95 Blazer....O2 or EGR?

[anelson1995]

I have a 95 Blazer, 4.3.,CPI. Have been having problems with it being intermittently hard to start, major hesitation, exhaust smell, no power. Some days it seems better than others. It's only driven by my wife and not the main vehicle so I've let it sit since it started except for when I've had time to work on it. Don't know when the check engine light came on because she said it never did. Turns out it's burnt out or something similar. Read the codes and got a few.

PO141
PO300
P1133
P1406

Have taken the EGR off and cleaned it out, put it back on with new gasket, cleaned it again. Pintle moves freely but I know that doesn't always mean it's not needing to be replaced. Changed plugs and wires (double checked to make sure firing order right), changed oil, filter, fuel filter, fuel pressure good, changed tranny fluid, filter, new Cat. When I pulled plugs, the three on the driver side were carbon coated pretty bad. Starts better when warm but still hard. Judging by the codes I need to replace the two O2 sensors and the EGR. Thinking I'm gonna do the O2 sensors first in case they are throwing things off with the EGR (is that possible?). Only problem is that the pre Cat sensor is a major *$&@# to get out because of being angle up toward the tranny pan. Before I get started I want to bounce this off you all and see if I'm headed in the right direction and see if there are any ideas to make things easier.

[anelson1995]

Oh, also replaced cap and rotor.

[MT-2500]

You need to run a good fuel pressure check on it first.
Watch for fast leak down. They are bad about leaking inside the intake.
Fuel reg and fuel feed lines both.
Here is some guide lines on checking fuel pressure. Your fuel pressure specs are 55/61.
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.
Yours is 55/61
Cold start should be 60/61 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 55/61 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 bad leak someplace.
Post back fuel pressure readings.

[MT-2500]

On the codes. First clear them and see if any comes back or what one first.
The code 300 is a missfire code if it comes back check over for a engine miss.
The 02 sensor codes may be caused fuel leak in the intake or engine miss or even EGR valve. Also check 02 sensor heater fuse no 5.
Make sure that the fuel pressure is up to specs and no fast leak down.
And the egr valve needs to be read out on a engine capable scanner to check and test in/ Watch for actual and desired pintle positions and also a good scanner will have a egr valve test built in it to test egr valve.
Like what was said check dist cap and tune up.
And get that miss spotted.
A engine missing or flooding fuel will mess up 02 sensor readings.

[anelson1995]

60 55 79 I called a buddy of mine that checked it for me and he said that everything was ok. He didn't have it written down but he thought it was at 60 cold start, 56 running, and 79 with the return line pinched. Also, I remembered a few more things. I have also replaced the Idle air sensor. It blows alot of carbon out the tail pipe too. Just put in some Seafoam and am letting it set for now figuring I wanted to do that before I think about putting any new O2's in.

[anelson1995]

Just noticed the post about the codes. Just cleared computer (pulled neg bat cable and both ECM fuses and let sit for 1/2 hour) Waiting to restart until after the Seafoam has had a chance to sit for a bit. Then I'll take it for a drive to burn off the Seafoam and to Advanced Auto to check for codes.

[MT-2500]

Originally Posted by anelson1995

Just noticed the post about the codes. Just cleared computer (pulled neg bat cable and both ECM fuses and let sit for 1/2 hour) Waiting to restart until after the Seafoam has had a chance to sit for a bit. Then I'll take it for a drive to burn off the Seafoam and to Advanced Auto to check for codes.

The fuel pressure specs are good just make sure it does not have a fast leak down on fuel pressure that would point to a leak in the intake.
If you have seafoamed it after you drive it a while and get it burned out clear codes again. The seafoam may stir up a few extra codes untill it gets cleaned out.
Let us know how it goes.

[anelson1995]

quick update.....started it up to burn out the seafoam. Due to the extra smoke caused by the Seafoam I noticed there is an exhaust leak on the passenger side of the engine compartment coming from point where the pipes connect to the manifold.

[MT-2500]

Well that looks like one more thing to keep in mind.
A exhuast leak can throw off the 02 sensor and even set a 02 sensor code.
See if you can catch any codes that may come back.

[anelson1995]

Got out on the road to burn off the Seafoam. All codes gone now except for the PO300 random misfire. Haven't done anything with the exhaust pipe thing yet. Assuming it just needs a donut gasket. It does run way better now after the Seafoam. Gonna start looking at the last code now.

[anelson1995]

Well, looks like I found the problem. Checked inside the plenum and it is a wet, carbon flaked, nasty mess. Guessing the guy that checked my fuel pressure didn't have a clue. Going to do the spider and nut kit next week. Will let ya know after that.