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Knock sensors plugged in wrapped in bubble wrap and still pulling timing? Help!

J

J57ltr

New member
Ok, so in my latest go-round with this car (05' GTP) we figured the knock sensor(s) were bad so I decided to pull them
both and change them. I have also had an issue where the pcm commands the bypass open and I drop boost to 0. Recently I have gotten P0068 which throws the car into Reduced power and that's freaking dangerous. In watching the sensors MAP, Baro, and MAF they seem to be in line but the 1900+ cfm at 6-7psi throws me off. So I went to G/sec.

ive been through all the vacuum lines with a fine tooth comb and am in the process of replacing all the plastic tubing with 3/16" steel line.

tonight I had readings of 267g/sec/ -2* timing and 1.6psi also dead rich on the O2 set as graph. Now the reason I am not using KR in this is because it simply won't work. If it works then nothing else does I've tried everything and nothing has helped. Not real sure what's going on just yet but if I can log the other items then I should be able to tell Kr.

So this brings me to tonight I got the car up on ramps and removed both the knock sensor wires and connected them to the new knock sensors wrapped in basically bubble wrap. It was cut up pieces of Mylar bubble sunshade. I Ty wrapped them in nice little bundles and tied them to the firmly to brackets and such that they cannot move and are dampend as much as you would expect. I went for a drive and didn't have the bog that usually (sometimes) occours. The timing was about 40* when I eased down the neighborhood, then at the stop in gear it was 15* which has been normal. Then I take off and it is in the 30's and 40's and as I lean on it the pressure spikes above 0 then drops back and timing goes to -2* other readings above.

what the hell is going on? Do I have to reset something?

Thanks,

Jeff
 


When you replaced the knock sensors, did you torque them to the correct specs? (I think 14lbs). Anything more/less they can give false readings.
 
crazyguy03 said:
I've never heard this before ... Source ?
Click to expand...

The torque is not very much on these sensors, when I look at service information on GM's web sight it specificly says that also. There has been GM video's in the past for service techs that talks about the issues with over-torqueing them and how much more sesative they become.
 
Last edited:
At the time of the test the connected sensors were wrapped in Mylar Bubble Wrap they were wire tied away. The old knock sensors were still in the block disconnected.

When I did get the new sensors in they were torqued to 14 ft lbs.

Jeff
 


Oh and I don't have the drop in timing to near 0 when starting out anymore. Still have some strange things going on, same thing as last night.

Jeff
 
dezebe1 said:
The torque is not very much on these sensors, when I look at service information on GM's web sight it specificly says that also. There has been GM video's in the past for service techs that talks about the issues with over-torqueing them and how much more sesative they become.
Click to expand...

Cool. Good to know. I will double check now knowing it's that sensitive. I think it was only a couple ft/lbs difference between the 2 sources I saw the specs listed on
 
J57ltr said:
At the time of the test the connected sensors were wrapped in Mylar Bubble Wrap they were wire tied away. The old knock sensors were still in the block disconnected.

When I did get the new sensors in they were torqued to 14 ft lbs.

Jeff
Click to expand...


So so how the hell did I have -15* timing with basically no knock sensors installed? Please read my first post, a the information is there. I know TL;DR. Well I put as much info so that someone that knows what's going on has the information they need to diagnose the problem. Ask me anything else and I will get you that info as well. Trying to figure this out and need a little help here.
 
J57ltr said:
Ok, so in my latest go-round with this car (05' GTP) we figured the knock sensor(s) were bad so I decided to pull them
both and change them. I have also had an issue where the pcm commands the bypass open and I drop boost to 0. Recently I have gotten P0068 which throws the car into Reduced power and that's freaking dangerous. In watching the sensors MAP, Baro, and MAF they seem to be in line but the 1900+ cfm at 6-7psi throws me off. So I went to G/sec.

ive been through all the vacuum lines with a fine tooth comb and am in the process of replacing all the plastic tubing with 3/16" steel line.

tonight I had readings of 267g/sec/ -2* timing and 1.6psi also dead rich on the O2 set as graph. Now the reason I am not using KR in this is because it simply won't work. If it works then nothing else does I've tried everything and nothing has helped. Not real sure what's going on just yet but if I can log the other items then I should be able to tell Kr.

So this brings me to tonight I got the car up on ramps and removed both the knock sensor wires and connected them to the new knock sensors wrapped in basically bubble wrap. It was cut up pieces of Mylar bubble sunshade. I Ty wrapped them in nice little bundles and tied them to the firmly to brackets and such that they cannot move and are dampend as much as you would expect. I went for a drive and didn't have the bog that usually (sometimes) occours. The timing was about 40* when I eased down the neighborhood, then at the stop in gear it was 15* which has been normal. Then I take off and it is in the 30's and 40's and as I lean on it the pressure spikes above 0 then drops back and timing goes to -2* other readings above.

what the hell is going on? Do I have to reset something?

Thanks,

Jeff
Click to expand...


i dont understand why you think the knock sensors are bad. if you have KR chances are they are working.

no idea if your stock, modded or what? so why did you pull the k/s in the first place?

this is your code. id get to fixing this up. http://www.obd-codes.com/p0068
 


He gets very random KR, in very weird areas. He has it in other threads. like 15* of KR when he is still at -13in vacuum
 
well that code is a maf code with a dash of tb sensor issue. i bet if thats fixed, not sure where to go with it but im sure thats the main issue.
 
When unlocking the torque converter or when the computer wants to downshift or perhaps prepares for a downshift the timing can and will drop to negative numbers and then bounce straight back to the "normal" numbers and carry on.

I've never really dealt with a grand prix that does this but my 2010 silverado with the 6 speed auto will do this on every shift. It's a form of torque management.
 
The car is totally back to stock (3.8" pulley) except the exhaust now. The knock sensors were defective I was getting KR when pulling away from a light slowly they. Even light throttle at 30mph 18" was causing KR. Then it would go away then come back. So I did what I described above and it went away, when pulling away from a light but doing a rolling WOT run that's what I got. So basically connected sensors with conductive bubble wrap the engine still lays over like its knocking. I changed both sensors and the off line performance is better but still have the engine lay over and -15* timing and rich according to the O2's LTFT and STFT are nowhere near 0 but I'll post that later.

Thanks
 


just to make sure your not ending up with an intermittent 3x/18x screwing with the 7x icm to pcm data....follow along and inspect the whole ICM harness down to the crank and cam and make sure it hasent been rubbed through by the belt or any pulleys.

twice ive found an icm harness intermittently grounding on the ac compressor clutch the third was grounding on the ap pulley and partially rubbed through by the belt. cars had all sorts of erratic timing and drivability issues
 
Are you actually seeing timing pulled directly from the knock sensors, or is it possibly something else pulling timing? I'm total noon when it comes to this, but there are other tables that can pull timing too right? What happens when you disconnect the knock sensors? Will the car run like this?
 
James, that's good info. I did find where the harness rubbed through the loom that goes the the ICM, I looked at the wires and it didn't seem to get to them. I'll take a closer look when I get a chance and split the look and look at every wire the other wires by the crank sensor everything is good. I had a good chance to look while
I was changing knock sensors.

Bandook,

When I was able to get the KR to read I could start the car let it warm up a little while I gathered stuff and whatnot. I would back out of the driveway and as soon as I started off the air would read 2-3* then jump to 15* then drop off as RPMs increased, the. Drop to 0. It was very erratic and some days it would other days it wouldn't. So I know it was pulling KR at that time. If KR works nothing else does, can't read ignition timing, MAF, Map or anything else. I had restarted the phone, reinstalled the app, deleted PID's I didn't need basically everything Kevin at BAFX recommend.

Corey,

I am not sure that the 04+ will do that without setting a code. It would be easy for the ECU to ping the sensor to see if it was there. I'm not sure it actually does this, but the thing is smart enough to reduce the throttle opening compared to the pedal input so the programming is pretty good at protecting the engine. Besides I did the above and changed both sensors front and rear, now it doesn't do the off idle knock but I'm getting the other problems I mentioned.

my LTFT on a 40 mile drive was -15 to +15 and my STFT was -6.2 to 0 this was almost all freeway with about 10 miles of highway with stop lights, this was earlier today.

now last night I really had something strange. I drove to a friends and when I left I was monitering 02, MAF, temp, intake temp and timing. Normally my 02 is real spikey which I see as normal for a narrow band 02. Then I was at a 30mph roll and stomped on it WOT well the engine started taking off and I was watching the MAF and it was a linear rise then started to taper off (I could feel the power start to drop) then the the MAF voltage dropped off and leveled out even though I had it floored. Timing reduced to -3 and then the engine started acting a little weird. The 02 stopped switching back and forth as quickly it would show rich for several seconds then lean for several seconds. When I pulled into the driveway it was still doing it. Shut the car off and restarted it and everything was back to normal.


i have had several times where the engine goes into reduced power. The other day I noticed one of my friends was ahead of me and I kicked out into the next lane to catch up. Got to about 3psi then let off then the HUD says check DIC and it's going through the traction control off reduced power and all that and when it does it sets the timing to 15* ATDC and dead rich. I quickly pulled over and shut the car off opened the door closed the door and restarted it then drove off like nothing happened.

Jeff
 
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