95 Blazer with 4.3L, 2 wheel drive and 147K mileage.

Problem: poor fuel mileage around town, 13-15mpg; highway mileage 21-22mpg, this problem has been going on for about2 years and if I think hard about this the mileage just dropped over time from 19mpg around town. Acceleration is poor at any speed.Recently it has beenintermittently slow to start and acts flooded when it lights off. We are in San Jose CA so it really not very cold.

History: Purchased new, we have always used Chevron and Techron about every 10k-15k, Redline oil, changed about 4k interval, recent tune up with quality parts, K&N filter, fairly new muffler and cat. The EGR valve is less than 2 years old, the last one was carbon clogged and recently this one tripped the code and when I pulled it off a carbon chunk fell out, it did not need cleaning.

It used to be my wife’s daily driver but was replaced in June 06 with a new C6. My daily driver was a 2001 3/4T 4WD Suburban. I retired the day my wife picked up the C6 (she still works) and have been using the Blazer, but it is not used every day.

I have an AutoXray scanner and could look at live readings if I knew what to look for.

Suggestions would be welcome.
Thanks,
David

 

When was the last time that a full tune up had been completed? What is the mileage? Has the upstream O2 sensor ever been replaced?

If your scanner has graphing capability, graph the O2 sensor mV output. If the O2 sensor has the appropriate activity, the curve will transition smoothly from lean (low mV - 200-300mV) to rich (high mV - 800-900mV). If the graph looks choppy and the high/low readings are not consistent, then the O2 sensor is getting lazy and may be negatively impacting your performance/efficiency. If that is the case, you may regain some lost mileage by replacing the upstream O2 sensor (the one closest to the engine located just after the 'Y' in the y-pipe).

 

Thanks for the reply!
The ERG was replaced at 136K
Complete tune up at 139K, wires plugs, rotor cap, fuel filter, pvc
O2 sensor at 145k

I’m not sure if the scanner can graph, however I believe it can be run into my laptop. I’ll check on that later today and also put the scanner on while driving to at least view the o2 sensor live.

One thing I am curious about is the condition of the injectors. Does it make any sense that they can be functioning poorly from internal wear (erosion due to fluid flow) or just have deposits that make for poor fuel flow especially when in typical around town driving they demand for changes in flow is high? Can injectors be taken out and cleaned?

Looking at the mileage poll my mileage does not look too bad but it did used to get 18-19 around town and I’m sure 13-14 is a sign of something amiss.
Thanks again for taking the time.
David

 

I would start by changing out your fuel filter with a new AC Delco. Those shouldn't be much more than $14. Then get some Mass Air Flow Sensor cleaner and clean your MAF. (especially since you put a K&N in there. Even from factory K&N filters emit residue on the sensors.) Also take a good inspection of your transmission fluid and rear end fluids and consider flushing them out with fresh synthetics! This should give you a great start and may help you with your problem. Also consider a radiator flush with new thermostat if they havent been done in 70k miles. The Chevron Techron is great maintenance on your injectors and fuel system so continue to do that. Not to crazy about Redline oil except for in motorcycles. I would use a Quaker State 'Torque' or Mobil 1 Truck/SUV super synthetic is what I use. Your truck should have no problem getting you another 150k miles especially since it is a 2wd if you keep flushing fluids and use quality gas. Hope this helps, & good luck!

 

This may seem dumb but I cannot find a MAF on this engine. The factory manual defines it and I find no reference to it anywhere I have looked. In the driveability manual the under hood layout is on page 1-9 engine code W it is not identified, and it is definitely not in the intake system. Perhaps I should clean the MAP.
I failed to mention at the same time I changed the EGR I also did a water pump and thermostat. The water temp seems to run consistently at 190. I have had trouble with sludge in cooling system and have had to replace on rusted out expansion plug above the starter. The cooling system, more specifically the heater core gurgles from time to time.
I cannot remember exactly the mileage but it had a complete trans flush including the torque converter, I’ll do the rear end soon. The trans has RedLine also.
On the fuel filter it has been changed about every 15k and I use a WIX.
Like all things automotive there are good and bad experiences. I have used Redline for longer than I can remember and when I put it in my Suburban trans the operating temp dropped 10 deg or more when I tow. I did first start to use it in a motorcycle based road race car….
It is funny how many things I have done but kind’a forget about until they get mentioned.
Please keep the suggestions coming and as I try stuff I’ll report.
Today I am cleaning the filter, I’ll clean the MAP, and maybe the idle air control.
Thanks
David

 

I believe the MAF is the first sensor on the air intake right after the filter. I get you mileage also but mine is partly due to awd.

 

yes, the MAF sensor is located between the filter box and the throttle body. Directly after the filter box as portcqb has stated.

If you have a gurgle to the cooling system, the system has air in it... You'll want to get that air out of there ASAP!

 

How do you know ifyour MAF needs a cleaning or is there a mileage when you should clean it?

 

Pretty much just take it out and have a look at the elements (you may have to disassemble it). If the elements look brown/black, then its time to clean it. The elements should look a silvery gray.

 

This model of the 95 does not have a MAF, my previous older fuel injected GM vehicles did and of course it was right after the filter.
Yesterday I cleaned the Idle Air Control, Intake Air Temperature, MAP, EGR, and the filter.
When I started it up the check engine light came on and the scanner said it was the IAC. Turns out it losses the base setting when disconnected and it had to be calibrated, simple but previously unknown to me.
None of the sensors seemed to be really dirty.
At idle the TPS voltage was 0.66v and the MAP 1.33v, the O2 sensor jumped around from 70 to 900mv which according to the manual is correct.
Time will tell but the first thing I noticed is that in half a dozen starts the hard starting seems to be gone. It will take a little time to find out if the around town mileage has improved.

David

PS other than hanging from a tree and suggestion on how to get the air out of the heater core?