Still runs like crap. Can't find the disconnect for the O2 sensor but in doing some more reading in the clymer manual I came across this bit of info. I am going by the fact that this is running too rich and will assume that something is not allowing the correct amount of air in. With that, I checked the manifold tuning valve. Now according to the manual if you check the voltage at the connector without the engine running there should be no voltage, which there isn't, but with the engine running it should read battery voltage and it doesn't. I am assuming they mean for you to do this with the cable disconnected, kind of hard to do with it connected. So, any thoughts on this, and do any of you have a better manual that is more specific to testing this. I have ran the motor with and without it connected and it doesnt change a thing. Could this have an adverse effect on the air/fuel mixture? I have a bad feeling that the PCM controls this by some means and if it isn't sending a signal to it I may be looking a messed up PCM. [&o]

Thanks for all your help so far, hopefully with your suggestions and tips I will get this beast running soon.

 

Ok, I have been reading along on your posts about these "issues" you are having. I hate to be blunt, but starting a new thread about the same problem DOES NOT mean you will find an answer any quicker. The fact that you "can't find" the O2 sensor "disconnect" leads me to believe that you shouldn't have wasted the money on a repair manual. Your money probably would have been better off spent explaining your problems to a competent mechanic. My reason for being short with you is the fact that you started off your life here with a statement about your wife's "POS 94 Blazer" (read it HERE).

The O2 sensors ARE located in the exhaust pipes! Just look along each pipe for an approximately 3" long 1" diameter protrusion with wires coming out the end of it. Follow those wires to the connector (or "disconnect" in your terminology). That is where you can disconnect & remove the O2 sensors.

The only place that I have had experience with a MTV (manifold tuning valve) was on my old Intrepid with the 3.5L v6. That engine had 2 separate intake sides (1 for each bank of cylinders) and the MTV would open up after 3500rpm to allow cross-feeding between the two halves of the intake manifold. I can not see what the function it would have on the 4.3L vortec. Anyway, if you are looking for voltage on an electronically actuated valve, you must have all electrical connections to said valve connected. You then must then pierce the insulation on the wire with your voltmeter probe to check for voltage.

In your other post (Click here), you said that you checked the MAP sensor and found that it was bad... What exactly did you check to come to that determination? Did you log the readings with a computer? Did you probe the wires with a voltage/ohm meter to see what the readings were? You said that you replaced it, but it "didn't do S&*$". Well, if it tested bad, then it must have been bad. If it did indeed test bad, then you have atleast fixed one of the possibly MANY problems that are currently present in your vehicle.

I love guys that read the manual and then take out the suedo shotgun and just start firing till the damn thing is empty (so to speak). A good place for you to start (instead of starting threads that simply go NO WHERE because of your attitude) would have been the SEARCH button up top (or click on the word SEARCH just a few words back). You would have possibly found that some problems are caused by a faulty ground connection between the PCM and the chassis/engine. That is one possibility. Another one would be to inspect your spark plugs for signs of the engine running rich. If the plugs are black and sooty (sp?), then it is quite possible that you either have injectors that are leaking when they are supposed to be shut or something is wrong in the sensors. An easy way to test the injectors is with the proper scan tools and injector leak down tests (I have the tools, but the average shade tree mechanic does not).

If you dont' see any abnormal leak down through the injectors, but rather you see that the fuel pressure does not hold steady after you turn the key off, then it is quite possible that you have a leaky CPI unit. The CPI unit is located under the upper intake manifold and has 6 plastic lines that run to each of the individual injectors (bad design in my book). Over time, these lines can crack and leak fuel down into the intake making the engine run rich, despite the corrective measures that the PCM is taking. You can tell if you have a leaking CPI unit by pulling off the upper intake manifold. If you see clean areas (nice shiny metal where everything else is covered with an oily soot) on the lower intake, then you know that you have a fuel leak. Some CPI unit leaks have been bad enough to fill a crankcase full of

 

Kyle: Well I do appreciate the reply and the advice. I will be honest in that the first thing I wanted to do was be blunt right back, but you know something, you are absolutely right. I went back and looked at all of my previuous posts and I did not give you folks a very good first impression, and to all of you a most sincere apology. I have found out more useful information and assistance in this forum and I do appreciate it.

As far as what I have done, I have not checked the oil but I will do that today. The O2 sensor I did find in the tailpipe and I just need to find where I can unhook it. The MAP, I did back probe by inserting a couple of small paper clips into the connector and reading the voltages, and they were out of specs, so your right in that it still could have been bad, but just one of many problems.

Anyway, thanks for the wake up call Kyle, I will keep a check on things in the future.

 

Not a problem, it happens to the best of us. Especially if you are new to online forums. This is one of 6 forums I frequent and have been around them for going on 5 years. Moderated on a few of them until time got tight. More often than not now, I get too blunt in my approach to new guys. This forum inparticular seems to have much more of the multiple posting going on and I am trying to think of ways to make it easier for new guys like yourself to find out common issues to check first. Many of the other forums I am on have 'Common Problems' threads stickied to the help section and I will suggest (if not start it myself) this to the moderators here.

Good luck and don't get discouraged. Problems are meant to be found and I'm sure that you will find the answers you need. And don't let my words bother you too much. I was overly harsh and for that I apologize.

 

Well, I am glad to see that no one got offended and that things are still as peaceful as ever in here!

swartlkk is a helpful and knowlegeable guy, so I 'm glad he's starightened things out in this post!

 

No problem here, no offense taken. Now then, if its okay with you I am going to start over. I have some things to go and check that Kyle suggested and then just start from scratch. I think that a common problem section would be a great idea.

Thanks

 

That sounds like a plan.

Good luck!

 

If you in fact don't have a connector in your 02 wiring, then the connector is where the wire attaches to the sensor. I have yet come across a vehicle that does not have a connector in the 02 wiring. All sensors have a connector, all sensors will fail over time and must be replaced, kind of hard to replace something that is permanently hardwired, and very few things are permanently hardwired on vehicles.

Trying to go from memory here as to what your problem(s) are.
On the old body style trucks with the snorkle style air intake system, there is a flap inside the intake that will open and close based on air temp. If this flap is stuck half closed or closed it will restrict the volume of air feeding the engine. this flap is used on cold starts, and draws heated air (not exhaust air) off the intake manifold until it warms up. IF you have this style intake (snorkle style) pull of the hose and look for the flap.

A rough running engine could also be from a cracked rotor cap, or worn cam position sensor (under rotor cap), faulty crank position snesor, coil, foulled plugs and a host of other stuff. The best is to eliminate them one at a time. Best way to do theat is post up what the problem is and what you have done to fix it. Like mentioned above.

 

Thanks hanr3, I just started a new post, started from scratch and layed it all out from the first time it started acting up until today. I appreciate your help and am heading back out to take another look at some of your suggestions.

Thanks