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2003 chevy trailblazer_ls
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Discussion Starter · #1 ·
Hello, long time reader first time poster.

I have 90000 miles on my 03 I6 Trailblazer 4 Issues

1.Hesitating shifting from around 45-50 MPH, Shifts in and out of overdrive to the point the truck is bucking! I Change a few quarts out of the tranny 2 days ago, still does it. What do you recommend?

2.Since I had a long weekend, I changed the spark plugs out. Very easy to do, easiest I have ever done. Anyway I noticed the 4th plug from the front came out very easy and was covered with fresh oil about the nut done. I have always used Mobil 1 since about 6K miles after breakin period, Is this OK?? Engine has been running fine. The boot was not soaked in oil and was not wet? WTF? I'm thinking of trading this thing in before total failure.

Also had the check engine light scanned:

3.Code: PO105? Dirty air filter? I might have over=oiled my K&N?

4.Code: PO422 Cat efficeincy? HELP, Should I change the O2 sensors?

This has been a good truck up until now, the shifting issue, and the oil pooling, has me thinking trade-in!! :confused:

Any and :bonk:all advise is Welcome!

I check this email, [email protected]
 

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2003 gmc envoy_slt
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7,190 Posts
Did you change the trans filter or just fluid? A filter change is due at 100k. 50k if you run it hard. Check the owners manual for specifics of heavy usage.
 

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2003 chevy trailblazer_ls
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5,268 Posts
oil pooling in the spark plug holes is normal.
your having 90,000 miles- so after this many miles some oil had pooled.
WHen I changed my plugs soon after 100,000, about 3 of the plugs had oil pooled.
now passed 145,0000 engine still purring along
 

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2003 chevy trailblazer_ls
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21 Posts
valve cover gasket

The pooling oil is coming from a leaking valve cover gasket. I don't know how long mine had been leaking but I noticed the same thing in my 5 and 6 cylinders when I changed my plugs at about 100,000 miles and then at about 108,000 miles the oil had pooled so much that my 6 cylinder started misfiring. Had the gaskets changed (not cheep - got a steel at $300 from local mechanic - dealer wanted over $600), and the issue went away. Hope this helps.
 

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2003 chevy trailblazer_ls
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if its leaking that much- like the poster below- in 8000 miles.. then its a problem.
If its just a small pool in 100,000- more normal
 

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2003 chevy trailblazer_ls
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Discussion Starter · #7 ·
Tranny shifting issue

Did you change the trans filter or just fluid? A filter change is due at 100k. 50k if you run it hard. Check the owners manual for specifics of heavy usage.

I just changed the oil.

One thing that might seem to be an easy explanation, i might have over oiled the K&N filter blocking the Mass air flow sensor. I will clean the throttle body and related sensors tonight.

Can anyone explain the shifting issue, or are these related?

Having all the stuff off for the plug change might have damaged or dirtied a sensor causing the bucking/shifting issue?
 

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2005 chevy trailblazer_lt
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434 Posts
Changing the tranny fluid, and cleaning the throttle body, while having the battery disconnected can help with the shifting issue. It did with mine. My issue was a little different, but you will be surprised how many things a dirty throttle body affects. I would recommend using a quality synthetic transmission fluid. I used RedLine D6.
 

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2003 chevy trailblazer_ls
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Discussion Starter · #9 ·
Most of the issues solved

Ok, using a clear jug 2 days ago, a emptied out 2.0 qts of tranny fluid thru the cooler line, I added 3, then the shifting issue started, after I changed the plugs I noticed the oil pooling.

Today: Added 6.5 Quarts of tranny fluid, after empting another 3 through the cooler line. 6.5!!!! Unexplained!!! yes 6.5 qts and the shifting issue went away!!!!! When at idle hot it is between the hash marks on the dip stick. I'am perplexed! Did it burn off 4 qts over the winter?

Changed out my K&N filter for a stock Fram, MY Po105 code went away, I also cleaned off the Mass air flow sensor with alcohol at the same time.

The only issue I have is the oil pooling on top of the spark plug, but at 90k, I would like to drive this thing 2-3 more years, this concerns me, I don't want this to lead to a major repair. I just need someone to concurr that it is ok!!!!

The tranny oil burnoff??? No oil leak on my driveway.

I need to change the Ujoints also its bangin again.
 

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2003 gmc envoy_slt
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So, you removed 5 qts and added 9.5 qts and it is still not up to the full line? That means you were down at least 4.5 qts. When you started to have shifting problems, did you check the fluid level? Was it showing anything on the stick?
 

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Discussion Starter · #11 ·
Yes it was on the stick barely, but when hot shut off it was higher.

I noticed the problem when I checked at idle and it was barely on the stick below cold. I added the extra 4 quarts took it for a hard ride, checked it on a level surface and it was between the hash marks hot @ idle.

Can you get a vapor lock in this tranny system? I don't understand, I have never had this issue.

Take 2.5 quarts out, added 2.5 quarts, and issue started? WT hell, then add another 4 qts and issue goes away?

What is it that low, that 0.3-0.5 quarts made the difference between running fine then looking to trade this thing in?

Lesson is, never check your tranny oil level cold, or hot when truck is sitting off, always check it running hot it will give you the best reading.
 
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