NEED HELP 2004 Trailblazer EXT 4x4 shifting problem bucking hard wind

deweymcr

Original poster
Member
Apr 7, 2018
5
Hillsboro, ND
I just bought this vehicle 6 months ago with 134k on it and body is in cherry condition. I have noticed that when I'm cruising at 75 mph with cruise control set, and come to a hill, it will shift down and rpm's will jump to 4k to 5k. I have since put 7000 miles on commuting back and forth to work. Yesterday I was bucking a hard wind. I would climb to around 70 mph and it would downshift and rpms would jump to 4k and I would actually lose speed down to 50 mph acting like tranny was slipping. I would let off accelerator and then I could slowly gain speed back up to 65-70 mph then it would do it again. Check engine light started flashing at one point. I have a Innova 3040 scan tool and the only code it would read is P0300. I realize I need to hook it up to a better scan tool, but I just wondering if someone has experienced these symptoms on their vehicle and what the problem might be before I start dumping money into it. Thanks for any help!
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Looks like you have a loss of power due to a misfire. It will give p0300 until it can pinpoint which cylinder is misfiring. If it's infrequent, it could take a while. You could get a Bluetooth OBD adapter and the Torque app on Android to look at the misfire data.

It is normal for the tranny to downshift if you are losing speed due to going uphill or wind to try and maintain the set speed. Same as if you were holding the speed with your foot. However, it will be compounded by the loss of power.
 

Chickenhawk

Member
Dec 6, 2011
779
It is also likely that your cat is clogged. If the misfire has been long term or your coolant gauge is even one tiny tick to the left of dead center when warm, your cat is likely clogged. A Check Engine light that flashes is a very bad sign and usually indicates that one should pull over.
 

deweymcr

Original poster
Member
Apr 7, 2018
5
Hillsboro, ND
I am installing/or have installed the following items:
-Cat converter
-Upstream/downstream O2 sensors
-Cam sensor
-VVT solenoid
-MAP sensor
-Fuel filter
-thermostat
I have fuel pressure regulator but have not installed(i dont see fuel in line and seems to hold vacuum, but smells like fuel)
After replacing all these sensors do I have to do a relearn or reflash. I keep hearing this on videos I have watched when trying to do research. Or is this something I can do without a special scan tool? I borrowed a snap on ethros but have since returned it. All I have is a Innova 3140. This vehicle has me completely frustrated! Thanks for any help advice in advance. pics are from a couple of weeks ago when it stranded me. was down to 20 miles an hour and would cut out at around 1200 rpm by the time I got it off Interstate hwy.
 

Attachments

  • IMG_2639.JPG
    IMG_2639.JPG
    489.5 KB · Views: 10
  • IMG_2640.JPG
    IMG_2640.JPG
    505.4 KB · Views: 9
  • IMG_2641.JPG
    IMG_2641.JPG
    466.5 KB · Views: 8
  • IMG_2643.JPG
    IMG_2643.JPG
    507.3 KB · Views: 8
  • IMG_E2639.JPG
    IMG_E2639.JPG
    488.7 KB · Views: 8
  • IMG_E2640.JPG
    IMG_E2640.JPG
    505.2 KB · Views: 7
  • IMG_E2641.JPG
    IMG_E2641.JPG
    465.6 KB · Views: 7
  • IMG_E2643.JPG
    IMG_E2643.JPG
    507.4 KB · Views: 7

I_Shoot_Back

Member
Feb 18, 2018
116
Ponoka
Id say plugged fuel filter. Looks like it's starving fuel. Probably wouldn't hurt to at least test the cat for back pressure.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
It's in open loop and load at 99%. Did you have it floored when you took these? That is no good as it goes into open loop automatically at WOT, which is normal. Idle and normal cruising would be better. Open loop just runs on preset values ignoring most sensors.

Lean running code, you should check for vacuum leaks first.
 

deweymcr

Original poster
Member
Apr 7, 2018
5
Hillsboro, ND
Thanks for reply's. I probably did have it to the floor on those freeze frames Mooseman. I was in heavy traffic at the time it started loosing power/speed and was trying to get off interstate. What baffles me is it was running fine, cruising at 75 mph and then started acting up. It had been running for around 20 minutes. I finished installing all the parts listed, except the fuel pressure regulator, started it up and it still throws a P0300 random misfire. Here's a couple of screen shots from my Innova 3040 scan tool. I have also replaced plugs-AC 41-110 Iridium.

08-31-2018 report.PNG08-31-2018 report 1.PNG
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
I have also replaced plugs-AC 41-110 Iridium.

Just to confirm, you have the 4.2L I6? Those are the wrong plugs. Should be 41-103.
 

deweymcr

Original poster
Member
Apr 7, 2018
5
Hillsboro, ND
Just to confirm, you have the 4.2L I6? Those are the wrong plugs. Should be 41-103.
I had to double check my order, it is the 41-103 plugs that I installed. I just ordered 6 new coil packs that will be here on Tuesday.

How long was it running? Coolant temp looks low, should be around 195-200 degrees.
it had been running around 3 minutes in that freeze frame. I can clear codes and run again with timer to know exactly when it stores code. it was a gates t-stat i installed:1535821334253.png
 

Forum Statistics

Threads
23,271
Posts
637,476
Members
18,472
Latest member
MissCrutcher

Members Online

No members online now.