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Roy
Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 1612
Experience:  ASE master tech for 40 years
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I have a 04 Monte Carlo ss 3.8 Super charged.15 seconds or

Resolved Question:

I have a 04 Monte Carlo ss 3.8 Super charged.15 seconds or so after start up, the engine "LOPES" then dies. Starts right back up but after about 15 sec it does it again. Replaced MAF and cleaned the IAC. Disconnected TPS while doing it and no change. Thoughts Customer stated that while at light it does that he hits pedal and most times will pull through it.
Submitted: 10 months ago.
Category: Chevy
Expert:  Roy replied 10 months ago.
good morning my name is XXXXX XXXXX I will assist you today

2 things come to mind right away. first is the egr may have carbon holding the pindel open just enough to produce a good vacuum leak.

the other is the fuel pressure regulator. remove the vacuum line and check if there is any fuel in the line. the diaphragm may be ripped allowing fuel directly into the intake

Roy
Customer: replied 10 months ago.

No fuel out the vac port.

Expert:  Roy replied 10 months ago.
and the egr???

also, check the fuel pressure

Roy
Customer: replied 10 months ago.

Fuel pressure is 44 idle cold. No egr gasket until after 12. Will have to pull then.

Expert:  Roy replied 10 months ago.
ok, i am going to a wedding. be back later to check on you.

roy
Customer: replied 10 months ago.

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

Customer: replied 10 months ago.


.

Customer: replied 10 months ago.
Relist: Other.
timelyness. He had other engagements.Not mad just need answer
Expert:  Roy replied 10 months ago.

sorry was at a wedding today. if you still want help let me know

 

Roy

Customer: replied 10 months ago.

Yep. Still need the help.

Expert:  Roy replied 10 months ago.

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??

 

roy

Customer: replied 10 months ago.

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%

Expert:  Roy replied 10 months ago.

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.

 

Roy

Customer: replied 10 months ago.

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?

Expert:  Roy replied 10 months ago.

could be a bad baro sensor which measures positive pressure instead of negative pressure.

 

I would not dismiss the injectors that easily.

 

Roy

Customer: replied 10 months ago.

Contacted owner and had dealership do injector service 4000 miles ago.

Expert:  Roy replied 10 months ago.

ok, and the baro sensor?? what reading do you have at idle and under load???

 

Roy

Customer: replied 10 months ago.

29.23 and doesn't change in idle or in gear under load with brake on.

Expert:  Roy replied 10 months ago.

the 29.23, what is that?? voltage?? hope not as it uses a 5 volt reference.

 

Roy

Customer: replied 10 months ago.


29.23 in/hg

Expert:  Roy replied 10 months ago.

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.

 

Roy

Customer: replied 10 months ago.

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?

Expert:  Roy replied 10 months ago.

I would replace the map/baro sensor and re test.

 

Roy

Customer: replied 10 months ago.

Map sensor on the drivers rear of the engine?up near the top?

Expert:  Roy replied 10 months ago.

correct, 3 wire connector and a vacuum line.

 

Roy

Customer: replied 10 months ago.

Put new map in and now reads 57.58 in/hg. Threw o2 sensor 1 performance code. Related?

Expert:  Roy replied 10 months ago.

that reading is way out of range. thats why the light came on.

 

what is the voltage reading??

 

Roy

Customer: replied 10 months ago.

Code was there before customer told me. The 27 is outta range or the 58 is outta range?

Expert:  Roy replied 10 months ago.

58 is out.

 

remove the connector and check for 5 volt reference voltage

 

Roy

Customer: replied 10 months ago.

put old MAP back in and now 9.6 in/hg and .60 volts.

Expert:  Roy replied 10 months ago.

ok, reading is much better but why did it change???

 

with it running it should be about 1.5-2 volts at idle.

 

Customer: replied 10 months ago.

29 and 58 numbers were the BARO numbers. MAP numbers were the other ones.

Expert:  Roy replied 10 months ago.

ok, with the new sensor, what were the baro numbers and the map numbers?? did they change under load???

 

Roy

Customer: replied 10 months ago.

they were the 58 baro and 1.3 map. Still did the same problem.

Expert:  Roy replied 10 months ago.
at idle??? under load??? need to see the 2 meaurements under those conditions to see that they are changing.
Customer: replied 10 months ago.

vac goes up and voltage goes up. WAY up when it starts lopeing till it dies

Expert:  Roy replied 10 months ago.
what is the voltage???????????
Customer: replied 10 months ago.

2.6 and 15.in/hg

Expert:  Roy replied 10 months ago.

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.

 

roy

Customer: replied 10 months ago.

They do. Customer is coming for car and taking to dealer. So no fix here.

Expert:  Roy replied 10 months ago.

sorry, diaging it from here is never easy.

 

Roy

Customer: replied 10 months ago.

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?

Expert:  Roy replied 10 months ago.
no, it will not.

I will be home tonight around 7. if you want to continue we should do it by phone.

Roy
Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 1612
Experience: ASE master tech for 40 years
Roy and 3 other Chevy Specialists are ready to help you
Customer: replied 10 months ago.

7 what time zone?

Customer: replied 10 months ago.

Did you get the number and what time zone are you in?

Expert:  Roy replied 10 months ago.
i am in central pa. just got home downing some dinner and then we will talk, give me about 1/2 hour that will be 8 pm est

Roy

No I did not get your number mine is(NNN) NNN-NNNN
Customer: replied 10 months ago.

XXX-XXX-XXXX

Expert:  Roy replied 10 months ago.
ok, i will call when i get done my dinner

Roy
Expert:  Roy replied 10 months ago.
some good reading for us


Supercharger Description and Operation

Description
The supercharger is a positive displacement pump that consists of two counter-rotating rotors in a housing with an inlet port and an outlet port. The rotors are designed with three lobes and a helical twist. An air bypass circuit is built into the housing. The rotors in the supercharger are designed to run at a minimal clearance, not in contact with each other or the housing. The rotors are timed to each other by a pair of precision spur gears which are pressed onto the rotor shafts. The forward end of the rotors are held in position by deep-groove ball bearings. The back end of the rotors are supported by sealed roller bearings.

The gears and ball bearings are lubricated by synthetic oil. The oil reservoir is self-contained in the supercharger and does not rely on engine oil for lubrication.

The cover on the supercharger contains the input shaft which is supported by two, deep-groove ball bearings and is coupled to the rotor drive gears. The pulley is pressed and keyed onto the input shaft. These bearings are lubricated by the synthetic oil contained in the same reservoir as the gears and rotor bearings.

Operation
The supercharger is designed to pump more air than the engine would normally use. This excess air creates a boost pressure in the intake manifold. Maximum boost can range from 48 to 63 kPa (7 to 9 psi) . Because the supercharger is a positive displacement pump and is directly driven from the engine drive belt system, boost pressure is available at all driving conditions.

When boost is not desired, such as during idle and light throttle cruising, the excess air that the supercharger is producing is routed through the bypass passage between the intake manifold and the supercharger inlet. This bypass circuit is regulated by a bypass valve which is similar to a throttle plate. The bypass valve is controlled by a vacuum actuator which is connected to the vacuum signal between the throttle and the supercharger inlet. Spring force from the actuator holds the valve closed to create boost, and vacuum pulls the valve open when the throttle closes to decrease boost. The open bypass valve reduces pumping loss thereby increasing fuel efficiency.

The solenoid valve attached to the bypass actuator is an electronically controlled, three-way valve. This valve, controlled by the PCM, determines whether pressure from the manifold is routed to the bypass actuator or closed off. The valve allows pressure from the manifold to open the bypass valve and regulate boost pressure during specific driving conditions.
Customer: replied 10 months ago.

Ordered new pcm per customer. Will be in Friday. Once flashed and ready and installed, I will let you know how it goes.

Expert:  Roy replied 10 months ago.
sounds good, I will call you friday evening

Roy
Customer: replied 9 months ago.

Put new computer in and did relearn procedure and the starter will not engage and it throws a security code in current codes.

Expert:  Roy replied 9 months ago.

ok, will call tonight

 

Roy

Customer: replied 9 months ago.

Something came up. Can you call sat after 830 am central until 5 pm central tomorrow?

Expert:  Roy replied 9 months ago.

just got home. eating dinner and I will call Roy

 

yes sir. tomorrow is better

Customer: replied 9 months ago.

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?

Expert:  Roy replied 9 months ago.
i will be here
Customer: replied 9 months ago.

Quick update.


 


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.

Expert:  Roy replied 9 months ago.
will be here

Roy
Customer: replied 9 months ago.

Finally got the pcm programmed correctly and what do you know, car runs fine now. Thank you!!!!!!!

Expert:  Roy replied 9 months ago.
good job... glad to hear it. congrats, happy customer and you are happy

Roy
Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 1612
Experience: ASE master tech for 40 years
Roy and 3 other Chevy Specialists are ready to help you

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