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2004 chevy trailblazer_lt
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I know there are pressure gauges out there that will tell you what the back pressure is for a cat converter - it's screwed in where the upstream O2 sensor goes and if the pressure is below a certain pressure (real low like under 4 psi if I recall correctly) then the cat is not clogged. You might check with an O'Reilly, Advance or AutoZone parts store to see if they have one in their loaner tool program.

For ground integrity, I would think that a decent digital multi meter would be most helpful there. You could either measure voltage drop or resistance.

For the starter, the best way is to measure current draw while it's cranking. Another way is to measure the battery voltage while cranking. Using a known, good, fully charged battery of adequate capacity, if the voltage drops way below say 9 Volts (do not quote me on this) the starter should be considered suspect.
 

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117 Deg F YIKES! Where are you, Needles, CA?
 

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Chevy Trailblazer 2008 LTZ (4.2L)
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Battery bolt torque is 11-12 INCH/LBS.
GM says....
1.Verify that all electrical components are off such as interior lights, all doors are closed, the underhood lamp, etc.
2. Clean any corrosion from the negative battery cable using a wire brush.
3. Position the negative battery cable (2) to the battery.
4. Tighten negative battery cable bolt.
Tighten the bolt to 15 N·m (11 lb ft).
 

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Discussion Starter #26
Ok, cat test and alternator test came out good. How and where do I test ground integrity? How would I appropriately add a ground?

I'm in Phoenix, az btw. Summers are brutal
 

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to test grounds, put the negative lead to battery negative. use the positive lead to test frame, engine block (pcm and firewall if ya feeling cocky). they should all read really low ohms- short.
 

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Lessee - you said you drive on Camelback - so I'm going to say that I think you live in Scottsdale AZ.
 

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I know there are pressure gauges out there that will tell you what the back pressure is for a cat converter - it's screwed in where the upstream O2 sensor goes and if the pressure is below a certain pressure (real low like under 4 psi if I recall correctly) then the cat is not clogged. You might check with an O'Reilly, Advance or AutoZone parts store to see if they have one in their loaner tool program.

For ground integrity, I would think that a decent digital multi meter would be most helpful there. You could either measure voltage drop or resistance.

For the starter, the best way is to measure current draw while it's cranking. Another way is to measure the battery voltage while cranking. Using a known, good, fully charged battery of adequate capacity, if the voltage drops way below say 9 Volts (do not quote me on this) the starter should be considered suspect.
I am not saying that testing for Voltage is not good, but even if one strand of copper is still intact, there'll be Voltage. But NOT Amps!

At the low voltages we have in our vehicles, Voltage drop is gonna be pretty hard to find unless it's a BIG drop and very obvious - like a hatchet cut through your battery cable - almost.

We always used a 10.3VDC standard at the battery during a 15 second, no ignition allowed, cranking test as our absolute minimum reserve capacity. If the battery couldn't deliver on that condition it was time for a new battery.

In any case - the true test of a battery is "Does it start your engine?" Right?

So what is it - battery almost dead or a starter that's pulling too much current?

The best test as far as I know - is to take one of the battery cables off and amp-clamp test the battery for capacity. I don't mean one of those tiny little handheld units that can 'tell you if the battery's dead' or not. You've gotta have a real AMPERAGE load draw-down to accurately test a battery.
I've seen those handheld units PASS a really bad battery - and vice versa.

I've always used the SUN Carbon Pile battery tester for my observations.
 

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Also will adding good grounds clear up my current any/all ground issues?
Yes - but ONLY if you have a defective connex someplace. I still prefer to fix the system to the same standards as the factory assembled it. Adding more ground wires can just confuse things and besides - those possibly defective grounds may or may not raise havoc in the umbilici loom or raceway and ultimately damage another wires that's not supposed to see 14.8 VDC - ever!
 

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So low ohms means a short?
Maybe. It depends on the quality of the 'touch' to ground it gets. If it's very firm, the test might read very low Ohms.
If the cable's corroded (already a resistive load) and the cable as it is goes directly to the engine, but the connex at the engine (bolt w/washer and etc.,) is crappy, then you can have a very problematic situation whereby you go to each and every ground connex and open them, wire brush them and using dielectric jell, put the shiny cable ends on shiny lead battery connections.

This is "The Columbus Method" - or "The Search until You Find Something" method of electrical troubleshooting.

OR you can just wait until a connex - ANY connex - starts throwing sparks and fireballs and you can say: "I found it!" rather excitedly.
Just be cool and say "That's what I wanted it to do!" and your friends and neighbors will come to call you the auto-electrical-mechanical-spiritual genius in your neighborhood.​

Next, you'll be reading tea leaves for their fortunes - a good job if the Vice Squad doesn't hear about you.
 

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Discussion Starter #35
Ok I was checking voltage across most of the parts under the hood to the batt. My batt alone was at a solid 12.68. With engine on and all other appliances OFF I noticed batt volts dropped to were at 14.33. I thought it was supposed to be closer to 14.6 to 14.7? Just seemed low to me I'm no expert. Also, when I turned engine off the batt volts only got up to 12.77. is that too low? How much does the alt charge the batt right after engine is turned off?
I also had 12.68 at all my underhood ground connections with engine off and key off. I'm thinking ground s are ok but again I'm no expert. Any and all help is welcome. Thx again everyone
 

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To me, the voltages look OK, but I'll defer to Ravalli for his professional opinion. One question to ask yourself when doing these measurements is are you using a run of the mill under $29.99 Home Depot/Lowes/Walmart/Menards/True Value Hardware digital multi-meter (DMM) with an accuracy of +/- 5% to 10%, or are you using a couple hundred dollar Fluke DMM that's been calibrated at the factory to a recognized standard with a known tolerance of +/- 0.01 VDC?

If you are like me, you are using a $29.99 DMM that reads "close enough" for most everything I need to work on. 14.33 volts is pretty darn close to the 14.6 - 14.7 range. Now if the alternator was only putting out 13.2 volts, then I would be suspicious of something amiss.
 

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Discussion Starter #37
Tonight I took the belt off to get a closer look at the alternator. I noticed the belt felt a little loose and sure enough, whatever the pulley rides on was making a quiet popping sound. I grabbed my fan with the clutch and water pump attached and gave it a good wiggle. It felt like the entire assembly could be pulled out. It also wiggles up and down like nobody's business. What is bad fan clutch or water pump
 

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If the alternator pulley is moving all around, then the alternator has some serious interior damage and yes, it can then cause all sorts of weird electric/electronic related problems.

Now, are you saying that the water pump and fan clutch are good and tight when you wiggle the fan?

If yes, then they are mechanically OK. If no, then they both should be replaced.

Also, a bad fan clutch can cause reduced engine power as well. If the 5 VDC reference voltage is grounding out or shorting out with another wire due to a break in the insulating at or near the fan clutch electrical connector, that will cause havoc on multiple systems. FYI, the throttle body's 5 VDC reference voltage is on the same electrical circuit as the fan clutch.
 
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