Running little rough

Maintenance/Repairs
1

i have a 1998 chevy blazer v6 4.3 about 130000 miles on it.the shop told me my car was running little rough and thay never said why it was.and there is no check engine light on.i did clean out throttle body and which it was really bad.put in new air filter.hope you guys can help me out.i do know is that i never know if spark plugs been change before i got car about 127000 miles on it…

2

Is the Check engine light on, and if so have the codes read and post them here.

The shop should have listed something that they thought might be the problem for the rough running.

If not, I’d replace the plugs, wires and distributor cap and rotors. I’d also run a can of good injector cleaner through the system with a 1/2 tank of gas, to see if cleaning the injectors would clean up.

You may also need a new fuel filter.

Yosemite

3

what is good injector cleaner ? i am going to replace plugs wires coil

4

+1 to Yosmite’s post, except that you may find that the vehicle doesn’t have a replaceable fuel filter.

5

there is no check engine light on

6

OP’s Blazer definitely has a replaceable fuel filter

I know this because we have tons of Blazers and Jimmys in our fleet, including 1998 models

7

So what was the reason for the car being in the shop in the first place if no diagnosis was done or parts replaced?

If it’s running rough then there could be one or many reasons for it. A diagnosis has to start somewhere; preferably with a scan for codes, a vacuum test, and a compression test.

If the engine has a mechanical fault you could throw parts at it all day long and accomplish nothing.

8

i had it in shop to get new transmission put in a use that is

9

A good injector cleaner is SeaFoam.

http://seafoamsales.com/sea-foam-motor-treatment/

When these engines start running a little rough, the first thing to check is the fuel pressure.

The fuel pressure spec on these engines is 60-66 PSI.

The reason why the fuel pressure is so high is, the fuel pressure is used to blow open the poppet valves in the spider assembly.

https://www.rockauto.com/catalog/moreinfo.php?pk=1053753&cc=1314133&jnid=505&jpid=13

If the fuel pressure is below spec, the poppet valves won’t open properly and engine can run rough.

So, try the SeaFoam, check the fuel pressure, and let’s hope the engine doesn’t need a new spider assembly. Because it’s located below the intake manifold.

Tester