Hey everyone. Have a problem that needs some fixing. I have a 98 Blazer 4x4 with 75,000 miles. Recently I noticed that my mpg went down from 22-23mpg to 15-18mpg. I realize winter driving doesn't help gas mileage but I have also noticed a drop in driving power. On a recent trip up to northern Wisconsin (5 hour drive) while driving approximately 70-75 mph my RPMs would suddenly jump from about 2000 to 23 or 2400 RPM with a noticeable stall or jump. Now the crazy thing is that is doesn't happen all the time. Just every once in awhile. I took it to a local mechanic and of course no codes came up. He checked out my transmission and everything was fine so he changed the fluid and filter. I haven't received my Blazer back but I'm assuming that it won't be fixed. Hopefully it will be but I'm not that optimistic. Any input would greatly be appreciated!

 

If the RPMs increase, that is likely your torque converter unlocking. But which is it? A stall, or a jump. Those are two different things in my vocabulary...

Concerning your fuel mileage, have you gotten fuel at a different station recently?

 

I would say more of a stall. I thought it was my tranny slipping.

I have gotten gas at different stations but the decrease has been ongoing for a few months. Seems like its getting worse.

Thanks for the quick reply.

 

Depending on your location, you may have oxygenated fuels in the winter time. Seeing as how it has been going down over the last few months, this could be the reason.

Have you ever done a tune up on it? Considering that the truck is 10 years old going on 11, it is highly likely that it is time to do cap/rotor, plugs, and wires. You also may want to replace the fuel and air filters if they have not been done recently.

 

I gave it a tune up last winter and only changed the plugs, wires, cap and fuel filter. Didn't mess with the rotor (Edit: or check/change distributor). I have a K & N air filter that I recently recharged. I also cleaned the MAF sensor afterwords just in case I got some oil on it from the recharge.

I'm in Madison WI BTW.

 

How soon after cleaning the filter did you clean the MAF? It is possible to get air cleaner oil on the MAF for a month or so (depending on how saturated the filter was) after a filter cleaning/recharge. Try cleaning the MAF again.

 

It was only a week or so after. I'll give it a shot.

 

Well its at it again. It only happens when my cruising RPMs are around 2k and I noticed that it is frequent while going uphill or slightly uphill. Today it was doing it constantly for about 3 minutes then stopped @70mph. Its extremely frustrating and I can't keep taking it to a mechanic because funds are low and we're expecting our first baby. Horrible timing for our only vehicle to be crapping out. Any suggestions?

 

Also, it kind of feels like the cruise control disengages when it jumps. The cruise isn't on....in fact it only works sometimes.

 

"Well its at it again" implies that it went away. What did you do to make it go away?

It is quite possible that the TCC (torque converter clutch) is causing the issues. Especially if you tap your brakes (just enough to activate the tail lights, but not slow you down) while holding steady on the gas pedal. The torque converter should unlock. If it smooths out, then the TCC is going out or the TCC solenoid is leaking past...