Hello everybody

I have problem with my 2WD 00 Jimmy it runs Rough in Idle but the rpm stable at 620 . Recently I change the brake booster with new one because I was think it is because of vacuum leak from it now the car run better but it is still it run Rough and I can feel the vibration of the engine. I replaced the injectors with new upgraded one before 3 years and the tune up include motor mounts was done before 6 years ago.

What can cause this problem ?


thank you

 

This can be so many different things. Its definitely solvable and some get lucky and guess right early on but most need to go through a detailed diagnostic flow to find the problem and address it. Broadly speaking it can be:

Fuel delivery/air
Ignition
Sensors, electrical/PCM
Engine mechanical issues

We first look at codes or ask for other symptoms to help pick a logical starting point so we don't just have to plow through the whole universe of possibilities randomly. Before we get started, are there:

Any codes
Other symptoms
Recent work that made it better or worse
A recent compression test
A recent fuel pressure leak down test
Inspection for exhaust leaks
A look at manifold vacuum



George

 

Hi GeorgeLG

No codes there. I don't know how to test the fuel pressure leak down and manifold vacuum do you have any articles or video on how to check. Also, I have one question about spark plugs when it should be changed ? because my spark plugs color changed to black.


thank you