2002 Blazer w/diminishing fuel economy

jaslilhon

I just took a long trip in my Blazer(1000 miles). I changed the spark plugs before the trip home. I tracked the fuel economy on the way home and it was about 17-18 on the highway. I used to get 22-23 highway. I had noticed a little smoke recently coming from the exaust upon start-up. This was even before the spark plug change. Is it maybe running too rich? What can I do at this point? I have about 97000 miles on the vehicle.

repairdog

Could be many things but what color smoke - white is water and black fuel or oil - smell should tell too. 97k so time for a cap/rotor and then possible plug wires. Air and fuel filters new? Clean the MAF sensor also. Then is the temp running at 195 as normal cause cold will run rich. Assume no codes or SES light on. With AC off on my mine at 70mph about 20 max with 3.73 gears and then at 80mph down to 18mpg. 4wd also and then with AC on drops about 2mpg lower. Autotrac 4 button systems are also lower cause the front driveshaft always turns where the 3 button ones don't. The normal 3.42 gears do alittle better as rpms lower and 2wds with less drivetrain loss.

jaslilhon

Thanks for all of the information. Just to clarify. It is the 4 door 4WD platform. It has 3.42 gears. I changed the plugs, wires, and cap and rotor. The smoke is white, but it doesn't last long at all. I haven't smelled it at this point. My fuel filter probably has about 15k on it now. My fuel pump went this summer. All was replaced at that point. The air filter is a K&N. I looked at it when I changed the plugs and it needs a cleaning. However, it doesn't look horrible. I also replaced the thermostat last winter...it was running below 195.
In addition, I do have a question concerning temperature regulation. During the summer when it was at 95 and higher outside. The Blazer was having trouble regulating its temp when it was sitting at lights or in a traffic jam. Should I replace it again?
Where is the MAF sensor located?

repairdog

Radiator pressure may be off so get a new Stant cap and the white smoke could be water (Dex cool) from the classic leaking lower intake manifold gasket on these 4.3s. Any slight lifter tapping at startup? When cold fill the reservior to the hot mark and run a few days and see if the level drops when cold again. Often the leak is into the valley and you never see it. Then look at the waterpump (2) small holes on top and bottom and see if thats leaking. Most auto stores have a free use rad pressure tester so you can do it yourself and you may spot a leak or see the pressure drop and good indication its the intake gasket. Fluid loose could be from a heater core also but you smell that inside the cabin.
MAF is in the air intake above the filter (metal grid holds the small resistors) and carfully spray clean with MAF, electronic or brake cleaner - not carb). Also if the cap does not solve the raise in temp and not the intake or waterpump, there the fan clutchup front - should be loud on start in hot weather then release and if idleing getting hot lock up again and get louder.

dan132

Can anyone say if you can take the oil pan off the engine with the engine still in truck? Thanks in advance.