This car has given me sh¤t since I bought it! I must have left 100 questions about this blazer all over the internet. I get one problem fixed, another one comes up.

This time it's a couple a things that ain't right, and I need to fix it myself.
No money to let a shop fix it.

The engine seems to be running real rich, my mpg is BAD!
Fuel smell out the exhaust and black soot on the exhaust tip.
It seems fine when cold, but not so fine when it heat up. Almost like it will stay in open loop.

The engine temperatur will fluctuate. It will go up and down on the temp gauge as the thermostat open and closes. Shuld it not come up to the correct temperature and STAY there? Could this be causing my CPM to go between open and closed loop?

One of the three bolts on the right exhaust manifold that hold the Y-pipe BROKE!
Could this give me a exhaust leak severe enough to make my engine run
rich?

One other thing is that sound of something loos coming from the exhaust, but there isn't anything loos in my exhaust. I have had it down and nothing is loos.

I have changed out most of the sensor, so it should not be a sensor problem.
And the vacuum lines are all new, NO vacuum leak!

I have also had some black smoke coming from the exhaust at start up, and it has been a bit hard to start from time to time, when it's cold outside.
Maybe the fuel spider as some leaks to it?

 

You're right. Black smoke indicates too much gas.
Sounds like you have a defective thermostat. Your engine temp shouldn't fluctuate that much. Don't really know if that would cause your engine to go between open and closed loop or not.
Do you have an exhaust leak at the right y pipe? I would certainly fix the bolt. You can buy just the one bolt, nut and spring. Dorman sells them for about $6.50 or so. See your friendly auto parts store. They'll hook you up. You are not supposed to reinstall them if they come out (the others). They are a one time good deal.
You say nothing is loose in the exhaust. How about the exhaust being loose and banging on the truck. Some places are pretty close.
Sounds like you have a fuel problem though. What is your pressure and does it bleed right off or stay there when the pump turns off? This is the first thing you need to know.

 

Sounds like you may be experiencing a clogged catalytic converter. If the exhaust has a rattle to it that sounds like it is coming from under the passenger seat, then the catalytic converter is likely shot. You need to fix that and the exhaust leak to get it running properly again. An exhaust leak can cause a rich condition if it is bad enough and that can cause the cat to clog and die.

Also, check your fuel pressure (specifically the leak down rate - shouldn't drop more than 2-3psi) after you fix the other stuff to make sure that you don't have a fuel leak causing the rich condition which would burn up the cat and further possibly cause an exhaust leak.

As far as the temperature goes, you may have air in the block. I would change the t-stat and get the system purged of all of the air to be sure.

 

Thanks for the answer! The termostat was changed just before christmas, and it has been doing this from the day the termostat was new. The old termostat wouldn't let the engine heat up at all. Now it will go up to 2/4 on the gauge which is normal temp (Celsius) and drop to 1/4. Go up again and down again.

I have bought the bolt, it's just to damn cold to go at it this time of year.

This is an old recording, but it was the same when I tested it yesterday

http://www.youtube.com/watch?v=tbnVPhffEyA

When I had the exhaust system down I took extra notice to the cat, it was new last summer, and it did look very clean at this point to.
Put a flashlight on one side and could see the light on the other side. Did this all over and could not find a black spot. Sure it could be loos, making the core rattle when the exhaust heats up.

 

What RPM is the Idle?

Out of the blue shot in the dark question here.. Whats the Volt Meter Reading?

 

Idle RPM 600-700, Never under 14 volt on the volt meter.

 

With it jumping like that, I would look at the bottom of the CPI. I know when I did a 95 some time back with a simular issue, the O rings that seal the lines into the CPI where bad. The CPI was coated but the bottom was clean like new on 4 out of the 6 lines. I put in new O ring rubbers and it smoothed out. I have also come upon FPRs that were not leaking but where bad (a few friends blazers) they had the cheap aftermarket FPRs that had the adjustment screws to them.

Rare but found a few that had bad IAC (idle air control), which would not back off when warmed up, so it was telling the ECM it was still cold and needed more fuel. Would not hurt to Ohm out the TPS also.

Just a thought

As for the T-stat, on most when temps are below 40, I have seen it go to normal op temp then drop when the T-stat opens just as you say yours does and stays at about 1/4 gage til it heats up again. But has wonderful heat at the vents (enough to cook you out at full boar). Most of these dont have the plastic cover guard under the motor w/ that oil filter door, a few still do. I would say that this means you have a really good clutch fan.

 

Ohhh, I forgot that one. The jumpy idle was a bad TPS. I changed that out and the jumpy idle was gone.

When I did my LIM gasket change, I did pull apart the CPI, without changing any o-rings when I put it back together.
So I could have made it leak. That would also explain the sulfur smell that comes from the exhaust. And my hard start

In other word there are a lot pointing towards a bad cpi.

I'm going to order a new cpi, a new exhaust system and some tune up parts from rockauto. And hope that will fix it

And if I understand you right, theres nothing wrong with my engine temp?