logged in early this morning but did not respond to the questions.

 

The check gauge light came on and no it did not over heat. Started running rough a couple days later. these are the normal check we made sure coolant level was good and no air in the system. found coolant hose to be bad and repaired. The Engine is Stock.

The Codes that were showed before we replaced all of the parts are P0505 which is idle air control system and P0217 engine coolant over temperature

 

Meant to say changed the temp sensor in head not changed heads. Checked the cat and air filter they were not clogged. Temp sensor in water pump wasnt reading it was at -40 so replaced temp sensor in water pump and found wires to be bad so we replaced wires and plug.

 

The "check gages" light comes on for several reasons. It would only come on for the coolant temp if the gauge was in the red = overheating. It will also come on for low system voltage and low oil pressure.

You indicate you have a 94. 93 though 95 are all OBD-1. P0505 and P0217 are OBD-2 codes, and could only be set by an OBD-2 LT1 (96/97). Your 94 should have 2-digit OBD-1 codes, such as DTC 14 = Engine Coolant Temperature (ECT) Sensor Circuit (signal voltage low, high temperature indicated). And, even if you had a 96/97 OBD-2, neither of those codes is valid. At least GM does not show either of them in the factory manual for the OBD-2 models.

Well, you still have a problem with the coolant temp sensor. How could your engine idle for 5 minutes, and the coolant not heat up? Only way possible is a thermostat stuck closed, but that would put the dash gauge into the red.

So far, none of this makes any sense. If you want help, you have to provide us with accurate info, that makes sense.

 

Where did you get those numbers? They aren't for a 94 LT1 or any Firebird that I know. They are OBD 2 codes and your scan is for an OBD 1.

 

sorry we used a newer snap on scanner to tell us what the codes were we had to convert the codes we originally didnt have 9495 scan sorry we didnt covert the codes first

 

Makes no sense. There simply is no such code for engine coolant over temp for a 94. Convert from what, convert to what?

 

I think this is somebody's idea of a bad joke. Time to check the IP address. I'm done with it.