My gas mileage does not appear to be what it should be. After driving 40 miles on full tank, the gauge shows 3/4ths full. At 18mpg, in a 19-gallon tank (2dr model), I should get somewhere around 342 miles out of a tank, which should also be about 85.5 miles for every quarter-tank.

This appears to mean that I'm getting more like 9 or 10 mpg; and I drive like an old geezer.

The reason I suspect the TPS is when I'm cruising down the road and barely have my foot on the gas, the throttle speed sometimes hops up & down between 1500 and 2500 rpms.

I was reading a previous post about "gas mileage nightmare", which was helpful in finding some possibilities, but I'm not sure where to begin on my Blazer.

Your help is greatly appreciated!

 

I have found some suggestions via this thread:
https://blazerforum.com/forum/2nd-ge...mileage-23431/

 

I continue to have the hopping up and down of the tachometer when the motor is "locked down" (5th gear?), and when I barely have my foot on the gas - it's almost as if the motor doesn't know which gear it wants to be in.

I bought a TPS but haven't decided if I should replace it yet.

In addition, my gas mileage has been terrible - 14 mpg (211 miles over 14.5 gallons).

I don't know if this means anything but I've never seen it before - the last time I filled up, I noticed the cap was wet with fuel on the inside.

I just replaced the fuel filter & put Lucas fuel treatment in, as well as cleaned out the MAF Sensor with CRC cleaner.
motor mount & front o2 sensor was replaced 6,000 miles ago.
motor was replaced 60,000 miles ago
Sending Unit & Fuel pump replaced 60,000 miles ago

 

Any ideas?

I replaced the TPS and got slighty better performance, but still have the fluctuation of the throttle as previously mentioned...

 

I had a similar issue with my '98 Blazer S10 4.3 4WD with 215k on the original engine/transmission. Fuel economy was only 18 mpg or so when I bought it new, but I spend a lot of time sitting in Seattle traffic at 0 mpg... I noticed a stuttering problem about two weeks after replacing the intake manifold gaskets - one rotted-out due to DexCool (regardless of what anyone says), but my coolant leaked externally.

Based on information provided in various threads here, I first replaced the distributor. There was a worn bushing and almost 2mm of axial 'play'. This did not fix the problem, and I had a P0122 DTC thrown with increasing frequency. Replacement of the TPS appears to have fixed the problem - only one week in, but no surging/stuttering. I noticed this behavior at constant sped/minimal load with the transmission in 'OD'. I tried light pressure on the brake pedal to evaluate torque converter lock-up without success. The behavior would be observed in '3rd gear' as well.

When I replaced the TPS I noticed a fair amount of 'wobble' in the rheostat even though static resistance/voltage measurements were within specifications.

My engin now idles around 550rpm, but previously was around 7-800rpm. From my recent fill-up, I was around 16mpg.

This is a little off-topic, but the TPS appears to be a critical sensor that has significant effect on engine performance.