ChainHartMachin

Hello,

I've attached a short log file of a frustrating knock count /retard problem... basically i get a bunch of counts and retard when flooring it from 10 mph and getting a 2-1 downshift. It counts like crazy starting at around 32 - 3600 RPM. What's strange is that I can punch it on the highway from 65 - 80 mph (4-3 downshift) and get no counts/retard at all. I've tried reducing timing and adding fuel. No real effect. I fixed two exhaust leaks, no effect. I've gone 2 heat ranges lower on spark plugs and no effect. I even tried 5 gallons of VP 100 octane (after pumping out my tank first), still no effect.

I believe my AE and PE fueling is in good shape and my timing is only 26 degrees. My motor has roller rockers. I suppose my exhaust could be hitting the floor, but would it really be this bad?

In the log I'm basically feathering through tirespin until it shifts to 2nd gear. The knock counts stop as my RPM's climb up after shifting into 2nd. The log file is a .csv that has been renamed to .txt.

Any ideas? Thanks much!

TORN

iTrader: (17)

Can't read the data, can u post the .csv file?

ChainHartMachin

If you change the extension to .csv from .txt you should be able to read it. TGO wouldn't let me upload the file if the extension was .csv.

TORN

iTrader: (17)

Ok I am no computer dummy but windows is not letting me change it.

ChainHartMachin

Sent

TORN

iTrader: (17)

Is this new or has it always pulled that much timing? 9 degrees retard is alot.

TORN

iTrader: (17)

Here's a pic of the log its the best I can do to get it posted.

ChainHartMachin

Even my VP 100 log has 8-9 degrees pulled on 2-1 downshifts. I can floor it on the highway and not get any counts. It may very well be maximum retard if you compare the "spark advance relative to TDB" compared with "spark advance relative to reference pulse". My reference angle is 69 degrees. Some of the frames have around -55 advance which would be 14 relative to TDC.

I was thinking of trying 110 octane Avgas (no catalytic converters ATM). But it seems like maybe the KS is picking up something besides real detonation.

Ronny

iTrader: (1)

I bet mechanical triggering the sensor. I was told a 4.3L KS is less sensitive.

RBob

iTrader: (1)

Noise from the tires spinning is being picked up. Make sure that the knock sensor isn't torqued too tight. Spec is 11 to 14 ft/lb of torque.

Check items such as the u-joints, rear trailing arms and torque arm bushings. With the tires spinning something in the rear suspension may be vibrating.

RBob.

ChainHartMachin

Re-torqued the sensor to 11 ft-lbs. It wasn't all that tight, but still good to check. As a side note, I wish GM had put the KS in its own blind hole rather than one that leads to the water jacket (it's natural to want to tighten the snot out of NPT plugs into water jackets).

I'll check the rest of my suspension tomorrow (I don't think my front torque arm bushing has ever been replaced). Would valve train noise behave this way? Or maybe transmission noise (pump whining)?

Thanks!

EagleMark

Sometimes your just a year to late... I had no idea knock could be affected that far from engine? That would explain the car, a year ago, with knock that would not go away, which was almost exact time as ladder bars rubber snubber was hitting spring...

The Knock Sensor is designed to be in water jacket to pick up vibrations from cylinders in water jacket.

It could be a motor mount/trans mount flexing and hitting metal. Your getting it a peak torque situation and then going away at higher RPM. Valve train or trans whine(not sure) would be same in all times. Your getting it at a certain peak torque situation.

ChainHartMachin

Torque arm bushing is cracked on the front side (closest to the transmission). I can pull on the torque arm itself and get it to move visibly.

U-joints feel okay all though it seems like the front one could have some minor play. I can get a slight thud noise if grab the drive shaft near the front u-joint pull it towards myself. Could this also be play in the tail shaft bushing?

I can try the torque arm bushing first and do a more thorough check of the u-joints while I replace the bushing. All I see for sale at autozone.com is the poly versions of the bushings. Any risks using these instead of the stock bushing (given that the tail shaft housing is what bears the load)?