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Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), Cadillac Mechanic
Category: Cadillac
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2002 cadillac escalade 6.0l codes p0300, p0171, p0174, p0135

Customer Question

2002 cadillac escalade 6.0l codes p0300, p0171, p0174
, p0135 have replaced both upstream o2 sensors, plugs, wires, checked intake gasket and intake, fuel filter, checked injectors with ohms meter,dropped exhaust, fuel pressure 50psi. had heads checked, and still running rough cannot figure out
Submitted: 1 year ago.
Category: Cadillac
Expert:  Gm Tech (Cam) replied 1 year ago.

hi there, I am Cam. Can you tell me more about the fuel pressure, when is that pressure set? Driving or just with the pump on? Does it hold while driving and under load?

Customer: replied 1 year ago.
just setting because you cannot drive
Expert:  Gm Tech (Cam) replied 1 year ago.

Ok, was that with the pump running or after it shut off, and how long did that pressure hold when shutting off?

Customer: replied 1 year ago.
it held the pressure for awhile
Customer: replied 1 year ago.
it has held for at least 30m
Expert:  Gm Tech (Cam) replied 1 year ago.

But with the pump running only, what is that reading? Spec is 55-62

Customer: replied 1 year ago.
about 53psi
Expert:  Gm Tech (Cam) replied 1 year ago.

OK, that is low. Spec on this engine is 55-62 psi. Not at 53 psi, that should allow you to drive it even at lower speeds. Which cylinders are misfiring then?

Customer: replied 1 year ago.
3,4,5,6
Expert:  Gm Tech (Cam) replied 1 year ago.

Was the exhaust tested for being plugged?

Customer: replied 1 year ago.
we dropped the cats down and still same
Expert:  Gm Tech (Cam) replied 1 year ago.

Ok, is it a dead misfire or occasional?

Expert:  Gm Tech (Cam) replied 1 year ago.

And I see you did not check the actual flow test of the injectors, is that correct?

Customer: replied 1 year ago.
constant misfire and no we did not
Expert:  Gm Tech (Cam) replied 1 year ago.

OK, Next we need to actually flow test the injectors. This is done with a scanner and fuel pressure gauge. The test, which is a built in test on the scanner powers the fuel pump to prime the system. Then it pulses each injector for the same period of time. You record the initial pressure then ending pressure and compare. The drop in all injectors needs to be all with in 10% of each other.

Customer: replied 1 year ago.
1-56-55 #2-55-53 #3-55-54 #4-57-55 #5-57-50 #6-58-54 #7-58-52 #8-57-55
Expert:  Gm Tech (Cam) replied 1 year ago.

Thats a large difference between them all, but how long did each cycle? normally the pressure drops to ~35 psi. I am assuming you swapped coil packs around to rule out coils, wires, plugs and such?

Customer: replied 1 year ago.
1-55-35 #2-55-29 #3-57-35 #4-57-33 #5-57-54 #6-55-36 #7-55-34 #8-55-29 cycled about 10-15 seconds.
new plugs & wires & tried coils
Expert:  Gm Tech (Cam) replied 1 year ago.

That #5 is almost no drop and that tells me its plugged. I would take out the injectors and see what the back side of them looks like.

Customer: replied 1 year ago.
they all look the same. what am i suppose to look for
.
Customer: replied 1 year ago.
are you still in contact with me because i will be closing shop at 5:00 est. will i be able to contact you on monday
Expert:  Gm Tech (Cam) replied 1 year ago.

Yes I am still here. No fine debris? I would swap them around see if the misfire moves since you have them out. I will be around monday if you need .

Customer: replied 1 year ago.
i will talk too you monday after we switch injectors
Expert:  Gm Tech (Cam) replied 1 year ago.

ok

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