HOWS IT GOING OUT THERE? I'M NEW TO THE CLUB. I HAVE A 2001 IMPALA, 3.4L. IT SOMETIMES HESITATES ON TAKE OFF, AND WILL SHAKE LIKE ITS MISFIRING AT HIGH SPEED, FROM 60MPH AND HIGHER. MOSTLY AT A STEADY SPEED. INSTALLED NEW PLUGS AND WIRES,COILS,FUEL FILTER,FUEL PUMP, THROTTLE POSITION SENSOR, AND VEHICLE SPEED SENSOR. STILL HAVE SAME PROBLEM.HOPE SOMEONE CAN HELP, THANKS

Have you had the fuel injectors checked yet? My first guess was going to be the coil packs, but you said you replaced that already.

Also... moving this the the Tech Section

Air Filter.

That's where I'd look next.

Edited November 5, 201015 yr by Camino LS6

Throwing any codes? Had them checked?

Throwing any codes? Had them checked?

NO CODES, ONE MECHANIC THAT LOOKED SAID HE GOT A HISTORY OF MISFIRES, COULD IT BE CAMSHAFT AND OR CRANKSHAFT SENSORS EVEN WITHOUT ENGINE LIGHT?

Air Filter.

That's where I'd look next.

CHANGED IT

Have you had the fuel injectors checked yet? My first guess was going to be the coil packs, but you said you replaced that already.

Also... moving this the the Tech Section

ONE MECHANIC THAT LOOKED DID'NT THINK IT WAS THE INJECTORS

Well, you're kinda running out of options as to what it could be. Even if he thinks it isn't the injectors it still could be, and it's one of the major things left.

Well, you're kinda running out of options as to what it could be. Even if he thinks it isn't the injectors it still could be, and it's one of the major things left.

any way for me to test it myself? and what about the camshaft and crankshaft sensors? thanks for your help by the way.

It doesn't sound like cam and cranks senor symptoms, but yes, the crank sensor especially can go bad without throwing a code. Have you done a fuel pressure test? Leak down test? I would also look into the injectors.

Check all vacuum lines while you're at it.

It doesn't sound like cam and cranks senor symptoms, but yes, the crank sensor especially can go bad without throwing a code. Have you done a fuel pressure test? Leak down test? I would also look into the injectors.

Come to think of it, the symptoms that LOVEACHEVY describe very well could be the crank position sensor. A friend's car (1st gen Santa Fe) behaved exactly the same way (bucking/hesitation under load at highway speeds, can't make it up hills, no engine codes) and the culprit ended up being the crankhaft position sensor.

Have you checked the fuel pressure regulator? Do you have any idle or starting problems?

Well, you're kinda running out of options as to what it could be. Even if he thinks it isn't the injectors it still could be, and it's one of the major things left.

It could very well be. My MINI is behaving the same way and I'm now 99% new injectors will be needed as the reprogramming didn't help...

My bet is a bad injector.