Powerless and get O2 sensor alarm

[frehol]

Hi,
Blazer -95 4wd vin W 4.3L V6 CPI

After I had it serviced the last time my Blazer feels like it lost its power. Slow acceleration and cant keep up speed when going uphill, at least not if I don't give it MUCH more gas then I used to before. When I demand some more power from it, uphill or towing a trailer, I get the SES light.

Went to the shop to read what error code and they said it was the O2 sensor (before the Cat). I had it changed but it did not help...

When it was serviced they changed all fluids, the air and fuel filters and the spark pluggs.

What should I check next?
What i causing the problem?

[Cloud Strife]

If they didn't clear the codes, then the light will stay on I believe.

[frehol]

Originally Posted by Cloud Strife

If they didn't clear the codes, then the light will stay on I believe.

They did clear the light, but it comes on again after a little while when driving a little harder like accelerating, uphill in constant speed (say 50 MPH), or pulling a trailer. It comes on easier if the engine is cold.

Then it goes off when I start the engine after some carefull driving for some miles.

Today I could feel howthe engine "got back to normal" when driving on the hiway, accelerator response returned...

[DelCoch]

Originally Posted by frehol

. . . After I had it serviced the last time my Blazer feels like it lost its power. . .

Since it wasn't that way before it was serviced I would say it's something they did or didn't do. Check the vacuum lines, maybe they left one off or loose. Check the spark plug wires, maybe they got a couple crossed or maybe one is shorting out to ground. What kind of spark plugs did they use?

After checking the above I would replace the cap, rotor, plug wires and new (proper) spark plugs.

[frehol]

Originally Posted by DelCoch

Since it wasn't that way before it was serviced I would say it's something they did or didn't do. Check the vacuum lines, maybe they left one off or loose. Check the spark plug wires, maybe they got a couple crossed or maybe one is shorting out to ground. What kind of spark plugs did they use?

After checking the above I would replace the cap, rotor, plug wires and new (proper) spark plugs.

When the SES light came on the first time I went back to the shop and they checked that all plug wires were in place and read the error code and said it was the bank1(?) O2 sensor and cleared the code. They said it was 99% certin the O2 sensor needed to be replaced, so they did it but without any result...

I'll try to look over the wires and plugs tonight. Dont know what brand of plugs they used but I think they use Delco...

Another thing we noticed after the service is that when we put it in Drive or Reverse (brake applied) we now hear a allmost like grinding noise that wasn't there before, what could it be?

[Cloud Strife]

Well my SES light came on when I left out the speed sensor on the wheel-hub assembly. Another thing may be the brake calipers could be locked and still applying the pads to the rotors.

Another would be that a wheel bearing is going out or you could be low on fluid somewhere.

[frehol]

Checked the ATF level and it was low. Filled it up to full again. But the SES light came on again this morning. And the transmission sounds more again after I filled it up. Is there anything they could have done wrong when they changed the ATF in the tranny?

Checked brakes and they where all right. Plugs and wires looks all right too...

I have a feeling of that the O2 sensor works fine sometimes and doesn't work other times. What can interfer with it, other than faulty wires?

/F

[MT-2500]

Originally Posted by frehol

Hi,
Blazer -95 4wd vin W 4.3L V6 CPI

After I had it serviced the last time my Blazer feels like it lost its power. Slow acceleration and cant keep up speed when going uphill, at least not if I don't give it MUCH more gas then I used to before. When I demand some more power from it, uphill or towing a trailer, I get the SES light.

Went to the shop to read what error code and they said it was the O2 sensor (before the Cat). I had it changed but it did not help...

When it was serviced they changed all fluids, the air and fuel filters and the spark pluggs.

What should I check next?
What i causing the problem?

Codes do not say replace sensors.
What was the code NO?
What brand plugs did you feed it?
How is that fuel pressure?
Your specs are 55/61 lbs of pressure.
Here is guide line for checking fuel pressure just us your specs and post back pressure readings.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

[frehol]

Hi,
I think the problem is solved. I reset the ECM by removing the two fuses for the ECM for 15 minutes and after that has the error not returned. The truck behaves as normal and no SES light anymore. Maybe they did somthing wrong when they reset the error code after replacing the O2 sensor.
Have not tried to pull a trailer on the highway yet but so far it looks all right.

Happy new year to all of you!

/Freddy