Hello. I have an o2 blazer with the 4.3l v6 in it. It has 104.000 miles. I noticed at idle my oil pressure gauge was reading 18-19... I got worried and went to the garage. I was told to replace oil pressure sending unit. So I did an made no difference. I then decidex to run 10w30 here in Vermont and I now notice my oil pressure is at 60 cold start, 40 driving (50mph) and 18-19 at idle BUT sometimes a steady 20 at idle... as soon as I give it gas it goes back up to 40psi. I also noticed while driving with 3/4 to half a tanm of gas my gauge will drop to E and check fuel light comes on. So if I stop and shut it off it will go back to correct reading. And my volt gauge will sometimes read 14 and other times it will read 16 v so I chacked it with my digital meter and it has 14.5 running at idle... It does need to be fixed cuz it makes a grinding sound. What is really going on here? And if u are at idle and put the electric windows up the rpms drop 200 rpm. Ive changed IAC, TPS. cleanex the throttle body. Cleaned MAF and PCV valve. New distributer pugs and wires. No difference. And I noticex it has a slight shake at idle... what is it? I hope its not the motor. Ive heard of the gauges going bad in these.

 

Hi Vermont Clyde! You guys are lucky on the snow this year with Killington opening early.

Oh well, enough about that. Go Bernie, right?

Oh well, enough about that. I am experiencing similar problems with my 2000 Blazer 4 door (125,000 miles). I run snow tires all year long, and also 5W-30 Mobil 1 oil. My oil pressure has been normal (when it's cold it's about 50 psi, and lowers to 20 or so when it's all warmed up, no fluctuations).
I've replaced the alternator on mine (probably 6 years ago) and am also not experiencing any issues with the volt gauge.
However, I have just begun experiencing problems very much like you are experiencing with the fuel gauge on the dash. When I'm stopped, it varies from full to empty sometimes but usually if I'm driving down the road it will read correctly. Please let me know what you find! Cheers, ski

 

Well im reading that the gas gauge is fuel pump sending unit. I did run some ATF in my old oil right before oil change and ALOT of black sediment was in the bottom of drain pan. So I will be doing it again soon. Im now running 5w-30 with lucas oil stabilizer and my op is line above 20 at idle and still line above 40 driving... but sometimes will idel at line after 40.... so im confused. Im going to do another flush and see what happens

 

To rule out the gauges on the oil pressure, get an add-on mechanical oil pressure gauge from an auto parts store, the kind that mounts under the dash and has a small tube that screws into the oil pressure port. Install it temporarily (or permanently) and read the pressure directly instead of electronically. If the pressures read differently, you found the issue. If they read the same, I would say you either have a worn oil pump or pressure regulator valve, or the bearing clearances are excessive allowing the lower volume of oil being pumped at idle to squirt out faster than the pump can provide it.

 

On my 95 Jimmy, the gas gauge fluctuates all the time, there is no baffling inside the tank so as the gas sloshes back and forth the sending unit float is "surfing the wave" and constantly varying the level signal sent to the gauge. Most fuel gauges are damped, meaning the movement from a change in signal is very slow, so quick changes from sloshing are essentially averaged out to the true reading. The one on mine is instant reading, giving a constant wagging of the needle unless the vehicle is running steady down a smooth road or has been stopped long enough for the gas to stop moving around. Usually just a 1/4 tank width movement though, not the full sweep of the gauge. A friend who has had a couple S10 Blazers said his did the same so it appears the slightly wagging needle is normal for these.


Dropping to E and staying there until the key is cycled sounds like a bad connection between the sending unit and the gauge.

 

hey Clyde this is for the 2002 series. I have a problem with all my gauges going out on occasions, as well as the fuel gauge going all over the place. Through knowing another who has the same vehicle I have found the fuel pump sending unit is known for going out on these models and to replace it you have to drop the fuel tank as far as other issues please remember the 2002 blazers are very tempermental and very territorial which is if you have anything off from the original specs your OBD will read there is a problem. Which might be nice to know if you ever have to get after market parts for it.

 

If you only have 18/19/20 oil presssures at idle,that`s normal.It will flucuate from time to time.My oil pressure gauge flucuates all the time.It will idle at 30lbs. at times,then idle at 20 lbs. other times.After the oil warms up, the gauge spikes to 60lbs while driving.Always check the oil level,that way you know your safe.You also said"when the gas gauge reaches 3/4 or more of a tank the low fuel light comes on!"That`s normal too.My blazer does the same thing.If and when the( low gas) light comes on,you usually have around about 6 gallons of gas still left in the tank.But as far as the motor not idling smooth, that`s something different.That should have been posted on a seperate topic.

 

It`s a bad idea flushing a engine with over 100,000 miles on it.

 

Mostly all gas gauges flucuates at times.If you`ve owned your blazer for awhile, if the gas gauge is acting up?Possiblity the sending unit is defective.If you decide to change out the sending unit all together..You may as well change out the whole fuel pump assembly while your at it.It wouldn`t make sense to just change out just the gas sending unit,you have to pull the gas tank either way you look at it.

 

Already had the tank out to replace the fuel pump with a Bosch unit, the old one died a week after I bought it this summer. New tank straps too, this thing has lived through a lot of Indiana winters, the old ones were rusty lace...

The gas gauge fluctuation from sloshing is apparently normal for these trucks, like I said there is no needle damping so the gauge instantly reads exactly what the float reports as the fuel level rises and falls. My tank (4 door) at least had no baffles in it, most steel tanks have a baffle or two installed to cut down on sloshing. I actually need a new sending unit anyway, the fuel return tube has been cut and a rubber hose spliced in. Rust pinhole too, amazingly my emergency repair of Gorilla Glue epoxy coating the tube has held up for several months now, I applied it with no hopes beyond a day or two but it has really held up!

I'm trying to keep this Jimmy as low buck as possible, I've got around $700 total in it. High mileage and kinda rusty in spots on the frame, I mainly bought it because I need a 4X4 to get to work some winter days. Kinda undecided to fix it up right and add some custom touches, or run it till it dies and grab a newer one with less rust to sink money into. The '95 was the year when they transitioned to OBDII, so even the PCM is a one year only thing!