Hi

i just installed Pacesetter LT + Hooker catback on my 96 Z28. My problem is that now the car has been running excessively rich since then and is not even running now (erratic idle as the car was running on 4 cylinders only).

What to know :

1) i crush the coolant temp sensor (on the head) during the install. I was running the engine with my manual fan switch on. Can the sensor miss cause a problem ?

2) i have race LT without EGR, cats ... but i was supposed to have engine code after removing rear o2 sensors, EGR, AIR. I don't have any code and when i scan the engine, it says there is no problem ???? why my 96 OBD2 don't throw me SE code ?? (i had it bone stock)

3) i made a reading of o2 sensors while running as it is now : front give me : 0.305 for one and 0.850 for the other . rear are both at 0.405 but i have remove the sensors.
Any opinion ? can i fouled an o2 sensor since the install and car runs erratic because of it ? fouled plugs too because of this possible to ???

Any opinion would be nice

Pierre

 

I'm assuming you broke the coolant temp sensor on the drivers side head. That only connects to the dash coolant gauge, and does not affect how the engine runs in any way. The sensor that supplies the PCM with the required data is in the water pump. If you managed to break the sensor on the water pump, it will cause all of the problems you are seeing.
Is your car an "export" model, that may be exempt from US emissions requirements, and hence not programmed for the same emissions codes?

And, have you driven the car for an appreciable distance since making the changes? It takes time for the PCM to insure the diagnostics for each system is "ready". It can't set codes until it verifies "system ready".
I suspect your rear O2 sensors are reading 0.450 and not 0.405. That would be normal for a missing sensor. The PCM supplies the 0.450V bias signal to the sensor, and if the sensor isn't there, the PCM "sees" its own bias voltage.

How are you measuring the O2 sensor voltages? Cold start or engine fully warmed up? If its warmed up, the pre-cat sensors should be cycling rapidly from .0xx volts to .9xx volts. If you look at a single frame from a scanner, its not really representitive of the true operating conditions. On the other hand, if the O2 sensor readings are "stuck" at those values, its not in closed loop. It takes about 3 minutes to go into closed loop, the O2 sensors have to be hot and working, and the coolant temp (as sensed by the sensor in the water pump) has to be over 140degF. Did you take your measurements under those conditions?

Things that can cause it to run rich after header install
-poorly made O2 sensor "extensions"
-sensors contaminated during removal and install
-sensor contaminated by "burn off" from cera-metallic header coatings
-anti-sieze used on O2 sensors
-leaks in the headers before the O2 sensors
-misfires due to broken plugs, burned or arcing wires.

 

Hi,

thanks for the long answer.

1) ok i though this temp sensor was the PCM one and also dash gauge

2) hum it is a Z28 originaly sold in New Caledonia where i live. I don't have the answer if it can be a special programming for export. and yes i have been driving twice before problem appear but small distance (less than 10 km)

3) hard to answer :

i made the measurement after engine supposed to be warm but as i don't have the coolant dash working, i putted my manual fan on always to be sure not overheating. Temp might be lower than usual

Yes rear o2 were 0.450

Reading from AutoXray 4000 scan were not stuck. I will check all the things you are suggest me to look at. Will be a pain to check all O2 sensor "extensions to see if poorly made .

If O2 sensors contaminated ? how to check ? How to clean them ?

 

another question : can i put my rear o2 sensors instead of the front ones ?

 

The harness connectors for the front and rear sensors are different. You can't switch them.

Diagnosing O2 sensors is always difficult. With your scanner, you should be able to pull the "long term fuel corrections" (also known as "BLM's"). If the engine was running normally, they would be at, or close to 128. But if you are having the problems I listed, the BLM's would be elevated, well above 128.... maybe even approaching 160.

Scan for both Bank 1 and Bank 2 BLM's at idle. The scanner should indicate the "Cell" it is in, and at idle it will be Cell 16. Since you have a scanner, you can watch the coolant temp sensor on it to make sure the coolant is warm enough to let the PCM go into "closed loop". You can verify its in closed loop by looking at the "short term fuel corrections", also know as "INT's". If they are steady at 128, its not in closed loop. When it goes into closed loop, the INT's will start jumping back and forth, above and below 128 in response to the injectors.

The scanner is your best friend if you know how to interpret the data.

 

Thanks for the answer. I will do the test again after lunch

About o2 sensor : harness are diffrent but as i cut the wires for extensions on front , i can also cut the rear ones wire and connect them instead ? The sensors themselves are same on front and rear ?

 

i have made another test . I let the engine go to 145°F

then on the o2 sensors :

front : one stay at 1.080. The other oscillate between 0.130 and 0.350
rear : they both stay at 0.445

i have a long term fuel trim on the scan but it stay on 0.0%

i have also short term fuel trim which are : +15% for bank 1 and -38% on bank 2.

I notice also my adavnce move to -20°

Just for more : when i stop the engine wait a moment and start the car : it start running well then it take a few minutes to have trouble. Also after a few minutes i have (now) an SES light but the scan can't see any code.

I'm beleiving i have a probleme with an o2 sensor