Need help....knocking.

[DoMiStIc_RuSh_06]

Hey everyone,

Term is doing some tuning on my car. We are on the second revision and my car seems to be knocking everytime i get into the throttle. Any ideas what it could be. I run 91 octane because that's all we have. Could it be the upper o2 sensor? Term thinks that it could be a faulty knock sensor, but how would I test/ detect this.

If you want I can put up my log.

I'm hoping term will chime in with more info.

[Terminator2]

I am still working on the knock what is really strange is the knock is no worse when I added 2* of timing so that makes me think it is due to either false knock, maybe a bad or improperly rotated knock sensor. Also your pedal position log are crazy looking you might have a bad pedal or somthing else with the ETC because the pedal position looks like a sine wave under certain conditions and it should not unless to have the world's shakiest foot.

[Iam Broke]

Same issue he had with the ETC last year IIRC.

It's very hard to see the leads coming off of the knock sensor under the intake Mani & rail, even with an inspection mirror but the leads are supposed to be oriented to the 9 o'clock position according to the SM. I fixed the orientation of mine when I had the IM off but it really made little or no difference.

[Terminator2]

I told him he should try to swap pedals with another car to see if the issue goes away. The timing does some wacky stuff when the pedal starts jerking up and down. Timing cuts close to 0* with no knock shown and the cam angles bounce all over the place. I have no idea why it is doing that other than a bad pedal or throttle body motor. The car really needs a skilled tech to look it over. GM dealers 90% of the techs at the GM dealers around here dont even know they make a turbo cobalt LOL.

A/F goes wacky sometimes as well. I have had 3 others cars I have tuned with that symptom (A/F bounces around randomly) and all had a bad purge soleniod.

[Iam Broke]

I'd replace the throttle position sensor on the pedal from what I remember from his logs last year.

[gmtech16450yz]

The car really needs a skilled tech to look it over.

Absolutely.

90% of the techs at the GM dealers around here dont even know they make a turbo cobalt LOL.

Unfortunately true also. Especially when you get out of the big cities or hi-tech areas. You just have to find one of the 10% guys. One thing you guys have to remember though is you're totally immersed in (for the most part) ONE car, with ONE computer and ONE engine. Of course you're going to know more about that ONE platform than most dealer techs. So don't discount the guy that doesn't know there's a turbo Cobalt, that doesn't necessarily mean he doesn't know anything else. I know, a lot of times it does, but you never know!

[1080112520]

i had this issue tuning the guy i am tuning in hawaii!!!!! ISSUE WAS RESOLVED ..... HE HAD IS AC ON WHILE TUNING CUZ I NOTICED IT, AND ASKED HIM TO TURN IT OFF. And kr went away, it didnt do it above 70% throttle but anything below it did. so i dunno if this woud help or not!!!

[DoMiStIc_RuSh_06]

I'm gonna try and swap pedals with some one. Maybe even throttle bodies. Should I unplug the evap solenoid and see if I makes a difference?

[DoMiStIc_RuSh_06]

I told him he should try to swap pedals with another car to see if the issue goes away. The timing does some wacky stuff when the pedal starts jerking up and down. Timing cuts close to 0* with no knock shown and the cam angles bounce all over the place. I have no idea why it is doing that other than a bad pedal or throttle body motor. The car really needs a skilled tech to look it over. GM dealers 90% of the techs at the GM dealers around here dont even know they make a turbo cobalt LOL.

A/F goes wacky sometimes as well. I have had 3 others cars I have tuned with that symptom (A/F bounces around randomly) and all had a bad purge soleniod.

I may order up a wb 02 sensor. From what I have read, that would cause the same issues. By the one I get it figured out my motor will prob be shot.

[Ch1ck3n]

i had this issue tuning the guy i am tuning in hawaii!!!!! ISSUE WAS RESOLVED ..... HE HAD IS AC ON WHILE TUNING CUZ I NOTICED IT, AND ASKED HIM TO TURN IT OFF. And kr went away, it didnt do it above 70% throttle but anything below it did. so i dunno if this woud help or not!!!

Man if that turned out to be the problem... Crazy ass cars.

[1080112520]

When ac is on itll cause the ac compressor to kick in and off, and apparantly data logging was picking it up damn them knock sensors. lol

[DoMiStIc_RuSh_06]

Well if it picks that up, could it pick up the vibration from where the Kn Sri bracket is bolted to the engine, the fact tHat the ic is mounted to the bumper support or the fact that the Injen cp is mounted to the intake manifold. I'm starting to think it could be false knock, because my car has vibration at idle and a little worse just off idle when we are seeing the noise spikes in the etc, which just so happens to be when the knock starts and it pulls the afr with it. I'm not very knowledgable on this shit tho.

[T-Man]

Two words; Grenade & Insurance.




Vibrations are probably from the rotated stg1 trans mount. Doubt that would cause your problems due to others having the same mod and being tuned... but anything is possible.

Best of luck to you on getting this sorted.

[DoMiStIc_RuSh_06]

I don't even have the mounts in yet lol.

[1080112520]

Mounts cause vibraions and ive seen them cause fake kr So it can happen. ANYTHING CAN HAPPEN. But even with your stock mount a cars knock sensor can see knock from vibration. I was tuning a evo 8 and we kept geting knock well what it was was his MOTOR MOUNT ITSELF. It was broke, causing the metal to metal clack lol. easy find but still a possible.

[DoMiStIc_RuSh_06]

Yeah, my car does vibrate quite a bit for having stock mounts. I'm gonna check this weekend. Try to do some investigating. Gonna throw the original plugs back in and stuff. Could be anything.

[1080112520]

do you have ngk step one colders.. I know i was getting kr on the ngks when i was gapped at .032so i gapped them down to .030 and it went away ( More then likley spark blowout)

[DoMiStIc_RuSh_06]

Hey I have the stock plugs. I may have to look at recalling them. Term just emailed me back and said the good news is that I don't have any wot knock it's all partial throttle.

[DoMiStIc_RuSh_06]

I pulled my plugs out today and they looked good. Still having the knock issue showing up to 3.7 degrees a couple times. Term has my ltfts nailed between -1.6 to 1.6 but my stfts are all over the place, negative then plus. Still trying to find someone to swap pedals with me. What gives, it's almost like this car lives to make my life miserable lol. Props to term for doing the what he can to help me.

[shabby]

At least post a log, i've had knock since the day i bought the car, it seems almost normal to get some knock.