cutting out under a load

**re209** · 04-08-2011

Hello everyone! I am a new member, but have been reading here for a while.

I bought a 2004 GTP a month ago with 99k miles. The day after I bought it the check engine light came on and gave a code for a "knock sensor bank 2 low". I run 93 octane fuel, I replaced plugs and wires, and eventually replaced the knock sensor itself. Still getting the same code.

This is new and not sure if it is related. The car idles perfect and even revs smoothly when parked. When I put it in gear it give it gas, it cuts out or chugs. The plugs and wires are 2 weeks old. The fuel pressure was reading 52 psi, so we replaced the fuel pump assembly and the fuel filter. Nothing changed. If I push the gas to the floor it will accelerate, but it chugs and you can hear predetination. The check engine light will flash if I accelerate moderately.

I have a good mechanic working on it, but there is probably more knowledge here than any 1 mechanic can hope to have. I would appreciate any assistance. Thanks!

**BillBoost37** · 04-08-2011

OH boy.. where to start.

Smack your hand for not fixing the knock issue originally (that's if you didn't...if you did..your good)

Kinda sounds like a maf sensor, but it could also be sounding like a plugged cat. Did you change the plugs at the same time? I'm going to jump around further and ask.. are any plug wires touching the O2 wiring? That does this kind of thing as well.

**re209** · 04-08-2011

Fuel pressure was a bit low and we believed that it may have been causing the knock by being to lean. I just checked the O2 sensor wires and all is clear of that. I brought up the cat to my mechanic and he said the cat doesn't usually go bad all of a sudden. I will ask that he checks it anyway at this point. Will the car still idle fine with a bad MAF? I believe that can be checked with a meter.

Another thing to mention is I am still getting excellent fuel economy. I was out of town when it started acting up and still got 29 mpg coming home 6 days ago.

**Juanmiguel** · 04-08-2011

Maybe check the knock sensor wiring? I'm not sure how bad it cuts, but that could be the PCM taking off timing because of the knock or false knock.

Flashing SES light means miss firing by the way.

**Bedwards** · 04-08-2011

Check coils as well. Also, what DTC is coming up?

**re209** · 04-08-2011

It is fixed. The plugs I put in 3 weeks ago went bad. They were replaced under warranty. I put in autolites first, they are garbage. I replaced them with AC delcos.

**t24moore** · 04-10-2011

FWIW I have been running autolites for years now with no problems heavily modded. And a cat can go bad if youre getting misfires because those can damage it so your mechanic is technically wrong there.