My 95 s10 Blazer, w motor, 4wd, gets about 7 miles per gallon, engines needs to crank for about 5 seconds to start, runs very rough at idle but smooths out when off of idle, but now runs kind of rough at speed too, doesn't matter if it is cold or warm it acts the same, the check engine light does not come on, I'm positive the truck is running rich, and it doesn't seem to have the power it should, it has 66,000 miles on it. I gave it new plugs, cap, roter, wires and that did not do anything, I took the EGR valve off it was clean with no carbon hanging it up, I put the EGR screen gasket on it, and I put a new O2 sensor in it all of which did not help. Any ideas out there. Thanks

 

Dont always rely on the check engine light to come on, I would take it to the local auto parts sotre and have them run the codes.

 

Is the cat plugged up? also I think you should have 4 02 sensors.

 

ACTUALLY i WENT THRU THE SCANNER THING ONCE BEFORE AND LUCKY ME MINE HAS A OBD1 CONNECTOR AND A OBD2 COMPUTER OR VISE VERSA AND NO ONE OTHER THAN A DEALER CAN READ IT, i looked at the o2 sensors and as far as I can tell it only has one, it was on the right side of the y-pipe and I saw nothing else, I found a boss on the tailpipe but no sensor or evidence of a wiring harness back there, I'm going to put a coolant sensor in it today but I don't expect any results.

 

I believe that some '95s are bastardized OBD1.5 interfaces (OBD1 connector w/ a mix of OBD1&OBD2 software). I think that your truck should only have 1 O2 sensor if it is indeed either OBD1 or OBD1.5. OBD2 Blazers only have 3 O2 sensors.

Do you have a MAF sensor? If so, when was the last time you cleaned it? Also, a bad MAP sensor could cause the symptoms you are describing as well, but a bad MAP should throw a code or atleast should show up when scanning the sensor data.

The plugs/wires/cap/rotor are good maintenance items to replace as well as the O2 sensor, but to go any further, you really have to have a better idea of what's going on with your truck. The shotgun approach can get very expensive once you get past the run of the mill repairs.

You should probably see how your fuel pressure is doing. It is possible that you have a leaking FPR (fuel pressure regulator) in the intake that is flooding out the engine at idle, but not affecting normal driving by a noticable amount. A fuel pressure test will show a bad FPR in a heart beat.

 

Well it doesn't have a MAF sensor it does have an intake air sensor and a MAP sensor, it was on a snap on scanner but nothing showed up on it other than it ran 11% rich and that person told me it was an O2 sensor but no codes or bad sensors were read and the scanner said it was ok to drive so that wasn't of much help. Testing the fuel pressure regulator sounds like a good idea, I'm not sure how to do it. I have a gauge with a shcraider valve on it that I use on my 85 vette TPI fuel rail but I don't have a clue if that will work or how to do it on the blazer.

 

There is a spot to plug the gauge in at the back of the fuel rail, I believe on the drivers side.