Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
No fuel out the vac port.
Fuel pressure is 44 idle cold. No egr gasket until after 12. Will have to pull then.
ok. Will reply when egr is pulled and checked. What should the fuel pressure range be? What should the Supercharger bypass valve be doing at idle and at throttle? Seems when it starts to stumble, I unplug the bypass solenoid and the idle smooth's out. coincidence or issue? Pulled EGR and it is nice and clear
sorry was at a wedding today. if you still want help let me know
Yep. Still need the help.
ok, fuel pressure should be 45-48 lbs.
What are the long term trims???
Did you check the back pressure on the cats???
Did you check the actual egr valve for the pindle seating and not being hung up from carbon??
Fuel pressure 46 running
-2 % Long term trim
Disconnected exh and still did it.
Used EVO scanner and operated egr and killed motor at 30%
all readings look good. the only other suspect I have is injectors. Have they been changed or professionally cleaned?? additives have little or no effect.
I find that improbable. When I pull a vac plug off a port the motor will kinda act like the problem . When it happens, the Bypass actuator acts like the ecm is calling for boost. (low vac condition) and opening allowing the supercharger to build pressure. So if its acting like a low vac condition,and no leaks, what could cause this?
could be a bad baro sensor which measures positive pressure instead of negative pressure.
I would not dismiss the injectors that easily.
Contacted owner and had dealership do injector service 4000 miles ago.
ok, and the baro sensor?? what reading do you have at idle and under load???
29.23 and doesn't change in idle or in gear under load with brake on.
the 29.23, what is that?? voltage?? hope not as it uses a 5 volt reference.
thats a vacuum reading. you have great vacuum at idle. the fact that it does not change under load tells me you may have a bad sensor as manifold vacuum drops under load and you indicated the reading stays the same.
Correct. With foot on brake and bring rpm up to 2500 in gear that reading didn't change. So what should I look for now?
I would replace the map/baro sensor and re test.
Map sensor on the drivers rear of the engine?up near the top?
correct, 3 wire connector and a vacuum line.
Put new map in and now reads 57.58 in/hg. Threw o2 sensor 1 performance code. Related?
that reading is way out of range. thats why the light came on.
what is the voltage reading??
Code was there before customer told me. The 27 is outta range or the 58 is outta range?
58 is out.
remove the connector and check for 5 volt reference voltage
put old MAP back in and now 9.6 in/hg and .60 volts.
ok, reading is much better but why did it change???
with it running it should be about 1.5-2 volts at idle.
29 and 58 numbers were the BARO numbers. MAP numbers were the other ones.
ok, with the new sensor, what were the baro numbers and the map numbers?? did they change under load???
they were the 58 baro and 1.3 map. Still did the same problem.
vac goes up and voltage goes up. WAY up when it starts lopeing till it dies
2.6 and 15.in/hg
ok, the readings are within spec.
look at the mass air flow. idle voltage and see if the voltage rises when the rpms go up.
They do. Customer is coming for car and taking to dealer. So no fix here.
sorry, diaging it from here is never easy.
Cust didn't even make it out of driveway. When first starts, boost gauge is up in the middle. When problem happens, boost gauge is at -10. SO since we checked all the other sensors, can the O2 code cause this runability problem?
7 what time zone?
Did you get the number and what time zone are you in?
Ordered new pcm per customer. Will be in Friday. Once flashed and ready and installed, I will let you know how it goes.
Put new computer in and did relearn procedure and the starter will not engage and it throws a security code in current codes.
ok, will call tonight
Something came up. Can you call sat after 830 am central until 5 pm central tomorrow?
just got home. eating dinner and I will call Roy
yes sir. tomorrow is better
We have now put the second pcm in the car and the security light will turn off after the first 10 min relearn step,but stays on for the other 2 10 min steps. Thoughts?
Put a friends tech 2 on it and the pcm was flashed wrong. Will be flashing it again today and installing later. Will let you know what happens.
Finally got the pcm programmed correctly and what do you know, car runs fine now. Thank you!!!!!!!