unfortunatly there are alot of things it could be. noones gonna be able to do anything but make suggestions as to what MAY be wrong. here's another noone has mentioned yet (I just had one w/this problem today, it was running extrememly rich). make sure the coolant temp. sensor is working properly. if it is unplugged, it will read -40 deg. F. and run very rich. you would prolly notice it running sluggish and chugging under like 2000 rpms. is your car running smoothly or is it hesitating? BTW, my car is white, and it gets the residue on the back bumper pretty badly too. I know there's nothing wrong w/my car exc. the tune is alittle on the rich side. thats what a mailorder tune gets you sometimes.

if I were you, Id bite the bullet and take it to a dealership. tell them about your concerns, and tell them not to do any work w/o you agreeing to it first. they can scan it and look for codes and any sensors that might be reading faulty, and see if that exh. mann. leak may be the cause or not. it'll cost you $75, but you wont be buying all kinds of new parts that it may not need trying to guess at what it could be. good luck w/it.
chris

 

I am going to atempt to get it smogged (doubting it will pass running so rich) and am going to have them run it on the computer.

 

I just went through this with my white 94. Mine was caused by loose exhaust manifold bolts causing a leak. Air was entering thr exhaust causing the O2 sensors to think the car was running lean and the PCM would make the mix richer to compensate causing the problem you are describing.

First thing I would do is fix the exhaust leak and see what happens from there...

 

Get that headder leak fixed. That would deffiantly cause your O2 sensors to read a false lean condition and dump alot of fuel in there!

 

What do I need to get done? I don't want to let my car loose in the dealership and have them tell me it needs a million things that is going to cost me an arm and a leg. And since you had the same thing fixed. About how much did it cost? Thanks.

 

How much do you think it would cost to get the leak fixed (considering it isn't a cracked manifold)? If it is a cracked manifold then it is going to cost me around $1000 for new headers and installation.

 

I change my O2s every 35000 miles. The more fuel they see, the quicker they die...

50000 miles is max life on O2s. When they start reading funny many things start happening.

Put in new O2s and fix the exhaust leak....unless this is fixed you will not be able to pinpoint the issue and neither will a dealer.

 

In my case the manifold bolts were loose but I replaced the manifold gaskets to be sure. You might be able to just torque the bolts and it should cost you less than an hour labor, no parts.

I wouldn't replace the O2 sensors yet. I have 252,000 miles on my Z without ever having to replace the O2 sensors and I have 216,000 miles on my Blazer without having to replace it. It has been my experience that they last a long time if nothing else has gone wrong to damage them.

Check the bolts to see to see if they are tight. Also look for a white chalky substance around the rear of the manifolds. This would indicate an exhaust leak. You may even hear the familiar ticking sound coming from the back of the block which comes with the exhaust leak.

 

It's good to see someone getting that many miles on a Blazer! I haven't been able to kill any S-truck nor this Lt1, knock on wood!

 

First off, what tools would I need to tighten these bolts? Then what steps would I need to take to get to the header bolts so I could tighten them. Also, will I tighten them from under the car or from the top.

 

if you put a fanswitch or colder thermostat that will do it our cars need to run at 210-220 on the factory tune. that was so they would pass emissions

 

i have a 160* stat so...

 

its either that or o2 sensors when i started running my car at a constant 160-180 no higher thats when i got the black soot on my car and the bad smell kick off the switch and no black. try to run cam2 or 106+ octane for one tank if it goes away its the stock tune and the thermo that is doing it

 

You will need to get to some from the top and some from the bottom. I am running stock manifolds and I think the bolts were 15mm (could be 14 or 16). I am not sure if your header bolts are the same size. You can probably reach most from the top and a mirror may help you see them better.

It is so easy to remove the Y pipe you may want to to get some from the bottom but it is not necessary. If you remove the Y pipe, you will need to raise all 4 corners of the car. You may need to remove the alternator to get to the right fron bolts.

Good luck...

 

I love the 5.7 liter! I used to have a 2.8L (1998) S-10 and it was a dog. I swore nothing but Chevy small blocks from then on. My Blazer is full size with a 5.7L (1994). Maybe I'll change it to an LT1!