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2002 chevy trailblazer_ls
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Discussion Starter · #1 ·
Hey guys, I know I should be out checking the obvious few things:
Get code read, clean throttle body, etc. But Im having a bit of trouble figuring out if there is one root to these problems:

1) Recently, truck has had trouble starting on the first try.
2) Exhaust and body damage repaired by dealer, truck runs fine.
3) Today: Drove it to the gas station, filled up, octane 89 as my PCMforless tune is set to. Then drove to the gym, no problems. Get out of the gym to drive home and then...
a) Really rough thumping felt through whole cabin+steering wheel all through the RPM range (up to 2000, anyway), in all gears, even Park.
b) Soon after, flashing CEL, then it stops and then comes back every few minutes
c) Engine temp dropping below quarter hash mark when slower, then getting closer to 210 mark at driving speeds (although out of caution, I kept it around 30mph and under 2000rpms as to not further any problems)
d) Idle is steady at ~600
e) might have just been me but there was a slightly funny smell under the hood, not sure how to describe it

From reading around here, I'm thinking either fan clutch, water pump, timing belt, starter, misfire (plugs bad or coilpacks bad)...

Truck is at ~96400 miles, had a new fan clutch done at 79000, Mobil1 oil change done 400 miles ago, was looking to do ACDelco spark plugs in the next few weeks.

I'm thinking I should take it up to Advance and get the codes read and start from there and clean the throttle body while I'm at it.

I am afraid to take it into a shop and ask them as they'll likely look everywhere but and charge me out the ass to do **** that isn't even relevant. And no, Roadie, I don't have a trusted independent mechanic (before you ask).
 

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Discussion Starter · #3 ·
My old roommate works at a garage here, I talked to him and I guess I'll have his shop do the work if the code doesn't point me to the exhaust shop that handled my exhaust repairs.

Another possibility: I had a new windshield put in, too. Maybe the installation caused the coilpack 4 to go nuts? It rained really hard the first 2 days after I got the truck back. But its been nice the past 2 days.

Either way. I'll go to the store tomorrow first thing, get the code and go from there. I guess I should write down the codes for misfirings, lean/rich, and other common things.
 

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had a similar problem and it was a tune issue. Unless you have efilive or hptuner you can tell if the gear ratios calibration is out of place. The whole time i tried to reflash my tune I ended up reading the tune on the pcm showing the gear ratios below my requirement. Just recently reflash my pcm o the required adjustments and the shifts are perfect. Felt like a new car.
 

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somekind of thumping... recently changed the fan clutch?

check to see that the water pumps shaft isnt loose. grab the fan and see if it moves side to side.
 

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Discussion Starter · #6 ·
So I get up this morning to take the truck to Advance for the codes and the issues are gone. But I took it to Advance anyway and interestingly enough, their scanner couldn't read that it was connected to the car. Figuring it was the device, I brought the truck to AutoZone a few blocks down the road; same thing.

I told the employee about the issue and he said it seemed like I may have gotten a bad "batch" of gasoline since this happened after I had filled up and let the car sit for a few hours. As always I got Chevron mid-grade. Not sure how much of that I believe.

So my OBDII port doesn't work?
:iagree:
So I drove it around a bit, and it seemed fine. Though the T-Stat reading seemed to never want to just sit on 210. I'm going to look into getting it replaced tomorrow, just for the sake of it.

Yes, rbarrios, the clutch was changed in March of 2007 at appx 79000. Haven't checked the fan blade yet. Will do when it gets a bit warmer out.
 

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yes- check the fuse that powers the cigarette lighthers. they use the same citcuit.
 

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Discussion Starter · #9 ·
somekind of thumping... recently changed the fan clutch?

check to see that the water pumps shaft isnt loose. grab the fan and see if it moves side to side.
Well, the issue happened again tonight. Seems it's only happened in the cold...

The fan actually moves almost freely, slight resistance, but I could move it in either direction.
 

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Discussion Starter · #10 ·
Good news...
Took the truck to my old roommate's shop, had his boss take a look.

The scanner port being out? Blown fuse. Threw a spare in there, got the code pulled. Cylinder #4 misfire. I swaped the coils myself, misfire moved to the new cylinder. So I had him order the coilpack, $90. His supplier couldn't get one. So I'm going to order one from RockAuto.

When I get the part, I'm doing plugs and cleaning the TB. Since I had the resonator off, I saw LOTS of crud on the inside of the butterfly valve. Going to get some cleaner for it and do it all at once. Hopefully this is it...

Now... I noticed a spot, where water might have sat, on top of the block, next to cylinder 4... How do I prevent this from happening again?
 

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seems like I seen a thread about this but I suggest some silicone maybe around it, thats what we do mudding.
 
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