Bucking Blazer

I started having a bucking problem with my Blazer. It acts like it is not getting any gas and the engine revs then it will kick in and go. Sometimes it will buck when you are driving like it is not getting any gas. I have changed fuel filter, got tune up, changed distributor,transmission service and got the mass flow intake cleaned. We have put it on the computer and they are telling me there are no error codes. The bucking and acting like it only happens after the car has been driven about an hour with the air on and after about 4 hrs with the air off. It also has to be hot outside like 90 and above. There are 124,000 miles on it. Any ideas? I have the local mechanics stumped.

What year, engine, auto, manual, etc? Full size or S10? TBI or CFI injection?

The only thing that comes to mind without more info is a failing fuel pump. The fuel pump on my 2000 Blazer has a bad rep. When the fuel pump on my wife’s 91 Taurus was failing, it could be driven 60-75 minutes before the fuel pump would act up.

Ed B.

How can an “engine rev”, and then, and then, “kick in and go”? Shouldn’t it go as it revs? Is the engine NOT driving the transmission (automatic, or manual transmission?)?
Could you explain, in longhand, and in detail, what is happening? Explain the “before”, the “during”, and the “after”. Women seem to be pretty good at this word thing. Is there one who can explain the situation to us? It could help us a lot.

Here is the long hand explanation of it. Once the car is driven and you come to a stop, it will buck and sputter like it is going to stall out and it is not getting any gas. Then as you push the gas pedal, it will rev the rmp’s up to about 4 or 5 then it will shoot forward still bucking and sputtering before it evens out and starts running normal. It will do this from a complete stop till it gets over 35 mph. And sometimes when you are driving and it will start bucking and sputtering and acting like it is going to stall out. It will shoot the rpm’s up to about 5 then it will start going again bucking, sputtering, and acting like it is going to stall out then it will even out and run normal. This has happened when it when I have been driving at 65-70 mph. I do not know how else to describe it. If this is not enough then let me know.

Your symptoms sound like a fuel pump is not putting out the full required pressure. Stick a gage on it and check it against the specs. My money is on a bad fuel pump. It’s one of the few things that won’t trigger a CEL when it goes bad.

I have this problem, but it’s completely random. No set time when it happens, but it tends to occur around 45mph or so, when it should be changing gears. I feel like it’s not really changing gears properly. When I took it to a mechanic they didn’t notice the problem at all. I own a 2001 blazer, 85k miles.