SES - P0172 & P1133

[mtrotter70]

Have a 95 Blazer S10 4.3. I think it's a OBD1.5 but not sure.
SES light goes on and off. Stays on for awhile and then usually goes
off around 1/2 tank.
Codes are:
P0172 - running rich
P1133 - O2 sensor fault bank 1, sensor 1?

How many o2 sensors does a '95 have?
Need to know which sensor to replace and exactly where it is located.
I looked underneath and see the o2 sensor in front of the cat
converter. Is this the one I should replace?
Would this cause a rough idle after driving on highway also?

[BlazerLT]

CPI or TBI injection?

[mtrotter70]

CPI. And computer hookup to read codes is in drivers side interior - this means it's OBD1.5 right?

[Fireplug]

You have a left bank on the left exhaust manifold, right bank on right exhaust manifold near the bottom of the pipe and precat o2 sensor and some had a post cat o2 sensor.
Just because you get a o2 code does not mean it bad.
You have to check why is it running rich .bAD INJ, BAD SPARK PLUG OR WIRE, o-2 most cases dont just go bad there is something else wrong that kills the o2.
Bank 1 sensor 1 in on the driverside exhaustmanifold
Fireplug

[BlazerLT]

On a 1995, there is only two oxygen sensors.

One before and one after the cat converter.

One before the cat: Bank 1 Sensor 1
One after the cat: Bank 1 Sensor 2

You should check for a leaking fuel injector which could be causing the rich condition.

Do you ever smell gas fumes coming from your engine when driving?

Does you truck sometimes take a bit to start up and doesn't fire up immediately?

[mtrotter70]

Thanks, blazerlt, for the info on o2 sensors.

I don't smell gas fumes coming from the engine or tailpipe.
Do smell some strong exhaust fumes sometimes though (rich).
Checked the oil and don't smell gas there either.

It does take awhile to start after sitting for over an hour or overnight.
Still gets 300 miles per tankful but could be a small leak?

[BlazerLT]

Yes, could be a leak in the injector.

Take off the upper plenum cover and check for washing inside the intake.

When all is fine both the passenger and drivers side should be dirty.

Passenger side washed clean in whole or patches = Injector fuel pressure regulator is shot. Replace the injector.

Driver's side washed = internal fuel line kit (nut kit) is cracked and leaking.

Open it up and take a look and post a picture here of it.

Also, you can remove the Vortec plate on top of the engine and remove the IMTV valve there and take a peek inside and look for a smell of gas and pools of fuel inside the intake.

Let us know, 70-80% of all CPI injectors from these years will fail. Only uncertain thing is when.

[mtrotter70]

Thanks. I'll see if I can pull the vortec plate and IMTV valve and check it out. If I can pull the upper plenum, I'll see if I can get a picture posted.

Any special tools needed to replace CPI/nut kit? Just buy a standard torx bit set?
I'm not sure about doing the job myself because I've had bad luck with
engine stuff before. You want to come over and help fix? (just kidding)
The repair shops around here want $800 to replace cpi/nut kit, if that's the problem.

[BlazerLT]

Here are some links to pictures etc and links to people who have done the job.

This is my time doing it:

http://www.s10forum.com/forum/showth...pi+replacement

Here is a tech link to the problem:

http://www.asashop.org/autoinc/feb2000/techtotech.htm

Here is a thread to everything you will want to know about the install. You will have to register, but it is worth it and some of the diagrams and photos are awesome.

http://www.s-seriesforum.com/forum/s...threadid=34668

Enjoy, do your research on it and it will be a sinch.

That is is it is leaking in the first place.

Passenger side washed clean = CPI injector broken
Driver's side washed cleaned = Nut kit split and leaking.

Good luck and god speed.

[mtrotter70]

I removed vortec cover and IMTV valve and lo and behold you could smell gas. Could see with a flashlight that the passenger side was washed clean. It looks like I'll be getting a new cpi and nut kit real soon.
**Thanks for all the help and info BLAZERLT**

[BlazerLT]

You got to bro!

1.) Also, pick up a new upper plenum gasket and replace the nutkit while you have the injector exposed. For $50 more you will solve all the problems with the fuel system and will be able to enjoy your truck without having the failure prone fuel lines taking your truck off the road again when they break and leak mass amount of fuel into the cylinders and hydrolock your engine.

2.) Also have some throttle body cleaner there and clean, scrape and toothbrush the EGR port you see on my s10forum posting.

3.) Don't drive your truck like this, it is dumping fuel into the oil and severely lessens the protective lubrication properties of the oil. As soon as you fix it, replace the oil. No ifs, ands, or buts.

4.) Before you put the upper plenum plate back on, test the new injector and nut kit by putting the key to the "ON" position to prime the nut kit and injector and check for leaks. Prime on for 5 seconds, off for 10 seconds and repeat this 4 times. DO NOT START!!

5.) Make sure all the plenum gasket is removed before you install a new one.

6.) Make sure you do not over torque the upper plenum bolts or you will strip them and you will need to install a new complete intake.

7.) Be careful, methodical, picky and gentle with this install and do everything properly and you will have your truck back again with more power and pull for your dollar. Fuel economy will go up also.

8.) After you might want to replace your O2 sensors seeing they need to be changed every 80k miles anyways and really help with fuel economy and power.

9.) Have you cat convertor back pressure tested to see if it is melted from the excess fuel being dumped and burned in the exhaust system.